5.6: The Sexual Experience
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 Studies consistently show that sexual desire for women is more sensitive to the context (meaningful or intimate connection) and the social and cultural environment (quality of relationships, stresses of the day, etc.). Generally speaking most men seek more sex than most women throughout most of the life span. Also, most men are more easily aroused by visual stimulation than are most women.
The Janus Report reported that 65% of men have an orgasm every time during love-making while females reported a much lower 15% every time. About 46% of women report “often” having an orgasm during love-making, compared to only 28% of men.  About 55% of men and 38% of women masturbate on a daily-monthly basis.
When filling out official documents, you are often asked to provide your name, birth date, and sex or gender. But have you ever been asked to provide your sex and your gender? It may not have occurred to you that sex and gender are not the same. However, sociologists and most other social scientists view sex and gender as conceptually distinct. Sex denotes biological characteristics and exists along a spectrum from male to female. Gender, on the other hand, denotes social and cultural characteristics that are assigned to different sexes. Sex and gender are not always synchronous, meaning they do not always line up in an easy-to-categorize way.


15.6: Summary
The equilibrium constant for an equilibrium involving the precipitation or dissolution of a slightly soluble ionic solid is called the solubility product, K sp , of the solid. For a heterogeneous equilibrium involving the slightly soluble solid M p X q and its ions M m+ and X n– :
the solubility product expression is:
The solubility product of a slightly soluble electrolyte can be calculated from its solubility; conversely, its solubility can be calculated from its K sp , provided the only significant reaction that occurs when the solid dissolves is the formation of its ions.
A slightly soluble electrolyte begins to precipitate when the magnitude of the reaction quotient for the dissolution reaction exceeds the magnitude of the solubility product. Precipitation continues until the reaction quotient equals the solubility product.
A Lewis acid is a species that can accept an electron pair, whereas a Lewis base has an electron pair available for donation to a Lewis acid. Complex ions are examples of Lewis acid-base adducts and comprise central metal atoms or ions acting as Lewis acids bonded to molecules or ions called ligands that act as Lewis bases. The equilibrium constant for the reaction between a metal ion and ligands produces a complex ion called a formation constant; for the reverse reaction, it is called a dissociation constant.
Systems involving two or more chemical equilibria that share one or more reactant or product are called coupled equilibria. Common examples of coupled equilibria include the increased solubility of some compounds in acidic solutions (coupled dissolution and neutralization equilibria) and in solutions containing ligands (coupled dissolution and complex formation). The equilibrium tools from other chapters may be applied to describe and perform calculations on these systems.


18.E: Specific Adaptive Host Defenses (Exercises)
18.1: Architecture of the Immune System
Adaptive immunity is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent if it is exposed to the virus again later.
Multiple Choice
Antibodies are produced by ________.
- plasma cells
- T cells
- bone marrow
- B cells
- Answer
-
A
Cellular adaptive immunity is carried out by ________.
- B cells
- T cells
- bone marrow
- neutrophils
- Answer
-
B
A single antigen molecule may be composed of many individual ________.
- T-cell receptors
- B-cell receptors
- MHC II
- epitopes
- Answer
-
D
Which class of molecules is the most antigenic?
- polysaccharides
- lipids
- proteins
- carbohydrates
- Answer
-
C
Matching
Match the antibody class with its description.
| ___IgA | A. This class of antibody is the only one that can cross the placenta. |
| ___IgD | B. This class of antibody is the first to appear after activation of B cells. |
| ___IgE | C. This class of antibody is involved in the defense against parasitic infections and involved in allergic responses. |
| ___IgG | D. This class of antibody is found in very large amounts in mucus secretions. |
| ___IgM | E. This class of antibody is not secreted by B cells but is expressed on the surface of naïve B cells. |
- Answer
-
d, e, c, a, b
Fill in the Blank
There are two critically important aspects of adaptive immunity. The first is specificity, while the second is ________.
- Answer
-
memory
________ immunity involves the production of antibody molecules that bind to specific antigens.
- Answer
-
Humoral
The heavy chains of an antibody molecule contain ________ region segments, which help to determine its class or isotype.
- Answer
-
constant
The variable regions of the heavy and light chains form the ________ sites of an antibody.
- Answer
-
antigen-binding
Short Answer
What is the difference between humoral and cellular adaptive immunity?
What is the difference between an antigen and a hapten?
Describe the mechanism of antibody-dependent cell-mediated cytotoxicity.
18.2: Antigens, Antigen Presenting Cells, and Major Histocompatibility Complexes
Major histocompatibility complex (MHC) molecules are expressed on the surface of healthy cells, identifying them as normal and “self” to natural killer (NK) cells. MHC molecules also play an important role in the presentation of foreign antigens, which is a critical step in the activation of T cells and thus an important mechanism of the adaptive immune system.
Multiple Choice
MHC I molecules present
- processed foreign antigens from proteasomes.
- processed self-antigens from phagolysosome.
- antibodies.
- T cell antigens.
- Answer
-
A
MHC II molecules present
- processed self-antigens from proteasomes.
- processed foreign antigens from phagolysosomes.
- antibodies.
- T cell receptors.
- Answer
-
B
Which type of antigen-presenting molecule is found on all nucleated cells?
- MHC II
- MHC I
- antibodies
- B-cell receptors
- Answer
-
B
Which type of antigen-presenting molecule is found only on macrophages, dendritic cells, and B cells?
- MHC I
- MHC II
- T-cell receptors
- B-cell receptors
- Answer
-
B
Fill in the Blank
MHC molecules are used for antigen ________ to T cells.
- Answer
-
presentation
MHC II molecules are made up of two subunits (α and β) of approximately equal size, whereas MHC I molecules consist of a larger α subunit and a smaller subunit called ________.
- Answer
-
β 2 microglobulin
Critical Thinking
Which mechanism of antigen presentation would be used to present antigens from a cell infected with a virus?
Which pathway of antigen presentation would be used to present antigens from an extracellular bacterial infection?
18.3: T Lymphocytes
The antibodies involved in humoral immunity often bind pathogens and toxins before they can attach to and invade host cells. Thus, humoral immunity is primarily concerned with fighting pathogens in extracellular spaces. However, pathogens that have already gained entry to host cells are largely protected from the humoral antibody-mediated defenses. Cellular immunity, on the other hand, targets and eliminates intracellular pathogens through the actions of T lymphocytes, or T cells.
Multiple Choice
What is a superantigen?
- a protein that is highly efficient at stimulating a single type of productive and specific T cell response
- a protein produced by antigen-presenting cells to enhance their presentation capabilities
- a protein produced by T cells as a way of increasing the antigen activation they receive from antigen-presenting cells
- a protein that activates T cells in a nonspecific and uncontrolled manner
- Answer
-
D
To what does the TCR of a helper T cell bind?
- antigens presented with MHC I molecules
- antigens presented with MHC II molecules
- free antigen in a soluble form
- haptens only
- Answer
-
B
Cytotoxic T cells will bind with their TCR to which of the following?
- antigens presented with MHC I molecules
- antigens presented with MHC II molecules
- free antigen in a soluble form
- haptens only
- Answer
-
A
A ________ molecule is a glycoprotein used to identify and distinguish white blood cells.
- T-cell receptor
- B-cell receptor
- MHC I
- cluster of differentiation
- Answer
-
D
Name the T helper cell subset involved in antibody production.
- T H 1
- T H 2
- T H 17
- CTL
- Answer
-
B
Fill in the Blank
A ________ T cell will become activated by presentation of foreign antigen associated with an MHC I molecule.
- Answer
-
cytotoxic
A ________ T cell will become activated by presentation of foreign antigen in association with an MHC II molecule.
- Answer
-
helper
A TCR is a protein dimer embedded in the plasma membrane of a T cell. The ________ region of each of the two protein chains is what gives it the capability to bind to a presented antigen.
- Answer
-
variable
Peripheral tolerance mechanisms function on T cells after they mature and exit the ________.
- Answer
-
thymus
Both ________ and effector T cells are produced during differentiation of activated T cells.
- Answer
-
memory
Short Answer
What is the basic difference in effector function between helper and cytotoxic T cells?
What necessary interactions are required for activation of helper T cells and activation/effector function of cytotoxic T cells?
18.4: B Lymphocytes and Antibodies
Humoral immunity refers to mechanisms of the adaptive immune defenses that are mediated by antibodies secreted by B lymphocytes, or B cells. This section focuses on B cells and discusses their production and maturation, receptors, and mechanisms of activation.
Multiple Choice
Which of the following would be a T-dependent antigen?
- lipopolysaccharide
- glycolipid
- protein
- carbohydrate
- Answer
-
C
Which of the following would be a BCR?
