8.5: Mental Health and Culture-Bound Syndromes
Culture Bound Syndromes are those in which changes in behavior and experiences have substantial effects on peoples lives. These are identified as syndromes not sicknesses. A syndrome is a group of symptoms when present together are characteristics of a specific disorder, disease, etc.[6] The patterns of the symptoms that characterize or indicate can be of a particular social condition like heavy pollution. Syndromes can be a culture bound syndrome like Anorexia Nervosa or they can be a biological syndromes like Down’s Syndrome. The word syndrome comes from the Greek meaning “run together”. Medical anthropology describes culture-bound syndrome as a combination of psychiatric and somatic symptoms that are considered to be an identifiable disease that is only discovered within a specific society or culture. There are no changes in the biochemical or structural of body organs or functions, and the disease is not recognized in other cultures. A substantial portion of mental disorders are at least partially if not completely conditioned by the culture in which they are found. Some disorders however are more culture-specific than others. The concept of culture-bound syndromes is a controversial subject to which many psychologists, medical doctors and anthropologists reject the concept.
Addiction
Addiction is a serious mental health issue that is present in cultures worldwide. Addiction is the condition of being mentally or physically reliant to a chemical substance, action, or item. Addiction is often sprouted from an early age. Factors that can effect an individual's likelihood of becoming a substance abuser can range from their upbringing and environment in their youth, to the people they chose to surround themselves with later on in life. Many substances are highly addictive upon first use such as heroin. Heroin has become one of the largest health concerns in many countries with alarming rates of growth. According to www.drugabuse.gov 90,000 people in the United States reported trying heroin for the first time in 2006, compared to the alarming 156,000 people who tried it just 6 years later in 2012. Addiction often originates as a mental disorder through the cravings and desires of addicts, but can soon develop into a physical dependence which can lead to many negative health effects. Addiction to many different drugs including heroin almost always quickly deteriorates the addict's body and is very often fatal.
Addiction can also occur due to cultural factors such as being addicted to a certain activity or a certain hobby a great deal to the point that it interferes with other activities that are necessary in everyday life for wellbeing.[11]
Obesity
Obesity is a condition affecting more than 300 million people.[12] Obesity is most common in first world countries and it affects millions of people. Obesity the term used to describe a person who is overweight to the point that it becomes the cause of many other afflictions that could potentially threaten their life. A person is obese when their body mass index (BMI) exceeds 30 kg/m 2 [12]The World Health Organization (WHO) considers obesity to be one of the top 10 causes of preventable death worldwide. Overweight individuals in developing countries are considered attractive and desirable due to connotations such as excess wealth, the ability to live lavishly and abundantly, etc. Interestingly, this is the opposite to the view of body weight in developed countries, where thinness implies beauty, wealth, and good health. One who is wealthy can eat a balanced and healthy (and often more expensive) diet and has the luxury, time and money to exercise in either a gym or with the help of a personal trainer.
Ataque de Nervios
Term used among Caribbean Latinos used to describe a culture-bound syndrome, or state of mind, characterized by uncontrollable shouting, crying, aggressiveness, shaking or trembling, fainting, and suicidal gestures. Ataque de nervios typically follows a stressful event - death of a loved one, divorce or other domestic conflicts. This affliction is shares features of a panic attack defined by the DSM-IV, an ataque , usually following a precipitating event, occurs in the absence of acute fear or apprehension, and is accompanied by amnesia for the ataque .
Mal de Ojo
Medical problems, such as vomiting, fever, diarrhea, and mental problems (e.g., anxiety, depression) could result from the mal de Ojo (evil eye) that an individual has experienced from another person. Mal de Ojo is initiated when a person of higher strength gazes upon the weaker counterpart out of envy or admiration.[13] The condition is common among infants and children; adults might also experience similar symptoms resulting from this mal de Ojo. There are many different ways in curing mal de Ojo. In Latin America the most common way is to have the parent rub an egg on the child while saying a prayer over the child then put the egg in a bowl and put it under the child's pillow. In the morning if the bowl has this white fog then you can tell the child was affected by the mal de Ojo. This process also cures it.[14]
Eating Disorders
Eating disorders are defined as any of a range of psychological disorders characterized by abnormal or disturbed eating habits. The most common eating disorder is anorexia nervosa.
Anorexia Nervosa
Anorexia Nervosa is a eating disorder and is commonly shortened to anorexia. Anorexia Nervosa is a psychiatric illness which is specifically defined as the "obsessive fear of gaining weight". This fear causes the individual to avoid food consumption. This disorder most commonly affects young teenage girls. In total, males account for only 10% of the reported cases. Bulimia Nervosa is a similar culture-bound syndrome to Anorexia Nervosa in which purging is the method of losing weight. Many times people who have these eating disorders though do not have one strict eating disorder. It tends to be a combination of anorexia, bulimia and binge eating. For example, a person may restrict themselves to not eating, but if they do they may go and work out excessively and then binge eat after [15] In some cases however, these eating disorders are developed as a coping mechanism for problems other than the common fear of weight gain. Providing its victims with a sense of control, anorexia and bulimia can help ease the mind even if the goal is to find stability in areas other than weight loss.
The process used to initially lose and prevent weight gain is voluntary starvation, but other methods such as purging, excessive exercise and the use of dietary pills are used also to control body image. One of the proposed reasons for the cause of this disease is the effect of images portrayed by the media on young women and men, demanding a necessity to be slim, because that is the only socially acceptable way to look
Symptoms include:
- Refusing, avoiding, or not wanting to eat in public
- Anxiety
- Weakness
- Brittle skin
- Shortness of breath
- Obsessiveness about calorie intake
- muscle loss/degeneration
- Additionally, anorexic people have a tendency to create a distorted, negative view of themselves "Anorexia" . [16]
Body Image and Fitness
Eating disorders such as anorexia nervosa are often caused by body image issues. Every culture around the world has varying ideas of what the “ideal body” should look like. These standards are especially high in the in United States. With an increasingly high exposure to social media, fashion magazines and beauty advertisements, adolescents in the US (especially young women) are feeling an increased pressure to obtain these “perfect bodies.” In recent years there have been cases of some people going to the extremes to be “perfect,” which are more often than not unhealthy and potentially life-threatening. For example eating disorders such as Anorexia nervosa or Bulimia nervosa.
Avoidant/Restrictive Food Intake Disorder
Avoidant/Restrictive Food Intake Disorder, or ARFID, is an eating disorder that was recently made independent from EDNOS (Eating Disorder Not Otherwise Specified) when the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) was released in 2013. Originally, there was a disorder labeled as "Feeding Disorder of Infancy or Early Childhood" which listed similar diagnoses, but this was removed in the DSM-V, as it was decided that ARFID was a disorder that also occurred in adults.
The disorder itself can be described similarly to a phobic fear, and usually stems from anxiety around new and unfamiliar foods, rather than with body image and self-esteem issues that are associated with eating disorders such as anorexia or bulimia.
To be diagnosed with ARFID, the DSM-V gives these criteria:
- Disturbance in eating or feeding, as evidenced by one or more of:
- Substantial weight loss (or, in children, absence of expected weight gain)
- Nutritional deficiency
- Dependence on a feeding tube or dietary supplements
- Significant psychosocial interference
- Disturbance not due to unavailability of food, or to observation of cultural norms
- Disturbance not due to anorexia nervosa or bulimia nervosa, and no evidence of disturbance in experience of body shape or weight
- Disturbance not better explained by another medical condition or mental disorder, or when occurring concurrently with another condition, the disturbance exceeds what is normally caused by that condition
A person with ARFID acts similarly to a child who is a "picky eater." They typically have a small number of "safe foods" that they eat normally and do not have any trouble with for the most part, but most new or unfamiliar foods outside of their safe ones cause seemingly irrational and extreme (sometimes phobic-level) fear and anxiety, often leading to a full-on anxiety/panic attack or breakdown. This may be caused by a food's appearance, smell, texture, or any other number of reasons.
Many teenagers and adults with ARFID have gone and continue to go undiagnosed and untreated for most of their lives, due to the disorder only being classified in recent years. It can also be assumed that the majority of people who have ARFID are completely unaware that their strange eating problems are likely a legitimate disorder, and not just "picky eating" that they never grew out of in childhood. ARFID can get in the way of not only a person's health, but also their social life: people with ARFID may tend to avoid social gatherings involving food, holidays that involve eating may become more anxiety-inducing than enjoyable, etc.
While there has not been much research done on the treatment of ARFID, many people choose Cognitive Behavioral Therapy or hypnotism as ways to work towards a normal food palette and healthy diet.
Amok
Malaysian sudden mood change/aggression.
Amok is the psychological disorder where males who typically have never acted out before experience a sudden mood change and become violent and angry. Deep shame experienced by the male often seems to be the cause of the sudden mood changes, these changes can be caused by situations and feelings such as jealousy or gambling losses.  Often people who have these mood shifts will end up being killed by a bystander out of self-defense or other reasons, or the person suffering from Amok will commit suicide. The word was derived from the Malay, Indonesian and Filipino word "amuk" which means "mad with rage." The term has been changed into slang in the United States and the phrase "Running Amok" is used to describe someone who is acting crazy or can't control themselves.
