9.2: Organizational Culture
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Learning Objectives
- Define organizational culture.
- Understand why organizational culture is important.
- Understand the different levels of organizational culture.
What Is Organizational Culture?
Organizational culture refers to a system of shared assumptions, values, and beliefs that show people what is appropriate and inappropriate behavior (Chatman & Eunyoung, 2003; Kerr & Slocum, 2005). These values have a strong influence on employee behavior as well as organizational performance. In fact, the term organizational culture was made popular in the 1980s when Peters and Waterman’s best-selling book In Search of Excellence made the argument that company success could be attributed to an organizational culture that was decisive, customer-oriented, empowering, and people-oriented. Since then, organizational culture has become the subject of numerous research studies, books, and articles. Organizational culture is still a relatively new concept. In contrast to a topic such as leadership, which has a history spanning several centuries, organizational culture is a young but fast-growing area within management.
Culture is largely invisible to individuals just as the sea is invisible to the fish swimming in it. Even though it affects all employee behaviors, thinking, and behavioral patterns, individuals tend to become more aware of their organization’s culture when they have the opportunity to compare it to other organizations. It is related to the second of the three facets that compose the P-O-L-C function of organizing. The organizing function involves creating and implementing organizational design decisions. The culture of the organization is closely linked to organizational design. For instance, a culture that empowers employees to make decisions could prove extremely resistant to a centralized organizational design, hampering the manager’s ability to enact such a design. However, a culture that supports the organizational structure (and vice versa) can be very powerful.
Why Does Organizational Culture Matter?
An organization’s culture may be one of its strongest assets or its biggest liability. In fact, it has been argued that organizations that have a rare and hard-to-imitate culture enjoy a competitive advantage (Barney, 1986). In a survey conducted by the management consulting firm Bain & Company in 2007, worldwide business leaders identified corporate culture to be as important as corporate strategy for business success. 1 This comes as no surprise to leaders of successful businesses, who are quick to attribute their company’s success to their organization’s culture.
Culture, or shared values within the organization, may be related to increased performance . Researchers found a relationship between organizational cultures and company performance, with respect to success indicators such as revenues, sales volume, market share, and stock prices (Kotter & Heskett, 1992; Marcoulides & heck, 1993). At the same time, it is important to have a culture that fits with the demands of the company’s environment. To the extent that shared values are proper for the company in question, company performance may benefit from culture (Arogyaswamy & Byles, 1987). For example, if a company is in the high-tech industry, having a culture that encourages innovativeness and adaptability will support its performance. However, if a company in the same industry has a culture characterized by stability, a high respect for tradition, and a strong preference for upholding rules and procedures, the company may suffer because of its culture. In other words, just as having the “right” culture may be a competitive advantage for an organization, having the “wrong” culture may lead to performance difficulties, may be responsible for organizational failure, and may act as a barrier preventing the company from changing and taking risks.
In addition to having implications for organizational performance, organizational culture is an effective control mechanism dictating employee behavior . Culture is a more powerful way of controlling and managing employee behaviors than organizational rules and regulations. For example, when a company is trying to improve the quality of its customer service, rules may not be helpful, particularly when the problems customers present are unique. Instead, creating a culture of customer service may achieve better results by encouraging employees to think like customers, knowing that the company priorities in this case are clear: Keeping the customer happy is preferable to other concerns, such as saving the cost of a refund. Therefore, the ability to understand and influence organizational culture is an important item for managers to have in their tool kit when they are carrying out their controlling P-O-L-C function as well as their organizing function.
Levels of Organizational Culture
Organizational culture consists of some aspects that are relatively more visible, as well as aspects that may lie below one’s conscious awareness. Organizational culture can be thought of as consisting of three interrelated levels (Schein, 1992).
At the deepest level, below our awareness, lie basic assumptions . These assumptions are taken for granted and reflect beliefs about human nature and reality.  Values are shared principles, standards, and goals. Finally, at the surface, we have artifacts , or visible, tangible aspects of organizational culture. For example, in an organization, a basic assumption employees and managers share might be that happy employees benefit their organizations. This might be translated into values such as egalitarianism, high-quality relationships, and having fun. The artifacts reflecting such values might be an executive “open door” policy, an office layout that includes open spaces and gathering areas equipped with pool tables, and frequent company picnics.
Understanding the organization’s culture may start from observing its artifacts: its physical environment, employee interactions, company policies, reward systems, and other observable characteristics. When you are interviewing for a position, observing the physical environment, how people dress, where they relax, and how they talk to others is definitely a good start to understanding the company’s culture. However, simply looking at these tangible aspects is unlikely to give a full picture of the organization, since an important chunk of what makes up culture exists below one’s degree of awareness. The values and, deeper, the assumptions that shape the organization’s culture can be uncovered by observing how employees interact and the choices they make, as well as by inquiring about their beliefs and perceptions regarding what is right and appropriate behavior.
Key Takeaway
Organizational culture is a system of shared assumptions, values, and beliefs that helps individuals understand which behaviors are and are not appropriate within an organization. Cultures can be a source of competitive advantage for organizations. Strong organizational cultures can be an organizing as well as a controlling mechanism for organizations. And finally, organizational culture consists of three levels: assumptions that are below the surface, values, and artifacts.
Exercises
- Why do companies need culture?
- Give an example of a company culture being a strength and a weakness.
- In what ways does culture serve as a controlling mechanism?
- If assumptions are below the surface, why do they matter?
- Share examples of artifacts you have noticed at different organizations.
1 Why culture can mean life or death for your organization. (September, 2007). HR Focus , 84 , 9.
References
Arogyaswamy, B., & Byles, C. H. (1987). Organizational culture: Internal and external fits. Journal of Management, 13 , 647–658.
Barney, J. B. (1986). Organizational culture: Can it be a source of sustained competitive advantage? Academy of Management Review, 11 , 656–665.
Chatman, J. A., & Eunyoung Cha, S. (2003). Leading by leveraging culture. California Management Review, 45 , 19–34.
Kotter, J. P., & Heskett, J. L. (1992). Corporate Culture and Performance . New York: Free Press.
Marcoulides, G. A., & Heck, R. H. (1993, May). Organizational culture and performance: Proposing and testing a model. Organizational Science, 4 , 209–225.
Schein, E. H. (1992). Organizational culture and leadership . San Francisco: Jossey-Bass.
Slocum, J. W. (2005). Managing corporate culture through reward systems. Academy of Management Executive, 19 , 130–138.


7.2: The Stages of the Listening Process
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Listening is a process and as such it doesn’t unfold in a linear, step-by-step fashion with a defined start and finish. Listening in action is a fast, complex process, with many overlapping components. However, in order to aid in your understanding of listening, we will break the process into five stages and cover each stage in this section: receiving, interpreting, recalling, evaluating, and responding.
Before we can engage other steps in the listening process, we must take in stimuli through our senses. In any given communication encounter, it is likely that we will return to the receiving stage many times as we process incoming feedback and new messages. We primarily take in information needed for listening through auditory and visual channels. Although we don’t often think about visual cues as a part of listening, they influence how we interpret messages. For example, seeing a person’s face when we hear their voice allows us to take in nonverbal cues such as facial expressions and eye contact.
Chapter 3, The Perception Process and Perception of Others, discussed some of the ways in which incoming stimuli are filtered. These perceptual filters also play a role in listening. Some stimuli never make it in, some are filtered into subconsciousness, and others are filtered into various levels of consciousness based on their salience. Salience is the degree to which something attracts our attention in a particular context. We tend to find salient those things that are visually or audibly stimulating and those that meet our needs or interests. Think about how it’s much easier to listen to a lecture on a subject that you find very interesting.
It is important to consider noise as a factor that influences how we receive messages. Some noise interferes primarily with hearing, which is the physical process of receiving stimuli through internal and external components of the ears and eyes, and some interferes with listening, which is the cognitive process of processing the stimuli taken in during hearing. While hearing leads to listening, they are not the same thing. Noise resulting from the physical context, such as other people talking, the sounds of traffic, and music interfere with the physiological aspects of hearing. Noise resulting from the individual context like stress and anger interfere primarily with the cognitive processes of listening.
During the interpreting stage of listening, we combine the visual and auditory information we receive and try to make meaning out of that information using schemata. The interpreting stage engages cognitive and relational processing as we take in informational, contextual, and relational cues and try to connect them in meaningful ways to previous experiences. It is through the interpreting stage that we may begin to understand the stimuli we have received. When we understand something, we are able to attach meaning by connecting information to previous experiences. If we have difficulty interpreting information, meaning we don’t have previous experience or information in our existing schemata to make sense of it, then it is difficult to transfer the information into our long-term memory for later recall. In situations where understanding the information we receive isn’t important or isn’t a goal, this stage may be fairly short or even skipped. After all, we can move something to our long-term memory by repetition and then later recall it without ever having understood it.
Our ability to recall information is dependent on some of the physiological limits of how memory works. Overall, our memories are known to be fallible. We forget about half of what we hear immediately after hearing it, recall 35 percent after eight hours, and recall 20 percent after a day (Hargie, 2011). Our memory consists of multiple “storage units,” including sensory storage, short-term memory, working memory, and long-term memory (Hargie, 2011).
Our sensory storage is very large in terms of capacity but limited in terms of length of storage. We can hold large amounts of unsorted visual information but only for about a tenth of a second. By comparison, we can hold large amounts of unsorted auditory information for longer—up to four seconds.
As stimuli are organized and interpreted, they make their way to short-term memory where they either expire and are forgotten or are transferred to long-term memory. Short-term memory is a mental storage capability that can retain stimuli for twenty seconds to one minute. Long-term memory is a mental storage capability to which stimuli in short-term memory can be transferred if they are connected to existing schema and in which information can be stored indefinitely (Hargie, 2011). Working memory is a temporarily accessed memory storage space that is activated during times of high cognitive demand. When using working memory, we can temporarily store information and process and use it at the same time.
When we evaluate something, we make judgments about its credibility, completeness, and worth. In terms of credibility, we try to determine the degree to which we believe a speaker’s statements are correct and/or true. In terms of completeness, we try to “read between the lines” and evaluate the message in relation to what we know about the topic or situation being discussed. We evaluate the worth of a message by making a value judgment about whether we think the message or idea is good/bad, right/wrong, or desirable/undesirable. All these aspects of evaluating require critical thinking skills, which we aren’t born with but must develop over time through our own personal and intellectual development. One danger within the evaluation stage of listening is to focus your evaluative lenses more on the communicator than the message. This can quickly become a barrier to effective listening if we begin to prejudge a communicator based on their identity or characteristics rather than on the content of their message.
