17Su11Lec8 - COGS17 Neurobiology of Cognition Summer 2011...

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COGS17 Neurobiology of Cognition Summer 2011 Lecture 8: Sexual Development and Behavior REMINDER : Hypothalamus controls Endrocrine (hormone ) systems via effect on adjacent Pituitary Gland (the “Master Gland”) - Produces Releasing Hormones that flow via blood vessels to Anterior Pituitary stimulating gland to release its own hormones - Produces other Hormones (e.g. Oxytocin ) sent (like NTs) via axons to Posterior Pituitary , then circulate in bloodstream Reproductive Hormones have Organizing Effects (influence behavior) - Both sexes have female ( Estrogens ) and male ( Androgens ) hormones, just in different proportions - These Steroid Hormones are produced mainly in Ovaries/Testes, but also in Hypothalamus and Adrenal Glands - NOTE: Typically, males have XY sex chromosomes, females have XX , but hormone activity is required to determine gender! ORGANIZING EFFECTS Fetal Development of Sexual Anatomy - Every mammalian fetus has the anatomical precursors for BOTH sexes - e.g. Gonads , earliest sex structure to develop, same initial structure will become Testes or Ovaries - e.g. Gentalia , same initial structures in all fetuses, develop into male or female anatomy, depending on Androgens/Not - e.g. Each fetus has both Wolffian and Muellerian ducts; Their development depends on Androgens/Not respectively; Other system degenerates - The genes controlling male/female body & brain development are also present in BOTH sexes, EXCEPT… - The “switch ” is on the male’s Y Chromosome ; it signals production of the Testis-Determining Factor ( TDF ) Enzyme - Occurs during Critical Period of fetal development (TDF appears : 6 th –8 th week; Genitals developed by 4 th month) - If TDF is NOT present => Female - Ovaries differentiate, Mullerian system develops, Wolffian regresses, female genitalia develop – regardless of geneotype ! - If fetus is XY , but lacks specific gene for TDF (or other TDF deficit), will develop internally & externally as female - If fetus is XO ( Turner’s Syndrome , no Y Chromosome) will develop internally & externally as female - Both non-XX above will be infertile , however, since two Xs required to produce ova (eggs) - If TDF is present => Male - Testes differentiate, producing Androgens , including Testosterone => Wolffian ducts and male genitalia develop
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17Su11Lec8 - COGS17 Neurobiology of Cognition Summer 2011...

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