Dhat Syndrome
The patient is preoccupied with the excessive loss of semen by nocturnal emissions. There is a fear that semen is being lost and mixed in urine. In the Hindu culture and religion, it is believed that "40 meals create one drop of blood, 40 drops of blood create one drop of bone marrow and 40 drops of marrow create one drop of semen." It is thought in the Hindu culture in India, although not isolated there, that the loss of semen can deteriorate your health and create health problems. Symptoms of Dhat Symdrome are depression, preoccupation, trouble sleeping, inability to perform sexually, exhaustion and headaches, and others. In order to treat these symptoms of depression and anxiety, counseling or anti-anxiety or anti-depression medications have been found to be of use. [7]
Genital Retraction Syndrome (Koro)
Retraction into body. (Malay Koro, Sudan melting penis/cell phone phenomenon)
Genital Retraction syndrome is a culture-bound syndrome occurring mostly in African and Asian men.  In South East Asia this syndrome has become known as “Koro”, which means “head of the turtle”. It can also be referred to as penis panic. In this case a large group of men can become panicked about their genitalia disappearing. Often these fears come about in cultures where witchcraft is used, or where biological education isn’t available. In 1997 lynch mobs in Ghana attacked foreigners they accused of being sorcerers capable of shrinking men’s penises.
Latah
Latah is a culture-bound syndrome that exist in Malaysian and Indonesian cultures. People showing signs of this syndrome respond to minimal stimuli with exaggerated startles. Sometimes, after becoming started, people suffering from this syndrome will obey the commands or imitate the actions of the people around them. Most occurrences of Latah are intentionally provoked to act as entertainment for those surrounding. Latah is very closely tied to specific factors in the cultural systems of the Southeast Asian societies in which it is found. The Latah syndrome exemplifies the very dynamic and complex ways in which neurophysiological, experiential, and cultural variables coincide with each other to produce a strongly marked phenomenon in these cultures. It is most widely known as a hyperstartling condition which mainly occurs in Malayan cultures.  During episodes of this behavior, Latah's are usually not held responsible for their actions. It is also closely related to another condition called Hyperexplexia. (SE Asia women, obey, not responsible for acts)
Piblokto
Piblokto, pronounced (pee-block-toh) and loosely translated from Inuit to English means "running crazy" is a hysterical/dissociative state. It occurs mostly in the winter season and typically shown in Inuit or Eskimo women and is characterized by short attacks of disturbed behavior that are not remembered by the individual afterward.
The symptoms can include running naked through the snow, an insensitivity to extreme cold, coprophagia (the consumption of feces), echolalia (the repetition of words), depression, screaming, crying, and violence towards other people and animals. Piblokto is most often seen in women of the Inuit tribe. These people inhabit the areas of northern Canada,Greenland, the coastal regions of Alaska and north eastern Asia/Russia. They are able to inhabit very harsh conditions and tolerate the snow and ice of the Arctic tundra for most of the year. There has never been a recorded case of Piblotko in children, although women in tribal groups have been recorded as having as many as 5 attacks of hysteria a day. The Inuit people's diet mainly consists wild game, whale and seal meat. A diet high in protein, selenium, and fats may help these people escape the risks of cancer but not the biological/psychological malady of Piblokto. Although commonly thought of as a psychological ailment, Piblotko may be linked to vitamin A toxicity, or hypervitaminosis A. Vitamin A toxicity is caused by an overconsumption of pre-formed Vitamin A, which is the result of high amounts of vitamin A in the diet at one time. This can lead to altered mental state, confusion, headache,and irritability, as well as many symptoms that are common to Piblotko. Piblotko has also been recorded in Inuit dogs and while these dogs are not considered infectious, they are shot when symptoms first occur and then eaten by the tribe. SAD- seasonal affective disease; loosely linked to this syndrome, as the weather and light are factors that play straight into symptoms like depression. [17]
Susto
Susto is a Folk Illness that is most commonly found in Latin America. The term "susto" comes from the Portuguese and Spanish word for fright. In this way, the illness is called “fright sickness”. It is also referred to as "spirit attacks," most common among Native Americans. The disease is usually generated from a traumatic experience like the death of a loved one, an accident, or anything else that might cause physiological pain. It is most common in women but can also be found in men and children. The illness in not recognized by Western Traditional Medicine, but is commonly compared to anxiety disorders.
Symptoms of susto can be nervousness, anorexia, insomnia, listlessness, despondency, involuntary muscle tics, and diarrhea. Treatments for this illness are mostly natural and herbal, such as consuming marijuana teas, Brazil wood, and orange blossom. The most effective treatments are done by what is called a healer and can include different sort of rituals. The closer these rituals are practiced to when the traumatic experience occurred, the better. It is also very important to recognize the event and not suppress it.
Susto is often compared to other biomedical illnesses. In 2002 studies about susto were conducted in; Latin communities, the United States, Mexico and Guatemala. First they defined susto in the different communities. Although the definition differed from region to region, the main idea was that susto was an illness caused by fright, and not necessarily loss of soul. It was seen as a serious illness that could even lead to death. But to better understand this folk illness, in biomedical culture and culture I am familiar with in United States, susto is best related to depressive disorders, post traumatic stress disorder, and somatoform disorders.[18]
Opsophagos
Opsophagos was an ancient Greek label given to anyone who had an extreme and irrepressible desire for eating fish.
The term is a definition one’s character, not literally their general palate for fish. Charging someone with the term is directed in a very negative manner- it parallels being indicted with having over-indulgent behavior, a taboo in Greek society. Opsophagos is synonymous with words like unsophisticated and barbaric- words opposite of rationality. The fish is simply a symbol for overindulgence.
Greek tall tales describe an opsophagos as a gluttonous and greedy man who would consume all prepared fish, sharing none with anyone. The painted image of an opsophagos was the opposite of an ideal human- a man with a heat-resistant throat to handle fish too hot for anyone else to eat, thus keeping the fish for only themselves.
Opposite of America’s Judeo-Christian tradition, Greek thought and morality is more flexible than the orthodox, black and white view of simple rights or wrongs. For example, instead of ruling out women or wine, Greeks believe in “nothing in excess”-enjoy life’s pleasure but under control. This is contrary to the American idea of suppressing vices and how negative habits should be cut out completely “cold turkey”.
http://www.nytimes.com/books/98/09/06/reviews/980906.06jenkynt.html
http://www.washingtonpost.com/wp-srv/style/books/reviews/courtesansandfishcakes0830.htm
Ghost Sickness
Ghost Sickness originates from the Navajo Nation and is believed to be a psychotic disorder associated with death. Common symptoms include fatigue, recurring nightmares, hallucinations, and a constant feeling of terror. The people of the Navajo Nation believe that a Chindi causes Ghost Sickness. A Chindi is the ghost of the Navajo Tribe and many believe that this ghost is released during a person’s dying breath, and it is also believed to nearly always be an evil force. A common manifestation of a Chindi is believed to be a Dust Devil, and the direction they spin signifies whether it is a ‘good’ Chindi or a ‘bad’ one; a clockwise spin is considered good – a counter-clockwise is considered bad. Other Native American tribes have modified beliefs of Ghost Sickness and have attempted to prevent or avoid passing it on. For example, the Lakota Tribe attempted a ban on mourning rituals in order to avoid the illness in the 1800's, but many still practice modified rituals.
Windingo
Windigo (or Witiko) A culturally bound syndrome found among the Algonkian Indians, NE United States and Eastern Canada. Windigo is the famous syndrome of obsessive cannibalism or the consumption of another’s flesh. Windigo has fallen under skeptical eyes and to many is now somewhat discredited. A modern medical diagnosis of this condition would probably label it as paranoia, due to the irrational perceptions of being persecuted for suffering from Windingo. Fear of prosecution is prevalent among victims of Windingo because of the cultural universal that eating humans is wrong. Windigo was supposed to have been brought about by consuming human flesh in desperate circumstances such as famines. Afterwards, the individual who consumed flesh was supposed to be haunted by cravings for human flesh and thoughts of killing and eating humans. In other words, Windigo is the unwanted transformation into a cannibal.
In the Great Lakes of Canada and the United States where climate was harsh, Windingo would develop among families who, isolated in their homes due to heavy snow storms, had inadequate food and supplies. Symptoms of Windigo include vomiting and lack of appetite. The individual would then begin to develop delusions of him or herself believing they are becoming a Windigo Monster. People suffering from Windigo psychosis claim to see others as edible, which only increases with time. As the individual becomes aware of the transformation they begin to deeply fear becoming a cannibal. Victims of Windigo psychosis often experience severe panic and anxiety. Suicide is common in order to prevent themselves from becoming Windigo monsters. [9]
Zar
Zar [10] is experienced in Ethiopia, Somalia, Egypt, Sudan, Iran, and other places in the Middle East and North Africa. The feeling you get when you have zar is spirit possession. Some symptoms that could occur are dissociation episodes including shouting, laughing, singing, weeping, or hitting the head against some sort of surface. Individuals may refuse to do simple tasks such as eat or go about their daily tasks in life; they may also show withdrawal and apathy. In some cases the person might develop a long-term relationship with the possessing spirit, but this is the rarest symptom. Zar can also be used as part of the training and practice of shamanistic healers. [11] This is usually practiced in Africa and is unfamiliar in Europe. Since this is a trance that is induced voluntarily as part of a shamanistic ritual, it is not considered a disorder.
Zar was experienced in many cases when immigrants would move from Ethiopia to Israel. This is when zar was known to happen the most. Zar as a voluntarily induced spirit would occur the most in Northern African countries. One of the most common possession phenomena in Africa and in other continents is the belief in possession by spirits, known as zar.


10.2.1: Null and Alternative Hypotheses (Exercises)
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Exercise \(\PageIndex{5}\)
You are testing that the mean speed of your cable Internet connection is more than three Megabits per second. What is the random variable? Describe in words.
Answer
The random variable is the mean Internet speed in Megabits per second.
