8.3: The "Long-Haired" Comets
Learning Objectives
By the end of this section, you will be able to:
- Characterize the general physical appearance of comets
- Explain the range of cometary orbits
- Describe the size and composition of a typical comet’s nucleus
- Discuss the atmospheres of comets
- Summarize the discoveries of the Rosetta mission
Comets differ from asteroids primarily in their icy composition, a difference that causes them to brighten dramatically as they approach the Sun, forming a temporary atmosphere. In some early cultures, these so-called “hairy stars” were considered omens of disaster. Today, we no longer fear comets, but eagerly anticipate those that come close enough to us to put on a good sky show.
Appearance of Comets
A comet is a relatively small chunk of icy material (typically a few kilometers across) that develops an atmosphere as it approaches the Sun. Later, there may be a very faint, nebulous tail, extending several million kilometers away from the main body of the comet. Comets have been observed from the earliest times: accounts of comets are found in the histories of virtually all ancient civilizations. The typical comet, however, is not spectacular in our skies, instead having the appearance of a rather faint, diffuse spot of light somewhat smaller than the Moon and many times less brilliant. (Comets seemed more spectacular to people before the invention of artificial lighting, which compromises our view of the night sky.)
Like the Moon and planets, comets appear to wander among the stars, slowly shifting their positions in the sky from night to night. Unlike the planets, however, most comets appear at unpredictable times, which perhaps explain why they frequently inspired fear and superstition in earlier times. Comets typically remain visible for periods that vary from a couple of weeks to several months. We’ll say more about what they are made of and how they become visible after we discuss their motions.
 Looking only at such images, it is easy to confuse comets and meteors. But seen in the real sky, they are very different: the meteor burns up in our atmosphere and is gone in a few seconds, whereas the comet may be visible for weeks in nearly the same part of the sky.
Comet Orbits
The study of comets as members of the solar system dates from the time of Isaac Newton, who first suggested that they orbited the Sun on extremely elongated ellipses. Newton’s colleague Edmund Halley (see the Note feature box) developed these ideas, and in 1705, he published calculations of 24 comet orbits. In particular, he noted that the orbits of the bright comets that had appeared in the years 1531, 1607, and 1682 were so similar that the three could well be the same comet, returning to perihelion (closest approach to the Sun) at average intervals of 76 years. If so, he predicted that the object should next return about 1758. Although Halley had died by the time the comet appeared as he predicted, it was given the name Comet Halley (rhymes with “valley”) in honor of the astronomer who first recognized it as a permanent member of our solar system, orbiting around the Sun. Its aphelion (furthest point from the Sun) is beyond the orbit of Neptune.
We now know from historical records that Comet Halley has actually been observed and recorded on every passage near the Sun since 239 BCE at intervals ranging from 74 to 79 years. The period of its return varies somewhat because of orbital changes produced by the pull of the giant planets. In 1910, Earth was brushed by the comet’s tail, causing much needless public concern. Comet Halley last appeared in our skies in 1986 (Figure \(\PageIndex{1}\)), when it was met by several spacecraft that gave us a wealth of information about its makeup; it will return in 2061.
EDMUND HALLEY: ASTRONOMY’S RENAISSANCE MAN
Edmund Halley (Figure \(\PageIndex{2}\)), a brilliant astronomer who made contributions in many fields of science and statistics, was by all accounts a generous, warm, and outgoing person. In this, he was quite the opposite of his good friend Isaac Newton, whose great work, the Principia (see Orbits and Gravity), Halley encouraged, edited, and helped pay to publish. Halley himself published his first scientific paper at age 20, while still in college. As a result, he was given a royal commission to go to Saint Helena (a remote island off the coast of Africa where Napoleon would later be exiled) to make the first telescopic survey of the southern sky. After returning, he received the equivalent of a master’s degree and was elected to the prestigious Royal Society in England, all at the age of 22.
In addition to his work on comets, Halley was the first astronomer to recognize that the so-called “fixed” stars move relative to each other, by noting that several bright stars had changed their positions since Ptolemy’s publication of the ancient Greek catalogs. He wrote a paper on the possibility of an infinite universe, proposed that some stars may be variable, and discussed the nature and size of nebulae (glowing cloudlike structures visible in telescopes). While in Saint Helena, Halley observed the planet Mercury going across the face of the Sun and developed the mathematics of how such transits could be used to establish the size of the solar system.
In other fields, Halley published the first table of human life expectancies (the precursor of life-insurance statistics); wrote papers on monsoons, trade winds, and tides (charting the tides in the English Channel for the first time); laid the foundations for the systematic study of Earth’s magnetic field; studied evaporation and how inland waters become salty; and even designed an underwater diving bell. He served as a British diplomat, advising the emperor of Austria and squiring the future czar of Russia around England (avidly discussing, we are told, both the importance of science and the quality of local brandy).
In 1703, Halley became a professor of geometry at Oxford, and in 1720, he was appointed Astronomer Royal of England. He continued observing Earth and the sky and publishing his ideas for another 20 years, until death claimed him at age 85.
Only a few comets return in a time measureable in human terms (shorter than a century), like Comet Halley does; these are called short-period comets. Many short-period comets have had their orbits changed by coming too close to one of the giant planets—most often Jupiter (and they are thus sometimes called Jupiter-family comets). Most comets have long periods and will take thousands of years to return, if they return at all. As we will see later in this chapter, most Jupiter-family comets come from a different source than the long-period comets (those with orbital periods longer than about a century).
Observational records exist for thousands of comets. We were visited by two bright comets in recent decades. First, in March 1996, came Comet Hyakutake, with a very long tail. A year later, Comet Hale-Bopp appeared; it was as bright as the brightest stars and remained visible for several weeks, even in urban areas (see the image that opens this chapter, \(\PageIndex{1}\)).
Table \(\PageIndex{1}\) lists some well-known comets whose history or appearance is of special interest.
| Name | Period | Significance |
|---|---|---|
| Great Comet of 1577 | Long | Tycho Brahe showed it was beyond the Moon (a big step in our understanding) |
| Great Comet of 1843 | Long | Brightest recorded comet; visible in daytime |
| Daylight Comet of 1910 | Long | Brightest comet of the twentieth century |
| West | Long | Nucleus broke into pieces (1976) |
| Hyakutake | Long | Passed within 15 million km of Earth (1996) |
| Hale–Bopp | Long | Brightest recent comet (1997) |
| Swift-Tuttle | 133 years | Parent comet of Perseid meteor shower |
| Halley | 76 years | First comet found to be periodic; explored by spacecraft in 1986 |
| Borrelly | 6.8 years | Flyby by Deep Space 1 spacecraft (2000) |
| Biela | 6.7 years | Broke up in 1846 and not seen again |
| Churyumov-Gerasimenko | 6.5 years | Target of Rosetta mission (2014–16) |
| Wild 2 | 6.4 years | Target of Stardust sample return mission (2004) |
| Tempel 1 | 5.7 years | Target of Deep Impact mission (2005) |
| Encke | 3.3 years | Shortest known period |
The Comet’s Nucleus
When we look at an active comet, all we normally see is its temporary atmosphere of gas and dust illuminated by sunlight. This atmosphere is called the comet’s head or coma . Since the gravity of such small bodies is very weak, the atmosphere is rapidly escaping all the time; it must be replenished by new material, which has to come from somewhere. The source is the small, solid nucleus inside, just a few kilometers across, usually hidden by the glow from the much-larger atmosphere surrounding it. The nucleus is the real comet, the fragment of ancient icy material responsible for the atmosphere and the tail (Figure \(\PageIndex{3}\)).
The modern theory of the physical and chemical nature of comets was first proposed by Harvard astronomer Fred Whipple in 1950. Before Whipple’s work, many astronomers thought that a comet’s nucleus might be a loose aggregation of solids, sort of an orbiting “gravel bank,” Whipple proposed instead that the nucleus is a solid object a few kilometers across, composed in substantial part of water ice (but with other ices as well) mixed with silicate grains and dust. This proposal became known as the “dirty snowball” model.
The water vapor and other volatiles that escape from the nucleus when it is heated can be detected in the comet’s head and tail, and therefore, we can use spectra to analyze what atoms and molecules the nucleus ice consists of. However, we are somewhat less certain of the non-icy component. We have never identified a fragment of solid matter from a comet that has survived passage through Earth’s atmosphere. However, spacecraft that have approached comets have carried dust detectors, and some comet dust has even been returned to Earth (Figure \(\PageIndex{4}\)). It seems that much of the “dirt” in the dirty snowball is dark, primitive hydrocarbons and silicates, rather like the material thought to be present on the dark, primitive asteroids.
Since the nuclei of comets are small and dark, they are difficult to study from Earth. Spacecraft did obtain direct measurements of a comet nucleus, however, in 1986, when three spacecraft swept past Comet Halley at close range (Figure \(\PageIndex{5}\)). Subsequently, other spacecraft have flown close to other comets. In 2005, the NASA Deep Impact spacecraft even carried a probe for a high-speed impact with the nucleus of Comet Tempel 1. But by far, the most productive study of a comet has been by the 2015 Rosetta mission, which we will discuss shortly.
The Comet’s Atmosphere
The spectacular activity that allows us to see comets is caused by the evaporation of cometary ices heated by sunlight. Beyond the asteroid belt, where comets spend most of their time, these ices are solidly frozen. But as a comet approaches the Sun, it begins to warm up. If water (H 2 O) is the dominant ice, significant quantities vaporize as sunlight heats the surface above 200 K. This happens for the typical comet somewhat beyond the orbit of Mars. The evaporating H 2 O in turn releases the dust that was mixed with the ice. Since the comet’s nucleus is so small, its gravity cannot hold back either the gas or the dust, both of which flow away into space at speeds of about 1 kilometer per second.
