What is growth? |

Process and Effects

The human body grows from conception until adult size is reached. Adult size is reached in females around the age of eighteen and in males around twenty or twenty-one, but there is considerable variation in either direction. (Nearly all numerical measurements of growth and development are subject to much variation.) On the average, males end up with a somewhat larger body size than females because of these two or three extra years of growth.

Growth begins after conception. The first phase of growth, including approximately the first month after conception, is called embryonic growth, and the growing organism is called an embryo. During embryonic growth, the most important developmental process is differentiation, the formation of the various organs and tissues. After the organs and tissues are formed, the rest of prenatal growth is called fetal growth and the developing organism is called a fetus. Respiratory movements begin around the eighteenth week of gestation, during the fetal stage; limb movements (such as kicking) begin to be felt by the mother around the twenty-fourth week, with a considerable range of variation. At birth, the average infant weighs about 3.4 kilograms (7.5 pounds) and measures about 50 centimeters (20 inches) in length.

Growth continues after birth and throughout childhood and adolescence. From the perspective of developmental biology, childhood is defined as the period from birth to puberty, which generally begins at twelve years of age, and adolescence continues from that point to the cessation of skeletal growth at around the age of eighteen in females and twenty or twenty-one in males. The long period of adulthood that follows is marked by a stable body size, with little or no growth except for the repair and maintenance of the body, including the healing of wounds. After about age sixty, there may be a slight decline in body height and in a few other dimensions.

By one year of age, the average baby is seventy-five centimeters (thirty inches) long and weighs ten kilograms (tewnty-two pounds). (There is actually a slight decline in weight in the first week of postnatal life, but this is usually regained by age three weeks.) For ages one to six, the average weight (in kilograms) can be approximated by the equation“weight = age 2 + 8.” For ages seven to twelve, growth takes place more rapidly: Average weight (in kilograms) can be approximated by “weight = age 3.5 - 2.5,” while average height (in centimeters) can be approximated for ages two to twelve by the equation “height = age 6 + 77.” Head circumference has a median value of about 34.5 centimeters at birth, 46.3 centimeters at an age of one year, 48.6 centimeters at age two, and 49.9 centimeters at age three. All these figures are about one centimeter larger in boys than in girls, with considerable individual variation. Median heights and weights, when differentiated by sex, reveal that boys and girls are generally similar until age fourteen, after which boys continue to gain in both dimensions.

Growth of the
teeth takes place episodically. In most children, the first teeth erupt between five and nine months of age, beginning with the central incisors, the lower pair generally preceding the upper pair. The lateral incisors (with the upper pair first), the first premolars, the canines, and the second premolars follow, in that order. All these teeth are deciduous teeth (“baby teeth”) that will eventually be shed, to be replaced during late childhood by the permanent teeth. At one year of age, most children have between six and eight teeth.

Growth takes place in several directions. Growth at the same rate in all directions is called isometric growth, which maintains similar proportions throughout the growth process. Isometric growth occurs in nautilus shells and a variety of other invertebrates. Most of human growth, however, is allometric growth, which takes place at different rates in different directions. Allometric growth results in changes in shape as growth proceeds. Moreover, different parts of the body grow at different rates and in different directions. During fetal development, for example, the head develops in advance of the fore and hind limbs, and the fetus at about six months of age has a head which is about half its length. The head of a newborn baby is about one-third of its body length, compared to about one-seventh for an adult. In contrast, the legs make up only a small part of the body length in either the six-month-old fetus or the newborn baby, and their absolute length and proportionate length both increase throughout childhood and adolescence.

Growth of the skeleton sets the pace for growth of the majority of the body, except for the nervous system and reproductive organs. Most parts of the skeleton begin as fast-growing cartilage. The process in which cartilage tissue turns into bone tissue is called ossification, which begins at various centers in the bone. The first center of ossification within each bone is called the diaphysis; in long bones, this ossification usually takes place in the center of the bone, forming the shaft. Secondary centers of ossification form at the ends of long bones and at certain other specified places; each secondary center of ossification is called an epiphysis. In a typical long bone, two epiphyses form, one at either end. Capping the end of the bone, beyond the epiphysis, lies an articular cartilage. Between the epiphysis and the diaphysis, the cartilage that persists is called the epiphyseal cartilage; this becomes the most rapidly growing region of the bone. During most of the growth of a long bone, the increase in width occurs by accretion, a
gradual process in which material is added at a slow rate only along a surface. In the case of a bone shaft, increase in width takes place only at the surface, beneath the surrounding membrane known as the periosteum. By contrast, the epiphyseal cartilage grows much more rapidly, and it also grows by interstitial growth, meaning that growth takes place throughout the growing tissue in all directions at once. As the epiphyseal cartilage grows, parts of it slowly become bony, and those bony portions grow more slowly.

During the first seven or eight years of postnatal life, the growth of the epiphyseal cartilage takes place faster than its replacement by bone tissue, causing the size of the epiphyseal cartilage to increase. Starting around age seven, the interstitial growth of the epiphyseal cartilage slows down, while the replacement of cartilage by bone speeds up, so that the epiphyseal cartilage is not growing as fast as it turns into bone tissue; the size of the epiphyseal cartilage therefore starts to decrease. At the time of puberty, the hormonal influences create an adolescent growth spurt during which the individual’s bone growth increases for about a one-year period. In girls, the adolescent growth spurt takes place about two years earlier than it does in boys—the average age is around twelve in girls, versus about fifteen in boys—but there are tremendous individual variations both in the extent of the growth spurt and in its timing. By age fourteen, most girls have already experienced most of their adolescent growth spurt, while most boys are barely beginning theirs. Consequently, the average fourteen-year-old girl is a bit taller than the average fourteen-year-old boy.

At around eighteen years of age in females and twenty or twenty-one years of age in males, the replacement of the epiphyseal cartilage by bone is finally complete, and bone growth ceases. The age at which this occurs and the resulting adult size both vary considerably from one individual to another. For the rest of adult life, the skeleton remains more or less constant in size, diminishing only slightly in old age.

Most of the other organs of the body grow in harmonious proportion with the growth of the skeleton, reaching a maximum growth rate during the growth spurt of early adolescence and reaching a stable adult size at around age eighteen in women and age twenty or twenty-one in men. The nervous system and reproductive system, however, constitute major exceptions to this rule. The nervous system and brain grow faster at an earlier age, reaching about 90 to 95 percent of their adult size by one year of age. The shape of the head, including the shape of the skull, keeps pace with the development of the brain and nervous system. For this reason, babies and young children have heads that constitute a larger proportion of their body size than do the heads of adults.

The growth of the
reproductive system also follows its own pattern. Most reproductive development is delayed until puberty. The reproductive organs of the embryo form slowly and remain small. The reproductive organs of children, though present, do not reach their mature size until adolescence. These organs, both the internal ones and the external ones, remain small throughout childhood. Their period of most rapid growth marks the time of puberty, which spans ages eleven through thirteen, with a wide range of variation. At this time, the
pituitary gland begins secreting increased amounts of the follicle-stimulating hormone (FSH), which stimulates the growth and maturation of the gonads (the ovaries of females and the testes of males). The ovaries or testes then respond by producing increased amounts of the sex hormones testosterone (in males) or estrogen (in females), which stimulate the further development of both primary and secondary sexual characteristics. Primary sexual characteristics are those which are functionally necessary for reproduction, such as the presence of a uterus and ovaries in females or the presence of testes and sperm ducts in males. Secondary sexual characteristics are those which distinguish one sex from another, but which are not functionally necessary for reproduction. Examples of secondary sexual characteristics include the growth of breasts or the widening of the hips in females, the growth of the beard and deepening of the voice in males, and the growth of hair in the armpits and pubic regions of both sexes.

