Ch 8 Sex Hormones.docx - Sex Hormones The gonads produce steroid hormones regulating reproduction Testes Leydig cells produce and secrete

Ch 8 Sex Hormones.docx - Sex Hormones The gonads produce...

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Sex Hormones The gonads produce steroid hormones, regulating reproduction Testes Leydig cells produce and secrete testosterone (androgen) Changes in voice, hair growth, genital size. Declines with age Ovaries Two major classes Progestins: help maintain pregnancy Estrogen: includes estradiol, sexual receptivity Ovulatory cycle FSH stimulates ovarian follicles to grow and secrete estrogens Induces the release of LH → triggers the release of an egg from a follicle → develops as a corpus luteum (estrogen is lower) → secretes progesterone to prepare uterus → progesterone goes down Oral contraceptives have small doses of synthetic hormones which exert continuous negative feedback on the hypothalamus and pituitary → inhibits the release of GnRH → prevents the release of LH (surge) that would normally release the egg Relations among gonadal hormones All based on the chemical structure of cholesterol Males and females differ in the relative amount they produce Hormonal and neural systems interact to produce integrated responses Four kinds of signals possible Neural-to-neural: male dove sees an attractive female Neural-to-endocrine: male sees possibility to mate → GnRH Endocrine-to-endocrine: stimulation of pituitary to release gonadotropins Endocrine-to-neural: testosterone alters excitability of neurons (displays courtship behavior) → females responds → another cycle Interactions between endocrine activity and behavior are cyclical Reproductive behavior Four stages Sexual attraction: emit stimuli that attract opposite sex Appetitive behaviors: helps establish or maintain sexual behavior Proceptive: females advertises readiness Males stay close to female Copulation: coitus, intromissions Refractory phase Coolidge effect: males that appears sexually satisfied w current partner will resume sexual activity if provided w a new partner Postcopulatory behavior: vary greatly w species Copulation brings gametes together Activational effect of testerone Neural circuitry of the brain regulates reproductive behavior
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  • Fall '08
  • Glendenning
  • Sexual intercourse, Sexual differentiation

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