Responding entails sending verbal and nonverbal messages that indicate attentiveness and understanding or a lack thereof. From our earlier discussion of the communication model, you may be able to connect this part of the listening process to feedback. Back-channel cues are the verbal and nonverbal signals we send while someone is talking and can consist of verbal cues like “uh-huh,” “oh,” and “right,” and/or nonverbal cues like direct eye contact, head nods, and leaning forward. Backchannel cues are generally a form of positive feedback that indicates others are actively listening. People also send cues intentionally and unintentionally that indicate they aren’t listening. If another person is looking away, fidgeting, texting, or turned away, we will likely interpret those responses negatively. Paraphrasing, which we will discuss in the Communication Competence section of this chapter, is a responding behavior that can also show that you understand what was communicated.


1.2.9: General Strategy for Factoring Polynomials
By the end of this section, you will be able to:
- Recognize and use the appropriate method to factor a polynomial completely
Before you get started, take this readiness quiz.
1. Find the GCF of \(2x^4-14x^3-4x^2\).
2. Find the product \((3y+4)(3y-4)\).
3. Find the coefficient of \(x\) in \((2x-7)(3x+3)\).
Recognizing and Using the Appropriate Method to Factor a Polynomial Completely
You have now become acquainted with all the methods of factoring that you will need in this course. The following chart summarizes all the factoring methods we have covered, and outlines a strategy you should use when factoring polynomials.
General Strategy for Factoring Polynomials
This chart shows the general strategies for factoring polynomials. It shows ways to find GCF of binomials, trinomials and polynomials with more than 3 terms. For binomials, we have difference of squares: a squared minus \(b\) squared equals a minus \(b\), \(a\) plus \(b\); sum of squares do not factor; sub of cubes: \(a\) cubed plus \(b\) cubed equals open parentheses \(a\) plus \(b\) close parentheses open parentheses a squared minus \(ab\) plus \(b\) squared close parentheses; difference of cubes: \(a\) cubed minus \(b\) cubed equals open parentheses \(a\) minus \(b\) close parentheses open parentheses a squared plus \(ab\) plus \(b\) squared close parentheses. For trinomials, we have \(x\) squared plus \(bx\) plus \(c\) where we put \(x\) as a term in each factor and we have a squared plus \(bx\) plus \(c\).  If \(a\) and \(c\) are not squares, we use the "ac" method. For polynomials with more than 3 terms, we use grouping.
General Strategy for Factoring Polynomials
-
What is the greatest common factor?
Factor it out if it is not \(1\). -
Is the polynomial a binomial, trinomial, or are there more than three terms?
If it is a binomial:-
Is it a sum?
Of squares? Sums of squares do not factor.
Of cubes? Use the sum of cubes pattern. -
Is it a difference?
Of squares? Factor as the product of conjugates.
Of cubes? Use the difference of cubes pattern.
- Is it of the form \(x^2+bx+c\)? Undo FOIL.
-
Is it of the form \(ax^2+bx+c\)?
If a and c are squares, check if it fits the trinomial square pattern.
Use the trial and error or “\(ac\)” method.
- Use the grouping method.
-
Is it a sum?
-
Check.
Is it factored completely?
Do the factors multiply back to the original polynomial?
Remember, a polynomial is completely factored if, other than monomials, its factors are prime !
Factor \(7x^3−21x^2−70x\).
Solution
| \(\quad 7x^3−21x^2−70x\) | |
|
What is the GCF? \(7x\). Factor out the GCF. |
\(=7x(x^2−3x−10)\) |
|
In the parentheses, is it a binomial, trinomial, or are there more terms Trinomial with leading coefficient 1. |
\(=7x(x+2)(x−5)\) |
| Is the expression factored completely? Yes, neither binomial can be factored. | |
| Check your answer. |
Multiply. \(\begin{align*} &7x(x+2)(x−5) \\ = & 7x(x^2−5x+2x−10)\\ = & 7x^3−21x^2−70x \quad\checkmark\end{align*}\) |
| Conclude. | The factorization of \(7x^3-21x^2-70x\) is \(7x(x+2)(x-5)\). |
Try It \(\PageIndex{2}\)
Factor \(8y^3+16y^2−24y\).
- Answer
-
\(8y(y−1)(y+3)\)
Try It \(\PageIndex{3}\)
Factor \(5y^3−15y^2−270y\).
- Answer
-
\(5y(y−9)(y+6)\)
Be careful when you are asked to factor a binomial as there are several options!
Factor \(24y^2−150\).
Solution
| \(\quad 24y^2−150\) | |
|
What is the GCF? \(6\). Factor out the GCF. |
\(=6(4y^2−25)\) |
|
In the parentheses, is it a binomial, trinomial or are there more than three terms? Binomial. Is it a difference? Of squares or cubes? Yes, squares. |
\(=6((2y)^2−(5)^2)\) |
| Write as a product of conjugates. | \(=6(2y−5)(2y+5)\) |
| Is the expression factored completely? Yes, neither binomial can be factored. | |
| Check your answer. |
Multiply. \(\begin{align*} & 6(2y−5)(2y+5) \\ =& 6(4y^2−25) \\ =&24y^2−150\quad \checkmark\end{align*}\) |
| Conclude. | The factorization of \(24y^2−150\) is \(6(2y−5)(2y+5)\). |
Try It \(\PageIndex{5}\)
Factor \(16x^3−36x\).
- Answer
-
\(4x(2x−3)(2x+3)\)
Try It \(\PageIndex{6}\)
Factor \(27y^2−48\).
- Answer
-
\(3(3y−4)(3y+4)\)
The next example can be factored using several methods. Recognizing the trinomial squares pattern will make your work easier.
Factor \(4a^2−12ab+9b^2\).
Solution
| \(\quad 4a^2−12ab+9b^2\) | |
|
What is the GCF? \(1\). Is it a binomial, trinomial, or are there more terms?Trinomial with \(a\neq 1\) The first term is a perfect square. Is the last term a perfect square? Yes. |
\(=(2a)^2−12ab+(3b)^2\) |
| Does it fit the pattern \(a^2−2ab+b^2\)? Yes | \(=(2a)^2 −2(2a)(3b)+ (3b)^2\) |
| Write it as a square. | \(=(2a−3b)^2\) |
| Is the expression factored completely? Yes. The binomial cannot be factored. | |
| Check your answer. |
Multiply. \begin{align*} & (2a−3b)^2 \\ = & (2a)^2−2(2a)(3b)+(3b)^2 \\=&4a^2−12ab+9b^2\quad \checkmark \end{align*} |
| Conclude. | The factorization of \(4a^2−12ab+9b^2\) is \((2a−3b)^2\). |
Try It \(\PageIndex{8}\)
Factor \(4x^2+20xy+25y^2\).
- Answer
-
\((2x+5y)^2\)
Try It \(\PageIndex{9}\)
Factor \(9x^2−24xy+16y^2\).
- Answer
-
\((3x−4y)^2\)
Remember, sums of squares do not factor, but sums of cubes do!
Factor \(12x^3y^2+75xy^2\).
Solution
| \(\quad 12x^3y^2+75xy^2\) | |
|
What is the GCF? \(3xy^2\). Factor out the GCF. |
\(=3xy^2(4x^2+25)\) |
|
In the parentheses, is it a binomial, trinomial, or are there more than three terms? Binomial. Is it a sum? Of squares? Yes. Sums of squares are prime. Is the expression factored completely? Yes. |
|
| Check. |
Multiply. \(\quad 3xy^2(4x^2+25) \) \(=12x^3y^2+75xy^2\quad \checkmark\) |
| Conclude. | The factorization of \(12x^3y^2+75xy^2\) is \(3xy^2(4x^2+25)\). |
Try It \(\PageIndex{11}\)
Factor \(50x^3y+72xy\).
- Answer
-
\(2xy(25x^2+36)\)
Try It \(\PageIndex{12}\)
Factor \(27xy^3+48xy\).
- Answer
-
\(3xy(9y^2+16)\)
When using the sum or difference of cubes pattern, being careful with the signs.
Factor \(24x^3+81y^3\).
Solution
| \(\quad 24x^3+81y^3\) | |
|
What is the GCF? \(3\). Factor it out. |
\(=3(8x^3+27y^3)\) |
|
In the parentheses, is it a binomial, trinomial,
Of squares or cubes? Sum of cubes. |
\(=3((2x)^3+(3y)^3) |
|
Write it using the sum of cubes pattern. \(a^3+b^3 = (a+b)(a^2-ab+b^2)\) |
\(=3(2x+3y)((2x)^2-2x\cdot 3y +(3y)^2)\) |
| Is the expression factored completely? Yes. |
\(=3(2x+3y)(4x^2-6xy+9y^2)\) |
| Check by multiplying. | |
| Conclude. | The factorization of \(24x^3+81y^3\) is \(3(2x+3y)(4x^2-6xy+9y^2\). |
Try It \(\PageIndex{14}\)
Factor \(250m^3+432n^3\).
- Answer
-
\(2(5m+6n)(25m^2−30mn+36n^2)\)
Try It \(\PageIndex{15}\)
Factor \(2p^3+54q^3\).
- Answer
-
\(2(p+3q)(p^2−3pq+9q^2)\)
Example \(\PageIndex{16}\)
Factor \(3x^5y−48xy\).
- Solution
-
\(\begin{array} {ll} &3x^5y−48xy \\ \text{Is there a GCF? Factor out }3xy &3xy(x^4−16) \\ \begin{array} {l} \text{Is the binomial a sum or difference? Of squares or cubes?} \\ \text{Write it as a difference of squares.} \end{array} &3xy\left((x^2)^2−(4)2\right) \\ \text{Factor it as a product of conjugates} &3xy(x^2−4)(x^2+4) \\ \text{The first binomial is again a difference of squares.} &3xy\left((x)^2−(2)^2\right)(x^2+4) \\ \text{Factor it as a product of conjugates.} &3xy(x−2)(x+2)(x^2+4) \\ \text{Is the expression factored completely? Yes.} & \\ \text{Check your answer.} & \\ \text{Multiply.} & \\ 3xy(x−2)(x+2)(x^2+4) & \\ 3xy(x^2−4)(x^2+4) & \\ 3xy(x^4−16) & \\ 3x^5y−48xy\checkmark & \end{array}\)
Try It \(\PageIndex{17}\)
Factor \(4a^5b−64ab\).