The comet continues to absorb energy as it approaches the Sun. A great deal of this energy goes into the evaporation of its ice, as well as into heating the surface. However, recent observations of many comets indicate that the evaporation is not uniform and that most of the gas is released in sudden spurts, perhaps confined to a few areas of the surface. Expanding into space at a speed of about 1 kilometer per second, the comet’s atmosphere can reach an enormous size. The diameter of a comet’s head is often as large as Jupiter, and it can sometimes approach a diameter of a million kilometers (Figure \(\PageIndex{6}\)).
Most comets also develop tails as they approach the Sun. A comet’s tail is an extension of its atmosphere, consisting of the same gas and dust that make up its head. As early as the sixteenth century, observers realized that comet tails always point away from the Sun (Figure \(\PageIndex{7}\)), not back along the comet’s orbit. Newton proposed that comet tails are formed by a repulsive force of sunlight driving particles away from the head—an idea close to our modern view.
The two different components that make up the tail (the dust and gas) act somewhat differently. The brightest part of the tail is called the dust tail , to differentiate it from a fainter, straight tail made of ionized gas, called the ion tail. The ion tail is carried outward by streams of ions (charged particles) emitted by the Sun. As you can see in Figure \(\PageIndex{8}\), the smoother dust tail curves a bit, as individual dust particles spread out along the comet’s orbit, whereas the straight ion is tail pushed more directly outward from the Sun by our star’s wind of charged particles
These days, comets close to the Sun can be found with spacecraft designed to observe our star. For example, in early July, 2011, astronomers at the ESA/NASA’s Solar and Heliospheric Observatory (SOHO) witnessed a comet streaking toward the Sun, one of almost 3000 such sightings. You can also watch a brief video by NASA entitled “Why Are We Seeing So Many Sungrazing Comets?”
The Rosetta Comet Mission
In the 1990s, European scientists decided to design a much more ambitious mission that would match orbits with an incoming comet and follow it as it approached the Sun. They also proposed that a smaller spacecraft would actually try to land on the comet. The 2-ton main spacecraft was named Rosetta , carrying a dozen scientific instruments, and its 100-kilogram lander with nine more instruments was named Philae .
The Rosetta mission was launched in 2004. Delays with the launch rocket caused it to miss its original target comet, so an alternate destination was picked, Comet Churyumov-Gerasimenko (named after the two discoverers, but generally denoted 67P). This comet’s period of revolution is 6.45 years, making it a Jupiter-family comet.
Since the European Space Agency did not have access to the plutonium-fueled nuclear power sources used by NASA for deep space missions, Rosetta had to be solar powered, requiring especially large solar panels. Even these were not enough to keep the craft operating as it matched orbits with 67P near the comet’s aphelion. The only solution was to turn off all the spacecraft systems and let it coast for several years toward the Sun, out of contact with controllers on Earth until solar energy was stronger. The success of the mission depended on an automatic timer to turn the power back on as it neared the Sun. Fortunately, this strategy worked.
In August 2014, Rosetta began a gradual approach to the comet nucleus, which is a strangely misshapen object about 5 kilometers across, quite different from the smooth appearance of Halley’s nucleus (but equally dark). Its rotation period is 12 hours. On November 12, 2014, the Philae lander was dropped, descending slowly for 7 hours before gently hitting the surface. It bounced and rolled, coming to rest under an overhang where there was not enough sunlight to keep its batteries charged. After operating for a few hours and sending data back to the orbiter, Philae went silent. The main Rosetta spacecraft continued operations, however, as the level of comet activity increased, with steamers of gas jetting from the surface. As the comet approached perihelion in September 2015, the spacecraft backed off to ensure its safety.
The extent of the Rosetta images (and data from other instruments) far exceeds anything astronomers had seen before from a comet. The best imaging resolution was nearly a factor of 100 greater than in the best Halley images. At this scale, the comet appears surprisingly rough, with sharp angles, deep pits, and overhangs (Figure \(\PageIndex{9}\)).
The double-lobed shape of 67P’s nucleus has been tentatively attributed to the collision and merger of two independent comet nuclei long ago. The spacecraft verified that the comet’s dark surface was covered with organic carbon-rich compounds, mixed with sulfides and iron-nickel grains. 67P has an average density of only 0.5 g/cm 3 (recall water in these units has a density of 1 g/cm 3 .) This low density indicates that the comet is quite porous, that is, there is a large amount of empty space among its materials.
We already knew that the evaporation of comet ices was sporadic and limited to small jets, but in comet 67P, this was carried to an extreme. At any one time, more than 99% of the surface is inactive. The active vents are only a few meters across, with the material confined to narrow jets that persist for just a few minutes (Figure). The level of activity is strongly dependent on solar heating, and between July and August 2015, it increased by a factor of 10. Isotopic analysis of deuterium in the water ejected by the comet shows that it is different from the water found on Earth. Thus, apparently comets like 67P did not contribute to the origin of our oceans or the water in our bodies, as some scientists had thought.
Key Concepts and Summary
Halley first showed that some comets are on closed orbits and return periodically to swing around the Sun. The heart of a comet is its nucleus, a few kilometers in diameter and composed of volatiles (primarily frozen H 2 O) and solids (including both silicates and carbonaceous materials). Whipple first suggested this “dirty snowball” model in 1950; it has been confirmed by spacecraft studies of several comets. As the nucleus approaches the Sun, its volatiles evaporate (perhaps in localized jets or explosions) to form the comet’s head or atmosphere, which escapes at about 1 kilometer per second. The atmosphere streams away from the Sun to form a long tail. The ESA Rosetta mission to Comet P67 (Churyumov-Gerasimenko) has greatly increased our knowledge of the nature of the nucleus and of the process by which comets release water and other volatiles when heated by sunlight.
Glossary
- comet
- a small body of icy and dusty matter that revolves about the Sun; when a comet comes near the Sun, some of its material vaporizes, forming a large head of tenuous gas and often a tail
- nucleus (of a comet)
- the solid chunk of ice and dust in the head of a comet
- tail
- (of a comet) a tail consisting of two parts: the dust tail is made of dust loosened by the sublimation of ice in a comet that is then pushed by photons from the Sun into a curved stream; the ion tail is a stream of ionized particles evaporated from a comet and then swept away from the Sun by the solar wind
Contributors and Attributions
Andrew Fraknoi (Foothill College), David Morrison (NASA Ames Research Center), Sidney C. Wolff (National Optical Astronomy Observatory) with many contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at https://openstax.org/details/books/astronomy ).


12.5D: Immune Complex Autoimmune Reactions
- Describe how immune complex autoimmune reactions arise
An immune complex is formed from the integral binding of an antibody to a soluble antigen. The bound antigen acting as a specific epitope, bound to an antibody is referred to as a singular immune complex. After an antigen-antibody reaction, the immune complexes can be subject to any of a number of responses, including complement deposition, opsonization, phagocytosis, or processing by proteases. Red blood cells carrying CR1-receptors on their surface may bind C3b-decorated immune complexes and transport them to phagocytes, mostly in liver and spleen, and return back to the general circulation. Immune complexes may cause disease when they are deposited in organs, e.g. in certain forms of vasculitis. This is the third form of hypersensitivity in the Gell-Coombs classification, called Type III hypersensitivity. Immune complex deposition is a prominent feature of several autoimmune diseases, including systemic lupus erythematosus, cryoglobulinemia, rheumatoid arthritis, scleroderma, and Sjögren’s syndrome.
In immunology, the Arthus reaction is a type of local type III hypersensitivity reaction. Type III hypersensitivity reactions are immune complex-mediated. They involve the deposition of antigen/antibody complexes mainly in the vascular walls, serosa (pleura, pericardium, synovium), and glomeruli. The Arthus reaction involves the in situformation of antigen/antibody complexes after the intradermal injection of an antigen (as seen in passive immunity). If the animal/patient was previously sensitized (has circulating antibody), an Arthus reaction occurs. Typical of most mechanisms of the type III hypersensitivity, Arthus manifests as local vasculitis due to deposition of IgG-based immune complexes in dermal blood vessels. Activation of complement primarily results in cleavage of soluble complement proteins forming C5a and C3a, which activate recruitment of PMNs and local mast cell degranulation (requiring the binding of the immune complex onto FcγRIII), resulting in an inflammatory response. Further aggregation of immune complex-related processes induces a local fibrinoid necrosis with ischemia-aggravating thrombosis in the tissue vessel walls. The end result is a localized area of redness and induration that typically lasts a day or so. Arthus reactions have been infrequently reported after vaccination against diphtheria and tetanus.
Key Points
- After an antigen – antibody reaction, the immune complexes can be subject to any of a number of responses including complement deposition, opsonization, phagocytosis, or processing by proteases.
- Immune complexes may cause disease when they are deposited in organs.
- The Arthus reaction involves the in situ formation of antigen/antibody complexes after the intradermal injection of an antigen (as seen in passive immunity).
Key Terms
- epitope : That part of a biomolecule (such as a protein) that is the target of an immune response.
- immune complex : An immune complex is formed from the integral binding of an antibody to a soluble antigen. The bound antigen acting as a specific epitope, bound to an antibody is referred to as a singular immune complex.


5.1.2E: Competition
-
- Last updated
- Save as PDF
- Anonymous
- LibreTexts
Learning Objectives
- Explain how competition can be both a help and a hinderance for people in any particular society or group
Competition is a contest between people or groups of people for control over resources. In this definition, resources can have both literal and symbolic meaning. People can compete over tangible resources like land, food, and mates, but also over intangible resources, such as social capital. Competition is the opposite of cooperation and arises whenever two parties strive for a goal that cannot be shared.