- CD4
- MHC II
- MHC I
- IgD
- Answer
-
D
Which of the following does not occur during the lag period of the primary antibody response?
- activation of helper T cells
- class switching to IgG
- presentation of antigen with MHC II
- binding of antigen to BCRs
- Answer
-
B
Fill in the Blank
________ antigens can stimulate B cells to become activated but require cytokine assistance delivered by helper T cells.
- Answer
-
T-dependent
T-independent antigens can stimulate B cells to become activated and secrete antibodies without assistance from helper T cells. These antigens possess ________ antigenic epitopes that cross-link BCRs.
- Answer
-
repetitive
Critical Thinking
A patient lacks the ability to make functioning T cells because of a genetic disorder. Would this patient’s B cells be able to produce antibodies in response to an infection? Explain your answer.
18.5: Vaccines
By artificially stimulating the adaptive immune defenses, a vaccine triggers memory cell production similar to that which would occur during a primary response. In so doing, the patient is able to mount a strong secondary response upon exposure to the pathogen—but without having to first suffer through an initial infection. In this section, we explore several different kinds of artificial immunity along with various types of vaccines and their mechanisms for inducing artificial immunity.
Multiple Choice
A patient is bitten by a dog with confirmed rabies infection. After treating the bite wound, the physician injects the patient with antibodies that are specific for the rabies virus to prevent the development of an active infection. This is an example of:
- Natural active immunity
- Artificial active immunity
- Natural passive immunity
- Artificial passive immunity
- Answer
-
D
A patient gets a cold, and recovers a few days later. The patient's classmates come down with the same cold roughly a week later, but the original patient does not get the same cold again. This is an example of:
- Natural active immunity
- Artificial active immunity
- Natural passive immunity
- Artificial passive immunity
- Answer
-
A
Matching
Match each type of vaccine with the corresponding example.
| ___inactivated vaccine | A. Weakened influenza virions that can only replicate in the slightly lower temperatures of the nasal passages are sprayed into the nose. They do not cause serious flu symptoms, but still produce an active infection that induces a protective adaptive immune response. |
| ___live attenuated vaccine | B. Tetanus toxin molecules are harvested and chemically treated to render them harmless. They are then injected into a patient’s arm. |
| ___toxoid vaccine | C. Influenza virus particles grown in chicken eggs are harvested and chemically treated to render them noninfectious. These immunogenic particles are then purified and packaged and administered as an injection. |
| ___subunit vaccine | D. The gene for hepatitis B virus surface antigen is inserted into a yeast genome. The modified yeast is grown and the virus protein is produced, harvested, purified, and used in a vaccine. |
- Answer
-
C, A, B, D
Fill in the Blank
A(n) ________ pathogen is in a weakened state; it is still capable of stimulating an immune response but does not cause a disease.
- Answer
-
attenuated
________ immunity occurs when antibodies from one individual are harvested and given to another to protect against disease or treat active disease.
- Answer
-
Artificial passive
In the practice of ________, scabs from smallpox victims were used to immunize susceptible individuals against smallpox.
- Answer
-
variolation
Short answer
Briefly compare the pros and cons of inactivated versus live attenuated vaccines.


10.7: The Delta Function
What happens when we feed the Fourier relations into one another? Plugging the Fourier transform into the inverse Fourier transform, we get \[\begin{align} f(x) &= \int_{-\infty}^\infty \frac{dk}{2\pi} \, e^{ikx} F(k) \\ &= \int_{-\infty}^\infty \frac{dk}{2\pi} \, e^{ikx} \int_{-\infty}^\infty dx' e^{-ikx'} f(x')\\ &= \int_{-\infty}^\infty dx' \int_{-\infty}^\infty \frac{dk}{2\pi} \, e^{ikx} e^{-ikx'} f(x')\\ &= \int_{-\infty}^\infty dx' \; \delta(x-x')\, f(x'),\end{align}\] In the last step, we have introduced \[\delta(x-x') = \int_{-\infty}^\infty \frac{dk}{2\pi} \, e^{ik(x-x')},\] which is called the delta function . According to the above equations, the delta function acts as a kind of filter: when we multiply it by any function \(f(x')\) and integrate over \(x'\) , the result is the value of that function at a particular point \(x\) .
But here’s a problem: the above integral definition of the delta function is non-convergent; in particular, the integrand does not vanish at \(\pm \infty\) . We can get around this by thinking of the delta function as a limiting case of a convergent integral. Specifically, let’s take \[\delta(x-x') = \lim_{\gamma \rightarrow 0} \, \int_{-\infty}^\infty \frac{dk}{2\pi} \, e^{ik(x-x')} \, e^{-\gamma k^2}.\] For \(\gamma \rightarrow 0\) , the “regulator” \(\exp(-\gamma k^2)\) which we have inserted into the integrand goes to one, so that the integrand goes back to what we had before; on the other hand, for \(\gamma > 0\) the regulator ensures that the integrand vanishes at the end-points so that the integral is well-defined. But the expression on the right is the Fourier transform for a Gaussian wave-packet (see Section 10.6), so \[\delta(x-x') = \lim_{\gamma \rightarrow 0} \; \frac{1}{\sqrt{4\pi\gamma}} \, e^{-\frac{(x-x')^2}{4\gamma}}.\] This is a Gaussian function of width \(\sqrt{2\gamma}\) and area \(1\) . Hence, the delta function can be regarded as the limit of a Gaussian function as its width goes to zero while keeping the area under the curve fixed at unity (which means the height of the peak goes to infinity).
The most important feature of the delta function is it acts like a filter. Whenever it shows up in an integral, it picks out the value of the rest of the integrand evaluated where the delta function is centered: \[\int_{-\infty}^\infty dx \; \delta(x-x_0)\, f(x) = f(x_0).\] Intuitively, we can understand this behavior from the above definition of the delta function as the zero-width limit of a Gaussian. When we multiply a function \(f(x)\) with a narrow Gaussian centered at \(x_0\) , the product will approach zero almost everywhere, because the Gaussian goes to zero. The product is non-zero only in the vicinity of \(x = x_0\) , where the Gaussian peaks. And because the area under the delta function is unity, integrating that product over all \(x\) simply gives the value of the other function at the point \(x_0\) .
Note
In physics, the delta function is commonly used to represent the density distributions of point particles . For instance, the distribution of mass within an object can be represented by a mass density function. Assuming one-dimensional space for simplicity, we define the mass density \(\rho(x)\) as the mass per unit length at position \(x\) . By this definition, \[M = \int_{-\infty}^\infty \rho(x)\, dx\] is the total mass of the object. Now suppose the mass is distributed among \(N\) point particles, which are located at distinct positions \(x_1\) , \(x_2\) , …, \(x_N\) , and have masses \(m_1\) , \(m_2\) , … \(m_N\) . To describe this situation, we can write the mass density function as \[\rho(x) = \sum_{j=1}^N \, m_j\, \delta(x-x_j).\] The reason for this is that if we integrate \(\rho(x)\) around the vicinity of the \(j\) -th particle, the result is just the mass of that single particle, thanks to the features of the delta function: \[\begin{align} \lim_{\varepsilon\rightarrow 0^+}\, \int_{x_j - \varepsilon}^{x_j + \varepsilon} \rho(x) \, dx &= \sum_{i=1}^N m_i\; \Big[\lim_{\varepsilon\rightarrow 0^+}\, \int_{x_j - \varepsilon}^{x_j + \varepsilon} \delta(x-x_i) \,dx\Big]\\ &= \sum_{i=1}^N m_i\; \delta_{ij} \\ &= m_j. \end{align}\] Likewise, integrating \(\rho(x)\) over all space gives the total mass \(m_1 + m_2 + \cdots + m_N\) .


7.3: Moderation Models, Assumptions, Interpretation, and Write Up
At the end of this section you should be able to answer the following questions:
- What are some basic assumptions behind moderation?
- What are the key components of a write up of moderation analysis?
Moderation Models
Difference between Mediation & Moderation
The main difference between a simple interaction, like in ANOVA models or in moderation models, is that mediation implies that there is a causal sequence. In this case, we know that stress causes ill effects on health, so that would be the causal factor.
Some predictor variables interact in a sequence, rather than impacting the outcome variable singly or as a group (like regression).
Moderation and mediation is a form of regression that allows researchers to analyse how a third variable effects the relationship of the predictor and outcome variable.
Moderation analyses imply an interaction on the different levels of M
Would the muscle percentage be the same for young, middle-aged, and older participants after training? We know that it is harder to build muscle as we age, so would training have a lower effect on muscle growth in older people?
