Endocrine System Hormones 2007-2008
Regulation Why are hormones needed? chemical messages from one body part to another communication needed to coordinate whole body homeostasis & regulation metabolism growth development maturation reproduction growth hormones
Regulation & Communication Animals rely on 2 systems for regulation endocrine system system of ductless glands secrete chemical signals directly into blood chemical travels to target tissue slow, long-lasting response nervous system system of neurons transmits electrical signal & release neurotransmitters to target tissue fast, short-lasting response
Regulation by chemical messengers Neurotransmitters released by neurons Hormones release by endocrine glands neurotransmitter endocrine gland axon hormone carried by blood receptor proteins receptor proteins target cell
Classes of Hormones Protein-based hormones polypeptides small proteins: insulin, ADH glycoproteins large proteins + carbohydrate: FSH, LH amines modified amino acids: epinephrine, melatonin Lipid-based hormones steroids insulin modified cholesterol: sex hormones, aldosterone
How do hormones act on target cells Lipid-based hormones hydrophobic & lipid-soluble diffuse across membrane & enter cells bind to receptor proteins in cytoplasm & nucleus bind to DNA as transcription factors Protein-based hormones hydrophilic & not lipid soluble can t diffuse across membrane receptor proteins in cell membrane trigger signal transduction pathway activate internal cellular response enzyme action, uptake or secretion of molecules
Action of lipid (steroid) hormones target cell cytoplasm S 2 receptor protein S 1 steroid hormone S protein carrier blood transcription factor S 4 DNA nucleus 3 mrna 5 protein plasma membrane ex: growth factors (hair, bone, muscle, gametes)
Action of protein hormones protein hormone 1 P signal signal-transduction pathway activates ion channel or enzyme plasma membrane receptor protein cytoplasm ATP activates enzyme activates enzyme 2 messenger transduction 2 Signal transduction pathway target cell produces an action 3 response
Action of epinephrine (adrenalin) 1 epinephrine activates adenylyl cyclase receptor protein cytoplasm GTP activates G protein GDP camp 3 2 ATP activates protein kinase-a 4 activates phosphorylase kinase activates glycogen phosphorylase adrenal gland released to blood liver cell glycogen 5 glucose 6
Maintaining homeostasis hormone 1 gland lowers body condition high specific body condition low raises body condition gland hormone 2 Negative Feedback Model
Nervous System Control Controlling Body Temperature nerve signals hypothalamus Feedback high body temperature (37 C) sweat low dilates surface blood vessels hypothalamus constricts surface blood vessels shiver nerve signals
Endocrine System Control Regulation of Blood Sugar insulin beta islet cells Feedback pancreas body cells take up sugar from blood liver stores glycogen reduces appetite high blood sugar level (90mg/100ml) low liver triggers hunger liver releases glucose pancreas liver glucagon alpha islet cells
Endocrine System Control Blood Osmolarity osmoreceptors in hypothalamus pituitary ADH increased water reabsorption increase thirst Feedback high nephron adrenal gland nephron increased water & salt reabsorption aldosterone blood osmolarity angiotensin low nephron (JGA) renin angiotensinogen JuxtaGlomerular Apparatus
Thirst Osmoreceptors in hypothalamus trigger release of ADH. Hypothalamus COLLECTING DUCT LUMEN COLLECTING DUCT CELL INTERSTITIAL FLUID ADH Drinking reduces blood osmolarity to set point. Increased permeability ADH Pituitary gland camp Second messenger signaling molecule ADH receptor Distal tubule Storage vesicle Exocytosis H 2 O Aquaporin water channels H 2 O reabsorption helps prevent further osmolarity increase. STIMULUS: Increase in blood osmolarity H 2 O Collecting duct (b) Homeostasis: Blood osmolarity (300 mosm/l) (a)
Nervous & Endocrine systems linked Hypothalamus = master nerve control center nervous system receives information from nerves around body about internal conditions regulates release of hormones from pituitary Pituitary gland = master gland endocrine system secretes broad range of hormones regulating other glands pituitary hypothalamus posterior anterior
Regulating metabolism Hypothalamus TRH = TSH-releasing hormone Anterior Pituitary TSH = thyroid stimulating hormone Thyroid produces thyroxine hormones metabolism & development bone growth mental development metabolic use of energy blood pressure & heart rate muscle tone digestion reproduction tyrosine + iodine thyroxine
Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine
Endocrine System Control Regulation of Blood Calcium thyroid calcitonin kidney reabsorption of Ca ++ Feedback Ca ++ deposited in bones Ca ++ uptake in intestines high activated Vitamin D bones release Ca ++ blood calcium level (10 mg/100ml) kidney reabsorption of Ca ++ low parathyroid parathyroid hormone (PTH)
Female reproductive cycle Feedback ovary estrogen egg matures & is released (ovulation) builds up uterus lining corpus luteum progesterone FSH & LH pituitary gland maintains uterus lining pregnancy fertilized egg (zygote) yes hcg corpus luteum GnRH no progesterone hypothalamus corpus luteum breaks down progesterone drops menstruation maintains uterus lining