Exercise \(\PageIndex{1}\)
You are testing that the mean speed of your cable Internet connection is more than three Megabits per second. State the null and alternative hypotheses.
Exercise \(\PageIndex{1}\)
The American family has an average of two children. What is the random variable? Describe in words.
Answer
The random variable is the mean number of children an American family has.
Exercise 9.2.8
The mean entry level salary of an employee at a company is $58,000. You believe it is higher for IT professionals in the company. State the null and alternative hypotheses.
Exercise 9.2.9
A sociologist claims the probability that a person picked at random in Times Square in New York City is visiting the area is 0.83. You want to test to see if the proportion is actually less. What is the random variable? Describe in words.
Answer
The random variable is the proportion of people picked at random in Times Square visiting the city.
Exercise 9.2.10
A sociologist claims the probability that a person picked at random in Times Square in New York City is visiting the area is 0.83. You want to test to see if the claim is correct. State the null and alternative hypotheses.
Exercise 9.2.11
In a population of fish, approximately 42% are female. A test is conducted to see if, in fact, the proportion is less. State the null and alternative hypotheses.
Answer
- \(H_{0}: p = 0.42\)
- \(H_{a}: p < 0.42\)
Exercise 9.2.12
Suppose that a recent article stated that the mean time spent in jail by a first–time convicted burglar is 2.5 years. A study was then done to see if the mean time has increased in the new century. A random sample of 26 first-time convicted burglars in a recent year was picked. The mean length of time in jail from the survey was 3 years with a standard deviation of 1.8 years. Suppose that it is somehow known that the population standard deviation is 1.5. If you were conducting a hypothesis test to determine if the mean length of jail time has increased, what would the null and alternative hypotheses be? The distribution of the population is normal.
- \(H_{0}\):_______
- \(H_{a}\):_______
Exercise 9.2.13
A random survey of 75 death row inmates revealed that the mean length of time on death row is 17.4 years with a standard deviation of 6.3 years. If you were conducting a hypothesis test to determine if the population mean time on death row could likely be 15 years, what would the null and alternative hypotheses be?
- \(H_{0}\):_________
- \(H_{a}\):_________
Answer
- \(H_{0}: \mu = 15\)
- \(H_{a}: \mu \neq 15\)
Exercise
The National Institute 9.2.14 of Mental Health published an article stating that in any one-year period, approximately 9.5 percent of American adults suffer from depression or a depressive illness. Suppose that in a survey of 100 people in a certain town, seven of them suffered from depression or a depressive illness. If you were conducting a hypothesis test to determine if the true proportion of people in that town suffering from depression or a depressive illness is lower than the percent in the general adult American population, what would the null and alternative hypotheses be?
- \(H_{0}\):_______
- \(H_{a}\):_______


5.4.2: Carbon Dioxide
Construct SALCs and the molecular orbital diagram for CO\(_2\).
Carbon dioxide is another linear molecule. This example is slightly more complex than the previous example of the bifluoride anion. While bifluoride had only one valence orbital to consider in its central H atom (the \(1s\) orbital), carbon dioxide has a larger central atom, and thus more valence orbitals that will interact with SALCs.
Preliminary Steps
Step 1. Find the point group of the molecule and assign Cartesian coordinates so that z is the principal axis.
The CO\(_2\) molecule is linear and its point group is \(D_{\infty h}\). The \(z\) axis is collinear with the \(C_\infty\) axis. We will use the \(D_{2h}\) point group as a substitute since the orbital symmetries are retained in the \(D_{2h}\) point group.
Step 2. Identify and count the pendant atoms' valence orbitals.
Each of the two pendant oxygen atoms has four valence orbitals; \(2s\), \(2p_x\), \(2p_y\), and \(2p_z\). Thus, we can expect a total of eight SALCs.
Generate SALCs
The SALCs for CO\(_2\) are identical in shape and symmetry to those described in the previous example for the bifluoride anion . But instead of cutting to the shortcut, we will systematically derive the SALCs here to demonstrate the process.
Step 3. Generate the \(\Gamma\)'s
Use the
\(D_{2h}\) character table
to generate four reducible representations (\(\Gamma's\)); one for each of the four types of pendant atom orbitals (\(s, \;p_x, \;p_y, \;p_z\)). For each \(s\) orbital, assign a value of 1 if it remains in place during the operation or zero if it moves out of its original place. For each \(p\) orbital, assign 1 if there is no change, -1 if it remains in place but is inverted, and 0 if it moves out of its original position. The four \(\Gamma\)'s are given below:
\[\begin{array}{|c|cccccccc|} \hline \bf{D_{2h}} & E & C_2(z) & C_2(y) &C_2(x) & i &\sigma(xy) & \sigma(xz) & \sigma(yz)\\ \hline \bf{\Gamma_{2s}} & 2 & 2 & 0 & 0 & 0 & 0 & 2 & 2 \\ \bf{\Gamma_{2p_x}} & 2 & -2 & 0 & 0 & 0 & 0 & 2 & -2 \\ \bf{\Gamma_{2p_y}} & 2 & -2 & 0 & 0 & 0 & 0 & -2 & 2 \\ \bf{\Gamma_{2p_z}} & 2 & 2 & 0 & 0 & 0 & 0 & 2 & 2 \\ \hline \end{array} \nonumber \]
Step 4. Break \(\Gamma\)'s into irreducible representations for individual SALCs
Reduce each \(\Gamma\) into its component irreducible representations. There are two strategies that can be used to do this. The quick and easy way is to do it "by inspection", but this only works well for simple cases. The other is by using the systematic approach for breaking a \(\Gamma\) into reducible representations
described previously
in section 4.4.2
using the following formula:
\[\text{# of } i = \frac{1}{h}\sum(\text{# of operations in class)}\times(\chi_{\Gamma}) \times (\chi_i) \label{irs} \]
In other words, the number of irreducible representations of type \(i\) is equal to the sum of the number of operations in the class \(\times\) the character of the \(\Gamma_{modes}\) \(\times\) the character of \(i\), and that sum is divided by the order of the group (\(h\)).
Using either approach results in the following eight irreducible representations (\(2A_{g} + 2B_{1u} + B_{2g} + B_{3u} + B_{3g} + B_{2u}\)):
\[\begin{array}{|c|c|cccccccc|} \hline \bf{D_{2h}} & E & C_2(z) & C_2(y) &C_2(x) & i &\sigma(xy) & \sigma(xz) & \sigma(yz)\\ \hline
\bf{\Gamma_{2s} = A_g + B_{1u}} &\bf{\Gamma_{2s}} & \bf{2} & \bf{2} & \bf{0} & \bf{0} & \bf{0} & \bf{0} & \bf{2} & \bf{2}\\
& A_{g} & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\
& B_{1u} & 1 & 1 & -1 & -1 & -1 & -1 & 1 & 1 \\
\hline \\ \hline
\bf{\Gamma_{2p_x} = B_{2g} + B_{3u}} &\bf{\Gamma_{2p_x}} & \bf{2} & \bf{-2} & \bf{0} & \bf{0} & \bf{0} & \bf{0} & \bf{2} & \bf{-2} \\
& B_{2g} & 1 & -1 & 1 & -1 & 1 & -1 & 1 & -1 \\
& B_{3u} & 1 & -1 & -1 & 1 & -1 & 1 & 1 & -1 \\
\hline \\ \hline
\bf{\Gamma_{2p_y}=B_{3g}+B_{2u}} & \bf{\Gamma_{2p_y}} & \bf2 & \bf-2 & \bf0 & \bf0 & \bf0 & \bf0 & \bf-2 & \bf2 \\
& B_{3g} & 1 & -1 & -1 & 1 & 1 & -1 & -1 & 1 \\
& B_{2u} & 1 & -1 & 1 & -1 & -1 & 1 & -1 & 1 \\
\hline \\ \hline
\bf{\Gamma_{2p_z} = A_{g}+B_{1u}} & \bf{\Gamma_{2p_z}} & \bf{2} & \bf{2} & \bf{0} & \bf{0} & \bf{0} & \bf{0} & \bf{2} & \bf{2}\\
& A_{g} & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 \\
& B_{1u} & 1 & 1 & -1 & -1 & -1 & -1 & 1 & 1 \\ \hline \end{array} \nonumber \]
Step 5. Sketch the SALCs
From the systematic process above, you have found the symmetries (the irreducible representations) of all eight SALCs under the \(D_{2h}\) point group. To sketch the SALC that corresponds to each irreducible representation, again we use the \(D_{2h}\) character table , and specifically the functions listed on the right side columns of the table.
Two \(A_g\) SALCs (one from \(s\) and one from \(p_z\)): The \(A_g\) SALCs are each singly degenerate and symmetric with respect to both the principal axis (\(z\)) and the inversion center (\(i\)) (based on its Mulliken Label ). We can look at the functions in the \(D_{2h}\) character table that correspond to \(A_g\) and see that it is completely symmetric under the group (because the combination of \(x^2,y^2,z^2\) shows that it is totally symmetric). This would be the same symmetry as an \(s\) orbital on the central atom. From this information, we know that these SALCs must have symmetry compatible with an \(s\) orbital on the central atom, and we can draw the two \(A_g\) SALCs shown in Figure \(\PageIndex{2}\).
Two \(B_{1u}\) SALCs (one from \(s\) and one from \(p_z\)): The Mulliken Label tells us that the \(B_{1u}\) SALCs are each antisymmetric with respect to both the principal axis and the inversion center. The function, \(z\), appearing with \(B_{1u}\) in the character table tells us that these SALCs have the same symmetry as the \(z\) axis, or a \(p_z\) orbital on the central atom. From this information, we know that these two SALCs should be compatible with a \(p_z\) orbital on the central atom, and we can draw the two \(B_{1u}\) SALCs shown in Figure \(\PageIndex{2}\).
