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Sex and Stress

C81BIO – Semester 2, Lecture 5. Sex and Stress. Dr. Mark Haselgrove. Overview of the lecture. Stress Fight or flight Control of glucocorticoids Health effects of stress. (2) Development of the Sex organs Gonads Internal sex organs ( and what happens when things go wrong )

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Sex and Stress

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  1. C81BIO – Semester 2, Lecture 5 Sex and Stress Dr. Mark Haselgrove

  2. Overview of the lecture • Stress • Fight or flight • Control of glucocorticoids • Health effects of stress • (2) Development of the Sex organs • Gonads • Internal sex organs (and what happens when things go wrong) • External Sex organs (and what happens when things go really wrong) (3) Sexual Maturation Hormones (4) Hormonal control of sexual behaviour Animal studies Human sexual behaviour

  3. Stress Some definitions… • Stress (n, vb): Walter Cannon • “Physiological reaction to the perception of aversive/threatening events” • Stressor: • “Stressful stimuli” • Stress response: • “individual’s reaction to a stressor”

  4. Stress Fight or flight? – Walter Cannon - Preparation for a threatening situation: Body’s energy reserves are mobilised by the adrenal gland: Adrenal medulla secretesepinephrine & nor-epinephrine - Epinephrine → affects glucose metabolism, muscle stored nutrients become available - Epinephrine & nor-epinepherine → ↑ heart rate (and blood pressure) Adrenal cortex secretesCortisol (a glucocorticoid) • - Glucocorticoids → Convert protien to glucose • Make fats available for energy • Increase blood flow • Increase behavioural responsiveness

  5. Stress Control of Glucocorticoids (1) PVN of the Hypothalamus secretes a peptide: CRH (2) CRH stimulates the anterior pituitary gland to release ACTH (3) ACTH enters the general circulation and stimulates the adrenal cortex to release glucocorticoids

  6. Stress Health effects of Long term stress Cohen (1953) survivors of concentration camps have poorer health later in life than controls Theorell et al. (1992) Subway train drivers that injure or kill people more likely to be ill, months later Selye (1976) All down toglucocorticoids: ↑ blood pressure, damage muscle tissue, ↑ infertility, suppress immune system, ↑ steroid diabetes, Inhibit growth

  7. Stress Effects of Long term stress on learning

  8. Development of the Sex organs Three classes of Sex organs: (i) gonads, (ii) internal genitalia (iii) external genitalia • Gonads (Testes/Overies). • First sex organ to develop • Have two roles: • (1) Produce sperm or ova. • (2) Secrete hormones - Organisation effects (determines sex organs & brain) • - Activation effects (effects occur later, produce sperm, induce ovulation, erection etc.) • Foetuses are undifferentiated till 6th week of pregnancy • Sry, (Sex-determining Region Y) gene on the Y chromosome – causes the gonads to become testes

  9. Development of the Sex organs - Internal Genitalia - Until 3rd month of gestation, embryo possesses the precursors to both♂ and ♀ sex organs - Mullerian System (♀) - Wolffian system (♂) - At this point one precursor withers - “Nature’s impulse is to create a girl” • - Testes secrete: • Anti-Mullerian hormone: de-feminising effect • Androgens (e.g. testosterone): masculinising effect

  10. Development of the Sex organs - Internal Genitalia - Can sometimes go wrong… Androgen insensitivity syndrome (Money & Ehrhardt, 1972) Genetically male (XY) Mutation prevents the formation of androgen receptors Primitive gonads → Testes Secrete: Anti-mullarian hormone (Prevents internal genitalia development) Androgens – no effect (thus no masculinisation)

  11. Development of the Sex organs - Internal Genitalia - Can sometimes go wrong… Persistent Mullerian duct syndrome (Warne & Zajac, 1998) Caused by either: (i) Absence of the anti-Mullerian hormone, or (ii) Absence of receptors for this hormone If it occurs in Genetic males: Androgens → Masculinising effect but no defeminisation occurs Thus individual develops both sets of internal sex organs

  12. Development of the Sex organs - Internal Genitalia - Can sometimes go wrong… Turner’s Syndrome “Natures impulse is to create a girl” Caused by the development of an X0 foetus - No Y chromosome (testes do not develop) - XX needed to produce ovaries (thus these are not present) - Still develop normal female internal and external genitalia however - Absence of ovaries means turner’s syndrome women cannot bear children

  13. Development of the Sex organs - Internal Genitalia - Can sometimes go wrong… Adrenogenital syndrome • A decrease in the levels of cortisol released from Adrenal cortex results in • abnormally high levels of adrenal androgens. Little effect on Males (but can accelerate onset of puberty) Major effects on Females: Enlarged clitoris, fused labia (ambiguous external sex organs)

  14. Development of the Sex organs - External Genitalia No female hormones needed for the development of external sex organs. Development of male sex organs dependent on an androgen (Explains characteristics of Turner’s syndrome)

  15. Sexual Maturation • Onset of puberty occurs when: • (1) Hypothalamus secretes: Gonadotrophin-releasing hormones (GnRH) • (2) Stimulates anterior pituitary gland to releasegonadatrophic hormones • (3)Stimulates the gonads to produce their hormones… (i) Follicle-stimulating hormone (FSH) (ii) Luteinizing hormone In Women: Produce follicles, and enables luteinisation (→ menstruation). Ovaries secrete estrogens In Men: Stimulate testes to produce sperm & secrete testosterone

  16. Hormonal control of Sexual Behaviour (1) Animal studies - Males Rats Studied more than any other laboratory animal: Upon encountering a receptive female: Nuzzling Genital sniffing, licking Mounting (and intromission) After about 10 intromissions (each lasting 0.25 s) ejaculation occurs. Refractory period – interval between successive ejaculations increases Once a male is “exhausted” –introducing a new female rejuvenates him: Coolidge effect (Beamer et al., 1969) in rams – depends upon identification by odour

  17. Hormonal control of Sexual Behaviour (1) Animal studies - Females More passive role in many mammals • Lordosis: Move tails away (if she has one) • Stand rigidly • Raise hind quarters Many female rodents have an active role in initiating sex: McClintock & Adler (1978) Quick, short hopping movements & ear wiggling Completely irresistible to male rat Male rats attempting to copulate with a non-oestrus female → female: flees or fights

  18. Hormonal control of Sexual Behaviour (2) Human sexual behaviour - Women Van Goozen et al (1997) Women initiate sex more during ovulation when estradiol levels are high

  19. Hormonal control of Sexual Behaviour (2) Human sexual behaviour - Men Testosterone: Bagatell et al (1994): Men given a GnHR antgonist, or a placebo GnHR group reported decreases in: Sexual interest Fantasys Intercourse - Effect removed by replacement doses of testosterone Works both ways: Thinking about sex ↑ testosterone: Hellhammer et al (1985): Watching an erotic film increases men’s testosterone

  20. Reading Carlson, N. R. (2007) Physiology of Behavior, Allyn & Bacon. Ch’s 10 & 17 Pinel, J. P.J. (2008) Biopsychology, Pearson. Ch’s 13 & 17 Kalat, J. W. (2007) Biological Psychology, Thompson. Ch’s 11 & 12 Email: Mark.Haselgrove@nottingham.ac.uk Next Week: Animal Learning with Dr. Cassaday

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