Competition can have both beneficial and detrimental effects. Positively, competition may serve as a form of recreation or a challenge provided that it is non-hostile. On the negative side, competition can cause injury and loss to the organisms involved, and drain valuable resources and energy. Many evolutionary biologists view inter-species and intra-species competition as the driving force of adaptation, and, ultimately, of evolution. However, some biologists, most famously Richard Dawkins, prefer to think of evolution in terms of competition between single genes, which have the welfare of the organism “in mind” only insofar as that welfare furthers their own selfish drives for replication. Some Social Darwinists claim that competition also serves as a mechanism for determining the best-suited group–politically, economically, and ecologically.
Many philosophers and psychologists have identified a trait in most living organisms that can drive the particular organism to compete. This trait, unsurprisingly called “competitiveness,” is viewed as an innate biological trait that coexists along with the urge for survival. Competitiveness, or the inclination to compete, has become synonymous with aggressiveness and ambition in the English language. Just as advanced civilizations integrate aggressiveness and competitiveness into their interactions, as a way to distribute resources and adapt, most plants compete for higher spots on trees to receive more sunlight. However, Stephen Jay Gould and others have argued that as one ascends the evolutionary hierarchy, competitiveness (the survival instinct) becomes less innate and more a learned behavior.
The term also applies to econometrics. Here, it is a comparative measure of the ability and performance of a firm or sub-sector to sell and produce/supply goods and/or services in a given market. The two academic bodies of thought on the assessment of competitiveness are the Structure Conduct Performance Paradigm and the more contemporary New Empirical Industrial Organisation model. Predicting changes in the competitiveness of business sectors is becoming an integral and explicit step in public policymaking. Within capitalist economic systems, the drive of enterprises is to maintain and improve their own competitiveness.
Key Points
- People can compete over tangible resources, such as land, food, and mates, but also over intangible resources, such as social capital.
- Many evolutionary biologists view inter-species and intra-species competition as the driving force of adaptation and, ultimately, of evolution.
- Many philosophers and psychologists have identified a trait in most living organisms that can drive the particular organism to compete.
Key Terms
- evolution : gradual directional change, especially one leading to a more advanced or complex form; growth; development
- innate : Inborn; native; natural; as, innate vigor; innate eloquence.


3.17: Applications of Open- and Short-Circuited Transmission Line Stubs
-
- Last updated
- Save as PDF
The theory of open- and short-circuited transmission lines – often referred to as stubs – was addressed in Section 3.16. These structures have important and wide-ranging applications.
In particular, these structures can be used to replace discrete inductors and capacitors in certain applications. To see this, consider the short-circuited line (Figure 3.16.1(a) of Section 3.16). Note that each value of \(l\) that is less than \(\lambda/4\) corresponds to a particular positive reactance; i.e., the transmission line “looks” like an inductor. Also note that lengths between \(\lambda/4\) and \(\lambda/2\) result in reactances that are negative; i.e., the transmission line “looks” like a capacitor. Thus, it is possible to replace an inductor or capacitor with a short-circuited transmission line of the appropriate length. The input impedance of such a transmission line is identical to that of the inductor or capacitor at the design frequency. The variation of reactance with respect to frequency will not be identical, which may or may not be a concern depending on the bandwidth and frequency response requirements of the application. Open-circuited lines may be used in a similar way.
This property of open- and short-circuited transmission lines makes it possible to implement impedance matching circuits (see Section 3.16 a ), filters, and other devices entirely from transmission lines, with fewer or no discrete inductors or capacitors required. Transmission lines do not suffer the performance limitations of discrete devices at high frequencies and are less expensive. A drawback of transmission line stubs in this application is that the lines are typically much larger than the discrete devices they are intended to replace.
Example \(\PageIndex{1}\): Emitter Induction Using Short-Circuited Line
In the design of low-noise amplifiers using bipolar transistors in common-emitter configuration, it is often useful to introduce a little inductance between the emitter and ground. This is known as “inductive degeneration,” “emitter induction,” or sometimes by other names. It can be difficult to find suitable inductors, especially for operation in the UHF band and higher. However, a microstrip line can be used to achieve the desired inductive impedance. Determine the length of a stub that implements a 2.2 nH inductance at 6 GHz using microstrip line with characteristic impedance \(50~\Omega\) and phase velocity \(0.6c\).
Solution
At the design frequency, the impedance looking into this section of line from the emitter should be equal to that of a 2.2 nH inductor, which is \(+j\omega L = +j2\pi fL = +j82.9~\Omega\). The input impedance of a short-circuited stub of length \(l\) which is grounded (thus, short-circuited) at the opposite end is \(+jZ_0\tan\beta l\) (Section 3.16). Setting this equal to \(+j82.9~\Omega\) and noting that \(Z_0=50~\Omega\), we find that \(\beta l \cong 1.028\) rad. The phase propagation constant is (Section 3.8): \[\beta = \frac{\omega}{v_p} = \frac{2\pi f}{0.6 c} \cong 209.4~\mbox{rad/m} \nonumber \] Therefore, the length of the microstrip line is \(l = \left(\beta l\right) / \beta \cong 4.9\) mm.


6.1A: Overview of the Musculoskeletal System
The musculoskeletal system is an organ system that enables an organism to move, support itself, and maintain stability during locomotion.
- Explain the purpose of the musculoskeletal system
Key Points
- The musculoskeletal system ‘s primary functions include supporting the body, allowing motion, and protecting vital organs.
- The musculoskeletal system is made up of the body’s bones (the skeleton), muscles, cartilage, tendons, ligaments, joints, and other connective tissue that support and bind tissues and organs together.
- The skeleton serves as the main storage system for calcium and phosphorus.
- The skeleton also contains critical components of the hematopoietic ( blood production) system and fat storage. These functions occur in red marrow and yellow marrow, respectively.
- To allow motion, different bones are connected by articulating joints. Cartilage prevents the bone ends from rubbing directly on to each other while the muscles contract to move the bones associated with the joint.
Key Terms
- red marrow : Red marrow or medulla ossium rubra, consists mainly of hematopoietic tissue, and gives rise to red blood cells (RBCs), platelets and most white blood cells (WBCs).
- musculoskeletal system : An organ system that gives animals (and humans) the ability to move, using the combined actions of the muscular and skeletal systems. It provides form, support, stability, and movement to the body.
- hematopoeisis : A biological process in which new blood cells are formed from hematopoietic stem cells (HSCs) within the marrow. All cellular blood components are derived from HSCs.
The musculoskeletal system (also known as the locomotor system) is an organ system that gives animals (including humans) the ability to move, using the muscular and skeletal systems. It provides form, support, stability, and movement to the body.
The musculoskeletal system is made up of the body’s bones (the skeleton), muscles, cartilage, tendons, ligaments, joints, and other connective tissue that supports and binds tissues and organs together.
Its primary functions include supporting the body, allowing motion, and protecting vital organs.
The bones of the skeletal system provide stability to the body analogous to a reinforcement bar in concrete construction.
Muscles keep bones in place and also play a role in their movement. To allow motion, different bones are connected by articulating joints, and cartilage prevents the bone ends from rubbing directly onto each other.
Skeletal System
A human skeleton : Image as overview of the human skeletal system.
The skeletal portion of the system serves as the main storage system for calcium and phosphorus. The importance of this storage is to help regulate mineral balance in the bloodstream. When the fluctuation of minerals is high, these minerals are stored in bone; when it is low, minerals are withdrawn from the bone.
The skeleton also contains critical components of the hematopoietic (blood production) system. Located in long bones are two distinctions of bone marrow: yellow and red. The yellow marrow has fatty connective tissue and is found in the marrow cavity. In times of starvation, the body uses the fat in yellow marrow for energy.
The red marrow of some bones is an important site for hematopoeisis or blood cell production that replaces cells that have been destroyed by the liver. Here, all erythrocytes, platelets, and most leukocytes form in bone marrow from where they migrate to the circulation.
Muscular System
Muscles contract (shorten) to move the bone attached at the joint. Skeletal muscles are attached to bones and arranged in opposing groups around joints. Muscles are innervated—the nerves conduct electrical currents from the central nervous system that cause the muscles to contract.
Three types of muscle tissue exist in the body. These are skeletal, smooth, and cardiac muscle.
- Only skeletal and smooth muscles are considered part of the musculoskeletal system.
- Skeletal muscle is involved in body locomotion.
- Examples of smooth muscles include those found in intestinal and vessel walls.
- Cardiac and smooth muscle are characterized by involuntary movement (not under conscious control).
- Cardiac muscles are found in the heart.
Tendons, Joints, Ligaments, and Bursae
A tendon is a tough, flexible band made of fibrous connective tissue, and functions to connect muscle to bone. Joints are the bone articulations allowing movement. A ligament is a dense, white band of fibrous elastic tissue.
Ligaments connect the ends of bones together in order to form a joint. These help to limit joint dislocation and restrict improper hyperextension and hyperflexion. Also made of fibrous tissue are bursae. These provide cushions between bones and tendons and/or muscles around a joint.
Musculoskeletal system : Image depicting the human muscular system (skeletal muscle)


2.7: Measures of the Spread of the Data
An important characteristic of any set of data is the variation in the data. In some data sets, the data values are concentrated closely near the mean; in other data sets, the data values are more widely spread out from the mean. The most common measure of variation, or spread, is the standard deviation. The standard deviation is a number that measures how far data values are from their mean, on average.
The standard deviation
- provides a numerical measure of the overall amount of variation in a data set, and
- can be used to determine whether a particular data value is close to or far from the mean.
The standard deviation provides a measure of the overall variation in a data set
The standard deviation is always positive or zero. The standard deviation is small when the data are all concentrated close to the mean, exhibiting little variation or spread. The standard deviation is larger when the data values are more spread out from the mean, exhibiting more variation.