All other SALCs shown below are derived using a strategy similar to the one in the two cases described above.
Draw the MO diagram for \(CO_2\)
Step 6. Combine SALCs with AO’s of like symmetry.
First we identify the valence orbitals on carbon: there are four including \(2s\), \(2p_x\), \(2p_y\), and \(2p_z\). Now we identify the symmetry of each using the \(D_{2h}\) character table. The symmetry of a central \(s\) orbital corresponds to the combination of functions \(x^2\), \(y^2\), and \(z^2\) in the character table; this is \(A_g\). The \(p_z\) orbital corresponds to the symmetry of the linear function \(z\) in the character table; this is \(B_{1u}\). And so on... The symmetries of the C valence orbitals are listed below. \[2s =A_g \\ 2p_x = B_{3u} \\ 2p_y = B_{2u} \\ 2p_z = B_{1u} \nonumber \]
Now that we have identified the symmetries of the eight oxygen SALCs and the four valence orbitals on carbon, we know which atomic orbitals and SALCs may combine based on compatible symmetries. We also need to know the relative orbital energy levels so that we can predict the relative strength of orbital interactions. The orbital ionization energies are listed in Section 5.3 .
With knowledge of both orbital symmetries and energies, we can construct the molecular orbital diagram. The carbon atom goes on one side of the diagram while the oxygen SALCs are drawn on the opposite side. Molecular orbitals are drawn in the center column of the diagram:
The SALCs on the right side of the diagram above are constructed from groups of either the \(2s\) atomic orbitals of oxygen, or the \(2p\) atomic orbitals of oxygen. Each SALC will combine with the atomic orbitals of carbon that have compatible symmetry; but the strength of the interaction depends on their relative energies. The individual valence atomic orbitals of oxygen have energies of \(-32.36 eV\) (\(2s\)) and \(-15.87 eV\) (\(2p\)), while the valence orbitals of carbon have energies of \(-19.47 eV\) (\(2s\)) and \(-10.66 eV\) (\(2p\)). The \(2s\) orbitals of the oxygen are far lower in energy (\(-32.36 eV\)) than all other valence orbitals, and so we should expect that molecular orbitals that are constructed from these oxygen \(2s\) will be mostly non-bonding. These mostly non-bonding orbitals are the \(a_{1g}\) and \(b_{1g}\) orbitals shown at the bottom of Figure \(\PageIndex{3}\). The \(a_g\) orbital is lower in energy than the \(b_{1u}\) due to slight mixing with other orbitals of \(a_g\) symmetry.
The bonding orbitals of \(CO_2\) include two \(sigma\) molecular orbitals of \(a_g\) and \(b_{1u}\) symmetry and two \(\pi\) molecular orbitals of \(b_{2u}\) and \(b_{3u}\) symmetry. Each of these bonding molecular orbitals possesses a higher-energy antibonding partner. The \(b_{2g}\) and \(b_{3g}\) SALCs that are formed from oxygen \(2p_x\) and \(2p_y\) orbitals have no compatible match with carbon valence orbitals; thus they form two \(b_{2g}\) and \(b_{3g}\) molecular orbitals, which are truly non-bonding and mostly oxygen in character. Still, notice that each orbital is spread across both oxygen atoms at once, and again we see that each non-bonding electron pair in the HOMO is very different in molecular orbital theory compared to Lewis theory. Each non-bonding pair is distributed over both oxygen atoms at once in molecular orbital theory, while in Lewis theory each lone pair is isolated to one atom or to localized bonds attached to that atom.


9.6: Summary
9.1 Overview of Entrepreneurial Finance and Accounting Strategies
Entrepreneurial financing is concerned with understanding the funding requirements for a new business and what sources of funds are available. Each source comes with different expectations and requirements. Equity financing provides the entrepreneur with maximum flexibility: Dividends are not required and can be made when cash flow is strong enough to meet all obligations of the firm. Debt financing restricts financial flexibility but can be cheaper under some circumstances. For example, SBA loans can be subsidized by the federal government. Financing is not a one-size-fits-all procedure.
9.2 Special Funding Strategies
For nonprofit organizations, achieving a sustainable funding strategy requires hard work, creativity, and a delicate balance of financial resources. These types of organizations need to create programs that will interest patrons who are willing to pay for activities. They also rely on the generosity of their benefactors beyond simple patronage in the form of donations, and they vie for extremely competitive grant funding.
Although loans and liabilities such as credit card debt can fund a new business, the repayment and additional interest charges are a real challenge to many entrepreneurs. Financing strategies that avoid loans, such as crowdfunding websites and bartering, offer opportunities for funding that are often more manageable.
Bootstrapping is the process of self-funding a startup business. Sometimes entrepreneurs will have no financial resources beyond their personal savings. This method of funding a business requires creative approaches to problem solving, generating business, and managing expenses. It can be a slower, more difficult process than a company with more funding might face, but in the long run, it can benefit the company’s strength and growth, and provide robust dividends to the founders.
9.3 Accounting Basics for Entrepreneurs
Accounting is concerned with how transactions are recorded in a way that helps entrepreneurs share information with stakeholders, including potential investors, and helps business owners make decisions about running their company.
9.4 Developing Startup Financial Statements and Projections
Entrepreneurs can use financial information for multiple purposes. These projections can help plan a new business. By forecasting the income and expenses of the first year, an entrepreneur can have a reasonable idea of the level of financing that may be required. Second, these projections can also show potential investors what the business will look like in the future and how long it might take them to get a return on their investment. Break-even points help illustrate a minimum amount of sales to cover expenses.


2.2: Polar Form of a Complex Number
A point \((x,y)\) in the plane can be represented in polar form \((r,\theta)\) according to the relationships in Figure \(\PageIndex{1}\).
Using these relationships, we can rewrite
\[\begin{align*} x+yi &= r\cos(\theta) + r\sin(\theta) i\\ &= r(\cos(\theta) + i \sin(\theta))\text{.} \end{align*}\]
This leads us to make the following definition. For any real number \(\theta\text{,}\) we define
\[ e^{i\theta} = \cos(\theta) + i\sin(\theta)\text{.} \]
For instance, \(e^{i\pi/2} = \cos(\dfrac{\pi}{2}) + i\sin(\dfrac{\pi}{2}) = 0 + i\cdot 1 = i\text{.}\)
Similarly, \(e^{i0} = \cos(0) + i\sin(0) = 1\text{,}\) and it's a quick check to see that \(e^{i\pi} = -1\text{,}\) which leads to a simple equation involving the most famous numbers in mathematics (except \(8\)), truly an all-star equation:
\[ e^{i \pi} + 1 = 0\text{.} \]
If \(z = x+yi\) and \((x,y)\) has polar form \((r,\theta)\) then \(z = re^{i\theta}\) is called the polar form of \(z\text{.}\) The non-negative scalar \(|r|\) is the modulus of \(z\text{,}\) and the angle \(\theta\) is called the argument of \(z\), denoted \(\arg(z\)).
On the left side of the following diagram, we plot the points
\(z = 2e^{i\pi/4}, w = 3e^{i\pi/2}, v = -2e^{i\pi/6}, u = 3e^{-i\pi/3}.\)
To convert \(z = -3 + 4i\) to polar form, refer to the right side of the diagram. We note that \(r = \sqrt{9 + 16} = 5\text{,}\) and \(\tan(\alpha) =\dfrac{4}{3} \text{,}\) so \(\theta = \pi - \tan^{-1}(\dfrac{4}{3})\approx 2.21\) radians. Thus,
\[ -3+4i = 5e^{i(\pi-\tan^{-1}(4/3))} \approx 5e^{2.21i}\text{.} \]
The product of two complex numbers in polar form is given by
\[ \displaystyle re^{i\theta}\cdot se^{i\beta} = (rs)e^{i(\theta+\beta)}\text{.} \]
- Proof
-
We use the definition of the complex exponential and some trigonometric identities. \[\begin{array} d re^{i\theta}\cdot se^{i\beta} &= r(\cos\theta + i\sin\theta)\cdot s(\cos\beta+i\sin\beta)\\ &= (rs)(\cos\theta + i\sin\theta)\cdot (\cos\beta+i\sin\beta)\\ &= rs[\cos\theta\cos\beta - \sin\theta\sin\beta + (\cos\theta\sin\beta+\sin\theta\cos\beta)i]\\ &= rs[\cos(\theta+\beta) + \sin(\theta+\beta)i]\\ &=rs[e^{i(\theta+\beta)}]\text{.} \end{array}\]
Thus, the product of two complex numbers is obtained by multiplying their magnitudes and adding their arguments, and
\[ \arg(zw) = \arg(z) + \arg(w)\text{,} \]
where the equation is taken modulo \(2\pi\text{.}\) That is, depending on our choices for the arguments, we have \(\arg(vw) = \arg(v)+ \arg(w) + 2\pi k\) for some integer \(k\text{.}\)
When representing a complex number \(z\) in polar form as \(z = re^{i\theta}\text{,}\) we may assume that \(r\) is non-negative. If \(r \lt 0\text{,}\) then \[\begin{array}d re^{i\theta} &= - |r|e^{i\theta}\\ &= (e^{i\pi})\cdot |r| e^{i\theta} \;\; \text{since} \; -1 = e^{i\pi}\\ &= |r|e^{i(\theta+\pi)}, \;\; \text{by Theorem 2.2.1} \end{array}\] Thus, by adding \(\pi\) to the angle if necessary, we may always assume that \(z = re^{i\theta}\) where \(r\) is non-negative.
