Principles of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyPrinciples of Animal PhysiologyEndocrine SystemPrinciples of Animal PhysiologyEndocrine SystemIntroduction▪ All cells secrete material into their environment for three main functions▸ Protection▸ Communication▸ FeedingPrinciples of Animal PhysiologyEndocrine SystemIntroduction▪ Types and functions of Secretions▸ Autocrine - secreted substance affects the secreting cell itself▸ Paracrine - substance affects neighboring cells▸ Endocrine - substance released into blood stream and affects distal target tissue▸ Exocrine - substance that is released onto the surface of the animal and other internalized structuresPrinciples of Animal PhysiologyEndocrine System▪ Cell communication through various pathwaysIntroductionPrinciples of Animal PhysiologyEndocrine System▪ It brings about changes via chemical messengers, hormones, released into the blood stream or hemolymph and carried to target organs.▸ Endocrinology - the study of hormones and the endocrine organs they control.▸ Endoceine system - all of the glands that secrete hormones♦ Endocrine and exocrine glands▸ Exocrine glands - have ducts through which their nonhormonal products travel to the membrene IntroductionPrinciples of Animal PhysiologyEndocrine SystemIntroduction▪Endocrine glands - release their substances into the surrounding fluid (ductless glands)▪They include the pituitary, thyroid, parathyroid, adrenal, pineal, and the thymus glands. Also included are the pancreas and gonads. They hypothalamus is called a neuroendocrine organ.▸ Know Table 7.1Principles of Animal PhysiologyEndocrine System▪ Endocrine organsIntroductionPrinciples of Animal PhysiologyEndocrine System▸Hormones - chemical messengers carried by the blood from endocrine glands to the cell upon which they act.♦ Are chemical messengers♦ Secreted into the blood by endocrine cells or neurons♦ Affect distal targets▸Affect target cells by controlling♦ Rate of enzymatic reactions♦ Transport of molecules across cell membrane♦ Gene expression and protein synthesis♦Stimulation of mitosisIntroductionPrinciples of Animal PhysiologyEndocrine SystemIntroduction▪ Tropic hormones▸ Its primary function is to regulate the production and release of other hormones▸ Stimulate and maintain their endocrine target tissue▸ Eg., TSH maintains the structural integrity of the thyroid gland, but also cause it to secrete its hormonesPrinciples of Animal PhysiologyEndocrine SystemIntroduction▪ Nontropic hormone▸ Exerts its effects on nonendocrine target tissues▸ Thyroid hormone increases the metabolic activity of almost every cellPrinciples of Animal PhysiologyEndocrine System▪ Complexity of Endocrine Function♦A single endocrine gland may produce multiple hormones♦A single hormone may be secreted by more than one endocrine gland♦A single hormone may have more than one type of target cell and may induce more than one effect♦Secretory rate may vary considerably over time♦A single target cell may be affected by more than one hormone♦A single chemical messenger may be a hormone or a neurotransmitter♦Some organ are purely endocrine while other may have nonendocrine functionsIntroductionPrinciples of Animal PhysiologyEndocrine System▪ Classification of hormones▸ Peptide hormones - 3 or more amino acids♦ Hydrophilic▸ Steroid hormones - derived from cholesterol♦ Lipophilic▸ Amine hormones - single amino acids♦ Hydrophilic▸ Endocrine-disrupting chemicals (EDCs)♦ Nonnative hormonelike substances♦By-products of manufactured organic compoundsIntroductionPrinciples of Animal PhysiologyEndocrine System▪ Peptide hormone - eg: Insulin▸ Synthesis - RER, preprohormone▸ Packaged in vescicles▸ In Golgi apparatus, pre to pro hormone then to hormone and fragments▸ Released into ECF when cell is signaled to do so▸ Transported in blood, half-life - minutes▸ Mechanism of action - bind to cell surface receptors. Many use cAMP and some use tyrosine kinase▸ Action - open or close membrane channels or modulate metabolic enzymatic activity or transport IntroductionPrinciples of Animal PhysiologyEndocrine System▪ Peptide hormone synthesis, packaging, and releaseIntroductionPrinciples of Animal PhysiologyEndocrine SystemIntroduction▪ Steroid hormones, eg: estradiol▸ Synthesis - SER, lipophilic, sythesized as needed▸ Found bound (inactive) to protein carriers in blood▸ Half-life - hours▸ Mechanism - diffuses across cell membrane to cytoplasmic and nuclear receptors. Interact with DNA▸ Slow response by cells - hoursPrinciples of Animal PhysiologyEndocrine System▪ Action of Steroid HormonesIntroductionPrinciples of Animal PhysiologyEndocrine System▪ Steroidogenic pathwaysIntroductionPrinciples of Animal PhysiologyEndocrine System▪ Amine hormones▸ Nitrogen-containing▸ Most derived from tryptophan or tyrosine▸ like peptide hormones (catecholamines) or like steroid hormones (thyroid hormones)▸ Thyroid hormones: produced