Biopsychology (11th Edition) Chapter 13 Neuroendocrine System PDF

Biopsychology (11th Edition) Chapter 13 Neuroendocrine System - Once inside a cell, the steroid molecules can...

Biopsychology (11th Edition) Chapter 13 Neuroendocrine System - Once inside a cell, the steroid molecules can bind to receptors in the cytoplasm or nucleus Endocrine Glands and, by so doing, directly influence gene ➔ Primary function is to release hormones expression Types of Glands: SEX STEROIDS Exocrine glands (e.g., sweat glands) Steroid hormones are produced by gonads - release their chemicals into ducts, which carry two main classes of gonadal hormones are: them to their targets, mostly on the surface of the o androgens body ▪ Most common is testosterone Endocrine glands (ductless glands) ▪ For male - release their chemicals, which are called o Estrogens hormones, directly into the circulatory system. ▪ estradiol is the most common estrogen. GONADS ▪ For female ➔ male testes and the female ovaries 3rd class steroid hormones ➔ primary function of the testes and ovaries is the o Progestins production of sperm cells and ova, respectively. ▪ most common progestin is After copulation (sexual intercourse), a single sperm progesterone, which in females cell may fertilize an ovum to form one cell called a prepares the uterus and the breasts zygote for pregnancy o which contains all of the information Adrenal Cortex necessary for the typical growth of a complete adult organism in its natural ➔ outer layer of the adrenal glands environment ➔ regulate glucose and salt levels in the blood, it is not generally thought of as a sex gland. sex chromosomes Pituitary ➔ pair of chromosomes ➔ contain the genetic programs that direct sexual pituitary gland development. ➔ referred to as the master gland because most of its o X chromosomes hormones are tropic hormones. - cells of females have two large sex Tropic hormones chromosomes o primary function is to influence the release of o Y chromosomes hormones from other glands (tropic means - Cells of males; one x chromosome and Y “able to stimulate or change something”). chromosome o For example, gonadotropin is a pituitary the sex chromosome of every ovum is an X tropic hormone that travels through the chromosome, whereas half the sperm cells have X circulatory system to the gonads, where it chromosomes, and half have Y chromosomes stimulates the release of gonadal hormones If a sperm cell with an X sex chromosome won, you two glands: the posterior pituitary and the anterior are a female; if one with a Y sex chromosome won, pituitary, which fuse during the course of you are a male. embryological development Hormones o posterior pituitary - develops from a small outgrowth of hypothalamic 3 classes: tissue that eventually comes to dangle from the (1) amino acid derivatives hypothalamus on the end of the pituitary stalk - hormones that are synthesized in a few simple o anterior pituitary steps from an amino acid molecule; - begins as part of the same embryonic tissue that - an example is epinephrine, which is released eventually develops into the roof of the mouth from the adrenal medulla and synthesized from - during the course of development, it pinches off tyrosine and migrates upward to assume its position next (2) peptides and proteins to the posterior pituitary - chains of amino acids - releases tropic hormones which qualify as the - peptide hormones are short chains master gland - protein hormones are long chains. FEMALE GONADAL HORMONE LEVELS ARE CYCLIC; (3) Steroids MALE GONADAL HORMONE LEVELS ARE STEADY - hormones that are synthesized from cholesterol, a type of fat molecule The major difference between the endocrine function - hormones that influence sexual development and of females and males is that in human females, the the activation of adult sexual behavior levels of gonadal and gonadotropic hormones go - influence cells by binding to receptors in cell through a cycle that repeats itself every 28 days or membranes, however, because they are small so. It is these more-or-less regular hormone and fat-soluble, they can readily penetrate cell fluctuations that control the female menstrual cycle. membranes and often affect cells in a second Control of the Pituitary way Biopsychology (11th Edition) Chapter 13 Hypothalamic stimulation and lesion experiments quickly established that the hypothalamus is the regulator of the anterior pituitary CONTROL OF THE ANTERIOR AND POSTERIOR PITUITARY BY THE HYPOTHALAMUS. two mechanisms by which the hypothalamus controls the pituitary: o one for the posterior pituitary o one for the anterior pituitary two major hormones of the posterior pituitary, vasopressin and oxytocin, are peptide hormones that are synthesized in the cell bodies of neurons in the paraventricular nuclei and supraoptic nuclei on each side of the hypothalamus Neurosecretory Gonadotropin-releasing hormone ➔ neurons that release hormones into general ➔ This releasing hormone stimulates the release of both circulation of the anterior pituitary’s gonadotropins: follicle- stimulating hormone (FSH) and luteinizing Oxytocin hormone (LH). ➔ stimulates contractions of the uterus during labor and Regulation of Hormone Levels the ejection of milk during suckling; 3 kinds of signals that regulate hormone release: vasopressin (antidiuretic hormone) signals from the nervous system ➔ facilitates the