Exercises
Convert the following points to polar form and plot them: \(3 + i\text{,}\) \(-1 - 2i\text{,}\) \(3 - 4i\text{,}\) \(7,002,001\text{,}\) and \(-4i\text{.}\)
Express the following points in Cartesian form and plot them: \(z = 2e^{i\pi/3}\text{,}\) \(w = -2e^{i\pi/4}\text{,}\) \(u = 4e^{i5\pi/3},\) and \(z\cdot u\text{.}\)
Modify the all-star equation to involve \(8\). In particular, write an expression involving \(e, i, \pi, 1,\) and \(8\), that equals \(0\). You may use no other numbers, and certainly not \(3\).
If \(z = re^{i\theta}\text{,}\) prove that \(\overline{z} = re^{-i\theta}\text{.}\)


4.5: Irreversible Processes
We know that during a reversible process of a closed system, each infinitesimal entropy change \(\dif S\) is equal to \(\dq/T\bd\) and the finite change \(\Del S\) is equal to the integral \(\int(\dq/T\bd)\)—but what can we say about \(\dif S\) and \(\Del S\) for an irreversible process?
The derivation of this section will show that for an infinitesimal irreversible change of a closed system, \(\dif S\) is greater than \(\dq/T\bd\), and for an entire process \(\Del S\) is greater than \(\int(\dq/T\bd)\). That is, the equalities that apply to a reversible process are replaced, for an irreversible process, by inequalities .
The derivation begins with irreversible processes that are adiabatic, and is then extended to irreversible processes in general.
4.5.1 Irreversible adiabatic processes
Consider an arbitrary irreversible adiabatic process of a closed system starting with a particular initial state A. The final state B depends on the path of this process. We wish to investigate the sign of the entropy change \(\Del S\subs{A\(\ra\)B}\). Our reasoning will depend on whether or not there is work during the process.
If there is work along any infinitesimal path element of the irreversible adiabatic process (\(\dw \ne 0\)), we know from experience that this work would be different if the work coordinate or coordinates were changing at a different rate, because energy dissipation from internal friction would then be different. In the limit of infinite slowness, an adiabatic process with initial state A and the same change of work coordinates would become reversible, and the net work and final internal energy would differ from those of the irreversible process. Because the final state of the reversible adiabatic process is different from B, there is no reversible adiabatic path with work between states A and B.
All states of a reversible process, including the initial and final states, must be equilibrium states. There is therefore a conceptual difficulty in considering reversible paths between two states if either of these states are nonequilibrium states. In such a case we will assume that the state has been replaced by a constrained equilibrium state of the same entropy as described in Sec. 4.4.3.
If, on the other hand, there is no work along any infinitesimal path element of the irreversible adiabatic process (\(\dw{=}0\)), the process is taking place at constant internal energy \(U\) in an isolated system. A reversible limit cannot be reached without heat or work (Sec. 3.2.1). Thus any reversible adiabatic change from state A would require work, causing a change of \(U\) and preventing the system from reaching state B by any reversible adiabatic path.
So regardless of whether or not an irreversible adiabatic process A\(\ra\)B involves work, there is no reversible adiabatic path between A and B. The only reversible paths between these states must be non adiabatic. It follows that the entropy change \(\Del S\subs{A\(\ra\)B}\), given by the value of \(\dq/T\bd\) integrated over a reversible path from A to B, cannot be zero.
Next we ask whether \(\Del S\subs{A\(\ra\)B}\) could be negative. In each infinitesimal path element of the irreversible adiabatic process A\(\ra\)B, \(\dq\) is zero and the integral \(\int_{\tx{A}}^{\tx{B}}(\dq/T\bd)\) along the path of this process is zero. Suppose the system completes a cycle by returning along a different, reversible path from state B back to state A. The Clausius inequality (Eq. 4.4.3) tells us that in this case the integral \(\int_{\tx{B}}^{\tx{A}}(\dq/T\bd)\) along the reversible path cannot be positive. But this integral for the reversible path is equal to \(-\Del S\subs{A\(\ra\)B}\), so \(\Del S\subs{A\(\ra\)B}\) cannot be negative.
We conclude that because the entropy change of the irreversible adiabatic process A\(\ra\)B cannot be zero, and it cannot be negative, it must be positive .
In this derivation, the initial state A is arbitrary and the final state B is reached by an irreversible adiabatic process. If the two states are only infinitesimally different, then the change is infinitesimal. Thus for an infinitesimal change that is irreversible and adiabatic, \(\dif S\) must be positive .
4.5.2 Irreversible processes in general
Figure 4.11 Supersystem including the experimental system, a Carnot engine (square box), and a heat reservoir. The dashed rectangle indicates the boundary of the supersystem.
To treat an irreversible process of a closed system that is nonadiabatic, we proceed as follows. As in Sec. 4.4.1, we use a Carnot engine for heat transfer across the boundary of the experimental system. We move the boundary of the supersystem of Fig. 4.8 so that the supersystem now includes the experimental system, the Carnot engine, and a heat reservoir of constant temperature \(T\subs{res}\), as depicted in Fig. 4.11. During an irreversible change of the experimental system, the Carnot engine undergoes many infinitesimal cycles. During each cycle, the Carnot engine exchanges heat \(\dq'\) at temperature \(T\subs{res}\) with the heat reservoir and heat \(\dq\) at temperature \(T\bd\) with the experimental system, as indicated in the figure. We use the sign convention that \(\dq'\) is positive if heat is transferred to the Carnot engine, and \(\dq\) is positive if heat is transferred to the experimental system, in the directions of the arrows in the figure.
The supersystem exchanges work, but not heat, with its surroundings. During one infinitesimal cycle of the Carnot engine, the net entropy change of the Carnot engine is zero, the entropy change of the experimental system is \(\dif S\), the heat transferred between the Carnot engine and the experimental system is \(\dq\), and the heat transferred between the heat reservoir and the Carnot engine is given by \(\dq'=T\subs{res}\dq/T\bd\) (Eq. 4.4.1). The heat transfer between the heat reservoir and Carnot engine is reversible, so the entropy change of the heat reservoir is \begin{equation} \dif S\subs{res} = -\frac{\dq'}{T\subs{res}} = -\frac{\dq}{T\bd} \tag{4.5.1} \end{equation} The entropy change of the supersystem is the sum of the entropy changes of its parts: \begin{equation} \dif S\subs{ss} = \dif S + \dif S\subs{res} = \dif S - \frac{\dq}{T\bd} \tag{4.5.2} \end{equation} The process within the supersystem is adiabatic and includes an irreversible change within the experimental system, so according to the conclusions of Sec. 4.5.1, \(\dif S\subs{ss}\) is positive. Equation 4.5.2 then shows that \(\dif S\), the infinitesimal entropy change during the irreversible change of the experimental system, must be greater than \(\dq/T\bd\): \begin{gather} \s{ \dif S > \frac{\dq}{T\bd} } \tag{4.5.3} \cond{(irreversible change, closed system)} \end{gather} This relation includes the case of an irreversible adiabatic change, because it shows that if \(\dq\) is zero, \(\dif S\) is greater than zero.
By integrating both sides of Eq. 4.5.3 between the initial and final states of the irreversible process, we obtain a relation for the finite entropy change corresponding to many infinitesimal cycles of the Carnot engine: \begin{gather} \s{ \Del S > \int\!\frac{\dq}{T\bd} } \tag{4.5.4} \cond{(irreversible process, closed system)} \end{gather}


9.13: Health Services
School nurses respond to emergencies, acute health needs, manage chronic health conditions, and provide referrals and support for primary care for both students and often staff as well. School nurses are also an integral part of the health team in that they can help identify physical hazards, provide individual and small group counseling and education for health issues, and support school-wide community health measures such as preventing the spread of infectious diseases. They may also play a role in ensuring quality health education curriculum, monitoring the availability of healthy foods (through the cafeteria, vending machines, etc.), and working with psychological counselors and social workers to support students' social and emotional well-being (National Association of School Nurses, 2017). The role of the school nurse is so integral to the WSCC model, that were it not for the heavy workload assigned to school nurses they would be an obvious choice to lead a school health advisory council (Seabert et al. 2021).
Since the 1960’s, schools have been recognized as a potential hub to offer increased access to healthcare in the communities that they serve. School-based health centers (SBHC) expand on the services offered by the school nurse to provide physical, mental, vision, and dental health services within the school setting. Schools that serve low-income communities, those with many uninsured or underinsured students, and those with limited access to healthcare (rural or urban), benefit highly from SBHCs. An SBHC may include pediatricians, physician’s assistants, nurse practitioners, dentists, mental health and substance abuse counselors and other healthcare providers. Some may even become Federally Qualified Health Centers and expand their services to student families, employees, and the community at large. Since most SBHCs are located on school property, they can make doctor’s appointments easier for parents and kids to get to. SBHCs can help address inequities in healthcare access and improve health outcomes for students experiencing poverty, adverse childhood experiences, and those at higher risk for health-risk behaviors. There is evidence that SBHCs are financially sustainable with a variety of grant funding sources, and can improve physical health outcomes, as well as the potential for positively influencing mental health outcomes and educational attainment. Although the role of SBHCs in sexual and reproductive health is controversial for some, they can also help to prevent teen pregnancies and STIs, as well as providing prenatal care for teens who do become pregnant (Arenson et al., 2019).


