Prepared by Jeffrey W. Grimm Western Washington University PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel Prepared by Jeffrey W. Grimm Western Washington University This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program. Copyright © 2011 Pearson Education, Inc. All rights reserved.

What’s Wrong with the Mamawawa? Chapter 13 Hormones and Sex What’s Wrong with the Mamawawa? Copyright © 2011 Pearson Education, Inc. All rights reserved.

Developmental and Activational Effects of Sex Hormones Developmental (or “organizational”) – influencing the development of anatomical, physiological, and behavioral characteristics that differentiate the sexes Activational – triggering reproduction-related behavior in mature individuals Adolescent surges have both developmental and activational effects Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neuroendocrine System: Glands Exocrine – release chemicals into ducts which carry them to their targets Sweat glands, for example Endocrine – ductless; release hormones directly into the circulatory system Only organs whose primary function is hormone release are referred to as endocrine glands Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 13.1 The endocrine glands. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neuroendocrine System: Glands Male testes produce sperm cells Female ovaries produce ova Sperm and ova each have 23 chromosomes Fertilization Sperm cell + ovum = zygote 23 pairs of chromosomes X and Y – sex chromosomes XX = female, XY = male Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Classes of Hormones Amino acid derivatives Epinephrine, for example (adrenal medulla) Peptides and proteins Short and long chains of amino acids Steroids Synthesized from cholesterol (fat) Fat-soluble – able to enter cells and bind to receptors in cytoplasm or nucleus Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Sex Steroids Released by gonads Androgens - e.g., testosterone Estrogens - e.g., estradiol Adult testes release more androgens and ovaries more estrogens Progestins – also present in both sexes Progesterone prepares uterus and breasts for pregnancy Adrenal cortex – also releases sex steroids Copyright © 2011 Pearson Education, Inc. All rights reserved.

Hormones of the Pituitary “Master gland” Tropic hormones influence the release of hormones by other glands Posterior pituitary – hormones synthesized in the hypothalamus Anterior pituitary – tropic hormones Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 13.2 A midline view of the posterior and anterior pituitary and surrounding structures. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Cyclic vs. Steady Gonadal Hormone Levels Female hormones go through a 28-day cycle, the menstrual cycle Male hormone levels are constant Anterior pituitary activity is controlled by the hypothalamus The hypothalamus determines whether hormone levels cycle Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neural Control of the Pituitary Bird research was first to implicate the control over pituitary function by the nervous system Light/dark cycling and breeding changed hormone release Lesion and stimulation experiments established the hypothalamus as the regulator of the anterior pituitary Did not explain how the signal was mediated as the anterior pituitary is not “connected” to the hypothalamus by neurons Copyright © 2011 Pearson Education, Inc. All rights reserved.

Control of the Pituitary by the Hypothalamus Posterior – neural input from hypothalamus Vasopressin – antidiuretic hormone Oxytocin – labor and lactation Synthesized in hypothalamic paraventricular and supraoptic nuclei These nuclei have terminals in the posterior pituitary Anterior pituitary – hypothalamopituitary portal system carries hormones from the hypothalamus to the anterior pituitary Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 13.4 Control of the anterior and posterior pituitary by the hypothalamus. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Discovery of Hypothalamic Releasing Hormones Thyrotropin-releasing hormone first isolated from the hypothalamus of sheep and then pigs Triggers the release of thyrotropin from the anterior pituitary Thyrotropin then stimulates release of hormones from the thyroid gland Copyright © 2011 Pearson Education, Inc. All rights reserved.

Regulation of Hormone Levels Neural All endocrine glands (except the anterior pituitary) receive neural signals From cerebral or autonomic neurons Hormonal Tropic hormones, negative feedback Nonhormonal chemicals Glucose, Ca2+, Na+ Copyright © 2011 Pearson Education, Inc. All rights reserved.

Pulsatile Hormone Release Hormones tend to be released in pulses Leads to often large minute-to-minute fluctuations in levels of hormones Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 13.5 A summary model of the regulation of gonadal hormones. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Hormones and Sexual Development of the Body Humans are dimorphic – exist in two forms Genetic information on the sex chromosomes normally determines male or female development Copyright © 2011 Pearson Education, Inc. All rights reserved.

Fetal Hormones and Development of Reproductive Organs: Gonads Initially there is a primordial gonad Cortex – potential to be an ovary Medulla – potential to be a testis If XY, The Sry gene on the Y chromosome triggers the synthesis of Sry protein If no Sry protein present, cortex develops into ovary Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 13.6 The development of an ovary and a testis from the cortex and the medulla, respectively, of the primordial gonadal structure that is present 6 weeks after conception. Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Fetal Hormones and Development of Reproductive Organs: Internal Reproductive Ducts Both sexes begin with two sets of reproductive ducts Wolffian system – male – seminal vesicles, vas deferens Müllerian system – female – uterus, vagina, fallopian tubes Copyright © 2011 Pearson Education, Inc. All rights reserved.