Growth takes place psychologically and socially as well as physically. Newborn babies, though able to respond to changes in their environment, seem to pay attention to such stimuli only on occasion. At a few weeks of age, the baby will respond to social stimuli (such as the sound of the mother’s voice) by smiling. Babies usually can grasp objects by five months of age, depending on the size and shape of the object. By six months, most babies will show definite signs of pleasure in response to social stimulation; this may include an open-mouth giggle or laugh. At seven months of age, most babies will respond to adult facial expressions and will show different responses to familiar adults as opposed to strangers. The age at which babies learn to crawl varies greatly, but most infants learn the technique by nine or ten months of age. Social imitation begins late in the first year of life. Also, by this time, children learn object permanence, meaning that they will search for a missing object if they have watched it being hidden. Walking generally develops around eighteen months of age, but the time of development varies greatly.

Jean Piaget
(1896–1980) was a pioneer in the study of the social and cognitive development of children. Piaget identified four stages of cognitive and social growth, which he called sensorimotor, preoperational, concrete operational, and formal operational. In the sensorimotor stage, from birth to about two years of age, infants begin with reflexes such as sucking or finger curling (in response to touching their palms). Starting with these reflexes, they gradually learn to understand their senses and apply the resulting information in order to acquire important adaptive motor skills that can be used to manipulate the world (as in picking up things) or to navigate about and explore the world (as in walking). Socially, infants develop ways to make desirable stimuli last by such acts as smiling. In the preoperational stage, which lasts from about two to six years of age, children acquire a functional use of their native language. Their imagination flourishes, and pretending becomes an important and frequent activity. Most of the thinking at the preoperational stage is egocentric, however, which means that the child perceives the world only from his or her own point of view and has difficulty seeing other points of view.

The concrete operational stage spans the years from about seven to eleven years of age. This is the stage at which children learn to apply logic to concrete objects. For example, they realize that liquid does not change volume when poured into a taller glass, and they develop the ability to arrange objects in order (for example, by size) or to classify them into groups (for example, by color or shape). The final stage is called the formal operational stage, beginning around age twelve. This is the stage of adolescence and adulthood, when the person learns to manipulate abstract concepts in such areas as ethical, legal, or mathematical reasoning. This is also the stage at which people develop the ability to construct hypothetical situations and to use them in arguments.

Complications and Disorders

Disorders of growth include dwarfism, gigantism, and several other disorders such as achondroplasia (chondrodystrophy). Dwarfism often results from an insufficiency of the pituitary growth hormone, also called somatostatin or somatotrophic hormone. Some short-statured individuals are normally proportioned, while others have proportions differing from those of most other people. An overabundance of growth hormone causes gigantism, a condition marked by unusually rapid growth, especially during adolescence. In some individuals, the amount of growth hormone remains normal during childhood but increases to excessive amounts during the teenage years; these individuals are marked by acromegaly, a greater than normal growth which affects primarily the hands, feet, and face.

Achondroplasia, also called chondrodystrophy, is a genetically controlled condition caused by a dominant gene. In people having this condition, the epiphyseal cartilages of the body’s long bones turn bony too soon, so that growth ceases before it should. Those exhibiting chondrodystrophy therefore have short stature and childlike proportions but rugged faces that look older than they really are.

Inadequate growth can often result from childhood malnutrition, particularly from insufficient amounts of protein. If a child is considerably shorter or skinnier than those of the same age, that child’s diet should be examined for the presence of malnutrition. Intentional malnutrition is one of the characteristic features of anorexia nervosa. The opposite problem, overeating, can lead to obesity, although obesity can also result from many other causes, including diabetes and other metabolic problems.

By the late twentieth century, human growth hormone, a drug used since the 1950s to help very short children grow, was being used for “off-label” purposes that included antiaging and body building. In 2002, researchers suggested an apparent link between the use of the hormone and cancer, specifically Hodgkin’s disease and colorectal cancer.

Perspective and Prospects

As a phenomenon, growth of both wild and domestic animals was well known to ancient peoples. Hippocrates (ca. 460–ca. 370 BCE), considered the founder of medicine, wrote a treatise on embryological growth, and Aristotle (384–322 BCE) wrote a longer and more complete work on the subject. During the Renaissance, Galileo Galilei (1564–1642) studied growth mathematically and distinguished between isometric and allometric forms of growth, arguing that the bones of giants would be too weak to support their weight.

The most important era in the study of human embryonic development was ushered in by the Estonian naturalist Karl Ernst von Baer (1792–1876), who discovered the human ovum. From this point on, detailed studies of human embryonic and postnatal development proceeded at a rapid pace, especially in Germany. Much of the modern understanding of growth in more general or mathematical terms derives from the classic studies of the British anatomist D’Arcy Wentworth Thomson (1860–1948). In the twentieth century, Piaget became a leader in the study of childhood social and cognitive growth phases.

Bibliography

Bar, Robert S., ed. Early Diagnosis and Treatment of Endocrine Disorders. Totowa, N.J.: Humana Press, 2003.

Behrman, Richard E., Robert M. Kliegman, and Hal B. Jenson, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia: Saunders/Elsevier, 2007.

Bukatko, Danuta, and Marvin W. Daehler. Child Development: A Thematic Approach. Belmont, Calif.: Wadsworth, 2012.

"Facts About Child Development." Centers for Disease Control and Prevention, September 12, 2011.

Galotti, Kathleen M. Cognitive Development: Infancy through Adolescence. Thousand Oaks, Calif.: SAGE Publications, 2011.

Goodman, H. Maurice. Basic Medical Endocrinology. 4th ed. Boston: Academic Press/Elsevier, 2009.

Kail, Robert V., and John C. Cavanaugh. Human Development: A Life-Span View. Belmont, Calif.: Wadsworth, 2013.

McMillan, Julia A., et al., eds. Oski’s Pediatrics: Principles and Practice. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.

Marieb, Elaine N. Essentials of Human Anatomy and Physiology. 9th ed. San Francisco: Pearson/Benjamin Cummings, 2009.

Moore, Keith L., and T. V. N. Persaud. The Developing Human. 8th ed. Philadelphia: Saunders/Elsevier, 2008.

Rosse, Cornelius, and Penelope Gaddum-Rosse. Hollinshead’s Textbook of Anatomy. 5th ed. Philadelphia: Lippincott-Raven, 1997.

Standring, Susan, et al., eds. Gray’s Anatomy. 40th ed. New York: Churchill Livingstone/Elsevier, 2008.

Tsiaras, Alexander, and Barry Werth. From Conception to Birth: A Life Unfolds. New York: Doubleday, 2002.