- Answer
-
\(4ab(a^2+4)(a−2)(a+2)\)
Try It \(\PageIndex{18}\)
Factor \(7xy^5−7xy\).
- Answer
-
\(7xy(y^2+1)(y−1)(y+1)\)
Example \(\PageIndex{19}\)
Factor \(4x^2+8bx−4ax−8ab\).
- Solution
-
\(\begin{array} {ll} &4x^2+8bx−4ax−8ab \\ \text{Is there a GCF? Factor out the GCF, }4. &4(x^2+2bx−ax−2ab) \\ \text{There are four terms. Use grouping.} &4[x(x+2b)−a(x+2b)]4(x+2b)(x−a) \\ \text{Is the expression factored completely? Yes.} & \\ \text{Check your answer.} & \\ \text{Multiply.} & \\ \hspace{25mm}4(x+2b)(x−a) & \\ \hspace{20mm} 4(x^2−ax+2bx−2ab) & \\ \hspace{20mm}4x^2+8bx−4ax−8ab\checkmark \end{array}\)
Try It \(\PageIndex{20}\)
Factor \(6x^2−12xc+6bx−12bc\).
- Answer
-
\(6(x+b)(x−2c)\)
Try It \(\PageIndex{21}\)
Factor \(16x^2+24xy−4x−6y\).
- Answer
-
\(2(4x−1)(2x+3y)\)
Taking out the complete GCF in the first step will always make your work easier.
Factor \(40x^2y+44xy−24y\).
Solution
\(\begin{array} {ll} &40x^2y+44xy−24y \\ \text{Is there a GCF? Factor out the GCF, }4y. &4y(10x^2+11x−6) \\ \text{Factor the trinomial with }a\neq 1. &4y(10x^2+11x−6) \\ &4y(5x−2)(2x+3) \\ \text{Is the expression factored completely? Yes.} & \\ \text{Check your answer.} & \\ \text{Multiply.} & \\ \hspace{25mm}4y(5x−2)(2x+3) & \\ \hspace{24mm}4y(10x^2+11x−6) & \\ \hspace{22mm}40x^2y+44xy−24y\checkmark \end{array}\)
Try It \(\PageIndex{23}\)
Factor \(4p^2q−16pq+12q\).
- Answer
-
\(4q(p−3)(p−1)\)
Try It \(\PageIndex{24}\)
Factor \(6pq^2−9pq−6p\).
- Answer
-
\(3p(2q+1)(q−2)\)
When we have factored a polynomial with four terms, most often we separated it into two groups of two terms. Remember that we can also separate it into a trinomial and then one term.
Factor \(9x^2−12xy+4y^2−49\).
Solution
| \(\quad 9x^2−12xy+4y^2−49\) | |
|
What is the GCF? \(1\). With more than 3 terms, use grouping. Last 2 terms have GCF equals to 1. Try grouping first 3 terms. Factor the trinomial with \(a\neq 1\). The first term is a perfect square. Is the last term of the trinomial a perfect square? Yes. |
\(=(3x)^2−12xy+(2y)^2−49\) |
| Does the trinomial fit the pattern \(a^2−2ab+b^2\)? Yes. | \(=(3x)^2 −2(3x)(2y)+ (2y)^2−49\) |
| Write the trinomial as a square. | \(=(3x−2y)^2−49\) |
|
Is this binomial a sum or difference of squares or cubes? Yes, a difference of squares. Write it as a difference of squares. |
\(= (3x−2y)^2−7^2\) |
| Write it as a product of conjugates. |
\(=((3x−2y)−7)((3x−2y)+7)\) \(=(3x−2y−7)(3x−2y+7)\) |
|
Is the expression factored completely? Yes. Check your answer. |
Multiply. \(\quad (3x−2y−7)(3x−2y+7)\) \(=9x^2−6xy−21x−6xy+4y^2+14y+21x−14y−49\) \(=9x^2−12xy+4y^2−49\quad \checkmark\) |
| Conclude. | The factorization of \(9x^2−12xy+4y^2−49\) is \((3x−2y−7)(3x−2y+7)\). |
Try It \(\PageIndex{26}\)
Factor \(4x^2−12xy+9y^2−25\).
- Answer
-
\((2x−3y−5)(2x−3y+5)\)
Try It \(\PageIndex{27}\)
Factor \(16x^2−24xy+9y^2−64\).
- Answer
-
\((4x−3y−8)(4x−3y+8)\)
- How do you check that you have factored correctly? Give an example.
- How many binomial factors could a polynomial of degree 5 have? Explain and give an example of the maximum number.
- Why might it be useful to factor?
- Use factoring to carry out the division: \(\dfrac{5x^3-5x^2+30x}{x^2+2x}\)
- If you know that \(2x-5\) is a factor of \(4x^2-4x-15\) help you to factor the latter? Explain.
Key Concepts
-
How to use a general strategy for factoring polynomials.
-
Is there a greatest common factor?
Factor it out. -
Is the polynomial a binomial, trinomial, or are there more than three terms?
If it is a binomial:
Is it a sum?
Of squares? Sums of squares do not factor.
Of cubes? Use the sum of cubes pattern.
Is it a difference?
Of squares? Factor as the product of conjugates.
Of cubes? Use the difference of cubes pattern.
If it is a trinomial:
Is it of the form \(x^2+bx+c\)? Undo FOIL.
Is it of the form \(ax^2+bx+c\)?
If \( a \) and \(c\) are squares, check if it fits the trinomial square pattern.
Use the trial and error or “\(ac\)” method.
If it has more than three terms:
Use the grouping method. -
Check.
Is it factored completely?
Do the factors multiply back to the original polynomial?
-
Is there a greatest common factor?


2.3: Atoms, Isotopes, Ions, and Molecules - Isotopes
- Discuss the properties of isotopes and their use in radiometric dating
What is an Isotope?
Isotopes are various forms of an element that have the same number of protons but a different number of neutrons. Some elements, such as carbon, potassium, and uranium, have multiple naturally-occurring isotopes. Isotopes are defined first by their element and then by the sum of the protons and neutrons present.
- Carbon-12 (or 12 C) contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 amu (six protons and six neutrons).
- Carbon-14 (or 14 C) contains six protons, eight neutrons, and six electrons; its atomic mass is 14 amu (six protons and eight neutrons).
While the mass of individual isotopes is different, their physical and chemical properties remain mostly unchanged.
Isotopes do differ in their stability. Carbon-12 ( 12 C) is the most abundant of the carbon isotopes, accounting for 98.89% of carbon on Earth. Carbon-14 ( 14 C) is unstable and only occurs in trace amounts. Unstable isotopes most commonly emit alpha particles (He 2+ ) and electrons. Neutrons, protons, and positrons can also be emitted and electrons can be captured to attain a more stable atomic configuration (lower level of potential energy ) through a process called radioactive decay. The new atoms created may be in a high energy state and emit gamma rays which lowers the energy but alone does not change the atom into another isotope. These atoms are called radioactive isotopes or radioisotopes.
Radiocarbon Dating
Carbon is normally present in the atmosphere in the form of gaseous compounds like carbon dioxide and methane. Carbon-14 ( 14 C) is a naturally-occurring radioisotope that is created from atmospheric 14 N (nitrogen) by the addition of a neutron and the loss of a proton, which is caused by cosmic rays. This is a continuous process so more 14 C is always being created in the atmosphere. Once produced, the 14 C often combines with the oxygen in the atmosphere to form carbon dioxide. Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the ocean, and is incorporated by plants via photosynthesis. Animals eat the plants and, ultimately, the radiocarbon is distributed throughout the biosphere.
In living organisms, the relative amount of 14 C in their body is approximately equal to the concentration of 14 C in the atmosphere. When an organism dies, it is no longer ingesting 14 C, so the ratio between 14 C and 12 C will decline as 14 C gradually decays back to 14 N. This slow process, which is called beta decay, releases energy through the emission of electrons from the nucleus or positrons.
After approximately 5,730 years, half of the starting concentration of 14 C will have been converted back to 14 N. This is referred to as its half-life, or the time it takes for half of the original concentration of an isotope to decay back to its more stable form. Because the half-life of 14 C is long, it is used to date formerly-living objects such as old bones or wood. Comparing the ratio of the 14 C concentration found in an object to the amount of 14 C in the atmosphere, the amount of the isotope that has not yet decayed can be determined. On the basis of this amount, the age of the material can be accurately calculated, as long as the material is believed to be less than 50,000 years old. This technique is called radiocarbon dating, or carbon dating for short.
Other elements have isotopes with different half lives. For example, 40 K (potassium-40) has a half-life of 1.25 billion years, and 235 U (uranium-235) has a half-life of about 700 million years. Scientists often use these other radioactive elements to date objects that are older than 50,000 years (the limit of carbon dating). Through the use of radiometric dating, scientists can study the age of fossils or other remains of extinct organisms.
Key Points
- Isotopes are atoms of the same element that contain an identical number of protons, but a different number of neutrons.
- Despite having different numbers of neutrons, isotopes of the same element have very similar physical properties.
- Some isotopes are unstable and will undergo radioactive decay to become other elements.
- The predictable half-life of different decaying isotopes allows scientists to date material based on its isotopic composition, such as with Carbon-14 dating.
Key Terms
- isotope : Any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei.
- half-life : The time it takes for half of the original concentration of an isotope to decay back to its more stable form.
- radioactive isotopes : an atom with an unstable nucleus, characterized by excess energy available that undergoes radioactive decay and creates most commonly gamma rays, alpha or beta particles.
- radiocarbon dating : Determining the age of an object by comparing the ratio of the 14C concentration found in it to the amount of 14C in the atmosphere.