Internal Reproductive Ducts Continued Third prenatal month: differentiation of ducts Testes produce testosterone and Müllerian-inhibiting substance Wolffian system develops, Müllerian degenerates, testes descend No testes – no testicular hormones Müllerian system develops, Wolffian degenerates Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 13.7 The development of the internal ducts of the male and female reproductive systems from the Wolffian and Müllerian systems, respectively. Copyright © 2011 Pearson Education, Inc. All rights reserved.

External Reproductive Organs External reproductive structures – genitalia – develop from one bipotential precursor Differentiation occurs in second month Testosterone produces male structures Without testosterone, female structures develop Copyright © 2011 Pearson Education, Inc. All rights reserved.

Puberty: Hormones and the Development of Secondary Sex Characteristics Fertility achieved Secondary sex characteristics develop Features unrelated to reproduction that distinguish sexually mature men and women Increase in release of anterior pituitary hormones Growth hormone – acts on bone and muscle Gonadotropic hormone Adrenocorticotropic hormone Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Puberty Continued Relative levels of androgens and estrogens determine whether male or female features develop Androstenedione – androgen necessary for the growth of axillary (underarm) and pubic hair in females (more evidence against mamawawa) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Sex Differences in the Brain Pfeiffer first discovered a sex difference in mammalian brain function Pfeiffer (1936) – gonadectomized and implanted gonads in neonatal rats Gonadectomy causes cyclic (female) gonadotropin release pattern Transplant of testes to males or females causes steady (male) gonadotropin release pattern Perinatal androgens lead to male pattern Copyright © 2011 Pearson Education, Inc. All rights reserved.

Aromatization Hypothesis Sex steroids are all derived from cholesterol and are readily converted from one to the other Aromatized testosterone becomes estradiol Evidence suggests that estradiol masculinizes the brain, at least in rodents Copyright © 2011 Pearson Education, Inc. All rights reserved.

Evidence that Estradiol Masculinizes the Neonatal Brain Neonatal injections of estradiol masculinize Dihydrotestosterone can’t be converted to estradiol – doesn’t masculinize Alpha fetoprotein deactivates circulating estradiol but does not cross the blood-brain-barrier Blocking aromatization or estradiol receptors interferes with masculinizing effects of testosterone Copyright © 2011 Pearson Education, Inc. All rights reserved.

Mother’s Estradiol Doesn’t Masculinize Female Brains In female rodents, Alpha fetoprotein in blood during perinatal period … Protects the female brain from estradiol Binds to circulating estradiol, so none gets to the brain In male rodents, testosterone enters the brain and then is converted to estradiol In humans, aromatization is apparently not necessary for testosterone to masculinize brain Copyright © 2011 Pearson Education, Inc. All rights reserved.

Modern Perspectives on Sexual Differentiation of the Mammalian Brain No single mechanism can account for the development of sexual dimorphisms of mammalian brains: Aromatase is only required for testosterone effects on masculinization in some areas of the brain Female brain development may not automatically occur in absence of estrogens Various dimorphisms emerge at different stages under different influences Sex chromosomes influence brain development independent of their effect on hormones Studies with gene knockout mice indicate that estradiol plays an active role in the female program of brain development Copyright © 2011 Pearson Education, Inc. All rights reserved.

Perinatal Hormones and Behavioral Development Masculinize – promoting male behavior (i.e., mounting) Defeminize – preventing female behavior (i.e., lordosis) Perinatal testosterone masculinizes and defeminizes Neonatal castration of male rats – feminizes and demasculinizes Copyright © 2011 Pearson Education, Inc. All rights reserved.

Three Cases of Exceptional Human Sexual Development Anne S. Elaine John Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Anne S. Knowing how normal development occurs, you should be able to understand what could cause abnormal sexual development Why might a woman not cycle and not have pubic or axillary hair? What determines whether male or female hormone patterns develop? What causes the growth of pubic and axillary hair? Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Anne S. Continued Anne is chromosomally male, XY Internalized testes, but no ovaries Hormone levels are those of a man Androgenic insensitivity syndrome Normal male androgen levels, but no response to them She does respond to estrogens, so she effectively has more estrogens than androgens – leading to the development of female secondary sex characteristics Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Elaine Born with somewhat ambiguous genitals but raised as a girl Developed male secondary sex characteristics in puberty Eventually diagnosed with adrenogenital syndrome Copyright © 2011 Pearson Education, Inc. All rights reserved.

Andrenogenital Syndrome Andrenogenital syndrome is caused by congenital adrenal hyperplasia Too little cortisol leads to compensatory excessive release of adrenal androgens in XX females May masculinize female genitalia and behavior – surgical and hormonal treatments needed at birth. Often tomboyish; late onset of menstruation Prior to modern treatments of 1950s, changes in sexual identity at puberty was unpredictable and likely to be traumatic Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. John/Joan A surgeon’s error led one of a pair of male twins to be raised as a girl Artificial vagina created Estrogen administered at puberty John/Joan never felt or acted like a girl – indicates that the key to one’s gender is in the brain John/Joan chose to become John later in life, but never recovered from the ordeal David Reimer (“John”) took his life in May, 2004 Copyright © 2011 Pearson Education, Inc. All rights reserved.