Example Research Question:
Does cyberbullying moderate the relationship between perceived stress and mental distress?
Moderation Assumptions
- The dependent and independent variables should be measured on a continuous scale.
- There should be a moderator variable that is a nominal variable with at least two groups.
- The variables of interest (the dependent variable and the independent and moderator variables) should have a linear relationship, which you can check with a scatterplot.
- The data must not show multicollinearity (see Multiple Regression).
- There should be no significant outliers, and the distribution of the variables should be approximately normal.
Moderation Interpretation
PowerPoint: Moderation menu, results and output
Please have a look at the following link for the Moderation Menu and Output:
Interpretation
The effects of cyberbullying can be seen in blue, with the perceived stress in green. These are the main effects of the X and M variable on the outcome variable (Y). The interaction effect can be seen in purple. This will tell us if perceived stress is effecting mental distress equally for average, lower than average or higher than average levels of cyberbullying. If this is significant, then there is a difference in that effect. As can be seen in yellow and grey, cyberbullying has an effect on mental distress, but the effect is stronger for those who report higher levels of cyberbullying (see graph).
Moderation Write Up
The following text represents a moderation write up:
A moderation test was run, with perceived stress as the predictor, mental distress as the dependant, and cyberbullying as a moderator. There was a significant main effect found between perceived stress and mental distress, b = -1.23, BCa CI [1.11, 1.34], z =21.38 , p <.001, and nonsignificant main effect of cyberbullying on mental distress b = 1.05, BCa CI [0.72, 1.38], z=6.28, p < .001. There was a significant interaction found by cyberbullying on perceived stress and mental distress, b = -0.05, BCa CI [0.01, 0.09], z=2.16, p =.031. It was found that participants who reported higher than average levels of cyberbullying experienced a greater effect of perceived stress on mental distress ( b = 1.35, BCa CI [1.19, 1.50], z=17.1, p < .001), when compared to average or lower than average levels of cyberbullying ( b = 1.23, BCa CI [1.11, 1.34], z=21.3, p < .001, b = 1.11, BCa CI [0.95, 1.27], z=13.8, p < .001, respectively). From these results, it can be concluded that the effect of perceived stress on mental distress is partially moderated by cyberbullying.


29.6A: Traumatic Brain Injury
Traumatic brain injury (TBI) occurs when an external force injures the brain and can be caused by a direct impact or by acceleration alone.
- Recognize the severity of traumatic brain injuries
Key Points
- Traumatic brain injury (TBI) occurs when an external force injures the brain and can be caused by a direct impact or by acceleration alone.
- Following the initial injury, brain trauma causes secondary events, like changes in cerebral blood flow and intracranial pressure, that contribute to the damage caused by the trauma.
- Brain injuries can be classified into mild, moderate, and severe categories; the Glasgow Coma Scale (GCS) is the most commonly used system for classifying TBI severity.
- Symptoms of TBI depend on the severity of the injury, whether the injury is diffuse or focal, and the part of the brain that is affected.

Key Terms
- Glasgow Coma Scale : (GCS) A neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment.
EXAMPLES
Examples of the causes of TBI include violence, transportation accidents, construction accidents, and sports. Examples of the symptoms of TBI include headache, nausea, dizziness, confusion, and trouble with memory, which can vary depending on the severity of the injury. Common long-term symptoms of moderate to severe TBI are changes in social behavior and cognitive changes, including problems with attention and planning.
Traumatic brain injury (TBI), also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism (closed or penetrating head injury), or other features, such as whether it occurs in a specific location or over a widespread area. Head injury usually refers to TBI, but is a broader category because it can involve damage to structures other than the brain, such as the scalp and skull.
TBI is a major cause of death and disability worldwide, especially in children and young adults. Causes include falls, vehicle accidents, and violence. Prevention measures include use of technology to protect those who suffer from automobile accidents, such as seat belts and sports or motorcycle helmets. Efforts to reduce the number of automobile accidents are also implemented, such as safety education programs and enforcement of traffic laws.
Causes of Traumatic Brain Injury
Brain trauma can be caused by a direct impact or by acceleration alone. In addition to the damage caused at the moment of injury, brain trauma causes secondary injury, a variety of events that take place in the minutes and days following the injury. These processes, which include alterations in cerebral blood flow and the pressure within the skull, contribute substantially to the damage from the initial injury.
Types of Brain Injuries
Brain injuries can be classified into mild, moderate, and severe categories. The Glasgow Coma Scale (GCS), the most commonly used system for classifying TBI severity, grades a person’s level of consciousness on a scale of 3–15 based on verbal, motor, and eye-opening reactions to stimuli. It is generally agreed that a TBI with a GCS of 13 or above is mild, 9–12 is moderate, and 8 or below is severe.
Side Effects and Complications
Subdural hematoma is a possible result of traumatic head injury : In this image, the single arrow marks spread of the subdural haematoma and the double arrow marks the midline shift.
TBI can cause a host of physical, cognitive, social, emotional, and behavioral effects, and the outcome can range from complete recovery to permanent disability or death. The 20 th century saw critical developments in diagnosis and treatment that decreased death rates and improved outcome. Some of the current imaging techniques used for diagnosis and treatment include CT scans (computed tomography) and MRIs (magnetic resonance imaging). Depending on the injury, treatment required may be minimal or may include interventions such as medications, emergency surgery or surgery years later. Physical therapy, speech therapy, recreation therapy, and occupational therapy may be employed for rehabilitation.
Complications are distinct medical problems that may arise as a result of the TBI. TBI can cause prolonged or permanent effects on consciousness, such as coma, brain death, persistent vegetative state (in which patients are unable to achieve a state of alertness to interact with their surroundings), and minimally conscious state. Lying still for long periods can cause complications including pressure sores, pneumonia or other infections, progressive multiple organ failure, and deep venous thrombosis, which can cause pulmonary embolism. Complications involving the blood vessels include vasospasm, in which vessels constrict and restrict blood flow, the formation of aneurysms, in which the side of a vessel weakens and balloons out, and stroke. Movement disorders that may develop after TBI include tremor, ataxia (uncoordinated muscle movements), myoclonus (shock-like contractions of muscles), and loss of movement range and control (in particular with a loss of movement repertoire). The risk of post-traumatic seizures increases with severity of trauma and is particularly elevated with certain types of brain trauma such as cerebral contusions or hematomas.


3.2: Experimental Design
The experiment is designed so that only one variable is tested at a time. The aspect that varies between groups is called the experimental (independent) variable . There can only be one experimental variable per experiment.
The group that receives the experimental treatment is the experimental group . For example, if the effect of aspirin on heart disease is being investigated, the experimental group is the group of individuals taking aspirin. There may be more than one experimental group within an experiment. For example, one group may take a pill containing no aspirin, another group consumes one aspirin a day, while a third group may take 2 aspirins a day.
The control group (control treatment) provides the baseline to which the experimental group will be compared. The control group is often a group that receives water or a placebo, or a group that receives the standard treatment. For example, in the aspirin study, the control group would receive a pill that looks the same as aspirin, but contains no active ingredient (a placebo).
Controlled variables are quantities that a scientist wants to remain constant between the experimental and control groups. The controlled variables insure that only one experimental variable is tested per experiment. There are usually a number of controlled variables in a single experiment. If you are examining the effect of aspirin on heart disease, controlled variables might include that all participants are adults, are the same sex, have no other health complications, similar levels of blood cholesterol, and non-smokers. Controlling these variables insures that only the experimental variable is investigated and the reliability of the data obtained is increased.
The dependent variable changes in response to experimental variable. Simply put, the dependent variable is what is measured to assess the experimental outcome.
Results must be counted or measured in some way so that discrete information can be obtained. In the aspirin example, the number of people who develop heart disease is counted as well as the age at which signs of heart disease are apparent.
The experiment should be conducted a number of times to insure that the results are real. In addition, within an experiment there should be an appropriate number of replications . An experiment designed to investigate the effects of fertilizer on plants would use many plants in each group.


3.3: Fieldwork Methods
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- Wikibooks - Cultural Anthropology
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In anthropology there are several types of fieldwork methods that are used while conducting research. Below we will go more into depth with several fieldwork methods that are used.
Observational Methods
The observational method is viewed as the least invasive method where the anthropologist minimally integrates themselves into the society they are studying and gathers data through verbal communication while attempting to remain non-intrusive of the culture.
This group of methods focuses on community interaction through language. It usually entails many open ended interviews with participants who are members of a group being studied. The researcher strives to learn as much as they can about the history of the community as well as the individuals within it in order to gain a full understanding of how their culture functions. Interviews can take place individually or with focus groups within the community based on age, status, gender, and other factors that contribute to differences within the community.