14.1: Data Preparation
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In research projects, data may be collected from a variety of sources: postal surveys, interviews, pretest or posttest experimental data, observational data, and so forth. This data must be converted into a machine-readable, numeric format, such as in a spreadsheet or a text file, so that they can be analysed by computer programs like SPSS or SAS. Data preparation usually follows the following steps:
Data coding. Coding is the process of converting data into numeric format. A codebook should be created to guide the coding process. A codebook is a comprehensive document containing a detailed description of each variable in a research study, items or measures for that variable, the format of each item (numeric, text, etc.), the response scale for each item (i.e., whether it is measured on a nominal, ordinal, interval, or ratio scale, and whether this scale is a five-point, seven-point scale, etc.), and how to code each value into a numeric format. For instance, if we have a measurement item on a seven-point Likert scale with anchors ranging from ‘strongly disagree’ to ‘strongly agree’, we may code that item as 1 for strongly disagree, 4 for neutral, and 7 for strongly agree, with the intermediate anchors in between. Nominal data such as industry type can be coded in numeric form using a coding scheme such as: 1 for manufacturing, 2 for retailing, 3 for financial, 4 for healthcare, and so forth (of course, nominal data cannot be analysed statistically). Ratio scale data such as age, income, or test scores can be coded as entered by the respondent. Sometimes, data may need to be aggregated into a different form than the format used for data collection. For instance, if a survey measuring a construct such as ‘benefits of computers’ provided respondents with a checklist of benefits that they could select from, and respondents were encouraged to choose as many of those benefits as they wanted, then the total number of checked items could be used as an aggregate measure of benefits. Note that many other forms of data—such as interview transcripts—cannot be converted into a numeric format for statistical analysis. Codebooks are especially important for large complex studies involving many variables and measurement items, where the coding process is conducted by different people, to help the coding team code data in a consistent manner, and also to help others understand and interpret the coded data.
Data entry. Coded data can be entered into a spreadsheet, database, text file, or directly into a statistical program like SPSS. Most statistical programs provide a data editor for entering data. However, these programs store data in their own native format—e.g., SPSS stores data as .sav files—which makes it difficult to share that data with other statistical programs. Hence, it is often better to enter data into a spreadsheet or database where it can be reorganised as needed, shared across programs, and subsets of data can be extracted for analysis. Smaller data sets with less than 65,000 observations and 256 items can be stored in a spreadsheet created using a program such as Microsoft Excel, while larger datasets with millions of observations will require a database. Each observation can be entered as one row in the spreadsheet, and each measurement item can be represented as one column. Data should be checked for accuracy during and after entry via occasional spot checks on a set of items or observations. Furthermore, while entering data, the coder should watch out for obvious evidence of bad data, such as the respondent selecting the ‘strongly agree’ response to all items irrespective of content, including reverse-coded items. If so, such data can be entered but should be excluded from subsequent analysis.
Missing values. Missing data is an inevitable part of any empirical dataset. Respondents may not answer certain questions if they are ambiguously worded or too sensitive. Such problems should be detected during pretests and corrected before the main data collection process begins. During data entry, some statistical programs automatically treat blank entries as missing values, while others require a specific numeric value such as or to be entered to denote a missing value. During data analysis, the default mode for handling missing values in most software programs is to simply drop any observation containing even a single missing value, in a technique called listwise deletion . Such deletion can significantly shrink the sample size and make it extremely difficult to detect small effects. Hence, some software programs provide the option of replacing missing values with an estimated value via a process called imputation . For instance, if the missing value is one item in a multi-item scale, the imputed value may be the average of the respondent’s responses to remaining items on that scale. If the missing value belongs to a single-item scale, many researchers use the average of other respondents’ responses to that item as the imputed value. Such imputation may be biased if the missing value is of a systematic nature rather than a random nature. Two methods that can produce relatively unbiased estimates for imputation are the maximum likelihood procedures and multiple imputation methods, both of which are supported in popular software programs such as SPSS and SAS.
Data transformation. Sometimes, it is necessary to transform data values before they can be meaningfully interpreted. For instance, reverse coded items—where items convey the opposite meaning of that of their underlying construct—should be reversed (e.g., in a 1-7 interval scale, 8 minus the observed value will reverse the value) before they can be compared or combined with items that are not reverse coded. Other kinds of transformations may include creating scale measures by adding individual scale items, creating a weighted index from a set of observed measures, and collapsing multiple values into fewer categories (e.g., collapsing incomes into income ranges).


6.3: Activity 8- Accessible Slider
Accessible Slider
Based on the Slider details on the previous page, apply what you have learned to the associated activity files to make the slider there accessible.
Files for this activity include:
Use the code surrounding the highlighted solutions on the previous page as a guide to find where the fixes should be applied. Repair the accessibility of the slider by applying the highlighted code to the /assets/ik_slider.js file.
Note: While we suggest using the highlighted solutions we’ve provided, you are free to come up with your own solutions as long as they produce the expected results listed in the marking rubric below.
Test your updated slider with ChromeVox to ensure each element described in the marking rubric below is functioning as suggested.
Requirements
When you have applied your changes and tested to be sure your slider functions as described, submit the URL to your slider.html file on your GitHub Pages site, to the file on the web server you are using to host your copy of the activity files, or to a GitHack URL.
Grading Rubric
| Criteria | Points |
|---|---|
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Slider Focusable:
Slider thumb is keyboard focusable. |
2.0 pts |
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Keyboard Operable:
Slider thumb moves using Left and Right Arrow keys, and the Home and End keys. |
5.0 pts |
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Min/Max Values Announced:
Minimum and maximum values are announced. |
1.0 pts |
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Value Announced:
When the slider moves, its new value is announced. |
2.0 pts |
| Total Points: | 10.0 |


6.3: Solving Absolute Value Inequalities and Writing Answers in Interval Notation
The previous section taught how to solve absolute value equations. This section teaches how to solve absolute value inequalities. To do so, first consider the following two properties:
Property 1: For all positive number \(b\), and all real numbers \(p\) and \(q\),
- \(|a| < b\) if and only if \(−b < a < b\).
The solution set is of the form \((p,q)\), a single open interval.
- \(|a| ≤ b\) if and only if \(−b ≤ a ≤ b\).
The solution set is of the form \([p,q]\), a single closed interval.
Before considering Property 2, it is important to define the union of two intervals. The union of any two intervals \(A\) and \(B\), is the set of elements in \(A\), or \(B\), or both. The union is represented with the symbol \(∪\).
Property 2: For all positive number \(b\), and all real numbers \(p\) and \(q\),
- \(|a| > b\) if and only if \(a < −b\) or \(a > −b\)
The solution set is of the form \((−∞, p) ∪ (q, ∞)\), a disjoint interval.
- \(|a| ≥ b\) if and only if \(a ≤ −b\) or \(a ≥ b\).
The solution set is of the form \((−∞, p] ∪ [q, ∞)\), a disjoint interval.
Note that before the properties of inequalities are applied, isolate the absolute value expression on either side of the inequality.
Solve the following inequalities and graph the solution set.
- \(|5x − 2| < 7\)
- \(|8x − 6| < −1\)
- \(2|x − 3| + 5 ≤ 9\)
Solution
- This is an absolute value expression less than a positive number of the form \(|a| < b\). Apply Property 1(i) with \(a = 5x − 2\) and \(b = 7\).
\(\begin{array} &&|5x − 2| < 7 &\text{Given} \\ &−7 < 5x − 2 < 7 &\text{Property 1 (i)} \end{array}\)
To solve the inequality, isolate \(x\). The previous step becomes,
\(\begin{array} &&−5 < 5x < 9 &\text{Add \(2\) to all sides} \\ &−1 < x < \dfrac{9}{5} &\text{Divide all sides by \(5\)} \end{array}\)
The Solution set is the single open interval \(\left(−1, \dfrac{9}{5} \right)\) and the graph is as shown in the figure below.
- Recall that the absolute value of any number is the distance from \(0\) to that number on the number line. This means, the absolute value of any number is always greater or equal to \(0\).
This example gives \(|8x − 6| < −1,\) which can not happen since a distance is never negative. So, the absolute value inequality has no solution and the solution set is the empty set, written \(\phi\).
- To solve \(2|x − 3| + 5 ≤ 9\), isolate the absolute value.
\(\begin{array} &&2|x − 3| + 5 ≤ 9 &\text{Given} \\ &2|x − 3| ≤ 4 &\text{Subtract \(5\) from both sides} \\ &|x − 3| ≤ 2 &\text{Divide both side by \(2\)} \end{array}\)
Now, \(|x − 3| ≤ 2\) is of the form \(|a| ≤ b\). Apply Property 1 (ii) with \(a = x − 3\) and \(b = 2\).
\(\begin{array} &&|x − 3| ≤ 2 & \\&− 2 ≤ x − 3 ≤ 2 &\text{Property 1(ii)} \\ &1 ≤ x ≤ 5 & \end{array}\)
The solution set is the single interval \([1, 5]\) and the graph is as shown in the figure below.
Solve and graph the solution set.
- \(\left| \dfrac{6 − x}{10} \right| ≥ 3\)
- \(2 < \left|\dfrac{3}{4} x − 3 \right| − 5\)
- \(|2 − 4x| ≥ −7\)
Solution
- The absolute value inequality \(\left| \dfrac{6 − x}{10} \right| ≥ 3\) is in the form of \(|a| ≥ b\). Apply Property 2 (ii) with \(a = \dfrac{6 − x}{10}\) and \(b = 3\) to solve the inequality.
\(\begin{array} & & &\left| \dfrac{6 − x}{10} \right| ≥ 3 &&\text{Given} \\ &\dfrac{6 − x}{10} ≤ −3 &\text{ or } &\dfrac{6 − x}{10} ≥ 3 &\text{Property 2 (ii)} \\ &6 − x ≤ −30 &\text{ or } &6 − x ≥ 30 &\text{Multiply by \(10\) both sides} \\ &−x ≤ −36 &\text{ or } &−x ≥ 24 &\text{Subtract \(6\) from both sides} \\ &x ≥ 36 &\text{ or } &x ≤ −24 &\text{Multiply by \(−1\)} \end{array}\)
Note that since the inequalities were multiplied by a negative number, namely \(−1\), the direction of the inequality changed.
The solution set is the union of the two intervals. Thus, \((−∞, −24] ∪ [36, ∞)\) is the solution set in interval notation. The graph of the solution is as shown in the figure below.
- Isolate the absolute value.
\(\begin{array} &&2 < \left|\dfrac{3}{4} x − 3 \right| − 5 &\text{Given} \\ &7 < \left| \dfrac{3}{4} x − 3 \right| &\text{Add \(5\) to both sides} \end{array}\)
Note that the above inequality is read from right to left as "the absolute value of the expression \(\dfrac{3}{4} x − 3\) is greater than \(7\)" or equivalently switch the order of the absolute value inequality to have \(\dfrac{3}{4} x − 3 > 7\), which is a more familiar form to solve.