Male Reproduction-Related Behavior and Testosterone Effects of orchidectomy (Bremer, 1959) Reduced sexual interest and behavior Rate and degree of loss varies Still have adrenal testosterone Level of male sexuality is NOT correlated with testosterone levels in healthy men Increasing male testosterone levels does NOT increase sex drive Copyright © 2011 Pearson Education, Inc. All rights reserved.

Female Reproduction-Related Behavior and Gonadal Hormones Rats and guinea pigs – surges of estrogen and progesterone initiate estrus, a period of fertility and receptivity Women – sexual motivation and behavior not tied to cycle Sex drive may be under androgenic control Copyright © 2011 Pearson Education, Inc. All rights reserved.

Human Female Sexuality and Androgens Testosterone increases the proceptivity of ovariectomized and adrenalectomized female rhesus monkeys Correlations seen between sexual motivation and testosterone Testosterone found to rekindle sexual motivation in ovariectomized and adrenalectomized women Copyright © 2011 Pearson Education, Inc. All rights reserved.

Anabolic Steroid Abuse Anabolic – growth-promoting No firm scientific evidence that muscularity and strength are increased Sex-related side effects High circulating hormones cause a reduction of natural release (negative feedback loop) Men – testicular atrophy, sterility, gynecomastia (breast enlargement) Women – amenorrhea (cessation of menstru-ation), sterility, hirsutism (excessive growth of body hair) Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neuroprotective Effects of Estradiol Reduces brain damage if given just before or after inducing cerebral hypoxia Reduces inflammation, encourages axonal regeneration, promotes synaptogenesis Increases adult neurogenesis May account for sex difference in longevity and some diseases Possible salutary cognitive effects Copyright © 2011 Pearson Education, Inc. All rights reserved.

Neural Mechanisms of Sexual Behavior Sexually dimorphic nucleus (SDN) Medial preoptic area of rat hypothalamus Larger in males, due to estradiol shortly after birth Size of male SDN correlated with testosterone levels and aspects of sexual activity Nuclei in preoptic, suprachiasmatic, and anterior regions of the hypothalamus are larger in men than in women Copyright © 2011 Pearson Education, Inc. All rights reserved.

Medial Preoptic Area of the Hypothalamus Contains the SDN Destruction abolishes male sexual behavior of mammalian males and females studied, but does not affect female sexual behaviors in females Stimulation elicits copulatory behaviors Evidence favors a motivational role for male sexual behavior Copyright © 2011 Pearson Education, Inc. All rights reserved.

Ventromedial Nucleus (VMN) of the Hypothalamus Contains circuits critical for female rat sexual behavior Lesion eliminates lordosis Microinjections of estrogen and progesterone induce estrus Lesions of periaqueductal gray (PAG) or the tracts to it eliminate lordosis Copyright © 2011 Pearson Education, Inc. All rights reserved.

Sexual Orientation and Sexual Identity Heterosexual – sexually attracted to members of the opposite sex Homosexual – sexually attracted to members of the same sex Bisexual – sexually attracted to members of both sexes Copyright © 2011 Pearson Education, Inc. All rights reserved.

Sexual Orientation and Genes 48% homosexual concordance rate for monozygotic twins; 16% for dizygotic twins Limited evidence for a particular gene related to homosexuality Copyright © 2011 Pearson Education, Inc. All rights reserved.

Sexual Orientation and Early Hormones Orchidectomy reduces sexual behavior of males, but does not redirect it Non-human studies indicate that perinatal hormones can influence sexual “orientation” Human research is less conclusive No differences in adult hormone levels Prenatal exposure to artificial estrogen has weak correlation with homo- or bisexuality in women Fraternal birth order effect: younger brothers are increasingly more likely to be homosexual Copyright © 2011 Pearson Education, Inc. All rights reserved.

What Triggers the Development of Sexual Attraction? May be due to adrenal cortex steroids Adrenal maturation occurs at about the same time (age 10) as sexual interest Copyright © 2011 Pearson Education, Inc. All rights reserved.

Is There a Difference in the Brains of Homosexuals and Heterosexuals? No reliable difference between the brains of heterosexuals and homosexuals has been discovered Copyright © 2011 Pearson Education, Inc. All rights reserved.

Copyright © 2011 Pearson Education, Inc. All rights reserved. Sexual Identity Sexual identity does not always coincide with a person’s anatomical sex Transsexualism Person believes that he or she is trapped in the body of the other sex Copyright © 2011 Pearson Education, Inc. All rights reserved.

Independence of Sexual Orientation and Sexual Identity Sexual attraction, sexual identity, and body type are sometimes unrelated Points to many possible differences in brain development, organization, and function between individuals Copyright © 2011 Pearson Education, Inc. All rights reserved.