chapter 10 notes

chapter 10 notes - CHAPTER 10: Sexual Behaviour A. Hormonal...

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CHAPTER 10: Sexual Behaviour A. Hormonal control: Reproductive cycles: In females (humans and most primates), called a menstrual cycle; in females of other mammalian species, called estrous cycles. Primary distinction between the two is the monthly growth/loss of uterine lining. Other features are similar, except that the estrous cycle of rats takes 4 days. Also, sexual behaviour of female mammals with estrous cycles is linked to ovulation, whereas female primates/humans can mate at any time during their menstrual cycle. Cycles consist of a sequence of events controlled by hormonal secretions of the pituitary glands and ovaries, which interact and affect each other. Cycle begins w/ secretion of gonadoptropins by anterior pituitary gland; these hormones stimulate growth of ovarian follicles- clusters of epithelial cells surrounding each ovum. Women usually produce one ovum/cycle; if 2 are made and fertilized, twins develop. As the follicles mature, they secrete estradiol, which causes growth of uterus lining; feedback from the increasing level of estradiol triggers release of LH by anterior PG. This surge causes ovulation: ovarian follicle ruptures, ovum is released; the ruptured follicle becomes a corpus luteum, which produces estradiol and progesterone. Progesterone maintains the endometrial lining of uterus and promotes receptivity. Meanwhile, ovum enters a Fallopian tube and ascends to uterus; if it meets sperm and becomes fertilized, it begins to divide and days later attaches itself to uterine wall. If it is not fertilized, corpus luteum stops secretions and lining of uterus begins to fall. Hormonal control of sexual behaviour in lab animals: Males: male sexual behaviour is quite varied; essential features however include intromission (entry of penis in vagina), pelvic thrusting, and ejaculation. Male rats reach sexual maturity between 45 and 75 days of age. When an adult male rat encounters a receptive female, he will nuzzle her, stiff her face/genitals, mount, short/shallow pelvic thrusts, deeper thrust+intromission, dismount. He will repeat this several times (from mounting to intromission)-8-15 times, 1 min apart. After this he ejaculates. He then refrains from sexual activity for some time (mins in rats). Most mammals will return to copulate several times and then show a longer pause called a refractory period, in which the male ejaculation cannot occur again for a while. Coolidge effect: despite the refractory period and the fact that many male mammals will become exhausted eventually from sex w/ same female, introducing a new female can restore/prolong his sexual activity significantly. Sexual behaviour of male rodents depends on testosterone and also oxytocin, a hormone
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This note was uploaded on 12/18/2011 for the course PSYC 211 taught by Professor Yogitachudasama during the Winter '09 term at McGill.

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chapter 10 notes - CHAPTER 10: Sexual Behaviour A. Hormonal...

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