23.10A: Hormonal Responses to Food
The endocrine system controls the release of hormones responsible for starting, stopping, slowing, and quickening digestive processes.
- Describe hormonal responses to food
Key Points
- The presence and absence of hormones that are released into the bloodstream generate specific digestive responses; they either stimulate or discontinue digestive processes.
- In hormone control, a negative feedback mechanism takes place when the stomach is empty and its acidic environment does not need to be maintained; as a result, a hormone is released to stop the release of hydrochloric acid, which was previously activated to aid digestion.
- In some cases, hormones work in tandem and sequentially to achieve important digestive functions, such as in the breakdown of acidic chyme, where hormones act in releasing the appropriate secretions in the appropriate stages of digestion.
- When digesting certain types of foods, such as ones high in fat, hormones can control the speed of food digestion and, therefore, absorption.
Key Terms
- endocrine system : a control system of ductless glands that secrete hormones which circulate via the bloodstream to affect cells within specific organs
- chyme : the thick semifluid mass of partly digested food that is passed from the stomach to the duodenum
- secretin : a peptide hormone, secreted by the duodenum, that serves to regulate its acidity
- cholecystokinin : any of several peptide hormones that stimulate the digestion of fat and protein
- somatostatin : a polypeptide hormone, secreted by the pancreas, that inhibits the production of certain other hormones
- gastrin : a hormone that stimulates the production of gastric acid in the stomach
Hormonal Responses to Food
The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. The endocrine system’s effects are slow to initiate, but prolonged in their response, lasting from a few hours up to weeks. The system is made of a series of glands that produce chemicals called hormones. These hormones are chemical mediators released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response.
One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl), which aids in the digestion of the majority of proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism.
In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum.
Digestive endocrine system : Hormones, such as secretin and cholecystokinin, play important roles in digestive processes. These hormones are released from endocrine tissue to generate specific controls in the digestion of chyme. As seen in the image, hormones are vital players in several bodily functions and processes.
Another level of hormonal control occurs in response to the composition of food. Foods high in lipids (fatty foods) take a long time to digest. A hormone called gastric inhibitory peptide is secreted by the small intestine to slow down the peristaltic movements of the intestine to allow fatty foods more time to be digested and absorbed.
Understanding the hormonal control of the digestive system is an important area of ongoing research. Scientists are exploring the role of each hormone in the digestive process and developing ways to target these hormones. Advances could lead to knowledge that may help to battle the obesity epidemic.


10: Ionic and Covalent Solids - Energetics
Learning Objectives
- Understand the geometric basis of radius ratio rules.
- Understand the chemical basis of structure maps and why they are better predictors of crystal structures than radius ratios.
- Use the Born-Mayer and Kapustinskii equations to calculate lattice energies of known and hypothetical compounds.
- Construct Born-Haber cycles using lattice energies and calculate unknown quantities in the cycles.
- Predict the stabilities of low and high oxidation states using lattice energies.
- Understand the quantum mechanical origin of the extra "resonance" stability of metals.
- Predict trends in the solubility and thermal stability of inorganic compounds using lattice energies.
In Chapter 8, we learned all about crystal structures of ionic compounds . A good question to ask is, what makes a compound choose a particular structure? In addressing this question, we will learn about the forces that hold crystals together and the relative energies of different structures. This will in turn help us understand in a more quantitative way some of the heuristic concepts we have learned about in earlier chapters, such as hard-soft acid-base theory.
-
- 10.4: Born-Haber Cycles for NaCl and Silver Halides
- Now that we have an equation for the lattice energy of an ionic crystal, we can ask the question of how accurate it is. Remember, we made several approximations in arriving at this formula. We assumed that the lattice was completely ionic, we ignored the van der Waals attractive energy of the ions, and we assumed that there was no covalent contribution to the bonding.
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- 10.5: Kapustinskii Equation
- Kapustinskii noticed that difference in ionic radii between the monovalent vs. divalent radii largely compensates for the differences in A/n between monovalent (NaCl, CsCl) and divalent (rutile, CaF2) structures. He thus arrived at a lattice energy formula using an average Madelung constant, corrected to monovalent radii.
-
- 10.8: Alkalides and Electrides
- Another interesting consequence of lattice energies involves the formation of certain salts containing Na- and e- anions. These compounds are known as alkalides and electrides, respectively. Most of these compounds have been discovered by Prof. James Dye at Michigan State University.
-
- 10.9: Resonance Energy of Metals
- The valence electrons in Na metal are in orbitals that are delocalized over the entire crystal. However in the Na+ e- "salt" form, the electrons are localized on specific anion sites. This localization imparts an additional kinetic energy (via the "particle in a box" effect) that adds to the total energy.


11.3: Censorship
The word censorship brings up ideas of suppressing explicit, offensive images and written material, perhaps of a sexual or political nature, or accounts of violence. What is considered prurient or sacrilegious or barbarity is not universal, however, so what was acceptable during one era may be banned in the next.
Michelangelo was a sculptor, painter, and architect. He considered his sculptural and architectural works to be of far greater importance than his relatively few painted works. But many know him today as much for the two frescoes, or wall paintings, he completed in the Sistine Chapel in Rome as for the far greater number of marble figures and buildings he created. The chapel is within the Pope’s residence in Vatican City, the seat of the Roman Catholic Church, in Rome. The first fresco Michelangelo painted on the 134-foot-long ceiling of the Sistine Chapel, from 1508 to 1512, is a complex series of nine scenes from the Book of Genesis, architectural elements, and figures. It was the first large-scale painting of his career. He returned to paint The Last Judgment on the wall behind the altar from 1535 to1541. (Figure 11.1)
The Catholic Church had changed tremendously in the twenty-four years between when the first work was completed and the second one begun. In 1517, the singular authority of the Catholic Church was called into question when Martin Luther, a German monk, issued a series of complaints against Church practices, especially the selling of indulgences, or pardoning of sins. As opposed to the complex hierarchy of the Church, and an emphasis on its teachings as the only means to salvation, Luther championed personal faith and adherence to the word of the Bible.Although his beliefs were denounced, and Luther was excommunicated from the Church in 1521, the new Protestant faith swept through northern Europe. The Protestant Reformation, as Luther’s attempts to revise the doctrines of the Roman Catholic Church were known, was not just a seri- ous threat to the Church’s authority, it prompted the wholesale examination and revision of the Church’s structure, activities, and methods.
Michelangelo began to paint The Last Judgment in 1535. In that time of upheaval and uncertainty, the subject of the faithful rising to their reward at Christ’s side in eternity while those who doubt or turn away fall to their eternal damnation could have been intended to reassure those remaining true to the Church. Rather than sticking to a clearly structured and hierarchical organization of figures, however, Michelangelo broke from tradition to show dynamic groups of moving, gesturing, and emotion-filled angels, saints, blessed, and damned. Although Christ is in the centerwith His right arm raised, it is not clear if He is caught up in the erratic and chaotic swirl of the figures surrounding Him or confidently directing them according to their fates. The lack of distinction was originally heightened by the uniformity of clothing, or lack thereof, as Michelangelo painted the majority of figures nude, removing signs of earthly status and riches.
When completed, the fresco was hailed as a masterpiece, but in the following decades, it came under sharp criticism. As the Protestant Reformation by Martin Luther and his followers con- tinued to revolutionize religious doctrine and practices throughout Europe, the Catholic Church formed The Council of Trent (1545-1563) in response. The Counter-Reformation remained ad- amant in condemning the new Protestant faith but did away with many excesses and leniencies that had grown within the Church, including art that served as a distraction from its proper use as a tool of worship. In its findings, The Council of Trent stated that used properly, art instructed the faithful to “order their own lives and manners in imitation of the saints; and may be excited to adore and love God; and to cultivate piety.” Michelangelo’s Last Judgment lacked the clarity of message and propriety now demanded in religious art so that, at odds with the Council’s decree, “there be nothing seen that is disorderly, or that is unbecomingly or confusedly arranged, nothing that is profane, nothing indecorous, seeing that holiness becometh the house of God.”
In 1565, two years after the Council’s decree and the year after Michelangelo’s death, Daniele da Volterra (1509-1566, Italy) was commissioned to paint drapery on the nude figures and alter the posi- tions of some that were deemed too indelicate. Some of his modifications, and others carried out in the eighteenth century, were removed when the fresco was cleaned and restored between 1980 and 1994.
- Scott Macleod, “The Life and Death of Kevin Carter,” Time , 24 June 2001, content.time.com/time/magazine/ article/0,9171,165071,00.html.


1: Introduction to Pharmacology
- Define pharmacokinetics and pharmacodynamics.
- Distinguish among a drug's chemical, generic, and trade name.
- Describe the paths a drug may take when it is free in circulation.
- Recognize and interpret a dose-response curve.
- Memorize the meaning of basic pharmacologic terminology such as agonist, antagonist and other bolded terms.
1.0 Introduction to Pharmacology
Pharmacology is the study of the effects of drugs on the function of living systems. Drugs may be chemical agents synthetically manufactured from plants or animals or genetically engineered products such as biopharmaceuticals. Pharmacokinetics is the term for what happens to the drug within the body or the body’s actions on the drug, while the action of drugs on the body is called pharmacodynamics .
The preparation of drugs is called pharmacy practice, with much of the practice focusing on pharmacotherapeutics and the treatment of disease. Most drugs are xenobiotics, a chemical that originates outside the body (also referred to as exogenous) and is introduced into the body by various routes of administration. For a drug to be effective, it must enter the body and be distributed to its site of action. This site of action is often a macromolecule receptor in the target tissue, but drugs may also be designed to interrupt a signaling pathway.