What is eczema? |

Causes and Symptoms

The term
eczema
refers to a noncontagious inflammation of the skin. Several types of eczema exist, resulting in a range of symptoms that vary in appearance, duration, and severity. The common characteristic, however, is red, dry, and itchy skin. Other symptoms may include scaling, thickening, or cracking of the skin, leading to infections and severe discomfort.

Atopic dermatitis,
the most common form of eczema, is characterized by itchy and cracked skin of the cheeks, arms, and legs. The onset of this chronic type of eczema occurs most often during infancy or childhood, although symptoms may continue into adulthood. The cause of atopic dermatitis is thought to be a hereditary predisposition to skin sensitivities to various environmental factors. These factors include irritants such as soaps, detergents, and rough clothes; allergens such as certain foods, pollen, or animal dander; and changes in climate or temperature. Other forms of eczema, such as contact dermatitis, have similar environmental causes. Seborrheic eczema, nummular eczema, and dishydrotic eczema may result from a combination of several possible causes. Emotional factors, such as stress or frustration, may aggravate the symptoms.

The diagnosis of eczema requires a careful and detailed observation of symptoms. Family and personal medical histories are often useful to determine the presence of allergies or exposure to allergens or irritants. Dermatologists may also use skin biopsies or blood tests to determine a tendency toward elevated allergic or immune response.

Treatment and Therapy

The treatment of eczema involves minimizing exposure to possible causes while at the same time managing symptoms to maintain a high quality of life. Identifying known allergens and irritants specific to the individual is an important first step. Lifestyle changes aimed at avoiding exposure to these possible causes can lower the frequency and duration of symptoms dramatically. Proper skin care to avoid excessive drying of the skin, including the use of moisturizers or creams and minimizing exposure to water, may also help reduce skin irritation. Avoiding scratching of existing irritations and eliminating sources of emotional stress are other ways that patients can lessen the severity of their symptoms. Dermatologists may prescribe additional treatments, such as corticosteroid creams and ointments, antihistamines, or antibiotics. In more severe cases, systemic corticosteroid treatments or phototherapy, the use of ultraviolet (UV) light, may be tried.

The approval of a new type of treatment for eczema called topical immunomodulators has changed the way eczema is treated in recent years. This new class of drug counteracts the inflammation of the skin without interfering in the body’s normal immune response. This treatment has been successful in preventing and even eliminating symptoms of eczema.

Bibliography:

Fry, Lionel. An Atlas of Atopic Eczema. New York: Parthenon, 2004.

Hellwig, Jennifer. "Eczema." Health Library, Mar. 11, 2013.

MedlinePlus. "Eczema." MedlinePlus, May 6, 2013.

National Eczema Society. National Eczema Society, n. d.

Rakel, Robert E., and Edward T. Bope, eds. Conn’s Current Therapy. Philadelphia: Saunders, 2007.

Ring, J., B. Przybilla, and T. Ruzicka, eds. Handbook of Atopic Eczema. 2d ed. New York: Springer, 2006.

Turkington, Carol A., and Jeffrey S. Dover. Skin Deep: An A-Z of Skin Disorders, Treatments, and Health. 3d ed. New York: Checkmark, 2007.

Westcott, Patsy. Eczema: Recipes and Advice to Provide Relief. New York: Welcome, 2000.

What is the relationship between work issues and substance abuse?

Economic Costs

Substance abuse is a common problem in the workplace in the United States. Contrary to popular stereotypes, as of 2014, 56.1 percent of adults with substance abuse problems were employed full time, and an additional 16.2 percent were part-time employees. About 8 percent of full-time employed adults and 6.6 percent of part-time employed adults reported heavy use of alcohol in the past month. In addition, a 2014 survey commissioned by the website Mashable found that 9.7 percent of Americans had gone to work at least once while under the influence of marijuana, 7.3 percent had done so after taking prescription drugs for recreational purposes, and 3.4 percent while under the influence of an illegal drug other than marijuana.

The abuse of these substances imposes heavy financial burdens on businesses in the United States. According to the Office of National Drug Control Policy, as of 2006–7, drug and alcohol abuse combined cost the US economy an estimated total of $416 billion per year, the majority of which was lost by employers. (The remainder of the cost was due to health care expenses and criminal prosecution.) Direct costs to employers included lost productivity from increased absenteeism and sick leave, compensation for workplace accidents and injuries, high employee turnover and the resulting cost of training new employees, higher disability payments and health care expenditures, drug testing and employee assistance programs, theft of or damage to company property, liability insurance, and involvement of law enforcement for drug-related crises in the workplace.

In addition to the direct costs of work-related substance abuse, employers must cover indirect costs. These costs include lowered employee morale, loss of competitiveness, damage to the company’s reputation because of declining quality of goods and services, and poor decisions made by substance-impaired managers or supervisors.

Some industries and occupations have higher rates of alcohol and substance abuse among employees than others. Industries with the highest rates of alcohol abuse include mining and construction, while accommodations, food services, arts, entertainment, and recreation rank high in both alcohol and illicit drug use. Management occupations are near the top in both categories, though they rank higher in drug use than in heavy alcohol use. Other industries with relatively high rates of substance use include utilities, retail trade, and real estate.

Work-related factors known to increase the risk of substance abuse among employees, including managers and supervisors, include high stress levels, repetitious tasks, working in isolation, long and irregular work shifts, access to alcohol or drugs, and relative lack of supervision. Small businesses are at greater risk than large companies, as they are less likely to have prevention and treatment programs for impaired employees and are less likely to screen potential employees for substance abuse problems.

Health and Public Safety Issues

The well-being and safety of other workers and the general public was a major reason for increased research into and legislation regarding work-related substance abuse in the early 1980s. A “zero tolerance” policy that includes mandatory drug testing of all US military personnel was introduced in 1981 following a plane crash on an aircraft carrier that killed fourteen crew members.

Research conducted since the mid-1980s has shown that workers who abuse drugs and alcohol, whether on the job or at home, are a threat to the safety of others and themselves. For example, about one-half of all visits to emergency rooms in the United States for traumatic injuries are related to alcohol abuse, and employees who abuse alcohol have health care costs 100 percent higher than those of other workers. Employees who use illegal drugs are twice as likely as nonusers to call in sick and four times as likely to be involved in a workplace accident. The Occupational Safety and Health Administration (OSHA) reports that 15 to 20 percent of workers who die on the job test positive for alcohol or drugs at autopsy.

In addition to accidental injuries, employees who abuse substances are also at increased risk of such long-term health consequences as cancer and other diseases of the heart, liver, and pancreas. Workers who abuse drugs and alcohol are also more likely to cause health problems for their coworkers by adding to workplace tensions. Violent behavior and accidents triggered by intoxication are obvious causes of injury to others; however, stress resulting from having to complete projects for impaired employees or to work extra shifts to make up for their absenteeism also can have long-term effects on the health and job satisfaction of other workers. Drug-related problem behaviors such as mood swings, unusually long breaks, hypersensitivity to criticism, missing deadlines, and borrowing or stealing money from colleagues to finance a drug habit lower the morale of other workers. Finally, more than one-half of workers who live with or are related to an alcoholic or drug addict report that their own productivity at work is affected by anxiety about their relative or roommate.