Now, \(\dfrac{3}{4} x − 3 > 7\) is of the form \(|a| > b\). Use Property 2 (ii) with \(a = \dfrac{3x}{4} − 3\) and \(b = 7\).
\(\begin{array} && &\dfrac{3}{4} x − 3 > 7 &&\text{Given} \\ &\dfrac{3}{4} x − 3 < −7 &\text{ or } &\dfrac{3}{4}x − 3 > 7 &\text{Property 2 (ii)}\\ &\dfrac{3}{4} x < −4 &\text{ or } &\dfrac{3}{4} x > 10 &\text{Add \(3\) to all sides} \\ &x < −\dfrac{16}{3} &\text{ or } &x > \dfrac{40}{3} &\text{Multiply both sides by \(\dfrac{4}{3}\).} \end{array}\)
The solution set is the union of the two intervals, \((− ∞, −\dfrac{16}{3}] ∪ [\dfrac{40}{3}, ∞)\). The graph of the solution is as shown in the figure below
- Since \(|2 − 4x|\) is always greater than or equal to \(0\) for any real numbers \(x\) then, the absolute value inequality is true for all real numbers. Let \(x\) be any real number, negative or positive, then the absolute value will either be \(0\) or a positive number.
So, the solution set is all the real numbers on the number line, as shown in the figure below. The solution set in interval notation is \((−∞, ∞)\).
Solve the following inequalities, write answers in interval notation, and graph the solution sets:
- \(|−6x + 1| < 20\)
- \(\left| \dfrac{2}{3} x + 5 \right| > 5\)
- \(\left| 5 − \dfrac{1}{4} x \right| < −71\)
- \(2 \left| − x + \dfrac{4}{5} \right| ≤ \dfrac{5}{2}\)
- \(−\dfrac{1}{7} < |x + 10| − 10\)
- \(|−12 − 3x| < −0.6\)
- \(\left|\dfrac{16 − 2x}{8} \right| ≥ 11\)
- \(|2 − 6x| − 5 ≥ −9\)
- \(\left| \dfrac{2}{3} x − \dfrac{1}{4} \right| ≤ \dfrac{1}{12}\)
- \(|.02x + 5| < .02\)
- \(\left| \dfrac{1}{2} − x \right| < 8\)
- \(| − 6x + 9| − 5 < −6\)


2.2: Social Health
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The capacity for an individual to develop and flourish is deeply influenced by immediate social surroundings – including their opportunity to engage positively with family members, friends or colleagues, and earn a living for themselves and their families – and also by the socioeconomic circumstances in which said individual find himself/herself. Restricted or lost opportunities to gain an education and income are especially pertinent socio-economic factors.
Psychoneuroimmunology is defined as the examination of the interactions among psychological, behavioral, and social factors with immunological and neuroendocrine outcomes. It is now well established that psychological factors, especially chronic stress, can lead to impairments in immune system function in both the young and older adults. In several studies of older adults, those who are providing care for a relative with dementia report high levels of stress and exhibit significant impairments in immune system functioning when compared with non-caregivers. Stress-induced changes in the immune system may affect a number of outcomes, including slowing the wound healing process and increasing susceptibility to infections.


3.1.6: Virginia Woolf (1882-1941)
A Room of One's Own British Modernism Virginia Woolf was born into the affluent and intellectual family of Sir Leslie and Julia Stephen. She was one of eight children; both of her parents had been widowed. Julia Stephen brought three children to her second marriage, Sir Leslie brought one, and they had four children together. Sir Leslie Stephen was a writer, critic, philosopher, and scholar. Virginia and her siblings grew up in an intellectually vibrant atmosphere, with access to their father's extensive library and frequent visits by many of the most important thinkers and writers of the late Victorian period. Woolf suffered a number of traumas as a child: her mother died when she was thirteen; one of her half-brothers sexually abused her; her half-sister died when she was fifteen. When Woolf was in her twenties, she lost both her father and a brother to illness. Woolf herself began in adolescence to suffer severe bouts of depression; in adulthood, these tended to regularly occur after she had completed a book. She attempted suicide more than once while depressed; sadly, she did finally kill herself in 1941, when she weighted her pockets with stones and drowned herself in a river near her home. Woolf, her siblings, and her husband were extremely influential in the Modernist movement. Together with her sister, Vanessa, and her brother Adrian, Woolf began holding intellectual salons in their home after the death of her father. Their gatherings of writers, intellectuals, and avant garde artists became known as "The Bloomsbury Group." The group included such notable figures as Lytton Strachey, E.M. Forster, and John Maynard Keynes. Woolf began publishing novels in 1915 with The Voyage Out , which was followed in 1916 by Night and Day . These two generally realistic novels were followed by her first truly innovative novel Jacob's Room in 1922 and her masterpieces, Mrs. Dalloway (1925) and To the Lighthouse (1927). In these later novels, Woolf found her distinctive voice and style, marked by poetic images and rhythms and extensive use of the stream of consciousness technique. Woolf was equally influential as a reviewer. In her essay on the fiction of her contemporaries, "Modern Fiction," she indicts their tendency to ignore the truths about life and humanity and focus instead on the minutiae of everyday life. Additionally, in 1917, Woolf and her husband Leonard founded the Hogarth Press, which published many of the most innovative writers of the period, including Elizabeth Mansfield, T.S. Eliot, and Freud. "A Room of One's Own" (1929), a lengthy essay generally now published alone, is actually a compilation of two lectures on "Women and Fiction" that Woolf delivered to women undergraduates at Cambridge. In the essay, Woolf comments on the need for women who aspire to write to have an independent income and a private space in which to be alone. Additionally, Woolf includes a speculative section on "Shakespeare's Sister" as she laments the absence of a canon of women writers. Woolf emphasizes the need for a truly androgynous voice as the way forward for twentieth century literature. Consider while reading:
- Who is Woolf addressing, and what is she encouraging the members of her audience to do?
- As Woolf characterizes "Oxbridge," (her shorthand for the universities at Oxford and Cambridge), how does she distinguish between the experiences of men and women students and faculty?
- Why does Woolf tell the story of Shakespeare's hypothetical sister Judith? What point is she making?
- What, according to Woolf, is the way forward for both male and female writers? Why does she advocate for a more "androgynous" voice in literature?
Written by Anita Turlington


1.9: Physical Stimulus and its Role with Emotions
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This topic is about the difference between physical feelings and mental feelings (feelings of emotions, of thoughts). It could be viewed that most stimulation is physical. More importantly, that physical feeling is mixed in with mental feelings. Also, that physical feeling is with you all the time and can even serve as a baseline for your emotions. Whenever you experience an emotion, or even in your general state, you are feeling physical feelings. If you look at this by the definition of stimulation then it makes sense that most stimulation is physical since stimulation is usually something strong, and physical feelings feel much more real and alive than mental ones. You know you are alive if you are experiencing pain. What happens when someone concentrates on physical feelings? Doing intense physical activity (like playing a sport), feeling pain, going to the bathroom, eating, and having sex are the five strongest physical feelings I can think of. However you also have physical feelings all the time because you are aware of yourself not only in a mental way but in a physical way. You are aware of the physical feelings your body produces all the time and how these feelings are mostly the same as time changes.  So intellectually your mental feelings are stronger if you are doing serious thinking, but if you are doing physical activity then your physical feelings are stronger. Also, your physical feelings interact with your mental feelings in a certain way, one might cause the other to increase, there might be a chain of cause and effect interaction.
This is related to the difference between emotion and thought because one distracts from the other, and physical feelings are more like emotions than thoughts. This is why pain isn't as much of an emotion than the other emotions because the other emotions are more mental and therefore intellectual. In fact, if you explore the feeling of pain it helps one to understand what a physical feeling is like because pain seems to be the strongest physical feeling. It is also a negative emotion similar to sadness, however, because it might make you feel sad very quickly or simultaneously. If it makes you feel sad simultaneously then it is like pain is an emotion because it is related to the feeling sad. So pain is a physical feeling that overlaps with the emotion sad. If someone is in pain it makes them sad, but that is much different from being sad in the normal way someone gets sad. It is like a physical sadness. Similarly if someone is having sex it might make them happy, but in a physical way much different from the normal emotion happy (that is pretty amusing). So saying pain is an emotion is like saying that sex is an emotion. Sex may provoke emotions but is it an emotion itself? The answer is really that physical feelings are so similar to emotions that the two are tied together. You get a small amount of real emotion from something physical whereby it seems like the emotion is part of the physical feeling because the physical feeling feels so much like a certain mental emotion.
People respond to emotions. They get a feeling or emotion, then they think about it. If a feeling is large enough to be felt consciously, then it is going to be thought about. “Thinking” is really processing in a larger context, thus all emotions are processed in the mind (even physical ones). In this way emotions become complicated, that is, life isn’t just continuous sensory stimulation. All the sensory stimulation adds up and people have feelings about the total amount of sensory stimulation. Either that or there is a deeper feeling which people get simply from being alive, that isn’t related to sensory stimulation. This feeling must come from something, however. The world (the physical world) is real and it exists, this is the only source of potential feeling (since that is the only thing to get feeling from). Pain feels extremely real, it might be that people are happy simply because it is an avoidance of pain, or that happy only exists relative to sad, so you understand how you are happy and can be happy because you know what happy is because you know it isn't extreme pain. It seems like pain is too large to be compared to regular sensory stimulation, like visual stimulation. This means that most emotions (if you consider pain to be an emotion, here I just mean that people are more distracted by the physical than the mental emotions) people have are from just their immediate environment, feeling things and touching things. Feeling their own body and the physical feelings they get from it. Vision doesn’t cause that much pleasure compared to physical.
When someone gets happy from emotions (non physical stimulus), however, they get very happy. This source of happiness must come at least partly from the physical, that is, they get happy because they feel better about their physical emotions (or when they get mentally happy, they can feel their body more because they are more alive and this experience is tied into being happy - the physical experience is also more real so it seems like your mental emotions derive from the physical). If someone is nice to them, then they feel like they are helping them, and this means helping them stay alive, which would prolong their life and the feelings get from their body. In a similar way, all emotions are tied into the physical. Part of what makes people happy is reward which they associate with prolonging their life. They feel deeply about prolonging their life because they get deep physical feelings from their body and from its existence. So emotions actually come partly from physical sensations, just not directly. That is if they were directly from physical sensations it would just be a physical sensation, but people feel deep emotions if it relates to protecting their physical sensations. In this way people are very animal-like. Seeing things and hearing things makes people feel good but this feeling is very mild. Most feeling comes just from a physical awareness of one’s own body. This makes sense considering that physical pain at its height is much worse than any emotional pain.
