Endocrine System - Lecture 15 (PDF)

ENDOCRINE SYSTEM Major Glands and Hormones ANSC 3080 G. Bedecarrats  Learning Objectives  Define the terms endocrine gland and hormone  Describe the classification of hormones by structure  Describe the major endocrine glands and their hormones  Endocrine Sys...

ENDOCRINE SYSTEM Major Glands and Hormones ANSC 3080 G. Bedecarrats  Learning Objectives  Define the terms endocrine gland and hormone  Describe the classification of hormones by structure  Describe the major endocrine glands and their hormones  Endocrine System  Endocrine: refers to an hormone that is  Produced and secreted within the body  Opposite of exocrine which is secreted outside body (mammary gland, lumen of digestive tract, etc…)  Acts at a distance from the release site  Paracrine: acts on nearby cells  Autocrine: acts on its own secreting cell  Neuroendocrine: synthesized by nervous tissue and carried in the blood  Gland:  Cluster of cells organized for synthesis / release of compound  Glands can be endocrine or exocrine A – Endocrine D – Paracrine B – Neural E – Autocrine C – Neuroendocrine  Hormones  Regulatory chemicals produced in an endocrine gland or scattered cells, secreted into the blood and carried to its target cell that responds by altering its metabolism  Involved in maintaining homeostasis  Subjected to tight regulation by feedback from target organs  Regulation of hormones synthesis and mode of action differ greatly based on their structure Mainly Negative Feedback Control Cyclic systems (loops) that control the amount of hormone released Occasionally positive Hypothalamus (+) LH Estrogen LH (pituitary) ovulation Follicle (ovary) (+) Time LH production by pituitary decreases sharply at ovulation since ovarian follicle which produces estrogen is removed  Structural Classification Steroid hormones: Stepwise conversion of cholesterol by multiple enzymes Lipid-soluble = leave production cells and enter target organ by diffusion through the membrane  HO A Cholesterol B C  CH3 CH3 CH2OH FYI C O C O C O HO OH  O O HO Pregnenolone Progesterone Cortisol CH3 CH2OH C O H O CH2OH O C HO HO C C O O O Corticosterone Aldosterone O Progesterone Peptides, proteins, glycoproteins: Chains of amino acids  sequence determines the primary structure and nature Transcription Translation DNA mRNA Protein (Nucleus) (Ribosome/Cytosol)  Genetic code = 3 base sequences code for 1 A.A.  After translation, protein can be modified:  Glycosylation = carbohydrate chains attached  Phosphorylation = phosphate group attached  Modified, packaged in the E.R. and Golgi  Secreted by exocytosis Amino-acid derivatives (thyroid hormones, catecholamines):  Generally derived from tyrosine and tryptophane 3' HO CH 2 CH C OH 5' NH 2 O Tyrosine I 3' 3' HO CH 2 CH C OH HO CH 2 CH C OH 5' 5' NH 2 O NH 2 O I Diiodotyrosine Tyrosine I I 3' 3 HO O CH 2 CH C OH 5' 5 NH 2 O I I Thyroxine HO 3' I I CH 2 CH C OH HO 3' 3 5' HO O CH 2 CH C OH NH 2 O 5 NH 2 O Dihydroxyphenylalanine (DOPA) I Triiodothyroinine HO HO HO H H HO CH2 CH2 NH2 HO C CH2 NH2 HO C CH2 NH CH3 OH OH Dopamine Norepinephrine Epinephrine Fatty acid derivatives or eicosanoids (prostaglandins): Derived from cell membrane phospholipids (arachidonic acid) Produced locally, have mainly autocrine, paracrine effects COOH Cell membrane phospholipids Arachidonic Acid Prostaglandins Prostacyclins Thromboxanes (PGE2 and PGF2) (PGI2) (TXA2) Major Glands  Pineal Gland  On the roof of the 3rd ventricule, encapsulated by meninges  Secretes melatonin  Under the indirect influence of the hypothalamic circadian center  Major role during sleep patterns and recognition of seasons  Melatonin secretion is stimulated during dark phases  Gastrointestinal Tract  Stomach wall  gastrin  local stimulation of acid secretion  Small Intestine: Secretin  stimulates the pancreas Cholecystokinin  stimulates pancreas and gall bladder Gastric inhibitory peptide  inhibits stomach activity Kidneys  Renin   aldosterone secretion by adrenal cortex  Erythropoietin   production of red blood cells in bone marrow  Adipose Tissue  Adipocytes release leptins and others adipokins  Leptin receptors can be found in the hypothalamus  Give information about energy storage status  Regulates appetite Gland Hormone Target Effects Pancreas Insulin + Many organs Glucose uptake Glucagon - Liver Glycogen formation Liver Somatomedins (IGFs) Multiple + Growth Adrenal med. Epinephrine Cardiovascular Stimulation Adrenal cortex Glucocorticoids Liver/muscles Glucose metabolism Aldosterone Kidneys Na and K flux Parathyroid Parathyroid Hormone Kidneys/bones Ca / PO4 metabolism Thyroid Thyroxin (T4) Most organs Metabolism/heat Triiodothyronine (T3) Growth/develop. Calcitonin Kidney/bone Ca deposition Ovaries Estradiol/ progesterone Repro. tract Control of repro and Testes Testosterone Mamm. gland sexual charact. Placenta Multitude of hormones Reproduction, pregnancy, parturition, mammary gland development