NSB 502 CH 10 Sex

Exam 2

3 important steps to sexual differentiation

1. bipotential gonad primordia

2. internal reproductive tract

3. external genitalia

Androgens

• masculinizing effects

• male sex steroid hormones

  • testosterone

  • dihydrotestosterone (5 alpha reductase)

Anti-Mullerian hormones

defeminizing effects

hypothalamus

GnRH

pituitary

gonadotropic hormones

gonads

estradiol and testosterone

Medial Preoptic Area (MPA)

rostral to hypothalamus

• forebrain region

• elicits male sexual behavior

• sexual activity activates MPA

  • increased FOS

Sexually dimorphic nucleus (SDN) of the MPA

one nucleus in MPA = 7x larger in males

Ventromedial nucleus of hypothalamus

• control of female sexual behavior

• lesions abolish lordosis

• estradiol & Progesterone activate this region

suprachiasmatic nucleus of hypothalamus

• larger in homosexual males

  • smaller in heterosexual males and females

INAH-3

3rd interstitial nucleus of anterior hypothalamus

• larger in heterosexual males

• smaller in females and homosexual males

effect of hormones males

intromission, pelvic thrusting, ejaculation, refractory period

effect of hormones females

oxytocin

• lactation

• posterior pituitary

• released at orgasm

estrous cycle

estradiol

• increases 40h before estrous

female becomes receptive

• lordosis

• courtship

corpus luteum secretes progesterone