In review, emotional pain has its source in physical feelings and pain. This also means that emotions are really physical things. Emotions cause physical feelings. Any “feeling” is really a physical feeling, even if it is from vision or hearing. The sensory feeling triggers a deeper physical feeling because the sensory feeling reminds you that you are alive and have a physical body. In this way all sensations are tied into your physical body.
This all just really means that the physical is much more "real" than emotions are. You could say that emotions are feelings by themselves, but whenever you experience an emotion, you are also experiencing physical sensations. The physical is always there and it is strong because it is real, it is who you are. It is like a baseline for your emotions, it is a reminder that you are alive. If there was no physical world, you couldn't experience emotions because emotions are in root all physical, since everything comes from sensory stimulation initially. Thinking of it that way, all emotions are physical themselves since they remind you of seeing and touching physical things, which brings up a sense of your physical presence in that environment. Also, if the emotion isn't physical, then how is it in any way real? How can someone feel something other than physically? Can you say, "I felt that intellectually?" How much sense does that make?


4: History of Communication Study
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Learning Objectives
After reading this chapter you should be able to:
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Identify the four early periods of communication study.
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Explain the major changes in communication study in the 20th century.
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Identify major scholars who helped shape the field of Communication.
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Discuss how Communication departments and professional organizations formed.
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4.1: History of Communication Study Overview
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Over time, the study of communication has largely been prompted by the current social issues of particular time periods. Knowing this, we’ll examine the pertinent questions, topics, and scholars of the Classical, Medieval, Renaissance, and Enlightenment periods to find out what they learned about communication to help them understand the world around them. Next, we will highlight the rapid growth of contemporary communication.
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4.2: The Classical Period (500 BCE-400 CE)
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It is largely agreed-upon that the formal study of communication began approximately 2,500 years ago in Greece and Sicily. It is here that we will begin our tour of Ancient Greece with the “fantastic four”—Aspasia of Miletus, Socrates, Plato, and Aristotle—who have come to be regarded as the foremother and forefathers of rhetoric and the field of Communication as a whole. Then, we’ll turn to scholars who extended the work of the fantastic four—Corax, Tisias, Cicero, Quintilian, and Pan Chao.
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4.3: The Medieval Period (400 CE-1400 CE)
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During the Medieval Period, the Greco-Roman culture was dominated by Christian influence after the fall of the Roman Empire. The church felt threatened by secular rhetorical works they considered full of pagan thought. While the church preserved many of the classical teachings of rhetoric, it made them scarce to those not in direct service to the church. A secular education was extremely hard to obtain during the Medieval Period for almost everyone.
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4.4: The Renaissance (1400-1600 CE)
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Secular institutions and governments started to compete with the church for personal allegiances. As more people felt comfortable challenging the church’s approach to education, reinvigorated attention to classical learning and fresh opportunities for scholarly education reemerged. As with the two previous periods we’ve examined, obtaining education for women was still tough, as many social limitations continued to restrict their access to knowledge.
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4.5: The Enlightenment (1600-1800 CE)
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A maturing Europe continued to see a lessening of tension between the church and secular institutions, and the transformation of the Communication field was a reflection of broader cultural shifts. Modernizations, such as the printing press, made the written word more readily available to the masses through newspapers and books thus, forever changing the ways people learned and communicated. This era was the precursor to the industrial revolution.
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4.6: New School- Communication Study in the 20th Century
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‘Topics such as persuasion, public speaking, political debate, preaching, letter writing, and education guided communication study in the early periods as these were the pressing social matters of the day. With the industrial revolution in full effect, major world changes took place that impacted the continuing advancement of communication study. We have seen more changes in the ways humans communicate, and communication study, in the past 100 years than in any other time in history.
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4.7: Communication Study Today and Tomorrow
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Today, many colleges and universities have Communication as part of their curriculum with departments titled with names like Speech, Speech Communication, and Communication. Likewise, our professional organizations are still active in growing and strengthening the field through teaching and research. Even with the increased recognition, there is still considerable growth, change, and movement taking place in communication study.
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4.8: History of Communication Study Summary
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4.9: History of Communication Study References
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Thumbnail: This painting illustrates rhetoric by depicting a lecture in a knight academy, painted by Pieter Isaacsz or Reinhold Timm for Rosenborg Castle. (Public Domain;
Pieter Isaacsz
via
Wikipedia
)


12.4: The Action Potential
Learning Objectives
- Describe the components of the membrane that establish the resting membrane potential
- Describe the changes that occur to the membrane that result in the action potential
The functions of the nervous system—sensation, integration, and response—depend on the functions of the neurons underlying these pathways. To understand how neurons are able to communicate, it is necessary to describe the role of an excitable membrane in generating these signals. The basis of this communication is the action potential, which demonstrates how changes in the membrane can constitute a signal. Looking at the way these signals work in more variable circumstances involves a look at graded potentials, which will be covered in the next section.
Electrically Active Cell Membranes
Most cells in the body make use of charged particles, ions, to build up a charge across the cell membrane. Previously, this was shown to be a part of how muscle cells work. For skeletal muscles to contract, based on excitation–contraction coupling, requires input from a neuron. Both of the cells make use of the cell membrane to regulate ion movement between the extracellular fluid and cytosol.
As you learned in the chapter on cells, the cell membrane is primarily responsible for regulating what can cross the membrane and what stays on only one side. The cell membrane is a phospholipid bilayer, so only substances that can pass directly through the hydrophobic core can diffuse through unaided. Charged particles, which are hydrophilic by definition, cannot pass through the cell membrane without assistance (Figure \(\PageIndex{1}\)). Transmembrane proteins, specifically channel proteins, make this possible. Several passive transport channels, as well as active transport pumps, are necessary to generate a transmembrane potential and an action potential. Of special interest is the carrier protein referred to as the sodium/potassium pump that moves sodium ions (Na + ) out of a cell and potassium ions (K + ) into a cell, thus regulating ion concentration on both sides of the cell membrane.
The sodium/potassium pump requires energy in the form of adenosine triphosphate (ATP), so it is also referred to as an ATPase. As was explained in the cell chapter, the concentration of Na + is higher outside the cell than inside, and the concentration of K + is higher inside the cell than outside. That means that this pump is moving the ions against the concentration gradients for sodium and potassium, which is why it requires energy. In fact, the pump basically maintains those concentration gradients.
Ion channels are pores that allow specific charged particles to cross the membrane in response to an existing concentration gradient. Proteins are capable of spanning the cell membrane, including its hydrophobic core, and can interact with the charge of ions because of the varied properties of amino acids found within specific domains or regions of the protein channel. Hydrophobic amino acids are found in the domains that are apposed to the hydrocarbon tails of the phospholipids. Hydrophilic amino acids are exposed to the fluid environments of the extracellular fluid and cytosol. Additionally, the ions will interact with the hydrophilic amino acids, which will be selective for the charge of the ion. Channels for cations (positive ions) will have negatively charged side chains in the pore. Channels for anions (negative ions) will have positively charged side chains in the pore. This is called electrochemical exclusion , meaning that the channel pore is charge-specific.
Ion channels can also be specified by the diameter of the pore. The distance between the amino acids will be specific for the diameter of the ion when it dissociates from the water molecules surrounding it. Because of the surrounding water molecules, larger pores are not ideal for smaller ions because the water molecules will interact, by hydrogen bonds, more readily than the amino acid side chains. This is called size exclusion . Some ion channels are selective for charge but not necessarily for size, and thus are called a nonspecific channel . These nonspecific channels allow cations—particularly Na + , K + , and Ca 2+ —to cross the membrane, but exclude anions.
Ion channels do not always freely allow ions to diffuse across the membrane. Some are opened by certain events, meaning the channels are gated . So another way that channels can be categorized is on the basis of how they are gated. Although these classes of ion channels are found primarily in the cells of nervous or muscular tissue, they also can be found in the cells of epithelial and connective tissues.
A ligand-gated channel opens because a signaling molecule, a ligand, binds to the extracellular region of the channel. This type of channel is also known as an ionotropic receptor because when the ligand, known as a neurotransmitter in the nervous system, binds to the protein, ions cross the membrane changing its charge (Figure \(\PageIndex{2}\)).
A mechanically gated channel opens because of a physical distortion of the cell membrane. Many channels associated with the sense of touch (somatosensation) are mechanically gated. For example, as pressure is applied to the skin, these channels open and allow ions to enter the cell. Similar to this type of channel would be the channel that opens on the basis of temperature changes, as in testing the water in the shower (Figure \(\PageIndex{3}\)).
A voltage-gated channel is a channel that responds to changes in the electrical properties of the membrane in which it is embedded. Normally, the inner portion of the membrane is at a negative voltage. When that voltage becomes less negative, the channel begins to allow ions to cross the membrane (Figure \(\PageIndex{4}\)).
A leakage channel is randomly gated, meaning that it opens and closes at random, hence the reference to leaking. There is no actual event that opens the channel; instead, it has an intrinsic rate of switching between the open and closed states. Leakage channels contribute to the resting transmembrane voltage of the excitable membrane (Figure \(\PageIndex{5}\)).
The Membrane Potential
The electrical state of the cell membrane can have several variations. These are all variations in the membrane potential . A potential is a distribution of charge across the cell membrane, measured in millivolts (mV). The standard is to compare the inside of the cell relative to the outside, so the membrane potential is a value representing the charge on the intracellular side of the membrane based on the outside being zero, relatively speaking (Figure \(\PageIndex{6}\)).
The concentration of ions in extracellular and intracellular fluids is largely balanced, with a net neutral charge. However, a slight difference in charge occurs right at the membrane surface, both internally and externally. It is the difference in this very limited region that has all the power in neurons (and muscle cells) to generate electrical signals, including action potentials.
Before these electrical signals can be described, the resting state of the membrane must be explained. When the cell is at rest, and the ion channels are closed (except for leakage channels which randomly open), ions are distributed across the membrane in a very predictable way. The concentration of Na + outside the cell is 10 times greater than the concentration inside. Also, the concentration of K + inside the cell is greater than outside. The cytosol contains a high concentration of anions, in the form of phosphate ions and negatively charged proteins. Large anions are a component of the inner cell membrane, including specialized phospholipids and proteins associated with the inner leaflet of the membrane (leaflet is a term used for one side of the lipid bilayer membrane). The negative charge is localized in the large anions.