Suppose that we are studying the amount of time customers wait in line at the checkout at supermarket \(A\) and supermarket \(B\). The average wait time at both supermarkets is five minutes. At supermarket \(A\), the standard deviation for the wait time is two minutes; at supermarket \(B\), the standard deviation for the wait time is four minutes.
Because supermarket \(B\) has a higher standard deviation, we know that there is more variation in the wait times at supermarket \(B\). Overall, wait times at supermarket \(B\) are more spread out from the average; wait times at supermarket \(A\) are more concentrated near the average.
Calculating the Standard Deviation
If \(x\) is a number, then the difference "\(x\) minus the mean" is called its deviation . In a data set, there are as many deviations as there are items in the data set. The deviations are used to calculate the standard deviation. If the numbers belong to a population, in symbols a deviation is \(x – \mu\). For sample data, in symbols a deviation is \(x – \overline{x}\).
The procedure to calculate the standard deviation depends on whether the numbers are the entire population or are data from a sample. The calculations are similar, but not identical. Therefore the symbol used to represent the standard deviation depends on whether it is calculated from a population or a sample. The lower case letter s represents the sample standard deviation and the Greek letter \(\sigma\) (sigma, lower case) represents the population standard deviation. If the sample has the same characteristics as the population, then s should be a good estimate of \(\sigma\).
To calculate the standard deviation, we need to calculate the variance first. The variance is the average of the squares of the deviations (the \(x – \overline{x}\) values for a sample, or the \(x – \mu\) values for a population). The symbol \(\sigma^2\) represents the population variance; the population standard deviation \(\sigma\) is the square root of the population variance. The symbol \(s^2\) represents the sample variance; the sample standard deviation s is the square root of the sample variance. You can think of the standard deviation as a special average of the deviations.
If the numbers come from a census of the entire population and not a sample, when we calculate the average of the squared deviations to find the variance, we divide by \(N\), the number of items in the population. If the data are from a sample rather than a population, when we calculate the average of the squared deviations, we divide by n – 1 , one less than the number of items in the sample.
Formulas for the Sample Standard Deviation
- \(s=\sqrt{\frac{\Sigma({x}_i-\overline{x})^{2}}{n-1}} \text { or } s=\sqrt{\frac{\Sigma {f}_i({x}_i - \overline{x})^{2}}{n-1}} \)
- For the sample standard deviation, the denominator is n – 1 , that is the sample size minus 1.
Formulas for the Population Standard Deviation
- \(\boldsymbol{\sigma}=\sqrt{\frac{\Sigma({x}_i - \mu)^{2}}{N}} \text { or } \sigma=\sqrt{\frac{\Sigma {f}_i({x}_i - \mu)^{2}}{N}} \)
- For the population standard deviation, the denominator is \(N\), the number of items in the population.
In these formulas, \(f_i\) represents the frequency with which a given value of x (that is, \(x_i\)) appears. For example, if a value appears once, \(f_i\) is one for that value. If a different value appears three times in the data set or population, \(f_i\) for that value is three.
There are two important observations to note concerning the variance and standard deviation: the deviations are measured from the mean, and the deviations are squared. In principle, the deviations could be measured from any point, however, our interest is measurement from the center weight of the data, what is the most usual value of the observation. Later we will be trying to measure the "unusualness" of an observation or a sample mean and thus we need a measure from the mean. The second observation is that the deviations are squared. This does two things, first it makes the deviations all positive and second it changes the units of measurement from that of the mean and the original observations. If the data are weights then the mean is measured in pounds, but the variance is measured in pounds-squared. One reason to use the standard deviation is to return to the original units of measurement by taking the square root of the variance. Further, when the deviations are squared it explodes their value. For example, a deviation of 10 from the mean when squared is 100, but a deviation of 100 from the mean is 10,000. What this does is place great weight on outliers when calculating the variance.
Types of Variability in Samples
When trying to study a population, a sample is often used, either for convenience or because it is not possible to access the entire population. Variability is the term used to describe the differences that may occur in these outcomes. Common types of variability include the following:
- Observational or measurement variability
- Natural variability
- Induced variability
- Sample variability
Here are some examples to describe each type of variability.
Example 1: Measurement variability
Measurement variability occurs when there are differences in the instruments used to measure or in the people using those instruments. If we are gathering data on how long it takes for a ball to drop from a height by having students measure the time of the drop with a stopwatch, we may experience measurement variability if the two stopwatches used were made by different manufacturers. For example, one stopwatch measures to the nearest second, whereas the other one measures to the nearest tenth of a second. We also may experience measurement variability because two different people are gathering the data. Their reaction times in pressing the button on the stopwatch may differ; thus, the outcomes will vary accordingly. The differences in outcomes may be affected by measurement variability.
Example 2: Natural variability
Natural variability arises from the differences that naturally occur because members of a population differ from each other. For example, if we have two identical corn plants and we expose both plants to the same amount of water and sunlight, they may still grow at different rates simply because they are two different corn plants. The difference in outcomes may be explained by natural variability.
Example 3: Induced variability
Induced variability is the counterpart to natural variability; this occurs because we have artificially induced an element of variation (that, by definition, was not present naturally): For example, we assign people to two different groups to study memory, and we induce a variable in one group by limiting the amount of sleep they get. The difference in outcomes may be affected by induced variability.
Example 4: Sample variability
Sample variability occurs when multiple random samples are taken from the same population. For example, if I conduct four surveys of 50 people randomly selected from a given population, the differences in outcomes may be affected by sample variability.
Example \(\PageIndex{1}\)
In a fifth grade class, the teacher was interested in the average age and the sample standard deviation of the ages of her students. The following data are the ages for a SAMPLE of \(n = 20\) fifth grade students. The ages are rounded to the nearest half year:
9; 9.5; 9.5; 10; 10; 10; 10; 10.5; 10.5; 10.5; 10.5; 11; 11; 11; 11; 11; 11; 11.5; 11.5; 11.5;
\[\overline{x}=\frac{9+9.5(2)+10(4)+10.5(4)+11(6)+11.5(3)}{20}=10.525\nonumber\]
The average age is 10.53 years, rounded to two places.
The variance may be calculated by using a table. Then the standard deviation is calculated by taking the square root of the variance. We will explain the parts of the table after calculating \(s\).
| Data | Freq. | Deviations | Deviations 2 | (Freq.)(Deviations 2 ) |
|---|---|---|---|---|
| \(x\) | \(f\) | \((x - \overline{x})\) | \((x – \overline{x})^2\) | \((f)(x – \overline{x})^2\) |
| 9 | 1 | \(9 – 10.525 = –1.525\) | \((–1.525)^2 = 2.325625\) | \(1 \times 2.325625 = 2.325625\) |
| 9.5 | 2 | \(9.5 – 10.525 = –1.025\) | \((–1.025)2 = 1.050625\) | \(2 \times 1.050625 = 2.101250\) |
| 10 | 4 | \(10 – 10.525 = –0.525\) | \((–0.525)2 = 0.275625\) | \(4 \times 0.275625 = 1.1025\) |
| 10.5 | 4 | \(10.5 – 10.525 = –0.025\) | \((–0.025)2 = 0.000625\) | \(4 \times 0.000625 = 0.0025\) |
| 11 | 6 | \(11 – 10.525 = 0.475\) | \((0.475)2 = 0.225625\) | \(6 \times 0.225625 = 1.35375\) |
| 11.5 | 3 | \(11.5 – 10.525 = 0.975\) | \((0.975)2 = 0.950625\) | \(3 \times 0.950625 = 2.851875\) |
| The total is 9.7375 |
The sample variance, \(s^2\), is equal to the sum of the last column (9.7375) divided by the total number of data values minus one \((20 – 1)\):
\(s^{2}=\frac{9.7375}{20-1}=0.5125\)
The sample standard deviation s is equal to the square root of the sample variance:
\(s=\sqrt{0.5125}=0.715891\), which is rounded to two decimal places, \(s = 0.72\).
Explanation of the standard deviation calculation shown in the table
The deviations show how spread out the data are about the mean. The data value 11.5 is farther from the mean than is the data value 11 which is indicated by the deviations 0.97 and 0.47. A positive deviation occurs when the data value is greater than the mean, whereas a negative deviation occurs when the data value is less than the mean. The deviation is –1.525 for the data value nine. If you add the deviations, the sum is always zero . (For Example \(\PageIndex{1}\), there are \(n = 20\) deviations.) So you cannot simply add the deviations to get the spread of the data. By squaring the deviations, you make them positive numbers, and the sum will also be positive. The variance, then, is the average squared deviation. By squaring the deviations we are placing an extreme penalty on observations that are far from the mean; these observations get greater weight in the calculations of the variance. We will see later on that the variance (standard deviation) plays the critical role in determining our conclusions in inferential statistics. We can begin now by using the standard deviation as a measure of "unusualness." "How did you do on the test?" "Terrific! Two standard deviations above the mean." This, we will see, is an unusually good exam grade.
The variance is a squared measure and does not have the same units as the data. Taking the square root solves the problem. The standard deviation measures the spread in the same units as the data.
Notice that instead of dividing by \(n = 20\), the calculation divided by \(n – 1 = 20 – 1 = 19\) because the data is a sample. For the sample variance, we divide by the sample size minus one \((n – 1)\). Why not divide by \(n\)? The answer has to do with the population variance. The sample variance is an estimate of the population variance. This estimate requires us to use an estimate of the population mean rather than the actual population mean. Based on the theoretical mathematics that lies behind these calculations, dividing by \((n – 1)\) gives a better estimate of the population variance.
