BSCI342-test2notes

BSCI342-test2notes - Puberty What? How? signaled by the...

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Puberty What? - stage in life at which individual is now able to reproduce - individual undergoes physiological, morphological, and behavioral changes How? - signaled by the pulsatile release of Gonadotropin Releasing Hormone (GnRH) from hypothalamus GnRH is released every 100 minutes, targeting gonadotrophs in anterior pituitary In Males - activation of hypothalamic pituitary testicular axis causes production of the sex steroid hormone called Androgens Hypothalamus GnRH Gonadrotrophs LH and FSH 1. LH – targets interstitial (Leydig) cells (as Leydig cells express LH receptors) upon stimulating Leydig cells, androgens are produced 1. DHEA 2. Androsterone 3. Testosterone (major androgen) 2. FSH – target sustentacular cells Biological Effects of Testosterone 1. differentiates male internal and external genitalia during embryonic and fetal development in utero 2. postnatally is needed in its potent form of DHT (dihydrotestosterone). .(5-10x potent) - DHT is converted from Testosterone using a 5-alpha enzyme -is so potent that is not present prior to birth by absence of 5-alpha reductase, XY male will have internal male genitalia but external female genitalia (“penis @ 12”) - DHT is also needed for growth/maintenance of reproductive structures prepuberty, but the levels of testosterone needed are low 3. DHT stimulates muscle growth increase in muscle mass (somatic/anabolic effect) 4. DHT stimulates bone tissue growth increase in bone density (somatic/anabolic effect) 5. DHT stimulates production of hormone Erythroproietin (EPO) - stimulates synthesis of erythrocytes (RBC’s)… this can allow low levels of EPO can be used to treat anemia 6. DHT is responsible for male sexual secondary characteristics - synergizes with growth hormone to cause growth spurt - stimulates apocrine sweat glands in armpits and pubic areas to screte viscous fluid, which causes body odor
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- stimulates body/ facial hair - stimulates sebaceous glands in skin to produce more oil, causing acne - increase in larynx (voice box)…. leads to deeper voice and developed Adam’s apple - increase in external genitalia (scrotum and penis) 7. DHT stimulates Libido (sex drive) 8. DHT stimulates skin to produce glycolipids, that moisten skin to prevent drying Abuse of Anabolic Steroids (synthetic testosterone) - increase of testosterone = increase of DHT 1. Cardiomegaly - overgrowth of cardiac muscle to render heart pump useless (cardiac failure) 2. Stimulates tumor growth in live and brain 3. Cause aggressive behavior (roid rage…psychosis, suicidal, homicidal) 4. Increase in RBC’s in blood, causes polycythemia - increased blood viscosity that compromises heart pump, leads to congestive heart failure In Females - activation of hypothalamic-pituitary-ovarian axis Hypothalamus GnRH Gonadotrophs LH and FSH 1. LH – causes synthesis of androgens and ovulation (via LH surge)… forms corpus lutein 2. FSH – causes maturation of the ovarian follicles (aromatase)
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This note was uploaded on 04/07/2008 for the course BSCI 412 taught by Professor Lee during the Spring '08 term at Maryland.

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BSCI342-test2notes - Puberty What? How? signaled by the...

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