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Bio Basis Exam 3 Notes.doc

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PSYC 2240
Alistair Mapp

Bio Basis Exam 3 Notes Hormones (page 62) • A hormone is a chemical that is secreted in most cases by a gland but also by other kinds of cells, and conveyed by the blood to other organs • A neurotransmitter is like a signal on a telephone line, it conveys a message directly and exclusively from the sender to the receiver • Hormones function more like a radio stations, they convey a message to any receiver that happens to be tuned in to the right station • Hormones are useful for long lasting changes in multiple parts of the body • Protein hormones and peptide hormones, composed of chains of amino acids • Attach to membrane receptors, where they activate a second messenger within the cell • Hormones secreted by the brain control the secretion of many other hormones • The pituitary gland, attached to the hypothalamus, consists of two distinct glands • Anterior pituitary and the posterior pituitary, release different sets of hormones • Posterior pituitary, composed of neural tissue, can be considered an extension of the hypothalamus • Neurons in the hypothalamus synthesize the hormones oxytocin and vasopression, which migrate down axons to the posterior pituitary. Later the posterior pituitary releases these hormones into the blood • The anterior pituitary, composed of glandular tissues, synthesizes six hormones, although the hypothalamus controls their release • The hypothalamus secretes releasing hormones, which flow through the blood to the anterior pituitary. There they stimulate or inhibit the release of ACTH, TSH, Prolactin, Somatoropin (also known as Growth Hormone), Gonadotropin • Negative feedback system Pituitary hormones The hypothalamus produces vasopressin and oxytocin, which travel to the posterior pituitary (really an extension of the hypothalamus The posterior pituitary releases those hormones in response to neural signals The hypothalamus also produces releasing hormones and inhibiting hormones, which travel to the anterior pituitary, where they control the release of six hormones synthesized there Chapter 11 – Reproductive Behaviors Sex and Hormones • Steroid hormones o Contain four carbon rings o Derived from cholesterol o Bind to membrane receptors, like neurotransmitters, exerting rapid effects o Enter cells and activate certain kinds of proteins in the cytoplasm 1 o Bind to receptors that bind to chromosomes, where they activate or inactivate specific genes • Sex hormones, a special category of steroids released mostly by the gonads and to a lesser extent the adrenal gland • Androgens – male hormones (ex. Testosterone) • Estrogens – female hormones (ex. Estradiol) • Both sexes have both types • Sex hormones affect the brain, the genitals, and other organs • Male and female bodies differ due to sex limited genes, which are activated by androgens and estrogens Organizing Effects of Sex Hormones • Organizing effects of sex hormones occur mostly at a sensitive stage of development, before birth • Determine whether the brain and body will develop female or male characteristics • Activating effects can occur at any time in life, when a hormone temporarily activates a particular response Sex Differences in the Gonads • Sexual differentiation begins with the chromosomes • Female has two X, male has an X and a Y • During early stage of prenatal development in mammals, both male and female have a set of Mullerian ducts and a set of Wolffian ducts • The male’s Y chromosome includes the SRY (sex determining region on the Y chromosome) gene, which causes the primitive gonads to develop into testes, which produce the hormone testosterone, causing more growth, and more production of testosterone • Positive feedback cycle, last for a period of early development • Wolffian ducts, precursors for other male reproductive structures • Testosterone causes the primitive Wolffian ducts to develop into structures that store semen (seminal vesicles) and the vas deferens (a duct from the testis into the penis) • A Mullerian inhibiting hormone (a peptide) causes degeneration of the Mullerian ducts, which are precursors to the female’s reproductive organs • Testosterone induced changes all lead to production of penis and scrotum • Because females do not have the SRY gene, their gonads develop into ovaries • The Wolffian ducts degenerate and the primitive Mullerian ducts develop and mature • Differentiation of the external genitals and some aspects of brain development depend mainly on the level of testosterone during a sensitive period, an early period when hormones have long-lasting effects • High level of testosterone causes the external genitals to develop the male pattern, and a low level leads to the female pattern 2 • Estrogens produce important effects on the internal organs, but they have little effect on the external • Sensitive period 3 and 4 months of pregnancy • Genetic male develops the female-typical pattern of anatomy and behavior if he lacks androgen receptors, if he is castrated, or if he is exposed to substances that block testosterone effects • Male development is a fragile, vulnerable process, can easily be altered • Nature’s “default setting” is to make every mammal a female • Add early testosterone and it becomes males, without testosterone, it develops as female regardless of the amount of estradiol or other estrogens • However, females lacking estradiol in prenatal environment may not develop normal sexual behaviour • Shows little sexual response to male or female • Estradiol contributes to female development in terms of brain differentiation, but not for external anatomy Sex Differences in the Hypothalamus • Sex hormones early in life bind to receptors in specific areas of the hypothalamus, amygdale, and other brain areas • Thereby induce anatomical and physiological differences between the sexes • Area in the anterior hypothalamus, known as the sexually dimorphic nucleus, is larger in the male than in the female and contributes to control of male sexual behaviour • Parts of the female hypothalamus can generate a cyclic pattern of hormone release, as in the human menstrual cycle • The male hypothalamus cannot • Testosterone produces its organizing effects on the hypothalamus by itself • Large amounts of estradiol can masculinize female rodents Activating Effects of Sex Hormones • At any time in life, current levels of testosterone or estradiol exert activating effects, temporarily modifying behaviour • Changes in hormonal secretions influence sexual behaviour within 15 minutes • Behaviours can also influence hormonal secretions • Hormones do not cause sexual behaviour, they alter the activity in various brain areas to change the way the brain responds to various stimuli • They also change sensitivity in the penis, vagina, and cervix Rodents • Arousal can depend on previous experience, sexually experienced rats are aroused more easily because the effects of previous experience sensitize the response to future stimuli • Removal of testes or ovaries results in decline in sexual activity 3 • Sex hormones activate sexual behaviour partly by enhancing sensations • Sex hormones bind to receptors that increase the responses of certain areas of the hypothalamus • Testosterone and estradiol prime brain areas to release dopamine • Dopamine stimulates sexual activity, serotonin inhibits it, in part by blocking dopamine release Humans • Sex hormones also affect several brain systems with functions not related to sex, such as pain and anxiety, and memory Men • Levels of testosterone correlate positively with sexual arousal and the drive to seek sexual partners • Married men and men in relationships have lower levels of testosterone • Testosterone is related to seeking partners • Decreases in testosterone levels generally decrease male sexual activity • Low testosterone is not the usual basis for impotence, the inability to have an erection • The most common cause is impaired blood circulation. Other common causes include neurological problems, reactions to drugs, and psychological tension • Erection depends partly on the fact that testosterone increases the release of nitric oxide Women • A woman’s hypothalamus and pituitary interact with the ovaries to produce the menstrual cycle • After the end of a menstrual period, the anterior pituitary releases follicle- stimulating hormone (FSH) which promotes the growth of a follicle in the ovary • The follicle nurtures the ovum (egg cell) and produces several types of estrogens, including estradiol • Ovum is not fertilized, the lining of the uterus is cast off (menstruation) and the cycle begins again. If the ovum is fertilized, the levels of estradiol and progesterone increase gradually throughout pregnancy • Birth-control pills prevent pregnancy by interfering with the usual feedback cycle between the ovaries and the pituitary • The periovulatory period, consisting of the days around the middle of the menstrual cycle, is the time of maximum fertility and high estrogen levels • Women initiate more sexual activity during this time Oxytocin • In addition to the sex hormones, the pituitary hormone oxytocin is also important for reproductive behaviour • Stimulates contractions of the uterus during delivery of a bay, stimulates the mammary gland to release milk 4 • Sexual pleasure also releases oxytocin, especially at orgasm Parental Behaviour • In birds and mammals, hormonal changes prepare the mother for parenthood • Late in pregnancy the female secretes large amounts of estradiol, prolactin, and oxytocin • Also change pattern of hormone receptors Variations in Sexual Behaviour Evolutionary Interpretations of Mating Behaviour Interest in Multiple Mates • More men than women seek opportunities for casual sexual relationships with many partners • Spreading one’s genes • Women can have no more than one pregnancy per 9 months What Men and Women Seek in a Mate • Common desirable traits, but women also look for good providers (wealth and success) • Women more likely to reject a man because of his smell than a man is to reject a woman because of her smell • Body odor relates to some of the same genes that control the immune system • Women are not attracted to men too similar to themselves, a mechanism to avoid inbreeding • Men tend to have a stronger preference for a young partner • Likely to remain fertile longer, more children by pairing with a younger woman Differences in Jealousy • Men more jealous of women’s infidelities than women have been of men’s infidelities • Men more upset by sexual infidelity, women more upset by emotional infidelity Gender Identity and Gender-Differentiated Behaviours • Gender identity – how we identify sexually and what we call ourselves • Biological differences between males and females are sex differences, differences that result from people’s thinking about themselves as male or female are gender differences • Gender identity is a human characteristic • Some develop an intermediate sexual appearance because of an atypical hormone pattern • A genetic male who has low levels of testosterone or a mutation of the testosterone receptors may develop a female or intermediate appearance 5 • A genetic female who is exposed to more testosterone than the average female can be partly masculinized • Most common cause of this condition is congenital adrenal hyperplasia (CAH) • The overdevelopment of the adrenal glands from birth, can produce too much testosterone • A true hermaphrodite, a rarity, has a testis on one side of the body and an ovary on the other, or a mixture of the two tissues on each side • Intersexes – sexual development which is ambiguous Interests and