The standard deviation, \(s\) or \(\sigma\), is either zero or larger than zero. Describing the data with reference to the spread is called "variability". The variability in data depends upon the method by which the outcomes are obtained; for example, by measuring or by random sampling. When the standard deviation is zero, there is no spread; that is, the all the data values are equal to each other. The standard deviation is small when the data are all concentrated close to the mean, and is larger when the data values show more variation from the mean. When the standard deviation is a lot larger than zero, the data values are very spread out about the mean; outliers can make \(s\) or \(\sigma\) very large.
Example \(\PageIndex{2}\)
Use the following data (first exam scores) from Dr. Doom's spring pre-calculus class:
\(33; 42; 49; 49; 53; 55; 55; 61; 63; 67; 68; 68; 69; 69; 72; 73; 74; 78; 80; 83; 88; 88; 88; 90; 92; 94; 94; 94; 94; 96; 100\)
- Create a chart containing the data, frequencies, relative frequencies, and cumulative relative frequencies to three decimal places.
-
Calculate the following to one decimal place:
- The sample mean
- The sample standard deviation
- The median
- The first quartile
- The third quartile
- \(IQR\)
- Answer
-
a. See Table \(\PageIndex{2}\) below
b.
- The sample mean = 73.5
- The sample standard deviation = 17.9
- The median = 73
- The first quartile = 61
- The third quartile = 90
- \(IQR = 90 – 61 = 29\)
|
Data |
Frequency |
Relative frequency |
Cumulative relative frequency |
|---|---|---|---|
|
33 |
1 |
0.032 |
0.032 |
|
42 |
1 |
0.032 |
0.064 |
|
49 |
2 |
0.065 |
0.129 |
|
53 |
1 |
0.032 |
0.161 |
|
55 |
2 |
0.065 |
0.226 |
|
61 |
1 |
0.032 |
0.258 |
|
63 |
1 |
0.032 |
0.29 |
|
67 |
1 |
0.032 |
0.322 |
|
68 |
2 |
0.065 |
0.387 |
|
69 |
2 |
0.065 |
0.452 |
|
72 |
1 |
0.032 |
0.484 |
|
73 |
1 |
0.032 |
0.516 |
|
74 |
1 |
0.032 |
0.548 |
|
78 |
1 |
0.032 |
0.580 |
|
80 |
1 |
0.032 |
0.612 |
|
83 |
1 |
0.032 |
0.644 |
|
88 |
3 |
0.097 |
0.741 |
|
90 |
1 |
0.032 |
0.773 |
|
92 |
1 |
0.032 |
0.805 |
|
94 |
4 |
0.129 |
0.934 |
|
96 |
1 |
0.032 |
0.966 |
|
100 |
1 |
0.032 |
0.998 (Why isn't this value 1? Answer: Rounding) |
Comparing Values from Different Data Sets
The standard deviation is useful when comparing data values that come from different data sets. If the data sets have different means and standard deviations, then comparing the data values directly can be misleading.
- For each data value x , calculate how many standard deviations away from its mean the value is.
- Use the formula: x = mean + (#of STDEVs)(standard deviation); solve for #of STDEVs.
- \(\# \text { of } S T D E V s=\frac{x-\text { mean }}{\text { standard deviation }}\)
- Compare the results of this calculation.
#of STDEVs is often called a "z-score"; we can use the symbol \(z\). In symbols, the formulas become:
| Sample | \(x=\overline{x}+z s\) | \(z=\frac{x-\overline{x}}{s}\) |
| Population | \(x=\mu+z \sigma\) | \(z=\frac{x-\mu}{\sigma}\) |
Example \(\PageIndex{3}\)
Two students, John and Ali, from different high schools, wanted to find out who had the higher GPA when compared to his school. Which student had the higher GPA compared to his own school?
| Student | GPA | School mean GPA | School standard deviation |
|---|---|---|---|
| John | 2.85 | 3.0 | 0.7 |
| Ali | 77 | 80 | 10 |
- Answer
-
For each student, determine how many standard deviations (#of STDEVs) his GPA is away from the average, for his school. Pay careful attention to signs when comparing and interpreting the answer.
\(z=\# \text { of STDE } \mathrm{Vs}=\frac{\text { value - mean }}{\text { standard deviation }}=\frac{x-\mu}{\sigma}\)
For John, \(z=\# \text { ofSTDEV } s=\frac{2.85 \cdot 3.0}{0.7}=-0.21\)
For Ali, \(z=\# \text { ofSTDEV } s=\frac{77-80}{10}=-0.3\)
John has the better GPA when compared to his school because his GPA is 0.21 standard deviations below his school's mean while Ali's GPA is 0.3 standard deviations below his school's mean.
John's z -score of –0.21 is higher than Ali's z -score of –0.3. For GPA, higher values are better, so we conclude that John has the better GPA when compared to his school.
Exercise \(\PageIndex{1}\)
Two swimmers, Angie and Beth, from different teams, wanted to find out who had the faster time for the 50 meter freestyle when compared to her team. Which swimmer had the faster time when compared to her team?
-
Swimmer Time (seconds) Team mean time Team standard deviation Angie 26.2 27.2 0.8 Beth 27.3 30.1 1.4 Table \(\PageIndex{5}\)
The following lists give a few facts that provide a little more insight into what the standard deviation tells us about the distribution of the data.
For ANY data set, no matter what the distribution of the data is:
- At least 75% of the data is within two standard deviations of the mean.
- At least 89% of the data is within three standard deviations of the mean.
- At least 95% of the data is within 4.5 standard deviations of the mean.
- This is known as Chebyshev's Rule.
For data having a normal distribution, which we will examine in great detail later:
- Approximately 68% of the data is within one standard deviation of the mean.
- Approximately 95% of the data is within two standard deviations of the mean.
- More than 99% of the data is within three standard deviations of the mean.
- This is known as the Empirical Rule .
- It is important to note that this rule only applies when the shape of the distribution of the data is bell-shaped and symmetric. We will learn more about this when studying the "Normal" or "Gaussian" probability distribution in later chapters.


Selenium
-
- Last updated
- Save as PDF
Learning Objectives
- Learn about the role of selenium
Selenium is a cofactor of enzymes that release active thyroid hormone in cells and therefore low levels can cause similar signs and symptoms as iodine deficiency. The other important function of selenium is as an antioxidant.
Selenium Functions and Health Benefits
Around twenty-five known proteins require selenium to function. Some are enzymes involved in detoxifying free radicals and include glutathione peroxidases and thioredoxin reductase. As an integral functioning part of these enzymes, selenium aids in the regeneration of glutathione and oxidized vitamin C. Selenium as part of glutathione peroxidase also protects lipids from free radicals, and, in doing so, spares vitamin E. This is just one example of how antioxidants work together to protect the body against free-radical induced damage. Other functions of selenium-containing proteins include protecting endothelial cells that line tissues, converting the inactive thyroid hormone to the active form in cells, and mediating inflammatory and immune system responses.
Observational studies have demonstrated that selenium deficiency is linked to an increased risk of cancer. A review of forty-nine observational studies published in the May 2011 issue of the Cochrane Database of Systematic Reviews concluded that higher selenium exposure reduces overall cancer incidence by about 34 percent in men and 10 percent in women, but notes these studies had several limitations, including data quality, bias, and large differences among different studies.[1] Additionally, this review states that there is no convincing evidence from six clinical trials that selenium supplements reduce cancer risk.
Because of its role as a lipid protector, selenium has been suspected to prevent cardiovascular disease. In some observational studies, low levels of selenium are associated with a decreased risk of cardiovascular disease. However, other studies have not always confirmed this association and clinical trials are lacking.
Dietary Reference Intakes for Selenium
The IOM has set the RDAs for selenium based on the amount required to maximize the activity of glutathione peroxidases found in blood plasma. The RDAs for different age groups are listed in Table \(\PageIndex{1}\).
| Age Group | RDA Males and Females mcg/day | UL |
|---|---|---|
| Infants (0–6 months) | 15* | 45 |
| Infants (7–12 months) | 20* | 65 |
| Children (1–3 years) | 20 | 90 |
| Children (4–8 years) | 30 | 150 |
| Children (9–13 years) | 40 | 280 |
| Adolescents (14–18 years) | 55 | 400 |
| Adults (> 19 years) | 55 | 400 |
| *denotes Adequate Intake |
Selenium at doses several thousand times the RDA can cause acute toxicity, and when ingested in gram quantities can be fatal. Chronic exposure to foods grown in soils containing high levels of selenium (significantly above the UL) can cause brittle hair and nails, gastrointestinal discomfort, skin rashes, halitosis, fatigue, and irritability. The IOM has set the UL for selenium for adults at 400 micrograms per day.
Dietary Sources of Selenium
Organ meats, muscle meats, and seafood have the highest selenium content. Plants do not require selenium, so the selenium content in fruits and vegetables is usually low. Animals fed grains from selenium-rich soils do contain some selenium. Grains and some nuts contain selenium when grown in selenium-containing soils. See Table \(\PageIndex{2}\) for the selenium content of various foods.
Table \(\PageIndex{2}\): Selenium Contents of Various Foods.
| Food | Serving | Selenium (mcg) | Percent Daily Value |
|---|---|---|---|
| Brazil nuts | 1 oz. | 544 | 777 |
| Shrimp | 3 oz. | 34 | 49 |
| Crab meat | 3 oz. | 41 | 59 |
| Ricotta cheese | 1 c. | 41 | 59 |
| Salmon | 3 oz. | 40 | 57 |
| Pork | 3 oz. | 35 | 50 |
| Ground beef | 3 oz. | 18 | 26 |
| Round steak | 3 oz. | 28.5 | 41 |
| Beef liver | 3 oz. | 28 | 40 |
| Chicken | 3 oz. | 13 | 19 |
| Whole-wheat bread | 2 slices | 23 | 33 |
| Couscous | 1 c. | 43 | 61 |
| Barley, cooked | 1 c. | 13.5 | 19 |
| Milk, low-fat | 1 c. | 8 | 11 |
| Walnuts, black | 1 oz. | 5 | 7 |
Source: US Department of Agriculture, Agricultural Research Service. 2010. USDA National Nutrient Database for Standard Reference, Release 23. http://www.ars.usda.gov/ba/bhnrc/ndl .