reabsorption of water by the kidneys signals from circulating hormones Two findings provided early support for the hypothesis signals from circulating nonhormonal chemicals that the release of hormones from the anterior pituitary REGULATION BY NEURAL SIGNALS was itself regulated by hormones released from the hypothalamus: ➔ All endocrine glands, with the exception of the anterior pituitary, are directly regulated by signals The first was the discovery of a vascular network, the from the nervous system hypothalamopituitary portal system, that seemed well ➔ Endocrine glands located in the brain (i.e., the suited to the task of carrying hormones from the pituitary and pineal glands) are regulated by cerebral hypothalamus to the anterior pituitary. neurons. The second finding was the discovery that cutting the ➔ endocrine glands located outside the CNS are portal veins of the pituitary stalk disrupts the release innervated by the autonomic nervous system— of anterior pituitary hormones until the damaged veins usually by both the sympathetic and parasympathetic regenerate branches, which often have opposite effects on Discovery of Hypothalamic Releasing Hormones hormone release releasing hormone REGULATION BY HORMONAL SIGNALS ➔ Each hypothalamic hormone that was thought to ➔ Circulating hormones often provide feedback to the stimulate the release of an anterior pituitary hormone very structures that influence their release: the pituitary gland, the hypothalamus, and other sites in release-inhibiting hormone the brain. ➔ each hormone thought to inhibit the release of an ➔ The function of most hormonal feedback is the anterior pituitary hormone maintenance of stable blood levels of the hormones Thyrotropin-releasing hormone REGULATION BY NONHORMONAL CHEMICALS ➔ triggers the release of thyrotropin from the anterior ➔ Glucose, calcium, and sodium levels in the blood all pituitary, which in turn stimulates the release of influence the release of particular hormones. hormones from the thyroid gland. ➔ For example, increases in blood glucose increase the ➔ Schally’s and Guillemin’s isolation of thyrotropin- release of insulin from the pancreas; in turn, insulin releasing hormone confirmed that hypothalamic- reduces blood glucose levels releasing hormones control the release of hormones PULSATILE HORMONE RELEASE from the anterior pituitary and thus provided the major impetus for the isolation and synthesis of other ➔ Hormone levels in the blood are regulated by releasing and release-inhibiting hormones. changes in the frequency and duration of the hormone pulses ➔ One consequence of pulsatile hormone release is that there are often large minute-to-minute fluctuations in the levels of circulating hormones Biopsychology (11th Edition) Chapter 13 - has the capacity to develop into female ducts (e.g., the uterus; the upper part of the vagina; and the fallopian tubes, through which ova travel from the ovaries to the uterus). third month of male fetal development, the testes secrete testosterone and Müllerian-inhibiting substance the testosterone stimulates the development of the Wolffian system, and the Müllerian-inhibiting substance causes the Müllerian system to degenerate and the testes to descend into the scrotum—the ball sac that holds the testes outside the body cavity The development of the Müllerian system occurs in any fetus that is not exposed to testicular hormones during the critical fetal period female fetuses, ovariectomized female fetuses, and orchidectomized male fetuses all develop female reproductive ducts Ovariectomy is the removal of the ovaries, and orchidectomy is the removal of the testes (the Greek word orchis means “testicle”). Gonadectomy, or castration, is the surgical removal of gonads—either ovaries or testes. EXTERNAL REPRODUCTIVE ORGANS bipotential precursor - both male and female genitals develop from the very same precursor Hormones and Sexual Development of the Body At the end of the third month of pregnancy, the bipotential Sexual Differentiation precursor of the external reproductive organs consists of four parts: Sexual differentiation in mammals begins at fertilization with the production of one of two different the glans kinds of zygotes: either one with an XX (female) pair - grows into the head of the penis in the male or of sex chromosomes or one with an XY (male) pair. the clitoris in the female It is the genetic information on the sex chromosomes the urethral folds that usually determines whether development will - fuse in the male or enlarge to become the labia occur along female or male lines minora in the female the lateral bodies FETAL HORMONES AND DEVELOPMENT OF - form the shaft of the penis in the male or the REPRODUCTIVE ORGANS hood of the clitoris in the female structure of the gonads, 6 weeks after fertilization. the labioscrotal swellings Notice that at this stage of development, each fetus, - form the scrotum in the male or the labia majora regardless of its genetic sex, has the same pair of in the female. gonadal structures, called primordial gonads development of the external genitals is controlled by the Primordial Gonads presence or absence of testosterone. If testosterone is present o has an outer covering, or cortex, which has at the appropriate stage of fetal development, male external the potential to develop into an ovary; and genitals develop from the bipotential