Legal Issues

Also associated with workplace substance abuse are specific legal issues. These issues include federal regulation of transportation and other safety-sensitive industries, mandates applied to companies that do business with the government, the response of law enforcement to drug-related workplace crime (such as possession and sale of drugs, embezzlement, property theft, and violent assault), the rights of employees regarding drug and alcohol testing, and the introduction of workplace drug policies.

The first major federal law in this field was the Drug-Free Workplace Act of 1988, which requires some federal contractors and all federal grantees to establish drug-free workplaces to receive grants or contracts from any federal agency. The precise requirements vary somewhat according to whether the contractor or grantee is an individual or an organization.

The US Department of Transportation and the Federal Motor Carrier Safety Administration have strict regulations regarding drug use and drug testing for employees whose jobs require a commercial driver’s license. Similarly, the Omnibus Transportation Employee Testing Act of 1991 requires periodic testing of airline pilots for alcohol or drug abuse, including the abuse of prescription drugs.

Another legal issue related to workplace substance abuse is the rights of employees regarding drug testing, specifically involving federal and state disability laws. In general, substance abuse has not been considered a disability such that firing an addicted employee could be considered harassment or discrimination. Nonetheless, to avoid future lawsuits by former employees, employers are usually advised to seek legal advice when introducing a workplace drug policy.

Drug-Free Workplace Programs

The high human and financial costs of work-related substance abuse have led more and more employers to introduce workplace policies intended to prevent and treat such abuse. OSHA has identified five essential features of a drug-free workplace policy: a written statement of company policy regarding drug use, testing, consequences for violations, and similar matters; training supervisors in appropriate handling of drug-related problems; educating employees; drug testing; and employee assistance programs or referral to professional counseling. To help employers draft policy statements that fit their particular workplace, the US Department of Labor offers an online, interactive drug-free workplace advisor.

One important aspect of such policies is the supervisor or manager’s role. Supervisors are advised to focus on and document problems with an employee’s performance or productivity when drug abuse is suspected, rather than attempting to diagnose substance use or provide informal counseling. In addition, supervisors are expected to protect employees’ confidentiality. One of the most challenging tasks in maintaining a drug-free workplace policy at all levels of a company is balancing the rights of affected employees to confidentiality and access to treatment with the rights of nonusers to a safe and drug-free workplace.

Bibliography

Bennett, Joel B., and Wayne E. K. Lehman, eds. Preventing Workplace Substance Abuse: Beyond Drug Testing to Wellness. Washington: APA, 2003. Print.

Bush, Donna M., and Rachel N. Lipari. "Substance Use and Substance Use Disorder by Industry." CBHSQ Report 16 Apr. 2015: n. pag. SAMHSA. Web. 9 Nov. 2015.

"Cost Benefits of Investing Early in Substance Abuse Treatment." Office of National Drug Control Policy. WhiteHouse.gov, 23 May 2012. Web. 9 Nov. 2015.

Desta, Yohana. "Nearly 10% of Americans Go to Work High on Weed." Mashable. Mashable, 17 Sept. 2014. Web. 9 Nov. 2015.

"Drugs and Alcohol in the Workplace." National Council on Alcoholism and Drug Dependence. NCADD, 26 Apr. 2015. Web. 9 Nov. 2015.

"How Illicit Drug Use Affects Business and the Economy." Office of National Drug Control Policy. WhiteHouse.gov, 23 May 2012. Web. 9 Nov. 2015.

National Business Group on Health. Center for Prevention and Health Services. An Employer’s Guide to Workplace Substance Abuse: Strategies and Treatment Recommendations. Washington: Author, 2009. National Business Group on Health. Web. 9 Nov. 2015.

United States. Department of Health and Human Services. Substance Abuse and Mental Health Services Administration. Center for Behavioral Health Statistics and Quality. Results from the 2014 National Survey on Drug Use and Health: Detailed Tables. Rockville: SAMHSA, 2015. SAMHSA. Web. 9 Nov. 2015.

United States. Department of Health and Human Services. Substance Abuse and Mental Health Services Administration. Center for Substance Abuse Prevention. Division of Workplace Programs. Making Your Workplace Drug-Free: A Kit for Employers. Rockville: SAMHSA, 2007. SAMHSA Store: Substance Abuse and Mental Health Publications. Web. 9 Nov. 2015.

Where is the sperm cell produced in the male body?

Sperm cells which are the male gametes (sex cells), are produced in the testes or male sex organs (gonads). The special process that produces the male sperm cells is called spermatogenesis and it is accomplished by meiosis.

Cells of the body are called somatic cells and contain the diploid amount of chromosomes represented by 2n. For humans, the 2n amount is 46 chromosomes, or 23 pairs. Cells inside the testes have the diploid or 2n...

Sperm cells which are the male gametes (sex cells), are produced in the testes or male sex organs (gonads). The special process that produces the male sperm cells is called spermatogenesis and it is accomplished by meiosis.

Cells of the body are called somatic cells and contain the diploid amount of chromosomes represented by 2n. For humans, the 2n amount is 46 chromosomes, or 23 pairs. Cells inside the testes have the diploid or 2n chromosome number because they are somatic cells. These diploid cells called primary spermatocytes undergo meiotic cell division eventually forming haploid sperm cells.

Meiosis is known as a reduction division. This cell division has two stages--meiosis I and II which eventually produces four haploid gametes or sperm cells from cells in the testis that undergo meiosis. Therefore, sperm cells will have 23 chromosomes which is the haploid amount of chromosomes in humans.

Males produce sperm cells from the time of puberty and throughout their lives. After fertilization -- the process by which a sperm nucleus fuses with an egg nucleus, the genes from each parent will be present in the newly created, diploid zygote. The processes of meiosis which creates haploid gametes (sperm and eggs) and fertilization which forms a diploid zygote make up the life cycle of humans.

I have included a diagram of spermatogenesis and another link to a detailed explanation of meiosis.

What is general surgery? |

Science and Profession

In all probability, surgery has been practiced as long as humans have had cutting tools. Ample reports of battlefield amputations exist almost from the beginning of reported time. Historians tell of rough field surgery, the hacking off of wounded limbs, and the sealing of wounds by searing the lacerated flesh. There are even suggestions that ancient civilizations, such as that of the Egyptians, practiced trepanning, cutting into the skull to operate on the brain.

Until the latter half of the nineteenth century, surgery was a brutal, dirty, and dangerous practice. About this time, the relationship between microorganisms and diseases was first enunciated, a relationship that explained why so many surgery patients sickened and died. It was also at this time that anesthetics were developed, which for the first time allowed the surgeon to deaden the patient’s pain.

Surgery today is one of the most respected medical specialties, requiring full training in the disciplines of medicine, as well as years of extensive work in surgical procedures. After becoming physicians, candidates for surgery spend years working under established surgeons learning the techniques that they will use in practice. They are subjected to intensive examination and receive certification only when their peers are convinced that they can perform their duties capably.

The tools and techniques of surgery that the surgical candidate must master present multiple challenges. In their training phase, surgeons learn to become skilled in the manipulation of all basic instruments used in surgery, such as the various designs of scalpels, scissors, retractors, forceps, and sutures. The training surgeon learns a wide variety of stitching techniques and the materials used in suturing. Most challenging perhaps is mastery of the many new techniques and instruments made available for modern surgeons to use.

