Biology 5: Endocrine System Peptide Hormones G-Protein Coupled Receptor (GPCR) Made of amino acids 1) 2) 3) 4) Cleaved from larger polypeptide Golgi modifies & activates hormone Put in vesicles released via exocytosis Polar – cannot pass through membrane, so uses extracellular receptor like GPCR Common 2nd messengers: cAMP, Ca2+, IP3 Notes: Epinephrine is a ligand 1st messenger. At the end of the GPCR process, Phosphodiesterase deactivates cAMP and GTP hydrolyzed back to GDP. Ex: Insulin Steroid Hormones • • • • • Made in Gonads & Adrenal Cortex, from Cholesterol Don’t dissolve, must be carried by proteins Non-polar, so CAN pass through membrane They activate nuclear receptors Direct action on DNA Direct vs. Tropic Hormones Direct Hormones: Act directly on target tissue/organ. Ex: Insulin. Ex: Estrogen / Testosterone / Cortisol Tropic Hormones: Require an intermediary. They only affect other endocrine tissues. Ex: GnRH and LH are both tropic. Amino Acid-Derivative Hormones Diabetes Share traits from both peptide & steroid hormones Type 1: No insulin, so glucose is not able to enter cells. Ex: Catecholamines use GPCR, Thyroxine bind intracellularly Type 2: Desensitized insulin receptors. Glucose unable to enter cells. Endocrine Organs & Hormones Hypothalamus Anterior Pituitary GnRHÞ GHRHÞ TRHÞ CRHÞ Dopamine (PIF) Þ "FSH + "LH "GH " TSH "ACTH ¯Prolactin ADH & Oxytocin:Produced in hypothalamus, released from posterior pituitary Pancreas Insulin Þ beta islets, ¯Glucose Glucagon Þ alpha islets, "Glucose Somatostatin Þ delta islets ¯Insulin, ¯Glucagon (GHIH) Gonads Testosterone in Testes Estrogen / Progesterone in ovaries FSHÞ LHÞ ACTHÞ TSHÞ Prolactin Þ Endorphins Þ GHÞ “FLAT PEG” mnemonic Male: Spermatogenesis Females: Growth of ovarian follicles Males: Testosterone Females: Induces ovulation Synth & release glucocorticoids from adrenal cortex Synth & release triiodothyronine and thyroxine from thyroid "Milk ¯Pain "Growth in bone/muscle "Glucose in bone/muscle Thyroid Gland T4 & T3Þ made by follicle cells "basal metabolic rate Calcitonin Þ Made by parafollicular (c) cells "Ca2+ in bone ¯Ca2+ in blood ¯Ca2+ absorption in gut "Ca2+ excretion from kidneys Parathyroid Glands Pineal Gland Melatonin controls circadian rhythm PTH Þ ¯Ca2+ in bone "Ca2+ in blood 2+ "Ca absorption in gut ¯Ca2+ excretion in kidneys Bone breakdown releases Ca2+ Activates Vitamin D (Calcitriol) * See appendix for more details on each hormone Posterior Pituitary ADHÞ ¯H2O output in urine vasoconstriction Oxytocin Þ " Uterine contractions "Milk "Bonding behavior POSITIVE FEEDBACK Adrenal Cortex Glucocorticoids: Cortisol / Cortisone "Glucose ¯Protein synthesis ¯Immune system Mineralocorticoids: Aldosterone ¯K+ in blood "Na+ in blood "H2O in blood due to osmosis "blood pressure Androgens: Converted to Testosterone and Estrogen in the gonads. Adrenal Medulla Catecholamines Epinephrine: Anti-histamine "Heart rate "BP Norepinephrine: "Heart rate "BP