Endocrine System PDF

 Today’s Learning Objectives Describe the chemical classification of Hormones Compare and contrast the mechanism of action of hydrophilic vs hydrophobic hormones. Compare and contrast the different types of Second Messenger Systems Describe the Hormonal Actions and Interactions from:...

 Today’s Learning Objectives Describe the chemical classification of Hormones Compare and contrast the mechanism of action of hydrophilic vs hydrophobic hormones. Compare and contrast the different types of Second Messenger Systems Describe the Hormonal Actions and Interactions from: Pituitary Gland Thyroid Gland Adrenal Gland Islets of Langerhans Describe the action of miscellaneous endocrine glands and Hormones 11-2 HORMONES: What are some hormones that you can think of? (without looking ahead… there are DOZENS) Comparison of Nervous & Endocrine Nervous system ▪ quick response (milliseconds) ▪ relatively short duration of effect ▪ works via electrical impulses (action potentials) and direct release of chemicals (neurotransmitters) across interstitial fluid to adjacent cells ▪ affects specific sets of cells (neuron, muscle, gland) resulting in specific responses (eg. muscle contraction or glandular secretion) Endocrine system ▪ slower response (minutes to hours) ▪ potentially long duration of effects (hours to days) ▪ works via chemical signals (“hormones”) which are released through interstitial fluid into blood capillaries ▪ affects multiple cells throughout the body that have specific hormone receptors (“target cells”) resulting in change of metabolic activities of cells (e.g. affects protein synthesis; ATP production)  Endocrine Glands Ductless glands that secrete hormones Chemicals secreted into blood to communicate (slow) Each hormone binds to a specific receptor on target cell Affects the metabolism of target cell  Check in with a neighbor Examine the table. Why are there differences between the release, transport and receptor location of peptide hormones vs steroid hormones? Chemical Classification of Hormones Amine: Derived from tyrosine or tryptophan Eg NE, Epi, produced by adrenal medulla Thyroxine (T4),triiodothyronine (T3) by thyroid gland Hydrophobic Polypeptide/protein: Chains of amino acids Ex: ADH, GH, insulin, glucagon Glycoproteins: Carbohydrate attached to protein LH, FSH, TSH  Chemical Classification (cont) Steroids: lipids derived from cholesterol Hydrophobic Ex: testosterone, estrogen, progesterone, cortisol Nearpod Code Q9PFL Review Question Steroid hormones are secreted by A. Adrenal cortex B. Gonads C. Thyroid D. Both A & B E. Both B & C  Hormone Function Signal Hormones affect only certain tissues or organs (target cells or target organs) Receives signal Target cells must have specific protein receptors Cell responds Hormone binding alters cellular activity  Steroid Hormone: Mechanism of Action Steroid hormone passes through the plasma membrane (non polar) Binds to receptor in the cytoplasm forming complex Complex moves into the nucleus 11-18  Steroid Hormone Receptor 2 Complexes Dimerize Bind to the hormone response element on the DNA Synthesis of RNA Called genomic action and takes at least 30 mins  Review Question: Which of these hormones have nuclear receptors? A. Epinephrine B. Insulin C. Glucagon D. Cortisol  Hormones That Use 2nd Messengers Water soluble hormones cannot pass through plasma membrane, so use cell surface receptors Actions are mediated by 2nd messengers Hormone is the 1st messenger 2nd messenger carries signal from receptor to inside of cell 11-24  Three Types of 2nd Messenger Systems 1. Adenylate cyclase – cAMP system 2. Phospholipase C- Ca++ system 3. Tyrosine Kinase system  Adenylate Cyclase-cAMP 1. Hormone binds to receptor, G-proteins dissociate 2. Activates adenylate cyclase (AC) 3. Converts ATP to cAMP (2nd messenger) 4. cAMP activates protein kinase 5. Protein kinase phosphorylates enzymes e.g Epinephrine, NE and their ꞵ-receptors, Glucagon, FSH 11-25  Phospholipase C- Ca++ system 1. Hormone binds to receptor 2. G proteins signal phospholipase C (PLC) 3. PLC forms inositol triphosphate (IP3) 4. IP3 cause CA++ channel to open in ER 5. Ca++ is 2nd messenger 6. Ca++ binds to calmodulin 7. Activates enzymes to bring about the desired responses e.g. Epi and α-receptors Tyrosine Kinase System: for insulin Receptor itself is a enzyme (tyrosine kinase) 1. Insulin binds to 2 units of receptor 2. Receptors dimerize (come together) 3. Tyrosine kinase phosphorylates itself > activated 4. Glucose uptake Glucose uptake by insulin Review Question Which of these hormones uses cAMP as a second messenger? A. Testosterone B. Cortisol C. Insulin D. Epinephrine Review Question Which of these