A common challenge in studying pharmacology is recognizing the thousands of drug names. Drugs have three different names: chemical, generic, and trade. Each drug's chemical structure and name are unique. For example, the chemical name for aspirin is 2-acetoxybenzoic acid, and its structure is
.
There is only one generic name for a drug. Most organizations, including the World Health Organization (WHO) and Food and Drug Administration (FDA), usually refer to drugs by their generic name (note generic names are not capitalized). The drug's trade name is assigned by the pharmaceutical company marketing the drug. The trade name is sometimes called the brand or proprietary name, such as Bayer's Aspirin.
1.1 Overview of Pharmacokinetics
A drug can enter the body by several different routes. Pharmacokinetics is what happens to the drug after it’s in the body. Pharmacokinetics focuses on the absorption, distribution, metabolism (also referred to as biotransformation), and elimination of the concentration of a drug in the body over time. Principles of chemistry are applied while studying pharmacokinetics because the interactions between drug and body molecules are simply a series of chemical reactions. Understanding the chemical encounters between drugs and biological environments is necessary to predict how much of a drug will be metabolized by the body. Most drug effects are temporary because the body has systems for drug detoxification and elimination. Toxicology is the branch of pharmacology that focuses on drugs that produce adverse or unwanted effects.
In Chapter 1, we will consider these issues broadly and go into more depth in the following chapters. As you read, refer to Figure 1.1 below.
Drugs Routes of Administration
- A drug may enter the body in a variety of ways: as an oral liquid, tablet, or capsule; as an inhaled vapor or aerosol; topically absorbed through intact skin or a mucous membrane; or injected into muscle, subcutaneous tissue, spinal fluid, or intravenously (directly into the bloodstream). The physical properties of the drug and the specific way the drug is prepared greatly influence the speed or rate of its absorption. Drugs given intravenously have the quickest absorption.
- If the drug is given orally and swallowed, it must be absorbed from the GI tract into the portal circulation (stomach → gut → portal vein → liver). If the drug is absorbed through the skin, mouth, lungs, or muscle, it will go directly into systemic circulation. If the drug is injected intravenously, 100% of the drug is “bioavailable” for distribution to tissues. This is not usually the case for other modes of administration. For example, an oral drug that is absorbed via portal circulation will first pass through the liver, which is the primary site of drug metabolism. Once a drug is metabolized, it is more likely to be excreted, causing less drug to reach the systemic circulation. This phenomenon is known as " first-pass " metabolism. First-pass metabolism reduces an oral drug’s bioavailability to less than 100%. Examples of drugs with a significant first-pass effect include alcohol, insulin, and morphine.
- Once in the bloodstream, a portion of the drug may exist as free drug, having been dissolved in plasma water and able to bind to other molecules. Some drug will be reversibly taken up by red cells, and other drugs will be reversibly bound to plasma proteins. Reversible means the chemical bond can be broken. For many drugs, the bound form of the drug accounts for 95-98% of the total concentration of the drug in the body. This is important because the free drug is active , traversing cell membranes and producing the clinically desired effect. It is also significant because protein-bound drug can act as a reservoir. When the chemical bonds are broken, the drug is released. Once the drug is unbound or in a free state, it can become active. The action of drugs that are protein-bound or those that bind to other reservoir sites in the body (adipose, bone) are prolonged and somewhat unpredictable.
- Unbound drug may then follow its concentration gradient and distribute into peripheral tissues. In some cases, the tissue contains the target site in others, the tissue is unaffected by the drug.
- The total amount of the drug within the body (in circulation and reservoir sites) reflects the volume of distribution. The volume of distribution determines the drug's equilibrium concentration after a specified dose. How long the drug is expected to remain in the body can be calculated using volume of distribution.
- Tissue-bound drug eventually reenters the bloodstream, where it perfuses the liver and kidneys. The liver metabolizes most drugs into inactive or less active compounds, which are more readily excreted. These metabolites and some of the parent compound (non-metabolized drug) may be excreted in the bile and eventually may pass out of the body in the feces. Alternatively, some of the drug may be reabsorbed again, farther down the GI tract (enterohepatic cycle). Any biotransformed drug that is not excreted in bile passes back into the systemic circulation.
- The parent drug and metabolites in the bloodstream may be excreted through kidney filtration, where a portion undergoes reabsorption and returns to plasma, and the remainder is excreted in the urine. Some drugs are actively secreted into the renal tubule. Another route of excretion is the lung; alcohol and anesthetic gases are eliminated by this route. Smaller amounts of drug are eliminated in sweat, tears, and breast milk.
- Biotransformation of a drug may sometimes produce very biologically active metabolites, which may be intended or unintended. A parent drug manufactured to be inactive until it is biotransformed after administration is referred to as a prodrug. Enalapril, clopidogrel, and codeine are examples of prodrugs.
1.2 Overview of Pharmacodynamics
Pharmacodynamics is the study of a drug's biochemical and physiologic effects on the body. The specific site of action of a drug is called the mechanism of action (MOA). The MOA for most drugs is binding to specific receptors on the surface or interior of cells. However, there are many other cellular components and non-specific sites that can serve as sites of drug action or drug targets.
- Water can be a target. The kidney does not reabsorb osmotic diuretics such as mannitol, and the osmotic load they create in the renal tubule forces the loss of water. Laxatives like magnesium sulfate work in the intestine by the same principle.
- Hydrogen ions can be targets. Ammonium chloride is sometimes used to acidify urine. When it is taken orally, the liver metabolizes the ammonium ion to urea, while the chloride is excreted in the urine. The loss of Cl- forces the loss of H+ in the urine, thus lowering the pH.
- Metal ions can be targets. Chelating agents like EDTA (ethylene diamine tetra-acetic acid) may be used to bind divalent cations like Pb++. Metal ions are most frequently drug targets in cases of poisoning.
- Enzymes are targets of many therapeutically useful drugs. Drugs may inhibit enzymes by competitive, non-competitive, or irreversible blockade at a substrate or cofactor binding site. Digitalis glycosides increase myocardial contractility by inhibiting the membrane enzyme, Na+-K+ - ATPase. Antimicrobial and antineoplastic drugs commonly work by inhibiting enzymes that are critical to the functioning of the cell. To be effective, these drugs must have at least some selective toxicities toward bacterial or tumor cells. This usually means that there is a unique metabolic pathway in these cells or some difference in enzyme selectivity for a common metabolic pathway the drug disrupts. An example of this is the inhibition of folate synthesis by sulfonamides. Sulfonamides are effective antibacterial agents because the bacteria depend on folate synthesis, whereas the host does not. This example will be covered in detail in one of our case discussions.
- Nucleic acids are targets for antimetabolites and some antibiotics. In the case of fluorouracil (5FU), the compound acts as a substitute for uracil and becomes incorporated into a faulty mRNA.
- Biologics are drugs designed to interrupt the immune system's signaling (e.g., interleukins, TNF-α) involved in the pathogenesis of chronic inflammatory disorders. Biologics are extracted or isolated from human, animal, or microorganism sources. They may also be produced by biotechnology.
- Finally, some drugs act by binding to specific receptors . These drugs have both structural specificity and selectivity. By interacting with a drug, receptors may be turned on (agonist) or turned off (antagonist). When a specific drug binds to a receptor, the physiologic activity regulated by that receptor increases or decreases An example of this is using a beta-1 adrenergic receptor blocker or antagonist to decrease heart rate.
Unfortunately, no matter how effectively a drug works in a laboratory simulation, its performance in the human body will not always produce the same results, and individualized responses to drugs must be considered. Although many responses to medications may be anticipated, one’s unique genetic makeup may also significantly impact one’s response to a drug. Pharmacogenetics is the study of how people’s genes affect their response to drugs.
Below are important concepts that we will return to repeatedly throughout the course.
- An agonist is a drug that binds to its "receptor" and produces its characteristic effect. Depending on the maximal effect a drug produces, that drug may be a full agonist or a partial agonist .
- An antagonist binds to the receptor without causing an effect, thereby preventing an active substance from gaining access. Antagonists, like enzyme inhibitors, may be competitive, non-competitive, or irreversible .
- Dose-response . It is expected that as the dose of the drug increases, the response should increase. The curve generated is usually sigmoidal when the effect is plotted against the log dose. The effect may be measured as a graded variable (change in blood pressure, force of contraction) or as a quantal variable (number dead/alive). The slope of the curve is characteristic of the particular drug-receptor interaction. When two drugs act by the same receptor mechanism, we expect to see two parallel log-dose response curves. Figure 1.2 shows a dose-response curve for Drugs A (red) and Drug B (blue). The characteristic sigmoidal shape shows that as the dose increases the response to the drug is greater until a plateau or maximal effect is reached. The curve for Drug A is to the left of the curve for Drug B, indicating that less (a lower dose) of Drug A is needed to elicit a response.
Dose Response Curve Comparing the Efficacy of Two Drugs
- ED 50 . The median effective dose, or the dose which produces a response in 50% of the sample. If the response is death (known as lethality), we call it the LD 50 . Importantly, the EC 50 refers to concentration rather than dose.
- Potency . Potency is often misused to mean “effectiveness.” Rather, a drug's potency refers to the dose (the molar concentration) required to produce a specific intensity of effect. If the ED50 of drugs A and B are 5 and 10 mg, respectively, the relative potency of A is twice that of B. Relative potency specifically applies to comparing drugs that act by the same mechanism and, therefore, have parallel dose–response curves.