Footnotes
- Dennert G, Zwahlen M, et al. Selenium for Preventing Cancer. Cochrane Database of Systematic Reviews. 2011; 5. http://www.ncbi.nlm.nih.gov/pubmed/21563143 . Accessed November 22, 2017.
Contributors and Attributions
-
University of Hawai’i at Mānoa Food Science and Human Nutrition Program : Allison Calabrese, Cheryl Gibby, Billy Meinke, Marie Kainoa Fialkowski Revilla, and Alan Titchenal


10.2: Employee Scheduling
- List the key aspects of efficient employee scheduling
Employee scheduling can be a tricky task. All employees have different needs and skills. Your retail operation also has different needs during different times of the day. It can be a challenge to coordinate the two. Depending on the type of retail establishment you are scheduling for, there are some tricks to creating the most economic schedule you can while keeping employees and customers happy.
Let’s say you are scheduling for a restaurant. If you operate from 7am to 9pm, there will be times of the day when you are busy, and times when you are not. The breakfast, lunch and dinner rushes will obviously need more coverage, but how do you cover those times while still maintaining happy employees?
- Know your employees. This includes knowing their skills, strengths and weaknesses to make sure the shift runs smoothly. Don’t have three dishwashers, one cook and no prep folks on a restaurant shift, or three sales clerks and no managers on a retail store shift (especially if none of the clerks have access to void a sale or accept a return).
- Build shifts around your star employees . If you have a few folks who you know can run the show, build a shift around them. This may include personality type, making sure you have someone outgoing covering the front of the house or someone who is meticulous covering the kitchen. Also insure that you have people with the right certifications on each shift. An example here might be insuring that you have a kitchen manager on each shift if it is a requirement of your licensing.
- Have a way for the employees to communicate with each other . A text list or a messenger app is the best way with the prevalence of smartphones. Have a way for employees to message others if they need a replacement or would like to trade shifts. Requiring employees to find their own substitutes for rescheduling will save you time as well.
- Get the schedule out in a timely manner. Employees can plan better if the schedule is out early. The best is if you can have it out two weeks before the end of the current schedule. This allows employees time to reschedule any personal commitments or trade shift.
- As much as possible, make sure to honor time off requests and work preferences. This isn’t always possible, but it does help to increase employee satisfaction and keep good employees! It can be a huge time consumer for the scheduler though, so keeping some type of document or cloud based system will work best for this task.
- Delegate responsibility to employees. Schedule one or two of your best employees on each shift, and then give everyone access to the incomplete schedule and let them fill in when they want to work. Note : this will not work for all businesses, but if you have one where it will work, it will save you a ton of time.
- Use part-time labor, if possible. Have a list of part-time available employees for those inevitable times when there is an emergency or you need someone quickly.
There will always be challenges in the scheduling process. This may be especially true when you are a new manager. Keep notes, make it as automated as possible with a good cloud based scheduling system and continue every scheduling cycle to streamline your processes. It becomes easier over time, but make sure to keep improving the process.
LEarn More
Contributors and Attributions
- Employee Scheduling. Authored by : Freedom Learning Group. Provided by : Lumen Learning. License : CC BY: Attribution


5.4: Disorders
-
- Last updated
- Save as PDF
- Wikipedia
Without balanced emotions, one's ability to interact in a social network will be affected in some manner (e.g. reading minds). In this part of the chapter some grave disorders will be presented- these are: depression , austism and antisocial behaviour disorders as psychopathy and sociopathy . It is important to mention that those disorders will mainly be considered in regard to their impact on social competence. To get a full account of the characteristics of each of the disorders, we recommend reading the particular articles provided by Wikipedia.
Autism
Autism is thought to be an innate condition with individual forms distributed on a broad spectrum. This means that symptoms can range from minor behavioral problems to major mental deficits, but there is always some impairment of social competence. The American Psychiatric Association characterizes autism as "the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activities and interests" (1994, diagnostic and statistical manual; DSM-IV). The deficits in social competence are sometimes divided into the so-called "triad of impairments", including:
(1)Social interaction This includes difficulties with social relationships, for example appearing distanced and indifferent to other people.
(2)Social communication Autists have problems with verbal and non-verbal communication, for example, they do not fully understand the meaning of common gestures, facial expressions or the voice tones. They often show reduced or even no eye-contact as well, avoid body contact like shaking hands and have difficulties to understand metaphores and "to read between the lines".
(3)Social imagination Autists lack social imagination manifesting in difficulties in the development of interpersonal play and imagination, for example having a limited range of imaginative activities, possibly copied and pursued rigidly and repetitively.
All forms of autism can already be recognized during childhood and therefore disturb the proper socialization of the afflicted child. Often autistic children are less interested in playing with other children but for example love to arrange their toys with utmost care. Unable to interpret emotional expressions and social rules autists are prone to show inappropriate behaviour towards the people surrounding them. Autists may not obviously be impaired therefore other people misunderstand their actions as provocation.
Still there are other features of autism- autists often show stereotyped behaviour and feel quite uncomfortable when things change in the routines and environment they are used to. Very rarely, a person with autism may have a remarkable talent, such as memorizing a whole city panorama including, for example, the exact number of windows in each of the buildings.
There are several theories trying to explain autism or features of autism. In an experiment conducted by Baron-Cohen and colleagues (1995) cartoons were presented to normal and autistic children showing a smiley in the centre of each picture and four different sweets in each corner (see picture below). The smiley, named Charlie, was gazing at one of the sweets. The children were asked question as: "Which chocolate does Charlie want?"
Autistic children were able to detect where the smiley was looking but unable to infer its 'desires'. (adapted graphic from Ward, J. (2006). The Students Guide to Cognitive Neuroscience . Hove: Psychology Press. page 316)
Normal children could easily infer Charlie's desires from Charlie's gaze direction whereas autistic children would not guess the answer.
Additional evidence from other experiments suggest that autists are unable to use eye gaze information to interpret people's desires and predict their behaviour which would be crucial for social interaction. Another proposal to explain autistic characteristics suggests that autists lack representations of other people's mental states (mindblindness - proposed by Baron-Cohen, 1995b).
Depression
Depression is a disorder that leads to an emotional disfunction characterized by a state of intensive sadness, melancholia and despair. The disorder affects social and everyday life. There are many different forms of depression that differ in strength and duration. People affected by depression suffer from anxiety, distorted thinking, dramatic mood changes and many other symptoms. They feel sad, and everything seems to be bleak. This leads to an extremely negative view of themselves and their current and future situation. These factors can lead to a loss of a normal social life that might affect the depressed person even further. Suffering from depression and losing your social network can thereby lead to a vicious circle.
Psychopathy and Sociopathy
Psychopathy and sociopathy are nowadays subsumed under the notion of antisocial behaviour disorders but experts are still quite discordant whether both are really separated disturbances or rather forms of other personal disorders e.g. autism. Psychopaths and sociopaths often get into conflict with their social environment because they repeatedly violate social and moral rules. Acquired sociopathy manifests in the inability to form lasting relationships, irresponsible behaviour as well as getting angry quite fast and exceptional strong egocentric thinking. While acquired sociopathy might be characterised by impulsive antisocial behaviour often having no personal advantage, developmental psychopathy manifests in goal directed and self-initiated aggression. Acquired sociopathy is caused by brain injury especially found in the orbitofrontal lobe (frontal lobe) and is thought to be a failure to use emotional cues and the loss of social knowledge. Therefore sociopaths are unable to control and plan their behaviour in a socially adequate manner. In contrast to sociopaths psychopaths are not getting angry because of minor reasons but they act aggressively without understandable reasons at all which might be due to their inability to understand and distinguish between moral rules (concerning the welfare of others) and conventions (consensus rules of society). Furthermore it even happens that they feel no guilt or empathy for their victims. Psychopathy is probably caused by a failure to process distress cues of others, meaning that they are unable to understand sad and fearful expressions and consequently suppress their aggression (Blair 1995). It is important to mention that they are nevertheless able to detect stimuli being threatening for themselves.


6.6: Checklist - Set Up a Chest Tube Drainage System
*Disclaimer: Always follow agency policy and manufacturer recommendations
Checklist: Set Up a Chest Tube Drainage System [1] , [2]
Note: Refer to agency policy and the manufacturer’s guidelines before setting up a system.
- Verify the provider’s order to determine the type of drainage system to use.
-
Gather the necessary equipment and supplies:
- Single-use, disposable, sterile chest drainage collection unit (water-seal–wet-suction system, water-seal–dry-suction system, or dry-seal–dry-suction system)
- Sterile water
- Nonsterile gloves
- Tape
- Sterile dressing
- Optional: commercial securement device, zip tie, suction source with regulator, and suction connection tubing
- Perform hand hygiene.
- Put on clean gloves.
- Maintain a sterile no-touch technique of the drainage system, including the tubing throughout the procedure.
- Remove any protective wrappers and prepare for setup. Stand the system upright. Use the floor or hangers on the unit. Attach the unit to bed frame, keeping the unit below the level of the insertion site of the chest tube.
-
Add sterile water or sterile normal saline to the appropriate compartments according to the manufacturer’s instructions:
- For a Two-chamber System Without Suction: Add sterile fluid to the water seal chamber to the required indicated level.
- For a Three-chamber System With Suction: Add sterile fluid to the water seal chamber, typically to the 2 cm mark. Add sterile fluid to the suction control chamber, typically to the -20 cm mark. Connect the tubing from the suction control chamber to the suction delivery system (wall or portable).
