HypothalamicPituitary Axis Hypothalamus releasing hormones peptides releaseinhibiting hormones

Hypothalamic-Pituitary Axis • Hypothalamus ~ releasing hormones (peptides) ~ release-inhibiting hormones (peptides) • Pituitary AP ~ tropins (peptides & glycoproteins) PP ~neurohormones (peptides)

The Importance of Phosphorylation State in Enzyme Regulation • Adding a PO 4 group transforms a protein from an inactive to an active state - Kinases, phosphorylases • Removing a PO 4 group deactivates a protein - Phosphatases, dephosphorylases

Importance of c. AMP: e. g. Cholera • Cholera toxin inhibits hydrolysis of GTP (active state) to GDP (inactive state) …thus, c. AMP is on CONTINUOUSLY • Continuous elevation of c. AMP causes net influx of Na+ & water into gut: -- severe diarrhea, dehydration, death

Second messengers • c. AMP ~ AC, PKA, Ca • c. GMP ~ GC, PKG, Ca • DAG & IP 3 ~ PLC, PKC (IP 3+Cai+Caex) • A Key feature: phosphorylation state of regulatory proteins

Calcium as a Signal • Very low Cai makes changes in it a strong signal • Ca+2 binding proteins have very high affinity for calcium, binding of Ca+ changes their conformation, they become active, initiate signals (troponin C, calmodulin) • 2 nd messenger

Cholesterol as a Precursor • Mineralocorticoids ~ salt/water balance (aldosterone) • Glucocorticoids ~ stress hormones (cortisol) (mobilization of a. a. , f. a. ; immune suppression) • Reproductive hormones ~ estrogens, androgens (estradiol, testosterone)

Stress Syndrome • Acute Stress ~ sudden fright - fight or flight response • Chronic Stress ~ prolonged stress (thermal, noise, etc) - deleterious (e. g. immunosuppression)

Thyroid gland • Response to low temp stress: TRH - TSH - TH (T 3, T 4) - Sensitizes tissues to epinephrine - Increases metabolic rate - TH+GH = affect development/maturation • If plasma TH low…low metabolic rate, cretininism (dev), low resistance to infection • Thyroid also regulates Calcium (PTH, Calcitonin)

Growth Hormone • Low blood glucose -- GRH Exercise -- GIH (reduces GH, TSH, etc) • GH: -increases blood glucose (gluconeogensis, blocks tissue glucose uptake, f. a. as energy source instead of glucose) - incr. cell proliferation, tissue growth - stimulates insulin release

Insulin ‘Funnel’ • Facilitates delivery of ‘energy’ to cells in the form of glucose • Insulin: - incr. cellular uptake of glucose (all tissues) - decr. glycogenolysis, incr. gluconeogenesis - incr. a. a. uptake & conversion to protein

Blood Glucose Regulation • Insulin secretion triggered by: High blood glucose, Glucagon, GH, GIP, Epinephrine, high blood a. a. --- lowers blood glucose • Glucagon, GH secretion triggered by low blood glucose---elevate blood glucose • Glucocorticoids triggered by stress--elevate blood glucose

Calcium Regulation ~ Thryoid ~ • High blood Ca 2+ -- calcitonin - stops bone mineralization - stops Ca 2+ reabsorption from renal tubules • Low blood Ca 2+ -- parathyroid hormone - incr bone mineralization - incr Ca 2+ reabsorption from renal tubules - incr Ca 2+ reabsorption from intestine (calcitrol)

Testosterone (Androgens) • Gn. RH - FSH, LH (gonadotropins) FSH - Sertoli cells ---spermatogenesis, inhibin LH - Leydig cells -- secrete testosterone • Negative feeback at Hypo & AP by: testosterone & inhibin • Testosterone: many targets & actions

Estradiol (Estrogens) • Gn. RH - FSH, LH (gonadotropins) • Ovarian follicles=thecal+granulosa cells LH - thecal cells --androgens(T) FSH - granulosa cells ---aromatase (T to E 2 ) • Negative feedback at Hypo & AP by E 2 , Progesterone (P 4), inhibin • Estradiol: many targets & actions

Ovarian Menstrual Cycle • Follicular Phase: 1) Gn. RH - FSH, LH FSH: follicles ~ develop LH: thecal cells ~ androgens (T) FSH: granulosa cells ~ aromatase (T to E 2) 2) Hi E 2 - LH/FSH surge - ovulation 3) corpus luteum formed fr. ruptured follicle • Luteal phase: C. L. ~ P 4, E 2 suppr. Gn. RH • w/o pregnancy, C. L. degenerates, menses

Summary of Hormone Actions • • • Glucocorticoids ~ increase blood glucose TH ~ incr metabolism, generate heat Insulin/Glucagon ~ regulate blood glucose GH ~ actions similar to glucagon PTH (calcitrol)/Calcitonin ~ regulate blood calcium • ADH ~ regulates Na/water balance

Insect Developmental Hormones • Neurohormones - prothoracicotropic hormone (PTTH) - eclosion - bursicon • Endocrines- know these two: - juvenile hormone (modified f. a. ) - ecdysone (steroid)

Patterns of Invertebrate Development • Hemi-metabolous (e. g. cricket) Egg - nymph (morphologically similar to adult)- instars (ecdysis occurs)-adult • Holo-metabolous (e. g. butterfly) Egg - larva - instars (ecdysis) - pupa adult

Hormonal Control of Insect Metamorphosis • Egg - larva - instar stages (ecydsis occurs) - High JH + ecdysone -- molting begins • Growth via molting continues til JH low • Low JH+ ecdysone --pupation (pupa stage= diapause/overwintering) • No JH +ecdysone--pupa -- moth!

Mammalian Salivary glands • • Apocrine glands Saliva ~ 99. 5% water, ions, p. H 5 - 8 Stress, dehydration, anticipation of food Saliva production & secretion under neural control (ANS) ~Receptor binding - 2 nd mess - incr Cai 2+vesicles of saliva released

The ‘Cost’ of Glandular Secretion E. g. Lactation • Mammals Mother does not gain weight despite high food intake because…. . - lactation is energetically costly E. g. 75% of food intake goes into milk production, 25% left over to support the increased metabolism associated with lactation and mother’s basal metabolism.