Steroid hormones Type of hormones, consists of 4 rings (made of C – carbons). •Derived from cholesterol •3 ways of action of steroid Hormones: Binds to receptors in membrane. Binds to and activate proteins in Cytoplasm. Acts on receptors linked to chromosomes. Sex hormones: Gonadal steroid hormones gonads: ovaries & testes •its hormones: gonadal steroids •androgens (Testosterone, Dihydrotestosterone), •estrogens•progesterone But, Gonads can produce both type of hormones (aromatase enzyme mediates Conversions) Organizing effects of sex hormones •Hormonal effects on the Brain and genitals. •Occurs in early stage of development. •Effects are long Lasting (indefinitely). Exps.: injections of androgens in female, or estrogens In male, at early (sensitive) stage. – Masculinization, feminization, Lordosis. The difference in external Genitals appearance (female vs. Male) stem from gradients of testosteronein early Sensitive period. •This “early sensitive period”: in humans (3 to 4 months Pregnancy).Activating effects of sex hormones •Consists of hormonal effects On the brain and genitals. •Occurs in later stage of development. – Any time in Life. – Mediated by testosterone or estradiol •Effects are limited on time (temporal). The default tendency of Nature is designed mammal for being female. Sex differences – Brain (Hypothalamus) In early stage of development, sex hormones binds to Receptors in Amygdala, Hypothalamus & others areas. Area of anterior Hypothalamus: sexually dimorphic nucleus (SDN). Controls of male (M) sexual Behavior. – Larger in male than female •In male rodents, testosterone induce Part of its organizing effects by entering the neurons in hypothalamus, and being Converted in estradiol, Which helps to masculinize males. •Estradiol does not masculinize female, Because Alpha-fetoproteinin rodents: binds to estrogen but not testosterone, controlling Downstream effects. •Removal of testes – tendency to decreases male sexual activity. •Impotence(problems of erection) are explained by Circulatory (blood), psychological tension, drugs, neurological problems, not Necessarily testosterone changes. •If Ovum fertilized, levels of estradiol and progesterone increases during Pregnancy. These affects serotonin type 3 receptors (5HT-3R) activity, that is Linked to nausea. • Periovulatory period Women experiences changes in sex behavior and perceptions. High estrogen Levels. – Effects in videos, work, faces Oxytocin: Also released by posterior Pituitary. •Uterus contraction •Foster releases of Mammary gland (milk). •After sexual pleasures (orgasm) – linked to anxiolytic Behavior.