precursor. Conversely, if each has an internal core, or medulla, which testosterone is not present, development of the external has the potential to develop into a testis genitals proceeds along female lines In the seventh week after conception, the Sry gene on the Y chromosome of a male triggers the synthesis Puberty: Hormones and Development of Secondary Sex of Sry protein and this protein causes the medulla of Characteristics each primordial gonad to grow and to develop into a Puberty testis ➔ the transitional period between childhood and INTERNAL REPRODUCTIVE DUCTS adulthood during which fertility is achieved, the two complete sets of reproductive ducts (six adolescent growth spurt occurs, and the secondary weeks after fertilization): sex characteristics develop o Wolffian system ➔ associated with an increase in the release of - has the capacity to develop into male hormones by the anterior pituitary reproductive ducts (e.g., the seminal vesicles, Secondary sex characteristics which hold the fluid in which sperm cells are ejaculated; and the vas deferens, through which ➔ those features other than the reproductive organs that the sperm cells travel to the seminal vesicles). distinguish sexually mature males and females. o Müllerian system Biopsychology (11th Edition) Chapter 13 growth hormone as adults they were treated with testosterone and given access to a sexually receptive female ➔ the only anterior pituitary hormone that does not have we know less about the role of hormones in the a gland as its primary target development of proceptive behaviors (solicitation behaviors) and in the development of sex-related Increases in the release of gonadotropic hormone behaviors that are not directly related to reproduction and adrenocorticotropic hormone cause the gonads and adrenal cortex to increase their release of DEVELOPMENT OF SEX DIFFERENCES IN THE gonadal and adrenal hormones, which in turn initiate BEHAVIOR OF HUMANS the maturation of the genitals and the development of Sexual Demorphisms secondary sex characteristics. In pubertal males, androgen levels are higher than - are instances where a behavior (or a structure) estrogen levels, and masculinization is the result; in typically comes in two distinctive classes (male or pubertal females, the estrogens predominate, and the female) into which most individuals can be result is feminization unambiguously assigned. - In the case of humans, it appears to be only Androstenedione reproduction-related behaviors that clearly fall ➔ an androgen that is released primarily by the adrenal into this category. cortex, is typically responsible for the growth of pubic - The presence or absence of prenatal hair and axillary hair (underarm hair) in females testosterone appears to be a major factor in the development of these behaviors Sexual Development of Brain and Behavior Sex Differences in the Brain FIRST DISCOVERY OF A SEX DIFFERENCE IN MAMMALIAN BRAIN FUNCTION Pfeiffer’s experiments (theory) had provided the first evidence of the role of perinatal (around the time of birth) androgens in overriding the preprogrammed cyclic female pattern of gonadotropin release from the hypothalamus and initiating the development of the steady male pattern AROMATIZATION HYPOTHESIS ➔ perinatal testosterone does not directly masculinize the brain; the brain is masculinized by estradiol that has been aromatized from perinatal testosterone Aromatization ➔ process where the aromatase converts testosterone to estradiol Alpha fetoprotein ➔ is present in the blood of rodents during the perinatal period, and it deactivates circulating estradiol by binding to it Development of Sex Differences in Behavior DEVELOPMENT OF REPRODUCTIVE BEHAVIORS IN LABORATORY ANIMALS Phoenix and colleagues (1959) were among the first Three Cases of Exceptional Human Sexual Development to demonstrate that the perinatal injection of Exceptional Cases of Human Sexual Development testosterone masculinizes and defeminizes a genetic female’s adult reproductive behavior complete androgen insensitivity syndrome as adults the female guinea pigs were injected with progesterone and estradiol and mounted by males, ➔ all her symptoms stem from a mutation of the they displayed less lordosis (the intromission- androgen receptor gene that rendered her androgen facilitating arched-back posture that signals female receptors totally unresponsive rodent receptivity) Adrenogenital syndrome lack of early exposure of male rats to testosterone both feminizes and demasculinizes their ➔ is caused by congenital adrenal hyperplasia—a reproductive behavior as adults. Male rats castrated congenital deficiency in the release of the hormone shortly after birth failed to display the typical male cortisol from the adrenal cortex, which results in copulatory pattern of mounting, intromission (penis compensatory adrenal hyperactivity and the insertion), and ejaculation (ejection of sperm) when Effects of Gonadal Hormones on Adults Biopsychology (11th Edition) Chapter 13 Male Sexual Behavior and Gonadal Hormones Two important generalizations can be drawn from Bremer’s study. o The first is that orchidectomy leads to a reduction in sexual interest and behavior o the second is that the rate and the degree of the loss are variable Dihydrotestosterone - a nonaromatizable androgen, restores the copulatory behavior of castrated male primates; however, it