- Efficacy . Also called maximal efficacy or intrinsic activity , this is the maximum effect the drug can produce. A potent drug may have a low efficacy, and a highly efficacious drug may have a low potency. For the clinician, efficacy is more important than potency (within limits).
- Affinity . The stickiness or affinity refers to the strength of the binding between drug and receptor. It is quantified by the dissociation constant Kd and takes into account the off-rate (unbound) divided by the on-rate (bound).
- Selectivity . Selectivity refers to the separation between a drug's desired (targeted) effects and its undesired effects. Ideally, a drug is completely specific , and an effective dose does not elicit any undesired effect. However, that is usually not the case. Most drugs are selective, not exclusive. As a drug concentration increases, the drug can lose its selectivity to one receptor and may bind to other receptors.
- Therapeutic window . For every drug, there exists some concentration that is just barely effective (the effective concentration ) and some dose that is just barely toxic (the Toxic Concentration ). Between the two is the therapeutic window where the safest and most effective treatment occurs.
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Index
. The therapeutic index is the ratio of toxic to effective doses at the level of 0% response: TD50/ED50. In animal toxicology studies, it is usually the LD50/ED50.
This chapter titled Introduction to Pharmacology is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Karen Vuckovic from Introduction to Pharmacology by Carl Rosow, David Standaert, & Gary Strichartz ( MIT OpenCourseWare ) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. Figures by Riley Cutler.


6.2: Common mathematical statements
In mathematics, we often want to prove that some statement \(P\) logically implies some other statement \(Q\text{;}\) i.e. we want to prove that \(P \Rightarrow Q\) or \((\forall x)(P(x) \Rightarrow Q(x))\text{.}\) Note that the universal form covers the common statement “all \(A\) are \(B\)”, since this can be rephrased “for all \(x\text{,}\) if \(x\) is \(A\) then \(x\) is \(B\)”.
Below are some common methods for proving \(P \Rightarrow Q\text{.}\) In the universal case \((\forall x)(P(x) \Rightarrow Q(x))\text{,}\) the domain of \(x\) may be infinite, so we cannot prove \(P(x) \Rightarrow Q(x)\) for each specific \(x\text{,}\) one-by-one. Instead, we treat \(x\) as a fixed but arbitrary object in the domain, and try to construct an argument proving \(P(x) \Rightarrow Q(x)\) which does not depending on knowing the specific object \(x\text{.}\) So all of the methods below can also be used in the universal case.
Since a conditional \(P \rightarrow Q\) is true automatically when \(P\) is false, it will be a tautology as long as we cannot have the case of \(P\) true and \(Q\) false at the same time. (See Figure 1.3.1 .) Therefore, we (almost always) begin a proof by assuming that \(P\) is true , and proceed to demonstrate that \(Q\) must then also be true , based on that assumption.


3.16: Outcome- Segmentation Decisions
What you’ll learn to do: explain the process of selecting an appropriate segmentation approach and deciding which customer segments to target for marketing activities
Now that you’ve learned about common segmentation approaches, how do you know when to apply them? When is geographic segmentation a better fit than demographic segmentation? When should you consider using both at the same time?
It comes down to your marketing goals: What are you trying to achieve?
The following section explains the process of aligning your goals with your segmentation approach and target market.
Learning Activities
The learning activities for this section include the following:
- Reading: Choosing a Segmentation Approach and Target Segments
- Case Study: eHarmony
- Self Check: Segmentation Decisions
Query \(\PageIndex{1}\)


11.23: Discussion- Pricing Strategy
Instructions
Write a post for the Discussion on this topic, addressing the questions below. You may use either written paragraph or bullet-point format. Part 1 should be 2–3 paragraphs in length or an equivalent amount of content in bullet-point form. Responses to your classmates’ posts should be 1–2 paragraphs or several bullet points in length.
Part 1: Pricing Strategy
Briefly describe pricing for your product or service. How does this compare to competitors, assuming competitors are at or near break-even point with their pricing? Analyze pricing alternatives and make recommendations about pricing going forward based on the following:
- How sensitive are your customers to changes in price?
- What revenue you need to break even and achieve profitability?
- What does the price says about your product in terms of value, quality, prestige, etc.?
Part 2: Respond to Classmates’ Posts
After you have created your own post, look over the discussion posts of your classmates and respond to at least two of them.
Part 3: Incorporate Feedback
Review the feedback you receive from classmates and your instructor. Use this feedback to revise and improve your work before submitting it as part of the “Complete Marketing Plan” assignment.
Grading Rubric for Discussion Posts
The following grading rubric may be used consistently for evaluating all discussion posts.
Discussion Grading Rubric
| Criteria | Response Quality: Not Evident | Response Quality: Developing | Response Quality: Exemplary | Point Value Possible |
|---|---|---|---|---|
| Submit your initial response | No post made – 0 pts | Post is either late or off-topic – 2 pts | Post is made on time and is focused on the prompt – 5 pts | Point value possible – 5 pts |
| Respond to at least two peers’ presentations | No response to peers – 0 pts | Responded to only one peer – 2 pts | Responded to two peers – 5 pts | Point value possible –5 pts |
Total Points Possible for Discussion Assignment: 10pts.
Contributors and Attributions
- Discussion: Pricing Strategy . Provided by : Lumen Learning. License : CC BY: Attribution


15.18B: Microbiota of the Skin
- Describe the types of skin flora and how they can be beneficial for the organism
The skin flora, more properly referred to as the skin microbiome or skin microbiota, are the microorganisms that reside on the skin. Most bacteria on the skin are found in the superficial layers of the epidermis and the upper parts of hair follicles. Skin flora are usually non-pathogenic, and either commensals (are not harmful to their host) or mutualistic (offer a benefit). The benefits bacteria can offer include preventing transient pathogenic organisms from colonizing the skin surface, either by competing for nutrients, secreting chemicals against them, or stimulating the skin’s immune system. However, resident microbes can cause skin diseases and enter the blood system creating life-threatening diseases particularly in immunosuppressed people. Hygiene to control such flora is important in preventing the transmission of antibiotic resistant hospital-acquired infections.
A major nonhuman skin flora is Batrachochytrium dendrobatidis, a chytrid and non-hyphal zoosporic fungus that causes chytridiomycosis, an infectious disease thought to be responsible for the decline in amphibian populations. The estimate of the number of species present on skin bacteria has been radically changed by the use of 16S ribosomal RNA to identify bacterial species present on skin samples direct from their genetic material. Previously such identification had depended upon microbiological culture upon which many varieties of bacteria did not grow and so were hidden to science. Staphylococcus epidermidis and Staphylococcus aureus were thought from cultural based research to be dominant. However, 16S ribosomal RNA research found that while common these species make up only 5% of skin bacteria. However, skin variety provides a rich and diverse habitat for bacteria. Most come from four phyla: Actinobacteria (51.8%), Firmicutes (24.4%), Proteobacteria (16.5%), and Bacteroidetes (6.3%).
There are three main ecological areas for skin flora: sebaceous, moist, and dry. Propionibacteria and Staphylococci species are the main species in sebaceous areas. In moist places on the body Corynebacteria together with Staphylococci dominate. In dry areas, there is a mixture of species, but b-Proteobacteria and Flavobacteriales are dominant. Ecologically, sebaceous areas have greater species richness than moist and dry ones. The areas with least similarity between people in species are the spaces between fingers, the spaces between toes, axillae, and umbilical cord stump. Most similar are beside the nostril, nares (inside the nostril), and on the back.
Skin microflora can be commensals, mutualistic, or pathogens. Often they can be all three depending upon the strength of the person’s immune system. Research on the immune system in the gut and lungs has shown that microflora aids immunity development. However, such research has only started upon whether this is the case with the skin. Pseudomonas aeruginosa is an example of a mutualistic bacterium that can turn into a pathogen and cause disease. If it gains entry into the blood system it can result in infections in bone, joint, gastrointestinal, and respiratory systems and it can also cause dermatitis. However,
Pseudomonas aeruginosa produces antimicrobial substances such as pseudomonic acid (that are exploited commercially such as Mupirocin). This works against staphylococcal and streptococcal infections. Pseudomonas aeruginosa also produces substances that inhibit the growth of fungus species such as Candida krusei, Candida albicans, Torulopsis glabrata, Saccharomyces cerevisiae, and Aspergillus fumigatus. It can also inhibit the growth of Helicobacter pylori. Fatty acids (caproic acid) on the skin inhibit bacteria, especially after puberty, when undecylic acid becomes the primary fatty acid on the skin. Undecylic acid provides resistance to ringworm fungus and other skin infections.
Another aspect of bacteria is the generation of body odor. Sweat is odorless. However, several bacteria may consume it and create byproducts which may be considered putrid by man (as in contrast to flies, for example, that may find them attractive/appealing). For example, Propionibacteria in adolescent and adult produce propionic acid in sebaceous glands.
Key Points
- Most bacteria on the skin are found in the superficial layers of the epidermis and the upper parts of hair follicles.
- Skin flora are usually non-pathogenic, and either commensals (are not harmful to their host) or mutualistic (offer a benefit).
- The benefits bacteria can offer include preventing transient pathogenic organisms from colonizing the skin surface, either by competing for nutrients, secreting chemicals against them, or stimulating the skin’s immune system.
- Resident microbes can cause skin diseases and enter the blood system creating life-threatening diseases particularly in immunosuppressed people.
Key Terms
- skin flora : the skin flora, more properly referred to as the skin microbiome or skin microbiota, are the microorganisms which reside on the skin.
- commensal : a term for a form of symbiosis in which one organism derives a benefit while the other is unaffected
- mutualistic : mutually beneficial.