May 2, 2014 – Chemical signals and hormones IV Announcements: - Final is NOT CUMULATIVE* - In lecture review session (Wed. May 7) - TA led review session (10am – 12pm, Wed. May 14, 151 Everett Lab 1. 2. 3. 4. 5. Pre-lecture quiz Review of stress responses Hormone-mediated physiological tradeoffs Interactions between the HPA and HPG axes Sex hormones * I will ask about recurrent themes (e.g. tradeoffs, negative feedback, etc.) Stress response Operates via two interrelated systems: • SAM (Sympathetic-adrenomedullary) (Short Term Response) • HPA (hypothalamic-pituitaryadrenocortical) (Chronic Response). SAM, adrenals, and epinephrine Summary of the “fight or flight” response 1.) Increases in HR, BP, O2 consumption, blood glucose and fatty acid concentrations. 2.) Redirection of blood flow from the skin and digestive system toward heart, brain, and muscles. 3.) Relaxation pulmonary smooth muscle to dilate bronchi and increase O2 uptake. Take home messages: 1.) Short term stress responses are EXTREMELY beneficial over the short term. 2.) Prolonged stress responses can be harmful. HPA axis and glucocorticoids • Adrenal cortex produces glucocorticoid hormones (GC). • Cortisol is most important human (GC), involved in regulating metabolism, immune response, and general homeostasis. • Elevated cortisol leads to: – Short term metabolism of fat stores into glucose – Increased hunger – Suppression of immune response; – Cardiovascular changes (e.g. increases in BP) Feedback inhibition by cortisol on ACTH Hypothalamus Pituitary gland Adrenal gland Figure 47-15 Stressed individual Unstressed individual Hormone-mediated Tradeoffs Interactions between stress, reproduction and immune function Hormone-mediated Tradeoffs: Interactions between stress, reproduction and immune function Testosterone treated Control Territory size Larger Smaller Singing frequency Higher Lower # of aggressive interactions Higher Lower Number of matings Higher Lower Number of offspring Higher Lower Offspring quality Lower Higher Survival Lower Higher Hormone-mediated Tradeoffs: Interactions between stress, reproduction and immune function Montane Urban Breeding season Shorter Longer Aggressiveness Higher Lower Male parental investment Higher Lower Testosterone Higher Lower Cortisol Higher Lower Stress response Higher Lower Hormone-mediated Tradeoffs Interactions between stress, reproduction and immune function HPG axis Gonads • Male testes produce sperm cells • Female ovaries produce ova • Fertilization – Sperm cell + ovum = zygote • Sex chromosomes – Humans: XX = female, XY = male – Birds: ZW = female, ZZ = male – Many vertebrates lack sex chromosomes entirely Sex Hormones – Released by Gonads • Androgens - e.g., testosterone (“male” hormones) • Estrogens - e.g., estradiol (“female” hormones) • Adult testes release more androgens and ovaries more estrogens • Progestins – also present in both sexes – progesterone prepares uterus and breasts for pregnancy • Adrenal cortex – also releases sex steroids HPG axis & Reproductive System Males Also known as Leydig cells Steps for spermatogenesis 1. GnRH released at hypothalamus -----> + section of FSH & LH at anterior pit. 2. a. FSH stimulates sertoli cells which stimulate spermatogenesis b. LH simulates Leydig cells which secrete testosterone Testosterone stimulates sertoli cells to stimulate spermatogenesis 3. a. testosterone has negative effects on GnRH b. testosterone has negative effects on LH & FSH c. Sertoli cells release inhibin which has negative effects on LH & FSH HPG axis & Reproductive System Males Females Figure 48-12 5. Degeneration of corpus luteum Secondary oocyte to oviduct 4. Ovulation Oocytes Follicle cells 3. Maturation of follicle 1. Formation of primary oocytes within follicles 2. Follicle growth Figure 48-13-2 FOLLICULAR PHASE Follicle growth LUTEAL PHASE Ovulation Corpus luteum degeneration Pituitary hormone cycle Hormone levels Ovarian cycle LH FSH 0 7 14 Days 21 28 Figure 48-14 FOLLICULAR PHASE LUTEAL PHASE Ovulation Follicle growth Corpus luteum degeneration Progesterone Follicles and corpus luteum secrete hormones Estradiol Negative feedback on LH Positive feedback on LH Negative feedback on LH, FSH Ovarian hormones and pituitary hormones exert feedback on each other