This type of research often strives to create an open dialogue, called a dialectic, in which information flows back and forth between researcher and subject. Think of this situation as a conversation between two people about homework or an upcoming exam. This dialectic poses a challenge to the objectivity of socially produced data. The challenge is dealt with through reflection on the inter-subjective creation of meaning. This leads anthropologists to value reflexive abilities in their ethnographic writing. Because many anthropologists also hope to help the communities they work with to make change on their own terms within the confines of their own culture, in some cases objectivity is abandoned in favor of community based activism and social change.
Participant Observation
Participant observation is a method for anthropological Fieldwork, used to collect data such that the anthropologist must create an intimate relationship between themselves and the culture studied. This method requires that an anthropologist participate in a social event that is part of a specific culture. This includes, but is not limited to, observing members of a culture by taking notes, eating the food that is provided, and participating in festivities. The goal of participant observation is to be involved in the culture like a member of that society, all while observing and studying the culture. An example of participation observation would be if an anthropologist went to a Native American Tribal gathering and took notes on the energy and traditions they were being shown. This anthropologist could participate in things like face painting or songs, and eat the food that the Natives eat. The information gathered in this observation is then recorded and reflected upon to gain further insight into the culture being studied. This observation method helps the anthropologist develop a deeper rapport with the people of the culture and can help others understand their culture further. This experience may result in the individuals opening up more to the anthropologist which allows them to understand more than an etic point of view of the culture.
Non-Participant Observation
In contrast to participant observation, non-participant observation is the anthropological method of collecting data by entering within a community but with limited interaction with the people within the culture. This anthropologist can be thought of as a fly on the wall. An etic approach that researchers often use to examine the details of how the subjects interact with one another and the environment around them. Detailed research such as body behavior (e.g. eye gaze, facial expression), speech styles (e.g. pitch) can be recorded through the nonparticipant method, but usually the emic approach is preferred when observing social context. An example of data collected through non-participant research would be the an estimation of how often women in a household wear high heels due to how worn out the carpet is.
The non-participant observation, although effective in providing some research, has limitations. One being, the observer affect. This is caused by the presence of the researcher having an influence over the participants' actions. The researcher may use systematic approaches of field notes, sampling and data to ensure and increase comfortable interactions. While using the non-participant observation method, the researcher's opinions may oppose that of the participant's on a certain issue. The only solution to this problem and to have a fuller and unbiased take on the research is to use both non-participant and participant method.
Ethnographic Method
Cultural data assumes the form of directly observable material items, individual behaviors, performances, ideas and arrangements that exist only in people's heads. From the perspective of the culture concept, anthropologists must first treat all these elements as symbols within a coherent system and must record observations with attention to the cultural context and the meanings assigned by the culture's practitioners. These demands are met through two major research techniques: participant observation and key informant interviewing.
After the initial orientation or entry period, which may take 3 months or longer, the researcher follows a more systematic program of formal interviews involving questions related to research hypotheses and specialized topics. Several different methods of selecting informants are possible. Usually, a few key informants are selected for in-depth sessions, since the investigation of cultural patterns usually calls for lengthy and repeated open-ended interviews. Selection of such a small number does not allow for strict assurance of a representative sample, so the anthropologist must be careful to choose subjects who are well informed and reliable. Ethnographic researchers will also train informants to systematically report cultural data and recognize significant cultural elements and interconnections as the interview sequences unfold.
Key informant selection is known as judgment sampling and is particularly important for the kind of qualitative research that characterizes ethnography. Anthropologists will very frequently also need to carry out quantitative research from which statistically validated inferences can be drawn. Accordingly, they must construct an either larger random sample or a total population census for more narrowly focused interviewing according to a closed questionnaire design. Other important quantitative data might include direct measurement of such items as farm size, crop yield, daily caloric intake, or even blood pressure, depending on the anthropologist's research focus. Aside from written observation and records, researchers will often provide ethnographic representations in other forms, such as collected artifacts, photographs, tape recordings, films, and videos.
Comparative Method
Since the beginning of anthropological studies, the Comparative Method has been a way to allow a systematic comparison of information and data from multiple sources. It is a common approach for testing multiple hypotheses on subjects including co-evolution of cultures, the adaptation of cultural practices to the environment, and kinship terms in local languages from around the world. The comparative method, may seem like an outdated form of fieldwork information gathering, however this method is still quite prevalent in modern day anthropological research. The use of this form of information gathering is intended to compare globalization, which uses a version of this method called multi-sited Ethnography by participant observation gathered from many different social settings. Another form of the comparative research method is shown through the Human Relations Area Files, which collects and organizes ethnographic texts from hundreds of societies all over the world. These files cover topics ranging from types of kinship systems, to trading practices found in all of human culture.
Anthropologists Ruth Mace--an anthropologist who specializes in evolutionary ecology--and Mark Pagel explore the comparative method of anthropological research in their article The Comparative Method in Anthropology . They explain how in the past decade there have been many expansions in other branches of anthropology, including cultural diversity as a scientific endeavor. This is when the comparative method is used by those interested in cultural evolution and by those who study other human sciences. However, "cultures cannot be treated as independent for purposes of investigating cross culture trends," therefore they must instead be studied in relation to one another: How two or more cultures grow together, or how they are researched together has the ability to outline the entire premise of the comparative method. Having been used for hundreds of years, this method is still one of the main forms of research for anthropologists all over the world.
Reflexivity
Reflexivity is the awareness of the researcher of the effect they may be having on the research. It involves a constant awareness and assessment of the researcher's own contribution to and influence on the researcher's subjects and their findings. This principle was perhaps first thought of by William Thomas, as the "Thomas Theorem". Fieldwork in cultural anthropology is a reflexive experience. Anthropologists must constantly be aware that the information they are gathering may be skewed by their ethical opinions, or political standings. Even an anthropologists' presence in that culture can affect the results they receive. Reflexive fieldwork must retain a respect for detailed, accurate information gathering while also paying precise attention to the ethical and political context of research, the background of the researchers, and the full cooperation of informants. In our everyday lives reflexivity is used to better understand ourselves by comparing our culture to others. For example, when someone talks about their religion, you may immediately disagree with specific aspects of their religion because you have not grown up believing it as they have. By being reflexive, one would be able to recognize their bias. Some anthropologists have taken this method to the extreme, Margaret Wilson, for example, wrote her book 'Dance Lest We all Fall Down' in a reflexive biographical manner; this accounted for her inability to fully integrate into Brazilian society. [2]
Intersubjectivity
Intersubjectivity is the realization that knowledge about other people emerges out of people's relationships with and perceptions of each other. The concept was first introduced by the principal founder of phenomenology, Edmund Husserl, and creates a "theoretical frame for thinking about the ways in which humans interpret, organize, and reproduce particular forms of social life and social cognition". Intersubjectivity is defined by five key principles. The first is that intersubjectivity is not limited to the concept of matching one's mental state with another’s mental state. Instead of a one-way transaction, intersubjectivity should be seen more as a type of mutual understanding. The second claim of Husserl's dissertation is that intersubjectivity is founded on the principle that we all share the same world, so that if two individuals were to "trade places", it would be present itself in the same way. Through empathetic insight, human beings achieve Platzwechsel , which is a term used in chess to mean "place exchange". The third claim is that intersubjectivity creates a synthesis of worldviews through the usage of empathy. Although there may be different perspectives in the relationship presented, the collective world is assumed to be the same through the bilateral insight of shared knowledge. The fourth claim is that intersubjectivity must precede meaningful interaction, as well as " The possibility of reflection on the self, discovery of the ego, capacity for performing any epoché, and the possibility of all communication and of establishing a communicative surrounding world as well". In other words, intersubjectivity is not the result of communication, instead it is the condition required for it to occur. Finally, the fifth claim is that intersubjectivity is the principle by which anthropologists must view their work. In order to properly create an account of a group of people, one must develop relationships with others and deduce perceptions through experience.
Participatory Action Research
This specific method requires a community commitment to change. It occurs in five steps:
- Education on the Process or Creating a Dialogue
- Collective Investigation
- Collective Interpretation
- Collective Action
- Transformation: Self-Determination and Empowerment
Because of the intrinsic qualities of this type of research (ideally being conducted by people with close ties or membership of a community), it is usually very applicable to situations in the community. The research is an analysis of the community's behavior by the community's members. Not only are they by necessity, motivated to work on the problem, but they will already have significant rapport with other community members which allows them to better address and analyze it. The dynamic attributes of the process allow constant reevaluation and change. This cyclic or regularly repeated tendencies can develop into healthy adaptation patterns in the community without outside contributions or aid.