After training and certification, some surgeons elect to practice general surgery. As the term implies, this field covers such diverse areas of the body as the stomach, gallbladder, liver, intestines, appendix, breasts, thyroid gland, salivary glands, main arteries and veins, lumps under the skin, hernias, and hemorrhoids. Other surgeons choose to specialize in disciplines that require still more training, such as heart surgery, bone (or orthopedic) surgery, and eye (or ophthalmic) surgery, to name some of the more prevalent specialties.

Modern surgery is a far-ranging practice involving all body structures and systems. It is also a practice that sees constant advancements and improvements in operating techniques, in instrumentation and tools, and in high-tech equipment. Microsurgery, in which the surgeon uses a microscope to view the operating field and manipulates tiny instruments to repair or excise tissue, was virtually unheard of at the middle of the twentieth century. It has since become common practice in nearly every surgical facility in the United States and other countries. At one time, a severed limb could never be reconnected, largely because it was impossible to repair severed nerves. With the use of microsurgery, however, arms, legs, hands, digits, and other severed body parts can be stitched back on to the body, often with much of their mobility restored.

Much minor surgery takes place in the physician’s office or clinic. These procedures are generally simple, involving the excision of skin growths such as warts or cancers, hemorrhoids, and other surface conditions. Emergency surgery in the office, clinic, or emergency room may be necessary to open an airway for a patient whose breathing is impaired or to remove obstructions.

Major surgery usually requires a hospital stay, and its main characteristics are anesthesia and aseptic technique. Anesthesia may be local, regional, or general. For local anesthesia, anesthetic is injected into the site of the operation. The patient is usually fully awake during the surgery but feels no pain in the affected area. In regional anesthesia, a whole part of the body is anesthetized, such as a leg or an arm. As with local anesthesia, the patient is awake during the procedure but may be sedated for comfort. In general anesthesia, the patient is put to sleep and immobilized, usually by injections, and inhaled anesthetics are administered throughout the course of the operation.

To create an aseptic, germ-free environment, the operating room and everything in it are subjected to rigorous sterilization. Surgeons and all operating room staff scrub with antiseptic soaps. They don complete uniforms of sterilized cloth or paper: caps, masks, gowns, gloves, and foot coverings. Avoiding transmission of disease in the operating room can be said to be as important as the operation itself. It is vital that the patient be made safe from infection by the staff and from pathogenic organisms in the ambient atmosphere of the hospital.

It is equally important that staff be protected from infection by the patient. Operating room personnel are particularly vulnerable to blood-borne infections, such as hepatitis B and human immunodeficiency virus (HIV). Surgery can be a bloody procedure. In some operations, copious blood spurts are common, and the likelihood of staff being spattered is high, as is the possibility of disease transmission. It is possible that there could be a cut or tear in the staff’s protective clothing and that the patient’s blood or other body fluids could make contact with an abrasion on the body or even land on mucous membranes of the mouth, nose, and throat, where they can infect the caregiver. This has happened so often that the US government has issued rigorous guidelines to high-risk health care personnel—particularly operating room staff—detailing specific procedures to follow to avoid disease transmission.

Diagnostic and Treatment Techniques

The surgeon is rarely the first physician whom the patient sees. Usually, a primary care physician makes a diagnosis and may confer with or send the patient to a specialist for confirmation of the diagnosis. When surgery is recommended, the surgeon confers with the primary care physician and/or the consulting specialist and is fully apprised of the patient’s condition. He or she reviews the patient’s history and inspects all relevant documents and diagnostic reports, such as X-rays, computed tomography (CT) scans, and other information that he or she needs to plan and perform the procedure.

For the most part, surgeons deal with their patients only in the immediate context of the operation. They meet before the operation, and surgeons look in on patients afterward to check on their progress and recovery. In some cases, follow-up visits to the surgeon are required.

In the operating room, the surgeon assembles the staff needed for the particular procedure. There will be an anesthesiologist, perhaps other specialized surgeons, and various general and specialized operating room nurses. The surgeon or the staff will also order everything needed for the procedure. There is an enormous range of specialized equipment that surgeons may use in their procedures. Cardiac surgeons use heart-lung machines, which take over the task of circulating the patient’s blood and allow the surgeon to open and enter the heart itself. The neurosurgeon may operate through specialized microscopic instruments.

A catalog of specialized endoscopes is available to surgeons, many of which allow them to operate through a tiny hole in the patient’s skin, rather than having to make massive cuts with a scalpel. Pulmonary surgeons use a bronchoscope to look down into the patient’s bronchial tubes, where they can perform such surgical operations as removing obstructions and excising cancerous tissue. Gastrointestinal surgeons use a gastroscope both to investigate conditions in the stomach and to take small tissue samples for biopsy. Colon and rectal surgeons use a colonoscope to remove polyps from the colon and rectum, a major step in the prevention and treatment of colon cancer. Major surgery, however, still involves cutting the patient open to repair what has gone wrong inside the body. Fortunately, this procedure has become safer and more specialized than ever been before.

Management of disease in the United States and other parts of the world has reached the point where there are surgical specialties to cover virtually all parts of the body individually. Some surgeons specialize in individual organs, such as the heart, lungs, brain, eyes, and ears. Some surgeons specialize in body systems such as bones or circulation. Furthermore, many surgeons hone their skills in certain specialized surgical techniques and become so adept that they are recognized as experts in highly complex and critical procedures, such as repairing detached retinas, performing heart transplants, correcting slipped disks, or sealing brain aneurysms.

Surgeons are major inventors and designers. Much of the instrumentation and many of the surgical tools that are used in the operating room were invented by surgeons. They often direct the fabrication of specialized tools and instruments to help them in their work. Most of the metal and plastic prostheses implanted to replace damaged internal structures were designed by surgeons. Orthopedic surgeons design prosthetic hips, knees, and other implants. Ophthalmic surgeons design corneal implants. The specialized surgeon knows his or her area of the body better than anyone else does and can visualize what sort of equipment or device is needed to improve the patient’s condition.

Surgeons are also at the forefront of major technical innovations that reach across the entire surgical field. They are adept at recognizing potential applications for new technology and adapting it to surgery. For example, fiber-optic science has been applied in surgical endoscopes. Cryosurgery, a technique of freezing tissue, is used in a wide range of procedures, from the removal of hemorrhoids to the reattachment of retinas.

Laser technology is employed in hundreds of surgical procedures. The laser is used for making incisions, for repairing tissue, and for excising diseased tissue, among other applications. One of the major areas that can benefit from the unique advantages of laser use is eye surgery. Ophthalmic surgeons use lasers to relieve diabetic retinopathy, glaucoma, macular degeneration, cataracts, and certain tumors, as well as to reattach torn retinas.

One of the critical qualities of the competent surgeon is judgment. No matter how thoroughly a surgeon may prepare for a procedure, there may be some surprises on the operating table. The surgeon learns the patient’s history and status and also reviews all the appropriate diagnostic documents, x-rays, and other visualizations, but unforeseen complications may arise during the operation. The surgeon must have the experience and competence to deal with the unexpected.

Perspective and Prospects

Up to the mid-nineteenth century, surgical procedures were probably responsible for as many deaths as cures. Today, surgery extends the lives of millions: heart disease victims, cancer patients, and victims of infection and accidents. Surgery helps improve the quality of life for patients with arthritis and rheumatism, gastrointestinal problems, lung disorders, and circulation problems.

