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Week 8 - Oct 15, 17 - Chapter 7(b) Reproduction and Physiology - PSYCH 3M03

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Aadil Merali Juma

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LECTURE 8 COURSE CODE Chapter 7: Reproduction and Physiology October 15, 17, 18, 2013  Pheromones, tactile stimuli, visual stimuli all input into sexual arousal  Courtship patterns vary among species  Sexual behaviour is largely innate once initiated  Male Sexual Behaviour o Mounting – positioning on the female to permit copulation o Intromission – insertion of the penis with pelvic thrusting; in mice, many intromissions; in humans, single intromission o Ejaculation – reflexive emission of sperm o Basic spinal reflexes – both can occur after spinal transection above the sacral vertebrate  Erection – parasympathetic NS  Ejaculation – sympathetic NS  Occurs in infancy (not full response)  Transect spinal cord in lab animal, causes peripheral paralysis, but these reflexes (in spine) still occur  Severed spinal cord in accident; can still show sexual responses o Hormones and Male Sexual Response  Chronic testosterone critical  More testosterone does not necessarily cause more sexual activity – testosterone slow acting organizational hormone  Inject testosterone into lab animal – may not demonstrate greater sexuality  Immediate testosterone not  Dependent on reaching a certain threshold of testosterone, usually met after puberty  Estrogen  Levels of testosterone are highest at the beginning of the day  Testosterone binds to portions of hypothalamus critical for sexual behaviour  Castration reduces male sexual response (not always); adrenals and experience  Doesn’t immediately remove sexual drive; weeks before impact occurs  ~ 1 week before losing ejaculation response, then lose intromission; ~1 month before mounting behaviour is eliminated  Some men and rhesus monkeys will sustain sexual activity despite castration for a few years (cannot ejaculate, but motor response still occurs)  Few men do not lose sexual response after castration  Testosterone levels from testes eliminated  Testosterone lingers in tissues; adrenal cortex compensates and secretes more testosterone  Male HPG Axis  Hypothalamus --GnRH --> Pituitary --LH--> Testes  Androgens (testosterone)  Hypothalamus secretes GnRH which stimulates the anterior pituitary to secrete LH and FSH, which stimulate testes to produce testosterone  Androgens produce secondary sex characteristics; go to brain and bind particularly to parts of the hypothalamus (pre-optic areas very important for male sexual behaviour)  Prenatal levels of androgens are critical  Happens after puberty; does not occur at birth, but is still innate  Male arousal facilitated by minor increases in arousal and catecholamine’s  Arousal dampened by major stress, fatigue, over arousal  Female Sexual Behaviour o Reflexes – spinal (eg/ lubrication, blood flow, lordosis); elicited reflexes  Lordosis – lift tail and arch back; allows for male mounting and intromission; observed in mice and non- human animals o Proceptivity – the extent to which a female will elicit copulations as reflected by her behaviour; solicit attention  Eg/ Baboons – blood flow to cause bright coloration of genital area during estrous (mid cycle)  Eg/ Cats – cats will scream and cry to get away if they are seeking mating  Eg/ Rats – dart and hop, wiggle ears  Eg/ Anesthesia to the cortex of the rat; sexual activity is liberated o Receptivity – a females state of responsiveness to sexual initiation by male  Dependent on estrogens; estradiol (prepares sexual response), progesterone (kicks in sexual response)  Eg/ Chimps and Rats – females often initiate sexual behaviour o Female sexual reflexes general inhibited by stress and stress hormones  Catecholamine’s; inject adrenaline, females will not mate 1 LECTURE 8 COURSE CODE  Female more sensitive to stress hormones, than males; stress steroids inhibit sexual response  Parasympathetic – facilitates sexual response and reproduction  Sympathetic – can kill male sexual activity (nervousness) and females; females more sensitive (more conservative) o Facilitated by parasympathetic NS o Sympathetic – ejaculatory in males; excitement in females  Stress can promote ejaculatory response, make it occur early (eg/ in novices) o Female HPG Axis  Hypothalamus --GnRH--> Anterior Pituitary --FSH--> Ovaries --> estrogen  Hypothalamus --GnRH--> Anterior Pituitary --LH--> Ovaries --> progesterone  Beginning of menstrual or estrual cycle; FSH stimulates production of estrogen in post-menstrual period, pre- ovulatory (when menstruation is over, estrogen rises; mid cycle LH spikes which stimulates progesterone production) ??  Pregnancy – progesterone dominates  Pre menstrual phase – progesterone drops; menstruation occurs  Most females will only mate mid cycle due to LH spike; narrow window of time in which non-human mammals will mate (during ovulation)  usually results in fertilization  Humans have evolved to mate throughout the cycle; might be due to pair bonding, which facilitates bi-parental care in K-selected offspring  few mating’s result in insemination and pregnancy; ovulation is a rarer event, sometimes does not occur in cycle during stress o Hormones and Female Sexual Response  In many mammals, estrogen and progesterone control female sexual response  Primate (including human) sex response is less dependent on progesterone and estrogen  Testosterone is more important in sexual response than estrogen and progesterone o Shown in rhesus monkeys, women o Hormones are not sexually dimorphic  Androgens may also be involved  Femininity and Masculinity o Presence or absence of testosterone during very early development permanently affects brain differentiation  Period of time that masculinity can be determined for life  Eg/ Castrate a mouse neo-natally; block testosterone action, animal will be less masculine and may not show male sexual behaviour (or show femininity)  Eg/ Give testosterone to female in last few days of gestation, brains and behaviour may be masculinized for life  Body form – determined by chromosomes (specifically, Y that determines androgenization of genetalia; default is female during first trimester) o Especially the SDN-POA of the hypothalamus  Recall: Hypothalamus control pituitary which secretes FSH and LH o This differentiation will impact sexual behaviour
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