With the ions distributed across the membrane at these concentrations, the difference in charge is measured at -70 mV, the value described as the resting membrane potential . The exact value measured for the resting membrane potential varies between cells, but -70 mV is most commonly used as this value. This voltage would actually be much lower except for the contributions of some important proteins in the membrane. Leakage channels allow Na + to slowly move into the cell or K + to slowly move out, and the Na + /K + pump restores them. This may appear to be a waste of energy, but each has a role in maintaining the membrane potential.
The Action Potential
Resting membrane potential describes the steady state of the cell, which is a dynamic process that is balanced by ion leakage and ion pumping. Without any outside influence, it will not change. To get an electrical signal started, the membrane potential has to change.
This starts with a channel opening for Na + in the membrane. Because the concentration of Na + is higher outside the cell than inside the cell by a factor of 10, ions will rush into the cell that are driven largely by the concentration gradient. Because sodium is a positively charged ion, it will change the relative voltage immediately inside the cell relative to immediately outside. The resting potential is the state of the membrane at a voltage of -70 mV, so the sodium cation entering the cell will cause it to become less negative. This is known as depolarization , meaning the membrane potential moves toward zero.
The concentration gradient for Na + is so strong that it will continue to enter the cell even after the membrane potential has become zero, so that the voltage immediately around the pore begins to become positive. The electrical gradient also plays a role, as negative proteins below the membrane attract the sodium ion. The membrane potential will reach +30 mV by the time sodium has entered the cell.
As the membrane potential reaches +30 mV, other voltage-gated channels are opening in the membrane. These channels are specific for the potassium ion. A concentration gradient acts on K + , as well. As K + starts to leave the cell, taking a positive charge with it, the membrane potential begins to move back toward its resting voltage. This is called repolarization , meaning that the membrane voltage moves back toward the -70 mV value of the resting membrane potential.
Repolarization returns the membrane potential to the -70 mV value that indicates the resting potential, but it actually overshoots that value. Potassium ions reach equilibrium when the membrane voltage is below -70 mV, so a period of hyperpolarization occurs while the K + channels are open. Those K + channels are slightly delayed in closing, accounting for this short overshoot.
What has been described here is the action potential, which is presented as a graph of voltage over time in Figure \(\PageIndex{6}\). It is the electrical signal that nervous tissue generates for communication. The change in the membrane voltage from -70 mV at rest to +30 mV at the end of depolarization is a 100-mV change. That can also be written as a 0.1-V change. To put that value in perspective, think about a battery. An AA battery that you might find in a television remote has a voltage of 1.5 V, or a 9-V battery (the rectangular battery with two posts on one end) is, obviously, 9 V. The change seen in the action potential is one or two orders of magnitude less than the charge in these batteries. In fact, the membrane potential can be described as a battery. A charge is stored across the membrane that can be released under the correct conditions. A battery in your remote has stored a charge that is “released” when you push a button.
Exercise \(\PageIndex{1}\)
What happens across the membrane of an electrically active cell is a dynamic process that is hard to visualize with static images or through text descriptions. View this animation to learn more about this process. What is the difference between the driving force for Na+ and K+? And what is similar about the movement of these two ions?
The question is, now, what initiates the action potential? The description above conveniently glosses over that point. But it is vital to understanding what is happening. The membrane potential will stay at the resting voltage until something changes. The description above just says that a Na + channel opens. Now, to say “a channel opens” does not mean that one individual transmembrane protein changes. Instead, it means that one kind of channel opens. There are a few different types of channels that allow Na + to cross the membrane. A ligand-gated Na + channel will open when a neurotransmitter binds to it and a mechanically gated Na + channel will open when a physical stimulus affects a sensory receptor (like pressure applied to the skin compresses a touch receptor). Whether it is a neurotransmitter binding to its receptor protein or a sensory stimulus activating a sensory receptor cell, some stimulus gets the process started. Sodium starts to enter the cell and the membrane becomes less negative.
A third type of channel that is an important part of depolarization in the action potential is the voltage-gated Na + channel. The channels that start depolarizing the membrane because of a stimulus help the cell to depolarize from -70 mV to -55 mV. Once the membrane reaches that voltage, the voltage-gated Na + channels open. This is what is known as the threshold. Any depolarization that does not change the membrane potential to -55 mV or higher will not reach threshold and thus will not result in an action potential. Also, any stimulus that depolarizes the membrane to -55 mV or beyond will cause a large number of channels to open and an action potential will be initiated.
Because of the threshold, the action potential can be likened to a digital event—it either happens or it does not. If the threshold is not reached, then no action potential occurs. If depolarization reaches -55 mV, then the action potential continues and runs all the way to +30 mV, at which K + causes repolarization, including the hyperpolarizing overshoot. Also, those changes are the same for every action potential, which means that once the threshold is reached, the exact same thing happens. A stronger stimulus, which might depolarize the membrane well past threshold, will not make a “bigger” action potential. Action potentials are “all or none.” Either the membrane reaches the threshold and everything occurs as described above, or the membrane does not reach the threshold and nothing else happens. All action potentials peak at the same voltage (+30 mV), so one action potential is not bigger than another. Stronger stimuli will initiate multiple action potentials more quickly, but the individual signals are not bigger. Thus, for example, you will not feel a greater sensation of pain, or have a stronger muscle contraction, because of the size of the action potential because they are not different sizes.
As we have seen, the depolarization and repolarization of an action potential are dependent on two types of channels (the voltage-gated Na + channel and the voltage-gated K + channel). The voltage-gated Na + channel actually has two gates. One is the activation gate , which opens when the membrane potential crosses -55 mV. The other gate is the inactivation gate , which closes after a specific period of time—on the order of a fraction of a millisecond. When a cell is at rest, the activation gate is closed and the inactivation gate is open. However, when the threshold is reached, the activation gate opens, allowing Na + to rush into the cell. Timed with the peak of depolarization, the inactivation gate closes. During repolarization, no more sodium can enter the cell. When the membrane potential passes -55 mV again, the activation gate closes. After that, the inactivation gate re-opens, making the channel ready to start the whole process over again.
The voltage-gated K + channel has only one gate, which is sensitive to a membrane voltage of -50 mV. However, it does not open as quickly as the voltage-gated Na + channel does. It might take a fraction of a millisecond for the channel to open once that voltage has been reached. The timing of this coincides exactly with when the Na + flow peaks, so voltage-gated K + channels open just as the voltage-gated Na + channels are being inactivated. As the membrane potential repolarizes and the voltage passes -50 mV again, the channel closes—again, with a little delay. Potassium continues to leave the cell for a short while and the membrane potential becomes more negative, resulting in the hyperpolarizing overshoot. Then the channel closes again and the membrane can return to the resting potential because of the ongoing activity of the non-gated channels and the Na + /K + pump.
All of this takes place within approximately 2 milliseconds (Figure \(\PageIndex{7}\)). While an action potential is in progress, another one cannot be initiated. That effect is referred to as the refractory period . There are two phases of the refractory period: the absolute refractory period and the relative refractory period . During the absolute phase, another action potential will not start. This is because of the inactivation gate of the voltage-gated Na + channel. Once that channel is back to its resting conformation (less than -55 mV), a new action potential could be started, but only by a stronger stimulus than the one that initiated the current action potential. This is because of the flow of K + out of the cell. Because that ion is rushing out, any Na + that tries to enter will not depolarize the cell, but will only keep the cell from hyperpolarizing.
Propagation of the Action Potential
The action potential is initiated at the beginning of the axon, at what is called the initial segment. There is a high density of voltage-gated Na + channels so that rapid depolarization can take place here. Going down the length of the axon, the action potential is propagated because more voltage-gated Na + channels are opened as the depolarization spreads. This spreading occurs because Na + enters through the channel and moves along the inside of the cell membrane. As the Na + moves, or flows, a short distance along the cell membrane, its positive charge depolarizes a little more of the cell membrane. As that depolarization spreads, new voltage-gated Na + channels open and more ions rush into the cell, spreading the depolarization a little farther.
Because voltage-gated Na + channels are inactivated at the peak of the depolarization, they cannot be opened again for a brief time—the absolute refractory period. Because of this, depolarization spreading back toward previously opened channels has no effect. The action potential must propagate toward the axon terminals; as a result, the polarity of the neuron is maintained, as mentioned above.
Propagation, as described above, applies to unmyelinated axons. When myelination is present, the action potential propagates differently. Sodium ions that enter the cell at the initial segment start to spread along the length of the axon segment, but there are no voltage-gated Na + channels until the first node of Ranvier. Because there is not constant opening of these channels along the axon segment, the depolarization spreads at an optimal speed. The distance between nodes is the optimal distance to keep the membrane still depolarized above threshold at the next node. As Na + spreads along the inside of the membrane of the axon segment, the charge starts to dissipate. If the node were any farther down the axon, that depolarization would have fallen off too much for voltage-gated Na + channels to be activated at the next node of Ranvier. If the nodes were any closer together, the speed of propagation would be slower.
Propagation along an unmyelinated axon is referred to as continuous conduction ; along the length of a myelinated axon, it is saltatory conduction . Continuous conduction is slow because there are always voltage-gated Na + channels opening, and more and more Na + is rushing into the cell. Saltatory conduction is faster because the action potential basically jumps from one node to the next (saltare = “to leap”), and the new influx of Na + renews the depolarized membrane. Along with the myelination of the axon, the diameter of the axon can influence the speed of conduction. Much as water runs faster in a wide river than in a narrow creek, Na + -based depolarization spreads faster down a wide axon than down a narrow one. This concept is known as resistance and is generally true for electrical wires or plumbing, just as it is true for axons, although the specific conditions are different at the scales of electrons or ions versus water in a river.
HOMEOSTATIC IMBALANCES: Potassium Concentration
Glial cells, especially astrocytes, are responsible for maintaining the chemical environment of the CNS tissue. The concentrations of ions in the extracellular fluid are the basis for how the membrane potential is established and changes in electrochemical signaling. If the balance of ions is upset, drastic outcomes are possible.
Normally the concentration of K+ is higher inside the neuron than outside. After the repolarizing phase of the action potential, K+ leakage channels and the Na+/K+ pump ensure that the ions return to their original locations. Following a stroke or other ischemic event, extracellular K+ levels are elevated. The astrocytes in the area are equipped to clear excess K+ to aid the pump. But when the level is far out of balance, the effects can be irreversible.