fails to restore the copulatory behavior of castrated male rodents Female Sexual Behavior and Gonadal Hormones Follicle ➔ ovarian structure in which eggs mature ➔ secrete estrogens Estrus ➔ a period of 12 to 18 hours during which the female is fertile, receptive (likely to assume the lordosis posture when mounted), proceptive (likely to engage in behaviors that serve to attract the male), and sexually attractive (smelling of chemicals that attract males) ➔ results from surges of estrogen and progesterone estrous cycle Brain Mechanisms of Sexual Behavior o the cycle of sexual receptivity Four Brain Structures Associated with Sexual Activity Female primates are the only female mammals motivated to copulate during periods of nonfertility CORTEX AND SEXUAL ACTIVITY ovariectomy has been shown to reduce sexual Interestingly, the activity in secondary visual cortex desire and frequency of sexual fantasies in human (occipitotemporal and inferotemporal cortices) occurs females during sexual arousal even when eyes are closed and ovarian hormone responsible for sexual desire in the activity in prefrontal cortex is suppressed during females: orgasm o estradiol cortical activation mediates feelings of release and o testosterone loss of control, changes in self-awareness, Anabolic Steroid Abuse disturbances of awareness of space and time, and feelings of love Anabolic steroids HYPOTHALAMUS AND SEXUAL ACTIVITY ➔ are steroids, such as testosterone, that have anabolic (growth-promoting) effects. Gorski and his colleagues discovered a nucleus in the ➔ Effects: medial preoptic area of the rat hypothalamus that o Cardiovascular effects linked to premature was several times larger in males, they called this death nucleus the sexually dimorphic nucleus. o Adverse effects on liver (i.e. growth of liver The medial preoptic area (which includes the sexually tumors) dimorphic nucleus) is one area of the hypothalamus o muscle spasms that plays a key role in male sexual behavior o muscle pains Destruction of the entire area abolishes sexual o blood in the urine behavior in the males of all mammalian species ➔ in males, high levels of this steroid: medial preoptic area lesions do not eliminate the o reduces gonadotrophin release sexual behaviors of females, but they do eliminate the o result in testicular atrophy (wasting away of male sexual behaviors (e.g., mounting) that are the testes) and sterility sometimes observed in females o leads to Gynecomastia (breast growth in Female rats with bilateral lesions of the ventromedial males) nuclei (VMN) do not display lordosis ➔ in female, anabolic steroids can: o produce amenorrhea (cessation of AMYGDALA AND SEXUAL ACTIVITY menstruation) With respect to sexual behavior, they seem to play a o sterility, hirsutism (excessive growth of body role in the identification of potential mating partners hair) based on sensory social signals, which are primarily o growth of the clitoris visual in humans and olfactory in rats o development of a masculine body shape Kluver-Bucy syndrome Biopsychology (11th Edition) Chapter 13 ➔ the effects on sexual behavior are humans display flat maternal immune hypothesis affect, hypersexuality, and a complete inability to ➔ has been proposed to explain the fraternal birth order focus their sexual advances to appropriate partners or effect locations ➔ mothers develop an immune response to VENTRAL STRIATUM AND SEXUAL ACTIVITY masculinizing hormones from male, such that a mother’s immune system will increasingly suppress Because orgasm is associated with pleasure, it the effects of masculinizing hormones in her younger comes as no surprise that the ventral striatum is sons activated in human volunteers by sexually provocative visual images What Triggers the Development of Sexual Attraction? ➔ McClintock and Herdt (1996) have suggested that the emergence of sexual attraction may be stimulated by adrenal cortex steroids. What Differences in the Brain Can Account for Differences in Sexual Attraction? ➔ LeVay (1991) found that the structure of one hypothalamic nucleus in gay males was intermediate in size to that of female heterosexuals and male heterosexuals Gender Identity ➔ the gender that a person most identifies with, including woman, man, transgender (an individual who identifies as a man, a woman, or some intersection thereof), or another gender category transgender person - has a gender identity that is inconsistent with their anatomical sex - face a strong conflict known as gender dysphoria.. For example: “I am a woman Sexual Orientation and Gender Identity trapped in a male body. Help!” Heterosexual ➔ women or men who are attracted to men or women, respectively gay or lesbian ➔ men who are attracted to men and women who are attracted to women, respectively bisexual ➔ sexually attracted to both men and women asexual ➔ not sexually attracted to others gender identity ➔ gender that a person most identifies with, including woman, man, transgender transgender ➔ an individual who identifies as a man, a woman, or some intersection thereof Sexual Orientation fraternal birth order effect ➔ finding that the probability of a male being gay increases as a function of the number of older brothers he has ➔ recent study of blended families found that the effect is related to the number of males previously born to the mother, not the number of older males one is reared with