correctly describes the role of inositol triphosphate (IP3) in hormone action? A. It activates adenylate cyclase B. It stimulates the release of Ca++ from the endoplasmic reticulum C. It activates protein kinase D. All of these Hormonal Actions and Interactions 11-11  Hormone Levels and Tissue Responses Effects of hormones depend on concentration Abnormally high concentration may have bad side effects Eg. male athletes taking large doses of anabolic steroids can develop breast, erectile dysfunction, increase risk for heart disease Desensitization/downregulation of receptors: Decreases the effect of hormone on the target The Pituitary Gland 11-35  Posterior Pituitary Gland Stores and releases 2 hormones made in the hypothalamus 1. ADH: increases H2O absorption in kidneys where specifically? 2. Oxytocin - Uterus contraction during labor - Milk let-down in lactating women 11-38  Clinical Example: Oxytocin Synthetic injections (pitocin) are given to pregnant women to induce labor, during Prolonged pregnancy Fetal membranes have burst leading to infection Preeclampsia, pregnancy induced high BP Injections are given after delivery to reduce uterus size & to squeeze blood vessels preventing hemorrhage 1. Growth hormone (GH) Anterior Pituitary Promotes growth of cartilage & bone Protein synthesis, Movement of amino acids into cells 2. Thyroid stimulating hormone (TSH) Stimulates thyroid to produce and secrete T4 and T3 3. Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete cortisol, aldosterone 11-39 GH Disorders – Pituitary dwarfism results from hyposecretion of GH during childhood – Gigantism results from hypersecretion of GH during childhood Height over ~ 8ʼ Puberty often delayed This individual exhibiting gigantism (right) stands 8 feet, 1 inch tall. The pituitary dwarf (left) is 2 feet, 5.37 inches tall.  Acromegaly Results from hypersecretion of GH during adulthood Face, jaws hands How would bones grow in adulthood?  Anterior Pituitary (cont) 4. Follicle stimulating hormone (FSH) stimulates growth of ovarian follicle sperm production 5. Luteinizing hormone (LH) causes ovulation secretion of testosterone in testes 6. Prolactin (PRL) stimulates milk production by mammary glands  Hypothalamic control of anterior pituitary via Hypothalamic-Pituitary Portal System Hypothalamus controls secretion of anterior pituitary Receives input from higher brain centers that can affect anterior pituitary secretion Emotional states, psychological stress can affect circadian rhythms, menstrual cycle, adrenal hormones 11-42 Fig. 11.16 Fig. 11.17 Review Question Compare and contrast the control that the hypothalamus has over anterior and posterior pituitary glands  Thyroid hormones Made in thyroid follicle Using iodine & tyrosine amino acid T4 (thyroxine) and T3 (triiodothyrodine) Set BMR , Protein synthesis Needed for growth & development  Clinical Examples involving TH Hypothyroidism low T4 & T3 levels Have low BMR, weight gain, lethargy, cold intolerance Endemic Goiter: iodine-deficiency High TSH (from?) Cretinism: fetal development hypothyroidism severe mental retardation 11-59 Endemic Goiter (iodine deficiency)  Hyperthyroidism High Thyroxine (T4) secretion High BMR, weight loss, nervousness, irritability, intolerance to heat Graves disease: Autoimmune disease Antibodies have TSH-like effects Not inhibited by negative feedback Excess stimulation of thyroid > Excess T4 Exopthalmos (Bulging eyes) Review Question The secretion of which of these hormones would be increased in a person with endemic goiter? A. TSH B. Thyroxine C. T3 D. All of these Review Question The hormone primarily responsible for setting the BMR & for promoting the maturation of the brain is A. Cortisol B. ACTH C. TSH D. Thyroxine (T4)  Parathyroid Glands Secrete Parathyroid hormone (PTH) Most important hormone for control of blood Ca2+ levels 11-62  Adrenal Medulla: Amine hormones Epinephrine & norepinephrine Controlled by sympathetic NS Activated during "fight or flight" response  Adrenal Cortex: Steroid hormones 1. Mineralocorticoids Aldosterone: salt & H2O absorption in kidneys 2. Glucocorticoids: Cortisol inhibits glucose uptake Inhibits inflammation Suppress immune system Weak androgens: Supplements sex steroids of gonads  Melatonin Secretion regulated by suprachiasmatic nucleus (SCN) of hypothalamus Circadian rhythms: Reset by daily environmental light/dark changes Synchronizes physiology with sleep/wake cycle & seasons Secreted at night and is inhibited by light Antigonadotropic effects in many animals In humans delays puberty  Gonads & Placenta Ovaries: – Estrogen & progesterone Testes: – testosterone Placenta – estrogen, progesterone, hCG Discussed in Reproductive 11-72