Astrocytes can become reactive in cases such as these, which impairs their ability to maintain the local chemical environment. The glial cells enlarge and their processes swell. They lose their K+ buffering ability and the function of the pump is affected, or even reversed. One of the early signs of cell disease is this "leaking" of sodium ions into the body cells. This sodium/potassium imbalance negatively affects the internal chemistry of cells, preventing them from functioning normally.
Visit this site to see a virtual neurophysiology lab, and to observe electrophysiological processes in the nervous system, where scientists directly measure the electrical signals produced by neurons. Often, the action potentials occur so rapidly that watching a screen to see them occur is not helpful. A speaker is powered by the signals recorded from a neuron and it “pops” each time the neuron fires an action potential. These action potentials are firing so fast that it sounds like static on the radio. Electrophysiologists can recognize the patterns within that static to understand what is happening. Why is the leech model used for measuring the electrical activity of neurons instead of using humans?
Review
The nervous system is characterized by electrical signals that are sent from one area to another. Whether those areas are close or very far apart, the signal must travel along an axon. The basis of the electrical signal is the controlled distribution of ions across the membrane. Transmembrane ion channels regulate when ions can move in or out of the cell, so that a precise signal is generated. This signal is the action potential which has a very characteristic shape based on voltage changes across the membrane in a given time period.
The membrane is normally at rest with established Na + and K + concentrations on either side. A stimulus will start the depolarization of the membrane, and voltage-gated channels will result in further depolarization followed by repolarization of the membrane. A slight overshoot of hyperpolarization marks the end of the action potential. While an action potential is in progress, another cannot be generated under the same conditions. While the voltage-gated Na + channel is inactivated, absolutely no action potentials can be generated. Once that channel has returned to its resting state, a new action potential is possible, but it must be started by a relatively stronger stimulus to overcome the K + leaving the cell.
The action potential travels down the axon as voltage-gated ion channels are opened by the spreading depolarization. In unmyelinated axons, this happens in a continuous fashion because there are voltage-gated channels throughout the membrane. In myelinated axons, propagation is described as saltatory because voltage-gated channels are only found at the nodes of Ranvier and the electrical events seem to “jump” from one node to the next. Saltatory conduction is faster than continuous conduction, meaning that myelinated axons propagate their signals faster. The diameter of the axon also makes a difference as ions diffusing within the cell have less resistance in a wider space.
Interactive Link Questions
What happens across the membrane of an electrically active cell is a dynamic process that is hard to visualize with static images or through text descriptions. View this animation to really understand the process. What is the difference between the driving force for Na + and K + ? And what is similar about the movement of these two ions?
Answer: Sodium is moving into the cell because of the immense concentration gradient, whereas potassium is moving out because of the depolarization that sodium causes. However, they both move down their respective gradients, toward equilibrium.
Visit this site to see a virtual neurophysiology lab, and to observe electrophysiological processes in the nervous system, where scientists directly measure the electrical signals produced by neurons. Often, the action potentials occur so rapidly that watching a screen to see them occur is not helpful. A speaker is powered by the signals recorded from a neuron and it “pops” each time the neuron fires an action potential. These action potentials are firing so fast that it sounds like static on the radio. Electrophysiologists can recognize the patterns within that static to understand what is happening. Why is the leech model used for measuring the electrical activity of neurons instead of using humans?
Answer: The properties of electrophysiology are common to all animals, so using the leech is an easier, more humane approach to studying the properties of these cells. There are differences between the nervous systems of invertebrates (such as a leech) and vertebrates, but not for the sake of what these experiments study.
Review Questions
Q. What ion enters a neuron causing depolarization of the cell membrane?
A. sodium
B. chloride
C. potassium
D. phosphate
Answer: A
Q. Voltage-gated Na + channels open upon reaching what state?
A. resting potential
B. threshold
C. repolarization
D. overshoot
Answer: B
Q. What does a ligand-gated channel require in order to open?
A. increase in concentration of Na + ions
B. binding of a neurotransmitter
C. increase in concentration of K + ions
D. depolarization of the membrane
Answer: B
Q. What does a mechanically gated channel respond to?
A. physical stimulus
B. chemical stimulus
C. increase in resistance
D. decrease in resistance
Answer: A
Q. Which of the following voltages would most likely be measured during the relative refractory period?
A. +30 mV
B. 0 mV
C. -45 mV
D. -80 mv
Answer: D
Q. Which of the following is probably going to propagate an action potential fastest?
A. a thin, unmyelinated axon
B. a thin, myelinated axon
C. a thick, unmyelinated axon
D. a thick, myelinated axon
Answer: D
Critical Thinking Questions
Q. What does it mean for an action potential to be an “all or none” event?
A. The cell membrane must reach threshold before voltage-gated Na + channels open. If threshold is not reached, those channels do not open, and the depolarizing phase of the action potential does not occur, the cell membrane will just go back to its resting state.
Q. The conscious perception of pain is often delayed because of the time it takes for the sensations to reach the cerebral cortex. Why would this be the case based on propagation of the axon potential?
A. Axons of pain sensing sensory neurons are thin and unmyelinated so that it takes longer for that sensation to reach the brain than other sensations.
Glossary
- absolute refractory period
- time during an action period when another action potential cannot be generated because the voltage-gated Na + channel is inactivated
- activation gate
- part of the voltage-gated Na + channel that opens when the membrane voltage reaches threshold
- continuous conduction
- slow propagation of an action potential along an unmyelinated axon owing to voltage-gated Na + channels located along the entire length of the cell membrane
- depolarization
- change in a cell membrane potential from rest toward zero
- electrochemical exclusion
- principle of selectively allowing ions through a channel on the basis of their charge
- excitable membrane
- cell membrane that regulates the movement of ions so that an electrical signal can be generated
- gated
- property of a channel that determines how it opens under specific conditions, such as voltage change or physical deformation
- inactivation gate
- part of a voltage-gated Na + channel that closes when the membrane potential reaches +30 mV
- ionotropic receptor
- neurotransmitter receptor that acts as an ion channel gate, and opens by the binding of the neurotransmitter
- leakage channel
- ion channel that opens randomly and is not gated to a specific event, also known as a non-gated channel
- ligand-gated channels
- another name for an ionotropic receptor for which a neurotransmitter is the ligand
- mechanically gated channel
- ion channel that opens when a physical event directly affects the structure of the protein
- membrane potential
- distribution of charge across the cell membrane, based on the charges of ions
- nonspecific channel
- channel that is not specific to one ion over another, such as a nonspecific cation channel that allows any positively charged ion across the membrane
- refractory period
- time after the initiation of an action potential when another action potential cannot be generated
- relative refractory period
- time during the refractory period when a new action potential can only be initiated by a stronger stimulus than the current action potential because voltage-gated K + channels are not closed
- repolarization
- return of the membrane potential to its normally negative voltage at the end of the action potential
- resistance
- property of an axon that relates to the ability of particles to diffuse through the cytoplasm; this is inversely proportional to the fiber diameter
- resting membrane potential
- the difference in voltage measured across a cell membrane under steady-state conditions, typically -70 mV
- saltatory conduction
- quick propagation of the action potential along a myelinated axon owing to voltage-gated Na + channels being present only at the nodes of Ranvier
- size exclusion
- principle of selectively allowing ions through a channel on the basis of their relative size
- voltage-gated channel
- ion channel that opens because of a change in the charge distributed across the membrane where it is located


3.18: Discussion- Take a Stance
In this module, you learned about the basics of essay-writing—finding thesis statements, organizing paragraphs, and supporting claims. At first, it may feel awkward to organize your thoughts into an essay, but organizing your thoughts to make an argument is something you do in regular conversations all the time. Think about the last heated discussion you were in—how did you defend your point of view? Did you include supporting claims or evidence? Did you mostly rely on emotional appeals (ethos), logical appeals (logos), or something else?
In this course, you will get practice taking a stance on an issue and defending your point of view. Let’s practice that now in the following discussion assignment.
STEP 1 : Pick ONE of the following questions to post about. Click on the link and read all of the corresponding background information about it from The New York Times, including the questions at the bottom of the page.
- Should Kids Be Social Media Influencers?
- Should Texting While Driving Be Treated Like Drunken Driving?
STEP 2 : Post your reply (in at least 250 words) in the discussion forum. Your response should include a clear stance on the issue with supporting evidence as to why you feel the way you do. Show that you can think critically on the topic by integrating your own thoughts, analysis, or experiences.
STEP 3 : Respond in two separate posts to two classmates (in at least 75 words). Explicitly address their responses and try to extend, complicate, or redirect their points in a substantive, knowledge-demonstrating way.
Contributors and Attributions
- Modification, adaptation, and original content. Provided by : Lumen Learning. License : CC BY: Attribution


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1.2.1: Cáo Xueqín (1715 or 1724 or 1764)
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Cáo Xueqín (c.1715-c.1763)
The Story of the Stone
(1791)
Chinese
Near East and Asia
The Story of the Stone
(also known as
The Dream of the Red Chamber
,
Hongloumeng
, or
Hung-lou-meng
) is a novel attributed to Cáo Xueqín of 18th-century China. Cáo (surname) Xueqín (literary name) is also known as Cáo Zhan or Ts'ao Chan. Generally regarded as the greatest Chinese novel, this novel shows the decline of the wealthy Jia (Chia) family. Cáo's own family experienced a similar decline during the Qing Dynasty (1644-1912). The first eighty chapters were written by Cáo and circulated in manuscript copies. In 1791, the writer Gao E (ca. 1740-ca. 1815) published a complete 120-chapter version, probably adding an additional forty chapters to the overall work. The novel portrays the experiences of close to forty main characters and about 400 minor characters. The framework of the story tells the tale of a flower that gives life to a conscious stone in the mythic world of the past; in the main narrative, the flower and the stone are both incarnated as humans and become part of a love triangle. In addition to the romance, the novel also sheds light on 18th-century Chinese society and probes into the ideas of truth and illusion. The first complete English translation is
The Story of the Stone
(1973-1986) by David Hawkes and John Minford.
Consider while reading:
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In what specific ways do you think this novel sheds light on 18th-century Chinese society?
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How do Confucianism, Daoism, and Buddhism function in the novel? How do these religio-philosophies seem to co-exist or conflict with one another in the novel?
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Compare the romantic aspect of this novel to another romantic story with which you are familiar. What are their notable similarities and differences?
Written by Kyounghye Kwon