Lecture 5 Hormones - Endocrinology The study of hormones,...

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Unformatted text preview: Endocrinology The study of hormones, the endocrine system, and their role in the physiology of the body The Endocrine System The body's slow chemical communication system; a set of glands that secrete hormones into the blood stream. Principal functions of the endocrine system Maintenance of the internal environment in the body (maintaining the optimum biochemical environment) Integration and regulation of growth and development Control, maintenance and instigation of sexual reproduction, including gametogenesis, coitus, fertilization, fetal growth and development and nourishment of the newborn Hormones A chemical released from living cells that travels some distance to target tissues to have a biological effect Secreted in very small amounts Transported, usually, in the blood Target cells have specific receptors Regulates cell reactions by affecting gene expression (often gene transcription factors) Behavioral Endocrinology The study of the relationship between hormones and behavior Hormones affect behavior and behavior feeds back to affect hormones Hormones Behavior Endocrine vs. Nervous System Major communication systems in the body Integrate stimuli and responses to changes in external and internal environment Both are crucial to coordinated functions of highly differentiated cells, tissues and organs Unlike the nervous system, the endocrine system is anatomically discontinuous Hormones travel via the bloodstream to target cells The endocrine system broadcasts its hormonal messages to essentially all cells by secretion into blood and extracellular fluid. Like a radio broadcast, it requires a receiver to get the message in the case of endocrine messages, cells must bear a receptor for the hormone being broadcast in order to respond. A cell is a target because it has a specific receptor for the hormone Most hormones circulate in the blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called target cells. A target cell responds to a hormone because it bears receptors for the hormone. Hormones and Behavior Hormones DO NOT act like "faucets" in which behavior spews forth if the hormone spigot is open. Hormonebehavior relationships are complex. It is NOT appropriate to say that hormones "cause" behavior. Rather, hormones change the probability that a particular behavior will be displayed in the appropriate social context hormones simply influence behavior. First endocrinology experiment Berthold's Experiment 1) Background: Naturalistic observations of changes in behavior and appearance of roosters with age and season. 2) Castrated 6 roosters. 3) Re-implanted a testis in 2 roosters. 4) Transplanted a testis from another bird in 2 roosters. 5) Left 2 castrated roosters to develop into capons. Normal Rooster Normal Rooster Capon Major endocrine glands The Hypothalamus Small structure at the base of the brain Regulates many body functions, including appetite and body temperature Regulates the pituitary gland The Pituitary Gland A sort of master gland It is a cherrysized endocrine gland The hormones it secretes affect the growth and secretion of other endocrine glands The real boss is the hypothalamus Anterior and Posterior Pituitary Embryologically distinct Release different hormones Anterior Pituitary releases Luteinizing hormone and growth hormone Posterior Pituitary releases Oxytocin Pancreas Both endocrine (hormones) and exocrine (enzymes) tissue Releases the hormone insulin The Adrenal Glands A pair of endocrine glands just above the kidneys They secrete epinephrine and norepinephrine In common with the pituitary, adrenals are two glands with distinct embryological origins. Adrenal medulla Adrenal cortex Both parts of the adrenals work together to regulate metabolism and cope with stress. Sex Hormones Sex hormones are secreted by the gonads and by the adrenal glands Androgens Masculinizing hormones Estrogens Feminizing hormones Gonads: Testes Male gonads Two functions Steroidogenic Gametogenic Primary Testicular Hormones Steroid Hormones Androgens Estrogens TESTOSTERONE and AGGRESSION In most mammals, males are more aggressive, and castration reduces aggressive behavior. Intermale and territorial aggression increase after puberty. After a fight, the winner has higher, the looser lower levels of testosterone. Criminals: Age at first violent offense correlates with testosterone levels. Violent women prisoners have higher testosterone levels than nonviolent ones. Testosterone and Marriage 750 700 650 600 Married Once Never Married Remarried Married and divorced Gonads: Ovaries Female gonads Two compartments Cyclic in function Hormones associated with gamete maturation were coopted over evolutionary time to regulate sexual behaviors. Steroidogenic Gametogenic Primary Ovarian Hormones Steroid Hormones Estrogens Progesterone Testosterone The female menstrual cycle Consists of 3 main phases Menses Follicular Phase Luteal Phase Each phase has differing relevant physiological changes Ovulation Ovulation has been the target of most studies on the menstrual cycle Other mammals have stereotyped sexual receptivity Human ovulation is "cryptic" Ovulation = once/month regulated by hormones Do women advertise fertility? More interest in sex? Fantasies Clothing preferences Gait Topless dancer study 1 2 Menstrual Cycle % feminization preferred low conception risk 20% 15% 10% 5% 0% high conception risk Significant effect of conception risk Japanese faces Caucasian faces PentonVoak et al. 1999, Nature Perrett et al. 1998, Nature Feminised Masculinised What do women prefer? When ovulating, women prefer more masculine faces. When not ovulating, they prefer only slightly masculine faces. High estrogen women showed especially strong shifts across the ovulatory cycle. ...
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