Triangulation Method
The triangulation method is the "combination of methodologies in the study of the same phenomenon". [3] It is used to investigate a single topic through individual perspectives or multiple methodologies. It is usually the preferred way to research because it can combine all methods of researching to get the best results. It uses qualitative and quantitative practices together. The qualitative practice gives the triangulation method its inquiry results. The quantitative practice gives it the validation results. It combines a scientific approach with an observational approach. According to the Administrative Science Quarterly, it is a "vehicle for cross-validation when two or more distinct methods are found to be congruent and yield comparable data". [4] The foundation of triangulation relies on one form of research being weak and the other form stepping up to make up for it. Relying on one form of research can create a bias. The general problem with measurement data, is the individual or group being researched tends to tell you what you want to hear instead of the full truth. Triangulation helps prevent bias by giving the researcher the opportunity to participate in individual, self-reported and observational methods with those being researched. Sampling bias generally means that the researcher doesn't have time to cover the entire group they are focusing on. Or they focus on what they think the important parts of a society are and don't study the less important aspects. Triangulation can combine phone research, face-to-face interviews, and online surveys to ensure that the researcher is getting the most accurate results. In all, the triangulation method for fieldwork can combine all aspects of research to create the most accurate and detailed results, taking different perspectives and various sources to culminate into the most accurate model or a culture.


13.4: Integration of Somatic Functions
By the end of this section, you will be able to:
- Describe the pathways that sensory systems follow into the central nervous system
- Differentiate between the two major ascending pathways in the spinal cord
- Describe the pathway of somatosensory input from the face and compare it to the ascending pathways in the spinal cord
- Explain topographical representations of sensory information
Sensory Nerves
Once any sensory cell transduces a stimulus into a nerve impulse, that impulse has to travel along axons to reach the CNS. In many of the special senses, the axons leaving the sensory receptors have a topographical arrangement, meaning that the location of the sensory receptor relates to the location of the axon in the nerve. For example, in the retina, axons from RGCs in the fovea are located at the center of the optic nerve, where they are surrounded by axons from the more peripheral RGCs.
Spinal Nerves
Generally, spinal nerves contain afferent axons from sensory receptors in the periphery, such as from the skin, mixed with efferent axons travelling to the muscles or other effector organs. As the spinal nerve nears the spinal cord, it splits into dorsal and ventral roots. The dorsal root contains only the axons of sensory neurons, whereas the ventral roots contain only the axons of the motor neurons. Some of the branches will synapse with local neurons in the dorsal root ganglion, posterior (dorsal) horn, or even the anterior (ventral) horn, at the level of the spinal cord where they enter. Other branches will travel a short distance up or down the spine to interact with neurons at other levels of the spinal cord. A branch may also turn into the posterior (dorsal) column of the white matter to connect with the brain. Typically, spinal nerve systems that connect to the brain are contralateral , in that the right side of the body is connected to the left side of the brain and the left side of the body to the right side of the brain.
Cranial Nerves
Cranial nerves convey specific sensory information from the head and neck directly to the brain. For sensations below the neck, the right side of the body is connected to the left side of the brain and the left side of the body to the right side of the brain. Whereas spinal information is contralateral, cranial nerve systems are mostly ipsilateral , meaning that a cranial nerve on the right side of the head is connected to the right side of the brain. Some cranial nerves contain only sensory axons, such as the olfactory, optic, and vestibulocochlear nerves. Other cranial nerves contain both sensory and motor axons, including the trigeminal, facial, glossopharyngeal, and vagus nerves (however, the vagus nerve is not associated with the somatic nervous system). The general senses of somatosensation for the face travel through the trigeminal system.
 Of these, the optic nerve and facial nerve carry sensory information, while the others carry motor information only.
The connections of the optic nerve are more complicated than those of other cranial nerves. Instead of the connections being between each eye and the brain, visual information is segregated between the left and right sides of the visual field. In addition, some of the information from one side of the visual field projects to the opposite side of the brain. Within each eye, the axons projecting from the medial side of the retina cross at the optic chiasm and create new bundles called the optic tract which synapse onto the thalamus and extend to occipital lobes . For example, the axons from the medial retina of the left eye cross over to the right side of the brain at the optic chiasm. However, within each eye, the axons projecting from the lateral side of the retina do not cross. For example, the axons from the lateral retina of the right eye project back to the right side of the brain. Therefore the left field of view of each eye is processed on the right side of the brain, whereas the right field of view of each eye is processed on the left side of the brain (Figure \(\PageIndex{1}\)).
DISORDERS OF THE...
Vision: Bilateral hemianopia
A unique clinical presentation that relates to this anatomic arrangement is the loss of lateral peripheral vision, known as bilateral hemianopia. This is different from “tunnel vision” because the superior and inferior peripheral fields are not lost. Visual field deficits can be disturbing for a patient, but in this case, the cause is not within the visual system itself. A growth of the pituitary gland presses against the optic chiasm and interferes with signal transmission. However, the axons projecting to the same side of the brain are unaffected. Therefore, the patient loses the outermost areas of their field of vision and cannot see objects to their right and left.
Sensory Pathways
Specific regions of the CNS coordinate different somatic processes using sensory inputs and motor outputs of peripheral nerves. A simple case is a reflex caused by a synapse between a dorsal sensory neuron axon and a motor neuron in the ventral horn. More complex arrangements are possible to integrate peripheral sensory information with higher processes. The important regions of the CNS that play a role in somatic processes can be separated into the spinal cord, brainstem, diencephalon, and cerebrum (cortex and subcortical structures).
Spinal Cord and Brainstem
A sensory pathway that carries peripheral sensations to the brain is referred to as an ascending pathway , or ascending tract. Various sensory modalities follow specific pathways through the CNS. Tactile and other somatosensory stimuli activate receptors in the skin, muscles, tendons, and joints throughout the entire body. However, the somatosensory pathways are divided into two separate systems on the basis of the location of the receptor neurons. Somatosensory stimuli from below the neck pass along the sensory pathways of the spinal cord, whereas somatosensory stimuli from the head and neck travel through the cranial nerves—specifically, the trigeminal system.
The dorsal column system (sometimes referred to as the dorsal column–medial lemniscus) and the spinothalamic tract are two major pathways that bring sensory information to the brain (Figure \(\PageIndex{2}\)). The sensory pathways in each of these systems are composed of three successive neurons.
The dorsal column system begins with the axon of a dorsal root ganglion neuron entering the dorsal root and joining the dorsal column white matter in the spinal cord. As axons of this pathway enter the dorsal column, they take on a positional arrangement so that axons from lower levels of the body position themselves medially, whereas axons from upper levels of the body position themselves laterally. The dorsal column is separated into two component tracts, the fasciculus gracilis that contains axons from the legs and lower body, and the fasciculus cuneatus that contains axons from the upper body and arms.
The axons in the dorsal column terminate in the nuclei of the medulla, where each synapses with the second neuron in their respective pathway. The nucleus gracilis is the target of fibers in the fasciculus gracilis, whereas the nucleus cuneatus is the target of fibers in the fasciculus cuneatus. The second neuron in the system projects from one of the two nuclei and then decussates , or crosses the midline, in the medulla. These axons then continue to ascend the brainstem as a bundle called the medial lemniscus . These axons terminate in the thalamus, where each synapses with the third neuron in their respective pathway. The third neuron in the system projects its axons to the postcentral gyrus of the cerebral cortex, where somatosensory stimuli are initially processed and the conscious perception of the stimulus occurs.
The spinothalamic tract also begins with neurons in a dorsal root ganglion. These neurons extend their axons to the dorsal horn, where they synapse with the second neuron in their respective pathway. The name “spinothalamic” comes from this second neuron, which has its cell body in the spinal cord gray matter and connects to the thalamus. Axons from these second neurons then decussate within the spinal cord and ascend to the brain and enter the thalamus, where each synapses with the third neuron in its respective pathway. The neurons in the thalamus then project their axons to the spinothalamic tract, which synapses in the postcentral gyrus of the cerebral cortex.
These two systems are similar in that they both begin with dorsal root ganglion cells, as with most general sensory information. The dorsal column system is primarily responsible for touch sensations and proprioception, whereas the spinothalamic tract pathway is primarily responsible for pain and temperature sensations. Another similarity is that the second neurons in both of these pathways project across the midline to the other side of the brain or spinal cord, so that sensation is perceived contralaterally. In the dorsal column system, this decussation takes place in the brainstem; in the spinothalamic pathway, it takes place in the spinal cord at the same spinal cord level at which the information entered. The third neurons in the two pathways are essentially the same. In both, the second neuron synapses in the thalamus, and the thalamic neuron projects to the somatosensory cortex.