Furthermore, surgery is continuously entering new areas of medicine. For example, operations can be performed in the uterus to correct anomalies in unborn fetuses. Many more such procedures are predicted for the future.

New areas of surgical expertise are opening constantly; new techniques, instrumentation, and equipment are making many old procedures obsolete. Practicing surgeons face a constant challenge in keeping abreast of what is happening all over the world and in deciding what avenues to explore for the benefit of their patients.

Bibliography

Brunicardi, F. Charles, et al., eds. Schwartz’s Principles of Surgery. 10th ed. New York: McGraw, 2015. Print.

Griffith, H. Winter. Complete Guide to Symptoms, Illness, and Surgery. 6th ed. New York: Perigee, 2012. Print.

Henry, Michael M., et al. Clinical Surgery. 3rd ed. Edinburgh: Elsevier/Saunders, 2012. Print.

Litin, Scott C., ed. Mayo Clinic Family Health Book. 4th ed. New York: Harper, 2009. Print.

Mulholland, Michael W., et al., eds. Greenfield’s Surgery: Scientific Principles and Practice. 5th ed. Philadelphia: Lippincott, 2011. Print.

Zollinger, Jr., Robert M., and E. Christopher Ellison. Zollinger’s Atlas of Surgical Operations. 9th ed. New York: McGraw, 2011. Print.

How do behavioral addictions affect parenting?

Parental Influence on Behavioral Addiction

Parents have three potential mechanisms by which they influence the development of behavioral addictions in their children. However, none of these mechanisms directly causes behavioral addictions.

The first and most fundamental parental mechanism is genetic inheritability. Addiction is promoted through a neuronal reward system in which the pleasure areas of the brain are stimulated and the behavior that brought the pleasurable experience is identified and repeated. A well-known example is the endorphin release or rush experienced by runners, cyclists, and other extreme athletes. At some point during the activity, the physical expenditure of energy triggers a release of brain chemicals (neurotransmitters), most notably endorphin, which the athlete experiences as pleasurable.

While this pleasurable response to vigorous exercise is almost universal and can be brought about by any number of strenuous physical activities, individual sensitivity is primarily genetically inherited. If it takes a lot of exercise before a parent experiences the pleasure of endorphin release, it is likely that his or her children will require much exercise before they experience the endorphin rush. What a parent contributes here is his or her child’s sensitivity to having the pleasure centers of the brain stimulated.

In the example of the runners’ high, just how much running has to occur before endorphins are released will vary among individuals, with most of the variation accounted for by how much exercise their parents would have had to do before their own endorphins were released. Largely determined by what was true for one’s parents is how much activity one has to engage in to bring on the pleasurable experience, how intense (and thus addictive) is that experience, and how long that experience lasts.

Parents’ genetic contributions influence their children’s addictive sensitivity, pleasurable intensity (which corresponds to addictive potential with the more the intensity, the greater the potential), and duration. Duration involves the length of the experience and how much behavior was required to result in the reward. Parents pass down a tendency toward or a tendency away from pleasurable addiction; they do not pass down specific behavioral addictions like pornography or kleptomania. The more excitable the parents’ brains, the more excitable the children’s brains are likely to be.

The second mechanism through which parents influence the development of behavioral addiction is through imitative, behavioral, and social learning. Parents who are addicted to exercise, gambling, social networking, or shopping, for instance, show their children that these behaviors are within the range of what this family will accept. Most behavioral addictions are merely extreme examples of normally encountered and readily observed behaviors that all individuals exhibit. When parents are addicted to any of these behaviors, children are exposed to the idea that the behaviors are acceptable or normal to some degree; the parents legitimate the behaviors through their actions. For example, most children will not see a spotlessly clean home as normal unless they are raised in an environment in which compulsive cleaning is the norm.

The third and most common mechanism for parents to influence and sustain behavioral addictions in their children is enabling. The cycle begins with children engaging in a commonly accepted behavior, such as video gaming. There also is a good chance that children have participated with their parents in that activity. It is common for parents, for example, to play video games with their children. However, because the threshold between normal, daily activity and driven addiction is more nuanced and not well defined, it usually takes a substantial period of time to go from family entertainment to individual addiction.

The behavior crosses the threshold into addiction when it directly or indirectly harms the child, interferes with other health- and growth-promoting activities (such as school work, socializing with friends, participating in family functions), and becomes the major focus or prime motivation for how the child allocates his or her time. Addicted children, like their adult counterparts, are on a quest to satiate urges and avoid the anxiety they will feel when those urges are not met. The addict’s focus is on how soon he or she will be able to satisfy the next urge.

Even with the foregoing conditions as a guideline, it still can be difficult to distinguish passion and dedication from compulsion and absorption. For example, when does excessive football practice become exercise addiction? Addiction is usually difficult to determine until the addiction is well established; at this point parents are at risk of knowingly or unknowingly promoting the addiction by sustaining the addictive behavior of the child.

The behavior that is troubling to parents and harmful to their children is allowed to continue because of parents’ uncertainty, unreliability, and hesitation about how they should respond to their child and his or her problem. Parents have ultimate authority and influence over their children’s lives; they provide life’s essentials—food, clothing, shelter, and security. They also provide life’s social essentials—identity, belonging, and support for a life outside the home through financial and material means.

Helping children is generally natural for parents. This predisposition becomes problematic when children begin to manipulate parents and other family members to fulfill their addictive cravings. When parents minimize or deny that their child’s behavior, such as excessive shopping or compulsive eating, is a problem, they enable the child to engage in these behaviors without having to identify that they have a problem.

Subconsciously, children study parental behavior and learn from it. This behavior cues children about what is allowable, what will be confronted, what will be ignored, and what will or will not be tolerated. By failing to identify the behavior and its impact on children and family as a problem, parents subconsciously influence how children see the addictive behavior. The addiction becomes something that is acceptable, “a phase,” or something that the child will outgrow.

Placed between the emotionally difficult situation of loving and supporting their children without unnecessarily challenging them, parents often take responsibility for the actions and behaviors of their children. This allows the child to dismiss responsibility for the consequences of their behaviors. This feeds the addiction because the child is never forced to look at the harmful consequences of his or her behavior.

Children with behavioral addictions often display both an alarming lack of concern for those they affect and a disarming, narcissistic, self-concern. In the jargon of addiction treatment, this behavior becomes an example of “It’s not the person but the addiction speaking.” At this stage, children have learned to manipulate their parents’ confusion and concern. Parents’ attempts to control children’s environments are vigorously opposed or cleverly bypassed. Children may lie, steal, and mislead to overcome the obstacles. The home environment becomes hostile, discordant, and conflict-ridden.

To establish stability, calm, and peace, parents begin to second guess how they should act around their addicted children, what they should or should not say, and what feelings they should share or keep to themselves. The relationship between parents and the addicted child may feel strained, forced, uncomfortable, and unfamiliar.

