PS263 Study Guide - Midterm Guide: Anterior Pituitary, Sexually Dimorphic Nucleus, Endocrine System
Document Summary
Sexual reproduction increases variation and thereby enables quick evolutionary adaptions to changes in the environment. Sex corrects errors: disadvantageous mutation in one gene could be balanced out by partner"s genes. Males and females both born with mullerian and wolffian ducts. Sry gene causes primitive gonads to develop into testes, testes produce androgens (positive feedback) and cause wolffian ducts to develop into seminal vesicles. Testes produce mullerian inhibiting hormone and mullerian ducts degenerate. With no sry, females mullerian ducts mature into ovaries, uterus, vagina and wolffian ducts degenerate. Steroid hormones (androgens, estrogens) exert effects by binding to membrane receptors, entering cells and activating proteins, and binding to receptors that bind to chromosomes where they activate/inactivate certain genes. Organizing effects: long lasting structural effects, set the stage for activating effects, sex hormones determining sex in first trimester. Activating effects: more temporary, continue only when hormone is present or shortly beyond, changes in hormonal secretions influence sexual behaviour within 15 minutes.