The trigeminal pathway carries somatosensory information from the face, head, mouth, and nasal cavity. As with the previously discussed nerve tracts, the sensory pathways of the trigeminal pathway each involve three successive neurons. First, axons from the trigeminal ganglion enter the brainstem at the level of the pons. These axons project to one of three locations. The spinal trigeminal nucleus of the medulla receives information similar to that carried by spinothalamic tract, such as pain and temperature sensations. Other axons go to either the chief sensory nucleus in the pons or the mesencephalic nuclei in the midbrain. These nuclei receive information like that carried by the dorsal column system, such as touch, pressure, vibration, and proprioception. Axons from the second neuron decussate and ascend to the thalamus along the trigeminothalamic tract. In the thalamus, each axon synapses with the third neuron in its respective pathway. Axons from the third neuron then project from the thalamus to the primary somatosensory cortex of the cerebrum.
The sensory pathway for gustation travels along the facial and glossopharyngeal cranial nerves, which synapse with neurons of the solitary nucleus in the brainstem. Axons from the solitary nucleus then project to the ventral posterior nucleus of the thalamus. Finally, axons from the ventral posterior nucleus project to the gustatory cortex of the cerebral cortex, where taste is processed and consciously perceived.
The sensory pathway for audition travels along the vestibulocochlear nerve, which synapses with neurons in the cochlear nuclei of the superior medulla. Within the brainstem, input from either ear is combined to extract location information from the auditory stimuli. Whereas the initial auditory stimuli received at the cochlea strictly represent the frequency—or pitch—of the stimuli, the locations of sounds can be determined by comparing information arriving at both ears. Auditory processing continues on to a nucleus in the midbrain called the inferior colliculus . Axons from the inferior colliculus project to two locations, the thalamus and the superior colliculus . The medial geniculate nucleus of the thalamus receives the auditory information and then projects that information to the auditory cortex in the temporal lobe of the cerebral cortex. The superior colliculus receives input from the visual and somatosensory systems, as well as the ears, to initiate stimulation of the muscles that turn the head and neck toward the auditory stimulus.
Balance is coordinated through the vestibular system, the nerves of which are composed of axons from the vestibular ganglion that carries information from the utricle, saccule, and semicircular canals. The system contributes to controlling head and neck movements in response to vestibular signals. An important function of the vestibular system is coordinating eye and head movements to maintain visual attention. Most of the axons terminate in the vestibular nuclei of the medulla. Some axons project from the vestibular ganglion directly to the cerebellum, with no intervening synapse in the vestibular nuclei. The cerebellum is primarily responsible for initiating movements on the basis of equilibrium information. Neurons in the vestibular nuclei project their axons to targets in the brainstem. One target is the reticular formation, which influences respiratory and cardiovascular functions in relation to body movements. A second target of the axons of neurons in the vestibular nuclei is the spinal cord, which initiates the spinal reflexes involved with posture and balance. To assist the visual system, fibers of the vestibular nuclei project to the oculomotor, trochlear, and abducens nuclei to influence signals sent along the cranial nerves.
The sensory pathway for vision starts with the optic tract. The optic tract has three major targets, two in the diencephalon and one in the midbrain. The connection between the eyes and diencephalon is demonstrated during development, in which the neural tissue of the retina differentiates from that of the diencephalon by the growth of the secondary vesicles. The connections of the retina into the CNS are a holdover from this developmental association. The majority of the connections of the optic tract are to the thalamus—specifically, the lateral geniculate nucleus . Axons from this nucleus then project to the visual cortex of the cerebrum, located in the occipital lobe. Another target of the optic tract is the superior colliculus. In addition, a very small number of retinal ganglion cells (RGCs) axons project from the optic chiasm to the suprachiasmatic nucleus of the hypothalamus. These RGCs are photosensitive, in that they respond to the presence or absence of light. Unlike the photoreceptors, however, these photosensitive RGCs cannot be used to perceive images. By simply responding to the absence or presence of light, these RGCs can send information about day length. The perceived proportion of sunlight to darkness establishes the circadian rhythm of our bodies, allowing certain physiological events to occur at approximately the same time every day.
Diencephalon
The diencephalon is beneath the cerebrum and includes the thalamus and hypothalamus. In the somatic nervous system, the thalamus is an important relay for communication between the cerebrum and the rest of the nervous system. The hypothalamus has both somatic and autonomic functions. In addition, the hypothalamus communicates with the limbic system, which controls emotions and memory functions.
Sensory input to the thalamus comes from most of the special senses and ascending somatosensory tracts. Each sensory system is relayed through a particular nucleus in the thalamus. The thalamus is a required transfer point for most sensory tracts that reach the cerebral cortex, where conscious sensory perception begins. The one exception to this rule is the olfactory system. The olfactory tract axons from the olfactory bulb project directly to the cerebral cortex, along with the limbic system and hypothalamus.
The thalamus is a collection of several nuclei that can be categorized into three anatomical groups. White matter running through the thalamus defines the three major regions of the thalamus, which are an anterior nucleus , a medial nucleus , and a lateral group of nuclei . The anterior nucleus serves as a relay between the hypothalamus and the emotion and memory-producing limbic system. The medial nuclei serve as a relay for information from the limbic system and basal ganglia to the cerebral cortex. This allows memory creation during learning, but also determines alertness. The special and somatic senses connect to the lateral nuclei, where their information is relayed to the appropriate sensory cortex of the cerebrum.
Cerebrum
As described earlier, many of the sensory axons are positioned in the same way as their corresponding receptor cells in the body. This allows identification of the position of a stimulus on the basis of which receptor cells are sending information. The cerebral cortex also maintains this sensory topography in the particular areas of the cortex that correspond to the position of the receptor cells. This mapping is often depicted using a sensory homunculus.
Likewise, the topographic relationship between the retina and the visual cortex is maintained throughout the visual pathway. The visual field is projected onto the two retinae, as described above, with sorting at the optic chiasm. The right peripheral visual field falls on the medial portion of the right retina and the lateral portion of the left retina. The right medial retina then projects across the midline through the optic chiasm. This results in the right visual field being processed in the left visual cortex. Likewise, the left visual field is processed in the right visual cortex. Though the chiasm is helping to sort right and left visual information, superior and inferior visual information is maintained topographically in the visual pathway. Light from the superior visual field falls on the inferior retina, and light from the inferior visual field falls on the superior retina. This topography is maintained such that the superior region of the visual cortex processes the inferior visual field and vice versa. Therefore, the visual field information is inverted and reversed as it enters the visual cortex—up is down, and left is right (Figure \(\PageIndex{3}\)). However, the cortex processes the visual information such that the final conscious perception of the visual field is correct. The topographic relationship is evident in that information from the foveal region of the retina is processed in the center of the primary visual cortex. Information from the peripheral regions of the retina are correspondingly processed toward the edges of the visual cortex. Similar to the exaggerations in the sensory homunculus of the somatosensory cortex, the foveal-processing area of the visual cortex is disproportionately larger than the areas processing peripheral vision.
In an experiment performed in the 1960s, subjects wore prism glasses so that the visual field was inverted before reaching the eye. On the first day of the experiment, subjects would duck when walking up to a table, thinking it was suspended from the ceiling. However, after a few days of acclimation, the subjects behaved as if everything were represented correctly. Therefore, the visual cortex is somewhat flexible in adapting to the information it receives from our eyes.
The cortex has been described as having specific regions that are responsible for processing specific information; there is the visual cortex, somatosensory cortex, gustatory cortex, etc. However, our experience of these senses is not divided. Instead, we experience what can be referred to as a seamless percept. Our perceptions of the various sensory modalities—though distinct in their content—are integrated by the brain so that we experience the world as a continuous whole.
In the cerebral cortex, sensory processing begins at the primary sensory cortex , then proceeds to an association area , and finally, into a multimodal integration area . For example, the visual pathway projects from the retinae through the thalamus to the primary visual cortex in the occipital lobe. This area is primarily in the medial wall within the longitudinal fissure. Here, visual stimuli begin to be recognized as basic shapes. Edges of objects are recognized and built into more complex shapes. Also, inputs from both eyes are compared to extract depth information. Because of the overlapping field of view between the two eyes, the brain can begin to estimate the distance of stimuli based on binocular depth cues .