In an environment of indecision, addicted children will continue to accept that all is well; they will do this until parents express concern or confrontation. Children then often respond in the extreme. Pleading, promises, punishment, coercion, and reward have lost their effectiveness at this point. Even if both parents and child do not want a discordant climate, they lack the language and direction to make sustainable changes for the better. However, in any family that is understood to function as a system, it takes only one member to effect change in the rest of the family and to prompt the family toward a healthier direction. Knowing what type of help to get, and where to get it, is critical to family recovery.

Parenting as a Cure

At the most basic level, parents must acknowledge how their responses may have made the addiction worse and treatment more difficult. Going against better judgment; not standing their ground; and punishing, bribing, and codependently watching and reacting to their troubled child have all made the family system less functional, trustworthy, and effective.

The first step in treating the addict and his or her family is for parents to accept how they may have helped sustain an addiction in their child. Parents can rarely control their children’s harmful behaviors, but they can control their responses to those behaviors. They can begin to control their dysfunctional responses.

Parents must educate themselves about addiction in general and the specific behavioral addiction of their child. This will include demonstrating healthier behaviors for the child. Parents should understand that they may do whatever they can to help their child but do nothing that supports the addiction.

Parents did not create the addiction, and they cannot control or cure it. Parents who educate themselves about healthy actions, rather than reactions, can begin to support their addicted child.

Progress is likely to be uneven. Parents can make great strides in recovery while the child seems to regress, or the reverse can occur. Critical to this stage of recovery is accepting that recovery from addiction involves a long-term commitment to practicing healthy behaviors. As long as one side incorporates even some positive behavioral changes, the entire family system will improve and the relationship between child and parents will begin to mend.

While these behavioral modifications are critical first steps toward a healthier, addiction-free life, they are not usually enough to address all aspects of the addiction. Routinely, parents’ and children’s recoveries will involve multidimensional treatment, often with a specially trained clinician and with group support. Some addicts will need to enroll in a treatment facility to facilitate their recovery.

It is vital that parents and the child work separately at modifying their behaviors first. The best place to start is with a counselor who is trained to work with addicts and their parents. The counselor will be able to set up a proper treatment plan and refer the patients to the right resources.

Parents should seek professional help and support groups for themselves too. Self-help groups such as Al-Anon, Alateen, and Co-Dependents Anonymous also are available for parents and other family members to receive additional support.

American Academy of Child and Adolescent Psychiatry. “Facts for Families.” Washington, DC: AACAP, 2011. PDF file.

Sadock, B. J., and V. A. Sadock, eds. Kaplan and Sadock’s Comprehensive Textbook of Psychiatry. Philadelphia: Lippincott, 2000. Print.

What is serotonin? |

Serotonin is a chemical that works as a
neurotransmitter
, which is a substance in the body that carries a signal from one nerve cell to another. It is one of several monoamine neurotransmitters, which include adrenaline and dopamine. The human body manufactures serotonin, which many researchers believe plays a role in mood balance. While some serotonin is manufactured and used in the brain, most of the body's supply is in the gastrointestinal tract.

Background

Serotonin was first discovered during the 1930s by Vittorio Erspamer, who isolated the molecules while seeking drugs from natural sources. He was studying cells in the smooth muscles of animals' intestinal tracts when he isolated serotonin, which he named enteramine. Irvine Page, Maurice Rapport, and Arda Green at the Cleveland Clinic were working on a substance they called serotonin in 1948. Page was studying hypertension and trying to understand what caused it. He believed it was something in the blood, but a substance kept showing up in his samples. Wishing to isolate the substance so he could remove it, he sought assistance from Rapport and Green. As a result of this work, in 1952 serotonin and enteramine were found to be one and the same.

Around this time, Betty Mack Twarog was studying neurotransmitters in mussels. She was unable to identify the neurotransmitter that regulated muscle relaxation in the mollusks. After she read the Cleveland Clinic researchers' paper on serotonin, she became intrigued, but the paper only addressed serotonin in mammals. About that time, Erspamer found enteramine in octopus salivary glands, and soon after this discovery, enteramine was identified as serotonin. Twarog obtained a sample of serotonin and soon confirmed her suspicions that the neurotransmitter in the mussels was serotonin. She later worked at the Cleveland Clinic and confirmed her theory that serotonin could be found in the brain. The work of these researchers was instrumental in the development of the field of neuroscience, which is the study of the nervous system.

Overview

The chemical name for serotonin is 5-hydroxytryptamine, or 5-HT. It is created by combining an amino acid called tryptophan and a chemical reactor called tryptophan hydroxylase. Between 80 and 90 percent of the body's serotonin is found in the gastrointestinal tract, but it is also found throughout the body in the central nervous system and in platelets.

Serotonin is important because it conveys signals between nerve cells. It cannot pass through the blood-brain barrier, which is a network of cells that restricts access to the brain, therefore all serotonin created in the brain must remain there. For this reason, it is impossible to measure serotonin levels in the brain using blood tests. The chemical is believed to be a necessary component in many functions, including appetite and digestion, memory, mood and social behavior, sexual desire and function, and sleep. Some studies have found a possible connection between disruption in the serotonin network and sudden infant death syndrome (SIDS).

Serotonin and Mood

Research has found a relationship between mood and serotonin, and for some time it was believed that serotonin affected mood. Scientists believed low levels of serotonin caused depression; however, studies have not shown this to be the case. Researchers working with mice that cannot manufacture serotonin found no signs of depression in the animals, though the mice did display compulsive and aggressive behavior. It is possible that depression causes a reduction in serotonin production. Other possible reasons for the apparent connection between mood and serotonin include low tryptophan levels, a failure or lack of receptor sites, failure of serotonin to reach receptor sites, and reduced brain cell regeneration.

Medications known as
selective serotonin reuptake inhibitors (SSRIs)
are prescribed as antidepressants because they have been found to affect serotonin levels. Like other neurotransmitters, serotonin is reabsorbed by the body after it has relayed a neural impulse. SSRIs hinder this absorption process, boosting serotonin levels. Some research suggests that high levels of serotonin improve transmission between brain cells, which improves one's mood.

Too much serotonin may cause health problems, however. Some substances, including dietary supplements such as St. John's wort, medications, and illegal drugs, can overstimulate the central nervous system and some serotonin receptors. Carcinoid tumors, which are often found in the gastrointestinal tract, also may cause high levels of serotonin. Such increases in serotonin may lead to a potentially life-threatening condition known as serotonin syndrome. Symptoms of this include agitation, confusion, diarrhea, headaches, increased heart rate and blood pressure, loss of muscle coordination, muscle rigidity, pupil dilation, shivering, and sweating.

Some research indicates that serotonin levels in the body may be increased without medications. Possible methods include eating foods such as carbohydrates that increase one's level of tryptophan; exercising; light, such as that used in treating seasonal affective disorder; and psychotherapy or other means to affect mood.

Gender and Age

Men and women appear to react differently to changes in serotonin levels. A 2007 study in the journal Biological Psychiatry indicated that men with reduced levels of serotonin in the brain became impulsive while women developed a poorer mood and increased caution. Other studies seem to indicate that the interaction of serotonin and hormones may affect women during menopause, the postpartum period, and the premenstrual period—times when hormone levels fluctuate.

Serotonin may also be a factor in aging issues such as dementia. A 2006 study found that the brains of many deceased patients with Alzheimer's disease were deficient in serotonin.