- For a Dry Suction System: Fill the water seal chamber with sterile solution, typically to the 2 cm mark. Adjust the suction control dial for the prescribed level of suction, typically between -10 to -40 cm. Connect the tubing from the suction control chamber to the suction delivery system (wall or portable). Do not occlude the suction control chamber when suction is used. On a dry suction system, do not occlude the positive-pressure relief valve because air will escape.
- Secure all tubing connections with tape or zip ties as indicated by agency policy.
- Discard used supplies, remove gloves, and perform hand hygiene.
- Help the patient into a comfortable position and place personal items, the tray table, and the call light within easy reach. Make sure the patient knows how to use the call light to summon assistance. To ensure the patient’s safety, raise the appropriate number of side rails and lower the bed to the lowest position. Ensure the bed is locked.
- Perform hand hygiene.
- Document the procedure.
Documentation Cues:
- Date and time that chest tube drainage system was initiated
- Type of chest tube drainage system used
- Location and size of chest tube inserted
- Amount of suction applied to the pleural cavity (if applicable)
- Presence or absence of bubbling or fluctuation in the water seal chamber (if applicable)
- Teaching provided to the client and family, understanding of education, and any need for follow-up teaching
- Clinical skills: Essentials collection (1st ed.). (2021). Elsevier. ↵
- Lippincott procedures. http://procedures.lww.com ↵


Skip to main content
-
-
2.1: Introduction to Life Cycles
-
Life Cycle Assessment (LCA) is a comprehensive life cycle approach that quantifies ecological and human health impacts of a product or system over its complete life cycle. It uses credible scientific methods to model steady-state, global environmental and human health impacts. It also helps decision-makers understand the scale of many environmental and human health impacts of competing products, services, policies or actions.
-
-
2.2: LCA/LCIA Concepts
-
Assumptions inherent in an LCA study are apt to change the results and conclusions derived from analysis. In addition, many different types of studies require various levels data collection and analysis. The goal and scope of a LCA defines its intent, targeted audience, and use. The intended use informs further decisions for scope, functional unit of comparison, and data collection.
-
-
2.3: Conclusions and Review
-
There are many tools to assist life cycle assessments. There are software and data packages designed for performing LCAs. No matter the form of the software, the use of some sort of LCA software and data management system is needed in LCAs. The life cycle inventory step of an LCA often requires a large data set listing hundreds of emissions to the environment.


3.4: Brain Maturation
-
- Last updated
- Save as PDF
Brain Weight
The brain is about 75 percent its adult weight by two years of age. By age 6, it is approximately 95 percent its adult weight. Myelination and the development of dendrites continues to occur in the cortex and as it does, we see a corresponding change in the child’s abilities. Significant development in the prefrontal cortex (the area of the brain behind the forehead that helps us to think, strategize, and control emotion) makes it increasingly possible to control emotional outbursts and to understand how to play games. Consider 4- or 5-year-old children and how they might approach a game of soccer. Chances are, every move would be a response to the commands of a coach standing nearby calling out, “Run this way! Now, stop. Look at the ball. Kick the ball!” And when the child is not being told what to do, he or she is likely to be looking at the clover on the ground or a dog on the other side of the fence! Understanding the game, thinking ahead, coordinating movement, and handling losing improve with practice and myelination.7
Visual Pathways
Children’s drawings are representative of the development of visual pathways; as children’s brains mature the images in their drawings change. Early scribbles and dots illustrate the use of simple motor skills. No real connection is made between an image being visualized and what is created on paper.
At age 3, the child begins to draw wispy creatures with heads and not much other detail. Gradually pictures begin to have more detail and incorporate more parts of the body. Arm buds become arms and faces take on noses, lips and eventually eyelashes.
Growth in the Hemispheres and Corpus Callosum
Between ages 3 and 6, the left hemisphere of the brain grows dramatically. This side of the brain or hemisphere is typically involved in language skills. The right hemisphere continues to grow throughout early childhood and is involved in tasks that require spatial skills such as recognizing shapes and patterns. The corpus callosum which connects the two hemispheres of the brain undergoes a growth spurt between ages 3 and 6 and results in improved coordination between right and left hemisphere tasks.
Contributors and Attributions
7. Lifespan Development - Module 5: Early Childhood by Lumen Learning references Psyc 200 Lifespan Psychology by Laura Overstreet, licensed under CC BY 4.0


1.3: Culture, Beliefs, Attitudes, and Stigmatized Illnesses
Cultural Lens and How Culture Influences Your Perceptions
Cultural Awareness, Sensitivity, and Safety
Culture can be defined in terms of the shared knowledge, beliefs, and values that characterize a social group. Humans have a strong drive to maintain the sense of identity that comes from membership in an identifiable group. In primeval and nomadic times, a person’s survival likely benefited from establishing strong bonds with an in-group of trusted relatives or clan-mates with whom one co-operated and shared, versus an out-group against which there was competition for scarce resources. Within the intermixing of modern society, many of us seek to retain a sense of cultural identity and may often refer to our cultural roots, or use double-barreled descriptions such as Asian-American. It is important that we are all aware of our own cultural influences and how these may affect our perceptions of others, especially in the doctor-patient encounter. In many subtle ways, the cultural identities of both doctor and patient affect their interaction, and in a diverse country this can form an exciting challenge.
Culture and individual
We all perceive others through the filter or perspective of our own cultural upbringing, often without being aware of it: communication can go wrong without our understanding why. The clinician must become culturally aware and sensitive, then culturally competent so that she or he can practice in a manner that is culturally safe.
Cultural awareness
Cultural competency in medical practice requires that the clinician respects and appreciates diversity in society. Culturally competent clinicians acknowledge differences but do not feel threatened by them. “Culturally competent communication leaves our patients feeling that their concerns were understood, a trusting relationship was formed and, above all, that they were treated with respect.” While a clinician will often be unfamiliar with the culture of a particular patient, the direct approach is often the best: ask the patient what you need to understand about her culture and background in order to be able to help her. A direct approach helps establish mutual respect and tailor the best and most appropriate care for each patient.
Awareness of one’s own culture is an important step towards awareness of, and sensitivity to, the culture and ethnicity of other people. Clinicians who are not aware of their own cultural biases may unconsciously impose their cultural values on other people. “As physicians, we must make multiple communication adjustments each day when interacting with our patients to provide care that is responsive to the diverse cultural backgrounds of patients in our highly multicultural nation.”
Cultural safety refers to a doctor-patient encounter in which the patient feels respected and empowered, and that their culture and knowledge has been acknowledged. Cultural safety refers to the patient’s feelings in the health care encounter, while cultural competence refers to the skills required by a practitioner to ensure that the patient feels safe.
To practice in a manner that is culturally safe, practitioners should reflect on the power differentials inherent in health service delivery. Taking a culturally safe approach also implies acting as a health advocate: working to improve access to care; exposing the social, political, and historical context of health care; and interrupting unequal power relations. Given that the patient exists simultaneously within several caring systems, influenced by their family, community, and traditions, the culturally safe practitioner allows the patient to define what is culturally safe for them.
Our culture influences the way we perceive virtually everything around us, often unconsciously. Several useful concepts describe issues that can arise:
- Ethnocentrism . The sense that one’s own beliefs, values, and ways of life are superior to, and more desirable than, those of others. For example, you may be trained in Western medicine, but your patient insists on taking a herbal remedy. You may be tempted to say “So, why are you consulting me, then?” Ethnocentrism is often unconscious and implicit in a person’s behavior. Personal reflection is a valuable tool for physicians to critically examine their own ethnocentric views and behaviors.
- Cultural blindness . This refers to attempts (often well-intentioned) to be unbiased by ignoring the fact of a person’s race. It is illustrated in phrases such as ‘being color blind’, or ‘not seeing race’. However, ignoring cultural differences may make people from another culture feel discounted or ignored; what may be transmitted is the impression that race or culture are unimportant, and that values of the dominant culture are universally applicable. Meanwhile, the person who is culturally blind may feel they are being fair and unprejudiced, unaware of how they are making others feel. Cultural blindness becomes, in effect, the opposite of cultural sensitivity.
- Culture shock . Most physicians come from middle-class families and have not experienced poverty, homelessness or addictions. Exposure to such realities in their patients therefore requires great adaptations and can be distressing. This is a common experience in those who have visited a slum in a developing country, but may also arise at home in confronting abortion, infanticide, or female circumcision.
- Cultural conflict . Conflict generated when the rules of one’s own culture are contradicted by the rules of another.
- Cultural imposition (or cultural assimilation or colonialism). The imposition of the views and values of your own culture without consideration of the beliefs of others.
- Stereotyping and generalization . What may be true of a group need not apply to each individual. Hence, talking about cultures can lead to dangerously prejudicial generalizations. Prejudice is the tendency to use preconceived notions about a group in pre-judging one of the group’s members, so applying cultural awareness to individuals can be hazardous. Yet, on the other hand, ignoring culture (cultural blindness) can be equally detrimental. The key is to acknowledge and be respectful of differences, and to ask patients to explain their perspective when in doubt.
Watch these brief videos from Think–Speak–Act Cultural Health to hear about specific cultural health examples.
The Relevance of Culture for Health
Culture influences health through many channels:
- Positive or negative lifestyle behaviors. While we often focus on the negative influences of lifestyle behavior—such as drug cultures, or the poor diet of some teen cultures, for example—we should not neglect the positive cultural influences on behaviors and practices. For example, Mormons and Seventh Day Adventists have been found to live longer than the general population, in part because of their lifestyle including the avoidance of alcohol and smoking, but also because of enhanced social support.
- Health beliefs and attitudes . These include what a person views as illness that requires treatment, and which treatments and preventive measures he or she will accept, as with the Jehovah’s Witness prohibition on using whole blood products.