Concept Review
The nerves that convey sensory information from the periphery to the CNS are either spinal nerves, connected to the spinal cord, or cranial nerves, connected to the brain. Spinal nerves have mixed populations of fibers; some are motor fibers and some are sensory. The sensory fibers connect to the spinal cord through the dorsal root, which is attached to the dorsal root ganglion. Sensory information from the body that is conveyed through spinal nerves will project to the opposite side of the brain to be processed by the cerebral cortex. The cranial nerves can be strictly sensory fibers, such as the olfactory, optic, and vestibulocochlear nerves, or mixed sensory and motor nerves, such as the trigeminal, facial, glossopharyngeal, and vagus nerves. The cranial nerves are connected to the same side of the brain from which the sensory information originates.
Sensory input to the brain enters through pathways that travel through either the spinal cord (for somatosensory input from the body) or the brainstem (for everything else, except the visual and olfactory systems) to reach the diencephalon. In the diencephalon, sensory pathways reach the thalamus. This is necessary for all sensory systems to reach the cerebral cortex, except for the olfactory system that is directly connected to the frontal and temporal lobes.
The two major tracts in the spinal cord, originating from sensory neurons in the dorsal root ganglia, are the dorsal column system and the spinothalamic tract. The major differences between the two are in the type of information that is relayed to the brain and where the tracts decussate. The dorsal column system primarily carries information about touch and proprioception and crosses the midline in the medulla. The spinothalamic tract is primarily responsible for pain and temperature sensation and crosses the midline in the spinal cord at the level at which it enters. The trigeminal nerve adds similar sensation information from the head to these pathways.
The auditory pathway passes through multiple nuclei in the brainstem in which additional information is extracted from the basic frequency stimuli processed by the cochlea. Sound localization is made possible through the activity of these brainstem structures. The vestibular system enters the brainstem and influences activity in the cerebellum, spinal cord, and cerebral cortex.
The visual pathway segregates information from the two eyes so that one half of the visual field projects to the other side of the brain. Within visual cortical areas, the perception of the stimuli and their location is passed along two streams, one ventral and one dorsal. The ventral visual stream connects to structures in the temporal lobe that are important for long-term memory formation. The dorsal visual stream interacts with the somatosensory cortex in the parietal lobe, and together they can influence the activity in the frontal lobe to generate movements of the body in relation to visual information.
Review Questions
Q. Which of these sensory modalities does not pass through the ventral posterior thalamus?
A. gustatory
B. proprioception
C. audition
D. nociception
- Answer
-
C
Q. Which nucleus in the medulla is connected to the inferior colliculus?
A. solitary nucleus
B. vestibular nucleus
C. chief sensory nucleus
D. cochlear nucleus
- Answer
-
D
Q. Visual stimuli in the upper-left visual field will be processed in what region of the primary visual cortex?
A. inferior right
B. inferior left
C. superior right
D. superior left
- Answer
-
A
Q. Which of the following is a direct target of the vestibular ganglion?
A. superior colliculus
B. cerebellum
C. thalamus
D. optic chiasm
- Answer
-
B
Critical Thinking Questions
Q. Following a motorcycle accident, the victim loses the ability to move the right leg but has normal control over the left one, suggesting a hemisection somewhere in the thoracic region of the spinal cord. What sensory deficits would be expected in terms of touch versus pain? Explain your answer.
A. The right leg would feel painful stimuli, but not touch, because the spinothalamic tract decussates at the level of entry, which would be below the injury, whereas the dorsal column system does not decussate until reaching the brainstem, which would be above the injury and thus those fibers would be damaged.
Q. A pituitary tumor can cause perceptual losses in the lateral visual field. The pituitary gland is located directly inferior to the hypothalamus. Why would this happen?
A. As the tumor enlarges, it would press against the optic chiasm, and fibers from the medial retina would be disrupted. These fibers carry information about the lateral visual field because the visual scene is reversed as the light passes through the pupil and lens.
Glossary
- anterior nucleus
- collection of nuclei of the anterior region of the thalamus
- ascending pathway
- fiber structure that relays sensory information from the periphery through the spinal cord and brainstem to other structures of the brain
- association area
- region of cortex connected to a primary sensory cortical area that further processes the information to generate more complex sensory perceptions
- binocular depth cues
- indications of the distance of visual stimuli on the basis of slight differences in the images projected onto either retina
- chief sensory nucleus
- component of the trigeminal nuclei that is found in the pons
- circadian rhythm
- internal perception of the daily cycle of light and dark based on retinal activity related to sunlight
- cochlear nuclei
- nuclei that receive first-order auditory input from the organ of Corti in the cochlea of the inner ear
- contralateral
- word meaning “on the opposite side,” as in axons that cross the midline in a fiber tract
- decussate
- to cross the midline, as in fibers that project from one side of the body to the other
- dorsal column system
- ascending tract of the spinal cord associated with fine touch and proprioceptive sensations
- fasciculus cuneatus
- lateral division of the dorsal column system composed of fibers from sensory neurons in the upper body
- fasciculus gracilis
- medial division of the dorsal column system composed of fibers from sensory neurons in the lower body
- hypothalamus
- major region of the diencephalon that is responsible for coordinating autonomic and endocrine control of homeostasis
- inferior colliculus
- last structure in the auditory brainstem pathway that projects to the thalamus and superior colliculus
- ipsilateral
- word meaning on the same side, as in axons that do not cross the midline in a fiber tract
- lateral geniculate nucleus
- thalamic target of the RGCs that projects to the visual cortex
- lateral group of nuclei
- collection of nuclei of the lateral region of the thalamus
- medial geniculate nucleus
- thalamic target of the auditory brainstem that projects to the auditory cortex
- medial lemniscus
- fiber tract of the dorsal column system that extends from the nuclei gracilis and cuneatus to the thalamus, and decussates
- medial nucleus
- collection of nuclei of the medial region of the thalamus
- mesencephalic nucleus
- component of the trigeminal nuclei that is found in the midbrain
- multimodal integration area
- region of the cerebral cortex in which information from more than one sensory modality is processed to arrive at higher level cortical functions such as memory, learning, or cognition
- nucleus cuneatus
- medullary nucleus at which first-order neurons of the dorsal column system synapse specifically from the upper body and arms
- nucleus gracilis
- medullary nucleus at which first-order neurons of the dorsal column system synapse specifically from the lower body and legs
- optic chiasm
- decussation point in the visual system at which medial retina fibers cross to the other side of the brain
- optic tract
- name for the fiber structure containing axons from the retina posterior to the optic chiasm representing their CNS location
- primary sensory cortex
- region of the cerebral cortex that initially receives sensory input from an ascending pathway from the thalamus and begins the processing that will result in conscious perception of that modality
- solitary nucleus
- medullar nucleus that receives taste information from the facial and glossopharyngeal nerves
- spinal nerve
- one of 31 nerves connected to the spinal cord
- spinal trigeminal nucleus
- component of the trigeminal nuclei that is found in the medulla
- spinothalamic tract
- ascending tract of the spinal cord associated with pain and temperature sensations
- superior colliculus
- structure in the midbrain that combines visual, auditory, and somatosensory input to coordinate spatial and topographic representations of the three sensory systems
- suprachiasmatic nucleus
- hypothalamic target of the retina that helps to establish the circadian rhythm of the body on the basis of the presence or absence of daylight
- thalamus
- major region of the diencephalon that is responsible for relaying information between the cerebrum and the hindbrain, spinal cord, and periphery
- topographical
- relating to positional information
- ventral posterior nucleus
- nucleus in the thalamus that is the target of gustatory sensations and projects to the cerebral cortex
- vestibular nuclei
- targets of the vestibular component of the eighth cranial nerve
Contributors and Attributions
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OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology


4.5: Absolute-Value Functions
To graph absolute-value functions, choose small values of \(x\), and compute the value of \(f(x)\) from the given function to create ordered pairs. Three ordered pairs is the minimum amount needed to graph an absolute value function. Be careful, because one ordered pair must represent the vertex, the point where the left and right sides of the function meet. To correctly graph the shape of the absolute-value function, the vertex must be found.
\(f(x) = a\vert x − h\vert+ k\) General Form of an Absolute-Value Function, with vertex \((h,k)\)
- \(a\) determines both the width and the orientation (facing up or down) of the function.
- \(h\) is the horizontal shift from the origin.
- \(k\) is the vertical shift from the origin.
Start by identifying the ordered pair of the vertex, and then find one ordered pair to the left of the origin, and to the right of the origin. Choose an x-value one unit to the left of the x-value of the origin, calculate \(f(x)\) and then choose an x-value one unit to the right of the x-value of the origin and calculate \(f(x)\). The graph will resemble a \(V\), either facing upward or downward, depending on the sign of \(a\).
Create a table of solutions and graph the following absolute-value function:
\(f(x) = \vert x − 4\vert\)
Solution
Comparing this function to the general form for absolute-value functions (shown above), \(a = 1\), \(h = 4\), \(k = 0\). The vertex is \((h, k)\) or \((4, 0)\).