Preferences of CAH girls • Genetic females with CAH or similar conditions are in most cases reared as girls • Sometimes affects behaviour (more attracted to boy toys) • Those with highest degree of testosterone exposure tend to have the highest interest in boys toys in childhood and the lowest romantic interest in men during adolescence Testicular Feminization • Certain individuals with an XY chromosome pattern have the genital appearance of a female • Androgen insensitivity, or testicular feminization • Lack androgen receptor • Condition occurs in various degrees, ranges from a smaller than average penis to genitals like those of a normal female Issues of Gender Assignment and Rearing • How should children with sexual disorders from birth be reared? • 1950s, medical doctors recommended that all intersexed people be reared as girls, using surgery if necessary to make their genitals look more feminine • Those with cloacal exstrophy (born with small penis, issues with development) and reared as girls often developed typical male interests, develop sexual attraction toward women • Girls with CAH history also have a difficulty adjusting after clitoris-reduction surgery • No sensation to the woman during sex, requires almost daily attention to prevent it from scarring over Sexual Orientation • Homosexual or bisexual behaviour occurs in both humans and nonhumans • Sexual orientation, like almost any other aspect of behaviour, shows natural variation • Factors in genetics and prenatal environment • Weaker genetic predisposition in women Behavioural and Anatomical Differences 6 • Homosexual and heterosexual people differ anatomically in many subtle ways • Bones of the arms, legs, and hangs are longer in heterosexual men than in homosexual men • Longer in homosexual women than in heterosexual women • Left and right hemispheres of the cerebral cortex are of nearly equal size in heterosexual females, and the right hemisphere is a few percent larger in heterosexual males • Homosexual males resemble heterosexual females in this regards • Shows sexual orientation is not an arbitrary decision, it is an integral part of the person Genetics • Higher probability of homosexuality in a monozygotic (identical) twin • Shows genetic link • Adoption studies also show environmental influences • Some genes occur more commonly in homosexual than heterosexual males Prenatal Influences • Sexual orientation is not related to adult hormone levels • Homosexuals and heterosexuals have about the same hormone levels Chapter 15 – Mood Disorders and Schizophrenia Major Depressive Disorder • People with major depression feel sad and helpless for weeks at a time • Not so much increased sadness, but significantly decreased happiness • More common in women than men • Depression occurs in episodes of various durations, almost no one is permanently depressed, and even without treatment, most people eventually feel better Genetics and Life Events • Moderate degree of heritability for depression • Genes are not specific to depression. More likely to suffer not only from depression, but also from anxiety disorders, ADD, alcohol or marijuana abuses, obsessive-compulsive disorder, and many other conditions • Risk of depression is particularly elevated among relatives of women with early- onset depression (beginning before age 30) • Several different genes have been found to increase the risk of depression • One gene controls the serotonin transporter gene, which regulates the ability of an axon to reabsorb serotonin after its release to recycle it for further use • The effects of a gene vary depending on the environment Nongenetic Biological Influences 7 • Viral infections, such as Borna disease, a viral infection of farm animals produces periods of frantic activity alternating with periods of inactivity • Giving birth also triggers occasional cases of depression • 20% of women report some degree of postpartum depression • Among older men, a declining level of testosterone is associated with increased probability of depression Abnormalities of Hemispheric Dominance • Studies of normal people have found a fairly strong relationship between happy moody and increased activity in the left prefrontal cortex • People with depression have decreased activity in the left and increased activity in the right prefrontal cortex Antidepressant Drugs • Usually drug or other treatment is found before a psychological disorder • Discovered by accident Types of Antidepressants • Tricyclics operate by blocking the transporter proteins that reabsorb serotonin, dopamine, and norepinephrine into the presynaptic neuron after their release • Prolongs the presence of the neurotransmitters in the synaptic cleft where they continue stimulating the postsynaptic cell • Selective serotonin reuptake inhibitors (SSRIs) are similar to tricyclics but specific to the neurotransmitter serotonin • Monoamine oxidase inhibitors (MAOIs) block the enzyme monoamine oxidase (MAO), a presynaptic terminal enzyme that metabolizes catecholamines and serotonin into active forms o Active inside the presynaptic button • When MAOIs block this enzyme, the presynaptic terminal has more of its transmitter available for release • Atypical antidepressants are a miscellaneous group, everything other than the three types just mentioned Effectiveness of Antidepressants • Most people eventually recover even without treatment • Antidepressants overall effectiveness could be described as lackluster • Some studies show that antidepressants are barely if at all better than placebos for people with mild depression • More of an effect for people with more severe depression • Can have very negative effects on children and adolescents Electroconvulsive Therapy (ECT) • Electrically induced seizure 8 • ECT originated with the observation that for people wi
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