physio 1

• Children begin to prefer sex-typed toys between the ages of 12 and 18 months.
• Young male monkeys spend more time with wheeled toys and balls, whereas young female monkeys prefer dolls, plush animals, and pots. These results suggest that at least part of the preference we see in toy selection among boys and girls may originate in biology.
• Aristotle argued that the sex of a child was the result of the temperature of semen at the time of conception
• Hot semen resulted in males, and cool semen resulted in females.
• Mothers provide an X chromosome to all their offspring; fathers determine the offspring's sex by providing either another X (producing a female) or a Y chromosome (producing a male).
• Without exposure to male hormones, all babies would be born with outwardly female appearance and behavior.
• Male and female structural development involves three distinct processes: the development of gonads, and internal organs, and of external genitalia.
• In a rare condition known as intersex, elements of both male and female development occur in the same fetus
• Up until the sixth week after conception, both male and female fetuses have identical primordial gonads that can develop into either ovary, the female gonads, or testes, the male gonads.
• At about six weeks after conception, a gene on the short arm of the Y chromosome, known as the sex-determining region of the Y chromosome, or SRY, is expressed in male embryos.
• Testis-determining factor, the protein encoded by the SRY gene, switches on additional genes that cause the primordial gonads to develop into testes.
• both male and female fetuses possess a male Wolffian system and a female Müllerian system.
• In males, the Wolffian system will develop into the seminal vesicles, the vas deferens, and the prostate.
• In females, the Müllerian system will develop into the uterus, the upper portion of the vagina, and the fallopian tubes.
• During the third month, the male's relatively new testes begin to secrete two hormones, testosterone, and anti-Müllerian hormone.
• Testosterone, one of several types of male hormone or androgen, promotes the development of the Wolffian system. Anti-Müllerian hormone initiates the degeneration of the Müllerian system.
• The development of the external genitalia follows the differentiation of the gonads during the sixth week after conception.
• The male external genitalia includes the penis and scrotum. The female external genitalia includes the labia, clitoris, and outer part of the vagina.
• No hormonal activity is required to develop female external genitalia. However, hormonal stimulation is essential for the development of male external genitalia.
• 5-alpha-dihydrotestosterone


  must be recognized by receptor sites for the male external genitalia to develop naturally.
• All edible tissues from animals contain a type of estrogen, or female hormone, called estradiol, so we can assume that humans have always experienced some level of exposure to outside sources of sex hormones.
• Phthalates, compounds frequently found in plastics and cosmetics, have been found to advance puberty in rats
• In prenatal and early postnatal development, sex hormones organize circuits in the brain that differ according to sex.
• Sex hormones are classified as steroids, chemicals that are synthesized from cholesterol in the gonads and lesser amounts, in the adrenal glands.
• Males and females both produce androgens and estrogens, but in different amounts.
• The hypothalamus exerts control over the release of sex hormones through its secretion of gonadotropin-releasing hormone (GnRH).
• melatonin


  a neurohormone implicated in the regulation of sleep and produced by the nearby pineal gland
• Light sensed by the retina increases GnRH secretion through its action on melatonin, melatonin inhibits the release of GnRH typically.
• Light increases GnRH release by reducing the inhibition usually produced by melatonin.
• estrus


  a period of hours or days in which the female is receptive to males
• In the females of species that undergo estrus hormones play an essential role in determining the timing and frequency of sexual behavior.
• Estrus coincides with ovulation in many species, making the likelihood of fertilization relatively high.
• During nonestrus periods, a female will not only reject sexual overtures from males, but she is also likely to respond aggressively to his advances.
• The sexual activity of human females, who do not display estrus, is under little if any, control of the hormones involved with ovulation.
• Human females show receptivity throughout the menstrual cycle. However, some women report feeling slightly more interest in sex around the time of ovulation
• A woman's ovaries produce testosterone as well as estrogens.
• On tests of mental figure rotations, women received their best scores when testosterone levels were high and their worst scores when estrogen levels were high. In contrast to performance on spatial tasks, verbal fluency, and manual dexterity in women appear to be correlated with higher levels estrogens
• Estrogens have a protective effect on memory in general, and verbal memory, in postmenopausal women
• Androgens influence male competitiveness, sexual frequency, and cognition.
• testosterone levels appear to increase in anticipation of competition.