To find two more ordered pairs, choose \(x = 3\) and \(x = 5\), then compute values of \(f(x)\).
| \(x\) | \(f(x)\) |
|---|---|
| 3 | \(f(3) = \vert 3 − 4\vert = \vert − 1\vert = 1\) |
| 4 | \(f(4) = \vert 4 − 4\vert = \vert 0\vert = 0\) |
| 5 | \(f(5) = \vert 5 − 4\vert = \vert 1\vert = 1\) |
Create a table of solutions and graph the following absolute-value function:
\(g(x) = \vert x + 2\vert − 5\)
Solution
Comparing this function to the general form for absolute-value functions (shown above), \(a = 1\), \(h = −2\), \(k = −5\). The vertex is (h, k)\) or \((−2, −5)\).
To find two more ordered pairs, choose \(x = −3\) and \(x = −1\), then compute values of \(g(x)\)
| Table of Solutions for \(g(x) = \vert x + 2\vert − 5\) | |
| \(x\) | \(g(x)\) |
| -3 | \(g(−3) = \vert − 3 + 2\vert − 5 = \vert − 1\vert − 5 = 1 − 5 = −4\) |
| -2 | \(g(−2) = \vert − 2 + 2\vert − 5 = \vert 0\vert − 5 = 0 − 5 = −5\) |
| -1 | \(g(−1) = \vert − 1 + 2\vert − 5 = \vert 1\vert − 5 = 1 − 5 = −4\) |
Create a table of solutions and graph the following absolute-value function:
\(h(x) = 3\vert x − 5\vert + 1\)
Solution
Comparing this function to the general form for absolute-value functions (shown above), \(a = 3\), \(h = 5\), \(k = 1\). The vertex is \((h, k)\) or \((5, 1)\).
To find two more ordered pairs, choose \(x = 4\) and \(x = 6\), then compute values of \(h(x)\).
| Table of Solutions for \(h(x) = 3\vert x − 5\vert + 1\) | |
| \(x\) | \(h(x)\) |
| 4 | \(g(−3) = \vert − 3 + 2\vert − 5 = \vert − 1\vert − 5 = 1 − 5 = −4\) |
| 5 | \(g(−2) = \vert − 2 + 2\vert − 5 = \vert 0\vert − 5 = 0 − 5 = −5\) |
| 6 | \(g(−1) = \vert − 1 + 2\vert − 5 = \vert 1\vert − 5 = 1 − 5 = −4\) |
Create a table of solutions and graph the following absolute-value function:
\(h(x) = \dfrac{1}{2} \vert x − 2\vert + 3\)
Solution
Comparing this function to the general form for absolute-value functions (shown above), \(a = \dfrac{1}{2} \), \(h = 2\), \(k = 3\). The vertex is \((h, k)\) or \((2, 3)\).
To find two more ordered pairs, choose \(x = 1\) and \(x = 3\), then compute values of \(h(x)\).
| Table of Solutions for \(h(x) = \dfrac{1}{2} \vert x − 2\vert + 3\) | |
| \(x\) | \(h(x)\) |
| 1 | \(h(1) = \dfrac{1}{2} \vert 1 − 2\vert + 3 = \dfrac{1}{2} \vert − 1\vert + 3 = \dfrac{1}{2} (1) + 3 = 3\dfrac{1}{2}\) |
| 2 | \(h(2) = \dfrac{1}{2} \vert 2 − 2\vert + 3 = \dfrac{1}{2} \vert 0\vert + 3 = 0 + 3 = 3\) |
| 3 | \(h(3) = \dfrac{1}{2} \vert 3 − 2\vert + 3 = \dfrac{1}{2} \vert 1\vert + 3 = \dfrac{1}{2} (1) + 3 = 3\dfrac{1}{2}\) |
Create a table of solutions and graph the following absolute-value functions:
- \(f(x) = \vert x + 6\vert\)
- \(g(x) = \dfrac{1}{3} \vert x − 3\vert + 5\)
- \(h(x) = 4\vert x + 2\vert + 2\)
- \(f(x) = \vert x − 1\vert − 5\)


5.1: What Law Is International Law?
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It is this depiction of international law that often culminated in the question of whether international law was really law. How could international legal norms be effective if their validity depended on the will of states, the very subjects international law should govern? This doubt in the validity and effectiveness of international law ultimately led to a rupture between the two disciplines of international law and international relations theory after the Second World War. Two scholars, Edward Hallett Carr and Hans Morgenthau, suggested around this time that international law was particularly inept for understanding the behaviour of nations. They were disappointed by what they identified as an idealistic belief in international law which, after all, had not prevented – for the second time – a world war. They proposed instead a more ‘realistic’ assessment of international relations based on power and interest. The founding realist school of international relations theory thus questioned the effectiveness and relevance of international law as a decisive influencing factor for the behaviour of states and for the assurance of international peace and security.
Much has changed since then. The international legal order has diversified in every possible way. There are countless bilateral and multilateral contracts between states (called treaties or conventions in international law), and more than 5,000 intergovernmental organisations and their different organs engage in the regulation and administration of nearly all aspects of international life.
International legal norms pervade global affairs. Every time you travel internationally, send an email, or update your social media profiles, there are not only domestic but supranational legal norms at play, including regional norms as in the European Union. Be it border control, diplomatic and consular relations between countries, the determination of flight and navigation routes, internet regulation, privacy, the use of postal and telecommunication services, industrial standards or cross-border environmental hazards – international law permeates these areas as much as the better-known fields of the protection of human rights, humanitarian interventions and the fight against transnational terrorism.
It is important to understand, then, that the question of whether and how international law matters depends not least on one’s conceptual outlook on international life. This chapter introduces you foremost to the (traditional ‘occidental’ or ‘Western’) normative understanding of international law in order to show you how international lawyers think and how they use international law. This implies a focus on valid legal rules that authoritatively regulate international life. Yet the understanding of international law as a system of legal norms is not the only possible approach, nor is it the solely valid one. In fact, there are numerous other approaches that complement the normative outlook on global law (Walker 2014). It is also important that the occidental depiction of international law is not the only one existing in the world. Scholars from outside the West have shown, for example, how the dominant view of international law neglects important and often earlier contributions to international law by other cultures. Asian, African and Latin American countries should form part of our understanding of international law. For example, international treaties existed already in Africa and Asia over three thousand years ago. Islamic legal thought, present in Persia, India, South Asia and Europe, also had legal regulations of how to conduct hostilities at least since the seventh century. There is not one single conception of international law or international politics.
By focusing on the normative understanding of international law, the chapter takes a modest approach and steers a middle ground. There are also conceptualisations that portray international law as a cosmopolitan order securing solidarity and peace in a ‘post-Westphalian’ world in which states have largely lost their status as sole sovereigns. On the other hand, there are theories that continue to question the social effectiveness and relevance of international legal norms to shape the behaviour of international actors. In addition, one can also analyse international law through empirical research that uses collected data about the social behaviour of actors as it is done, for example, to scrutinise the effectiveness of human rights norms. Yet, a purely empirical analysis has difficulty in conveying the idiosyncrasy of normative thinking and argumentation in international law. Even if collected data shows instances of non-compliance with human rights norms, it would be wrong to draw conclusions from this about the binding character or range of social effects of these norms.
International lawyers as a particular group of professionals learn techniques to determine which legal norms exist and which are applicable to the relevant actors in a certain situation. Lawyers speak of the sources and subjects of law. They learn how to apply these norms using specific techniques, such as interpretation or the balancing of conflicting rights. These professional techniques are not value-neutral or objective but involve subjective choices and politics. An approximation to objectivity and ideals of justice is achieved only through specific procedures that need to be followed, recognised modes of argumentation and particular processes of decision-making. In a nutshell, international law consists of certain conventions on argumentation and modes of conflict resolution that some regard as a craft, others as an art. Most likely it is both.


10.4: Driving and Resisting Forces
IDENTIFY AND INTERPRET DRIVING AND RESISTING FORCES ON VARIOUS SLOPES COMPOSED OF VARIOUS GEOLOGIC MATERIALS, INCLUDING GEOLOGIC AND HUMAN CAUSED CHANGES THAT CAN INCREASE OR REDUCE MASS MOVEMENT.
[Insert brief introductory statement here.]
Open Educational Resources
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- Reading: Landslide Types and Processes
Contributors and Attributions
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Original content from Kimberly Schulte (Columbia Basin College) and supplemented by Lumen Learning . The content on this page is copyrighted under a Creative Commons Attribution 4.0 International license.