Bibliography

Bouchez, Colette. "Serotonin: 9 Questions and Answers." WebMD. WebMD, LLC. 19 Mar. 2015. http://www.webmd.com/depression/features/serotonin

McIntosh, James. "What Is Serotonin? What Does Serotonin Do?" MNT. MediLexicon International Ltd. Web. 19 Mar. 2015. http://www.medicalnewstoday.com/articles/232248.php

Nauert, Rick. "Mice Study Suggests Lack of Serotonin Not Behind Depression." Psych Central. Psych Central. 28 Aug. 2014. Web. 20 Mar. 2015. http://psychcentral.com/news/2014/08/28/mice-study-suggests-lack-of-serotonin-not-behind-depression/74206.html

Whitaker-Azmitia, Patricia Mack. "The Discovery of Serotonin and Its Role in Neuroscience." Nature. Nature Publishing Group. 1999. Web. 20 Mar. 2015. http://www.nature.com/npp/journal/v21/n1s/full/1395355a.html

In the short story, "Sweat," by Zora Neale Hurston, how does the title represent the tears Delia was crying from the abuse she received?

In Hurston's short story, "Sweat," the main character is Delia. She suffers different types of abuse throughout the story. As a washer woman, she works very hard to support herself and her husband, Sykes. At one point in the story, she talks about how much she sweats--both literally and figuratively--when she works in order to pay for the house and their needs. She gets little support (financially or emotionally) from her husband and is essentially...

In Hurston's short story, "Sweat," the main character is Delia. She suffers different types of abuse throughout the story. As a washer woman, she works very hard to support herself and her husband, Sykes. At one point in the story, she talks about how much she sweats--both literally and figuratively--when she works in order to pay for the house and their needs. She gets little support (financially or emotionally) from her husband and is essentially doing everything herself.

The idea of sweat also symbolizes the tears Delia has shed at the amount of abuse Sykes has done to her. He torments her constantly and is very mean to her. He parades around town with his mistress and brings a live snake (the thing Delia fears most) into her house just to make her miserable. Sweat, then, is both the perspiration and the tears that Delia makes because of her hard life and the abuse she suffers.

What are the effects of the following events on the Aggregate Expenditures and income in the Keynesian model?a) The fraction of the...

In essence, what you are asking here is what sorts of things affect aggregate demand/expenditures in the Keynesian model.

The Keynesian model says that aggregate expenditures (and therefore national income) are made up of four parts.  These parts are consumer spending, government spending, business investment, and net exports.  Three of these are represented in your question.

When people spend a greater percentage of their income on imports, net exports decrease because more money is spent...

In essence, what you are asking here is what sorts of things affect aggregate demand/expenditures in the Keynesian model.

The Keynesian model says that aggregate expenditures (and therefore national income) are made up of four parts.  These parts are consumer spending, government spending, business investment, and net exports.  Three of these are represented in your question.

When people spend a greater percentage of their income on imports, net exports decrease because more money is spent on imports than previously.  Therefore, aggregate expenditures decline.  The other two factors cause aggregate expenditures to rise.  When businesses are more confident, they are more likely to invest (which means to purchase capital goods).  They feel that the economy will do well, so they are willing to buy more so as to expand their businesses.  When marginal tax rates fall, people have more money to spend.  This is important to the economy because consumer spending (usually called consumption) makes up the largest part of aggregate expenditures in most economies.  When people spend more, consumption increases, thus increasing aggregate expenditures.

Thus, the first factor you mention in this question will decrease aggregate expenditures in the Keynesian model but the other two factors will increase it.

How would I write a critical appreciation of any poem? Please explain with an example.

A simple way to structure a critical analysis of a poem is to follow a D-A-C format. "D" represents the denotation of the piece, or the face value meaning. Simply relate in straightforward terms what the poem is describing, or if it is a story poem, summarize the story. The "A" stands for appreciation. In this section, discuss the techniques the poet uses to create a powerful and/or lyrical effect. You might think about asking yourself why the poem is in your anthology, or why this poem has become famous or well loved. Think about both literary devices and sound devices. Literary devices include symbolism, figurative language (such as similes, metaphors, personification, metonymy, synecdoche, hyperbole, and understatement), and irony. Sound devices include rhyme, rhythm, meter, repetition, alliteration, consonance, assonance, and onomatopoeia. "C" stands for the connotation, or deeper meaning, of the poem. How do the face value meaning, the literary techniques, and sound devices work together to create a message about an important subject? 

As an example, here is a D-A-C analysis of "I Wandered Lonely as a Cloud" by William Wordsworth. 

D: In this poem, the speaker tells us about taking a walk and coming upon a field thick with daffodils. Later, the speaker is able to remember that scene often, and each time it fills him with the same joy he experienced when he first saw the lovely field of flowers.

A: The poem is written in four six-line stanzas, each with a rhyme scheme of ababcc. Each line is consistently iambic pentameter in rhythm and meter. This gives the poem a lilting feeling, like taking a jaunty walk; the rhythm and meter reinforce the feeling of a happy outing. The poem uses two similes that compare the speaker to a floating cloud and the daffodils to stars. The first helps establish a peaceful mood for the poem while the second helps the reader visualize how many daffodils there were. The poet personifies the daffodils and the waves by saying they danced; the daffodils also "toss[ed] their heads." This helps create a happy mood. The number "ten thousand" is hyperbole, giving the reader a sense of the abundance of flowers the poet saw. The poet uses assonance in lines 21 - 22, repeating the short /i/ sound, which reinforces the contented feeling of the solitude the poet describes. In the final line, the alliteration and consonance of "dances with the daffodils" provides emphasis and creates a dancing rhythm. 

C: The poem points out how one happy experience in nature can have ongoing effects because the memories are so strong and so pleasant that they bring back the joy of the original experience.

In "Two Kinds," by Amy Tan, what does America symbolize to the narrator’s mother?

The narrator's mother sees America as the land of opportunity. The first sentence of the story states this right away." My mother believed you could be anything you wanted to be in America." America has always been lauded as the land of opportunity and this proved to be enticing to immigrants from many other countries. Jing-mei notes that her mother had lost everything in China: "her mother and father, her home, her first husband, and...

The narrator's mother sees America as the land of opportunity. The first sentence of the story states this right away." My mother believed you could be anything you wanted to be in America." America has always been lauded as the land of opportunity and this proved to be enticing to immigrants from many other countries. Jing-mei notes that her mother had lost everything in China: "her mother and father, her home, her first husband, and two daughters, twin baby girls." So, one can certainly sympathize with the mother and understand how the "land of opportunity" would be a welcome change after suffering such loss. 

But the mother is convinced in realizing that opportunity for her daughter. She is convinced that Jing-mei can become a child prodigy. When Jing-mei becomes a successful chess player, her mother lives vicariously through her. Jing-mei becomes caught in an identity struggle. Her mother pressures her to become successful to the point that Jing-mei feels like she is being controlled. Her mother uses the strict discipline that she's learned from her Chinese culture in order to force Jing-mei to succeed. Jing-mei wants some freedom and this is a result of her American cultural influence. Her mother doesn't quite understand this. She simply wants her daughter to be successful. Coming from such tragedy and actually seeing her daughter succeed makes the mother more convinced that America is in fact the land of opportunity. This is why she continued to push Jing-mei.