- Reactions to being sick . A person’s adoption of the sick role (and, hence, how he or she or he reacts to being sick) is often guided by his or her cultural roots. For instance, “machismo” may discourage a man from seeking prompt medical attention, and culture may also influence from whom a person will accept advice.
- Communication patterns, including language and modes of thinking. Beyond these, however, culture may constrain some patients from expressing an opinion to the doctor, or may discourage a wife from speaking freely in front of her husband, for example. Such influences can complicate efforts to establish a therapeutic relationship and, thereby, to help the patient.
- Status . The way in which one culture views another may affect the status of entire groups of people, placing them at a disadvantage. The resulting social inequality or even exclusion forms a health determinant. For example, women in some societies have little power to insist on condom use.
What elements of a patient’s culture should a health care provider consider when deciding how best to manage a case?
Cultural influences may affect a patient’s reaction to the disease, to suggested therapy, and to efforts to help them prevent recurrences by changing risk factors. Therefore, it may be important for health care providers to find out about such possibilities; they can explain that they need them to tell about their family’s and community’s feelings about health recommendations. Health care providers should explain that they are not familiar with their community and want them to tell if they may have beliefs or obligations that the health care provider should be aware of, such as any restrictions on diet, medications, etc., if these could be relevant.
Difference between cultural competence and cultural safety
Cultural competence is included within cultural safety, but safety goes beyond competence to advocate actively for the patient’s perspective, to protect their right to hold the views they do. When a patient knows that you will honor and uphold their perspective and not try to change it, they will be more likely to accept your recommendations.  This pattern of self-reflection, education and advocacy is also practiced at the organizational level.
Asian women, in general, and Vietnamese women, in particular, have been identified as ethnic groups that are not participating in breast cancer screening programs in the U.S. The reasons are complex and Vietnamese women may be especially vulnerable due to cultural variances in beliefs, health practices, language barriers, lack of access to care due to socio-economic factors, as well as the long term effects of the migration that occurred at the close of the Vietnam war.
Find out about how culture impacts health decisions and access by visiting each of the websites linked in the list below:
- Hispanic-Latino Culture
- Chinese Culture
- Iraqi Culture
- Vietnamese Culture
- Lesbian, Gay, Bisexual, and Transgender Health Issues
What are some of the positive and/or negative ways that culture impacts an individual’s health care decisions and access?
- Answer
-
Some Ethiopians living in the United States may avoid getting treatment if the medical facility is central and visible to their community. This could be due to the social stigma of TB (tuberculosis) in that culture combined with a cultural identity that highly values community participation. So, in order for Ethiopian-Americans to be more likely to get treatment for TB, the medical facility needs to be located in place where patients can come and go without being seen easily.
Stigmatized Illnesses and Health Care
Being disabled because of a disease or injury can lead to benefits – for example, a parking space that is close by. In some instances, the benefits are very attractive but, in most countries of the world, the disabled have no access to any governmental help, and insurance premiums are so high that only a minority of the population can participate in disability compensations schemes. In some situations, disability due to a war injury or to some other situation that confers hero status can also bring social respect and moral prestige to the disabled person.
For the vast majority of disabled people, however, the disadvantages of disability are much more important than its advantages. A restriction of the possibility of participation in normal social life and limitations in the pursuit of personal happiness are often grave and depressing for the person with an impairment that causes a disability.
When the disease or the situation that has produced impairment is stigmatized, the limitations of functions are aggravated and the possibility of compensating disability is significantly reduced. There are a number of diseases that are stigmatized—mental disorders, AIDS, venereal diseases, leprosy, and certain skin diseases. People who have such diseases are discriminated in the health care system, they usually receive much less social support than those who have non-stigmatizing illnesses and—what is possibly worst—they have grave difficulties in organizing their life if their disease has caused an impairment that can lead to disability and handicaps.
Mental disorders probably carry more stigma (and consequent discrimination) than any other illness. The stigma does not stop at the persons who are suffering from a stigmatized illness. Their immediate and even remote families often experience significant social disadvantages. The institutions that provide mental health care are stigmatized. Stigma reduces the value of the persons who have a mental disorder in the eyes of the community and the government.
Medications that are needed in the treatment of mental disorders, for example, are considered expensive even when their cost is much lower than the cost of drugs used in the treatment of other illnesses: they are not considered expensive because of their cost but because they are meant to be used in the treatment of people who are not considered to be of much value to the society.
The awareness of the fact that stigmatization is one of the major—if not the major—obstacles to the improvement of care for people with stigmatized illnesses is gradually growing. In a number of countries governments, non-governmental organizations, and health institutions have launched campaigns to reduce stigma related to illness. They display posters and distribute leaflets, as well as organize radio and television programs.
There is, however, an important sector employing many individuals that does not participate very actively in the reduction of stigma and in efforts to eliminate the discrimination that follows it. It is the health sector—which, by its definition, could gain from the reduction of stigma almost as much as the individuals who have the stigmatized illness. The managements of general hospitals, as well as heads of various medical departments often refuse to have a department of psychiatry and, if they accept it, they usually assign the worst accommodation for it—in a remote corner of the hospital grounds, for example, or in the lowest (sometimes partly underground) floor. In the order of priority for maintenance or renovation work departments of psychiatry come last although they are often in a pitiful state. Doctors who are not involved in mental health care participate and sometimes excel in making fun of the mentally ill, of psychiatrists, and of mental illness. They will often refuse to deal with physical illness in a person with a mental disorder and send such patients to their psychiatrist, although they are better placed to deal with the physical illness than the psychiatrist.
Nor are the psychiatrists and other mental health care staff doing as much as they should about the reduction of stigma. They seem unaware of the stigmatizing effects of their use of language—they speak of schizophrenics when they should say a person with schizophrenia and about misbehavior or lack of discipline when they should make it clear that behavioral abnormalities are part of the illness they are supposed to recognize and treat. In some countries they requested and received longer holidays or somewhat higher salaries saying that they deserve this because they deal with dangerous patients—although they have publicly proclaimed that mental illness is a disease like any other. They often disregard complaints about the physical health of people with mental disorders and do not do much about them, thus providing sub-optimal care and contributing to the tendency to dismiss whatever people with mental illness may be saying. In their teaching activities, stigmatization as well as the prevention of discrimination and its other consequences often receive only minimal attention.
Perhaps it is impossible for the health care workers themselves to launch large anti-stigma programs: what, however, they should and can do is to examine their own behavior and activity to ensure that they do not contribute to stigmatization and consequent discrimination. They should also participate in the efforts of others to reduce stigma or initiate such efforts whenever possible. Doing nothing about stigma and discrimination that follows it is no longer an acceptable option.
The Cultural Meaning of Illness
Our culture, not our biology, dictates which illnesses are stigmatized and which are not, which are considered disabilities and which are not, and which are deemed contestable (meaning some medical professionals may find the existence of this ailment questionable) as opposed to definitive (illnesses that are unquestionably recognized in the medical profession) (Conrad and Barker 2010). For instance, sociologist Erving Goffman (1963) described how social stigmas hinder individuals from fully integrating into society. The stigmatization of illness often has the greatest effect on the patient and the kind of care he or she receives.  Facilities for these diseases may be sub-par; they may be segregated from other health care areas or relegated to a poorer environment.  Contested illnesses are those that are questioned or questionable by some medical professionals. Disorders like fibromyalgia or chronic fatigue syndrome may be either true illnesses or only in the patients’ heads, depending on the opinion of the medical professional. This dynamic can affect how a patient seeks treatment and what kind of treatment he or she receives.
In terms of constructing the illness experience, culture and individual personality both play a significant role. For some people, a long-term illness can have the effect of making their world smaller, more defined by the illness than anything else. For others, illness can be a chance for discovery, for re-imaging a new self (Conrad and Barker 2007). Culture plays a huge role in how an individual experiences illness. Widespread diseases like AIDS or breast cancer have specific cultural markers that have changed over the years and that govern how individuals—and society—view them.
Today, many institutions of wellness acknowledge the degree to which individual perceptions shape the nature of health and illness. Regarding physical activity, for instance, the Centers for Disease Control (CDC) recommends that individuals use a standard level of exertion to assess their physical activity. This Rating of Perceived Exertion (RPE) gives a more complete view of an individual’s actual exertion level, since heart-rate or pulse measurements may be affected by medication or other issues (Centers for Disease Control 2011a). Similarly, many medical professionals use a comparable scale for perceived pain to help determine pain management strategies.
Consider these questions:
- What diseases are the most stigmatized?
- Which are the least?
- Is this different in different cultures or social classes?
Solution
Look at these sources to find some answers
Cultural Lens and How Culture Influences Your Perceptions: “The cultural lens and how culture influences your perceptions of others” AFMC Primer on Population Health, The Association of Faculties of Medicine of Canada Public Health Educators’ Network, phprimer.afmc.ca/Part1-TheoryThinkingAboutHealth/Chapter3CulturalCompetenceAndCommunication/Culturalawarenesssensitivityandsafety (Accessed March 11, 2012). License: Creative Commons BY-NC-SA
Example: Breast Cancer in Asian Women: Breast Cancer in Asian Women by Denise Little, Ethnomed, CC-BY-NC-ND, http://ethnomed.org/clinical/cancer/breast-cancer-in-asian-women
Stigmatized Illnesses and Health Care: Stigmatized Illnesses and Health Care, Norman Sartorius, Croatian Medical Journal, 2007 June; 48(3): 396–397, CC-BY-NC, www.ncbi.nlm.nih.gov/pmc/articles/PMC2080544/
The Cultural Meaning of Illness: OpenStax College, CC-BY, The Social Construction of Health , Connexions, May 18, 2012, http://cnx.org/content/m42927/1.2 /