BSC2086 Anatomy Physiology II Exam 1 Study Guide Lesson 3 Endocrine System Part I Endocrine System Regulates long term processes o Growth o Development o Reproduction Uses chemical messengers to relay information and instructions between cells Homeostasis and Intercellular Communication Direct Communication Exchange of ions and molecules between adjacent cells across gap junctions o Occurs between two cells of same type 1 BSC2086 Anatomy Physiology II Exam 1 Study Guide o Highly specialized relatively rare o Ex Cardiac muscle Paracrine Communication Uses chemical signals to transfer information from cell to cell within a single tissue o Communication between close cells short distance of the same type o Most common form of intercellular communication Endocrine Communication Endocrine cells release chemicals hormones into bloodstream o Long distance communication of cells o Alters metabolic activities of many tissues organs simultaneously Paracrine factors can enter bloodstream but their concentrations are usually too low to Target Cells Specific cells that possess receptors needed to bind and read hormonal affect distant cells tissues messages Hormones Chemical messengers transported through blood o Stimulate synthesis of enzymes or structural proteins o Increase OR decrease rate of synthesis Turn existing enzyme or membrane channel on or off o Long lasting effects Synaptic Communication Occurs across synaptic clefts o Travels very short distance to reach target cell o Ideal for crisis management fast reaction o Chemical message neurotransmitter o Limited to very specific area o Response usually not long lasting o Nervous system faster than endocrine system Ex E mail vs postal snail mail 2 BSC2086 Anatomy Physiology II Exam 1 Study Guide Hormones Hormones can be divided into three 3 groups o Amino acid derivatives o Peptide hormones o Lipid derivatives Hormones circulate freely or travel bound to special carrier proteins o Lipid soluble hormones require special carriers for transport in blood Amino Acid Derivatives Small molecules structurally related to amino acids o Derivatives of Tyrosine Thyroid hormones Catecholamines adrenal glands Dopamine o Derivatives of Tryptophan Serotonin Melatonin produced in pineal gland Peptide Hormones Chains of amino acids Epinephrine norepinephrine produced by adrenal medulla of o Most synthesized as prohormones inactive molecules converted to active hormones before or after they are secreted o Glycoproteins Proteins more than 200 amino acids long with carbohydrate side chains Thyroid Stimulating Hormone TSH Luteinizing Hormone LH Follicle Stimulating Hormone FSH o Short Chain Polypeptides Antidiuretic Hormone ADH Oxytocin OXT Each nine 9 amino acids long o Small Proteins Growth Hormone GH 191 amino acids Prolactin PRL 198 amino acids Hypothalamus Heart Thymus Digestive tract Pancreas Posterior lobe of pituitary gland Several hormones produced in other organs o Short polypeptides small proteins includes all hormones secreted by Lipid Derivatives o Eicosanoids Derived from arachidonic acid a 20 carbon fatty acid Paracrine factors that coordinate cellular activities affect enzymatic processes like blood clotting in extracellular fluids Prostaglandins Involved primarily in coordinating local cellular activities 3 BSC2086 Anatomy Physiology II Exam 1 Study Guide Converted to thromboxanes vasoconstrictor prostacyclins vasodilator in some tissues o Also have strong paracrine effects o Steroid Hormones Derived from cholesterol Released by Reproductive organs o Males testes androgens o Females ovaries estrogens progestins Cortex of adrenal glands corticosteroids Kidneys calcitriol Remain in circulation longer than secreted peptide hormones because they are bound to specific transport proteins in the plasma Free Hormones Remain functional for less than 1 hour are inactivated when they o Diffuse out of bloodstream bind to receptors on target cells o Are broken down absorbed by cells of liver or kidneys o Are broken down by enzymes in plasma or interstitial fluids Thyroid steroid proteins o Remain in circulation longer because most are bound to carrier proteins o Enter the bloodstream More than 99 attach to special transport proteins Bloodstream contains substantial reserve of bound hormones Catecholamines peptide hormones o Are NOT lipid soluble unable to penetrate plasma membrane o Bind to receptor proteins at outer surface of plasma membrane extracellular receptors Eicosanoids o Are lipid soluble o Diffuse across plasma membrane to reach receptor proteins on inner surface of plasma membrane intracellular receptors Mechanisms of Hormone Action Hormone Receptor Protein molecule to which a particular molecule binds strongly o Responds to several different hormones Presence or absence of specific receptor determines a cell s hormonal sensitivity o Different tissues have different combinations of receptors A cell can respond to multiple hormones as long as that cell has receptors First Messenger Hormone for that hormone o Must trigger a second messenger inside the cell to cause a change within the cell o Bind to receptors in plasma membrane o Can t have direct effect on activities inside target cell o Use intracellular intermediary to exert effects o May act as enzyme activator inhibitor or cofactor o Results in change in rates of metabolic reactions Important second messengers o Cyclic AMP cAMP derivative of ATP 4 BSC2086 Anatomy Physiology II Exam 1 Study Guide receptors hormone hormone o Cyclic GMP cGMP derivative of GTP o Calcium ions Amplification The binding of a small number of hormone molecules to membrane receptors that leads to thousands of second messengers in the cell o Magnifies effect of hormone on target cell o Ex Cue ball hormone strikes many billiard balls second messenger but can then hit many more billiard balls Down Regulation Presence of a hormone triggers decrease in number of hormone o When levels of particular hormone are high cells become less sensitive to that Up Regulation Absence of a hormone triggers increase in number of hormone receptors o When levels of a particular hormone are low cells become more sensitive to that G Protein Enzyme complex coupled to membrane receptor o Involved in link between first messenger and second messenger G Proteins cAMP o Adenylate cyclase enzyme is activated when hormone binds to receptor at membrane surface and changes concentration of second messenger cyclic AMP cAMP within cell Binding or
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