Exam 8 Physiology Study Guide 3 21 Endocrine System Other communication system besides nervous system Moves through plasma blood carried signals blood levels tested to see communication Distance is not a problem has widespread effects Regulated by feedback mechanism like proprioception NTs Speed SLOW endocrine neural But has benefits lasts longer more widespread Pathway Gland neuron releases endocrine hormone effector physiological change Endocrine hormone differs in 1 Type how they are created 2 Mechanism of action how they act in the body Types of Endocrines 1 Amine endocrines have nitrogen group All derived from tyrosine C group starting point for all same basic structure Shape and charge important for binding ligands protein deficiency leads to other issues such as neurological Examples T3 and T4 produced by thyroid gland ONLY nonpolar amine endocrines Dopamine produced by hypothalamus Norepinephrine epinephrine produced by adrenal medulla sympathetic 2 Peptide endocrines short amino acid chain Synthesized as prohormone proendocrine inactive form of endocrine Why Protects from doing job within cell messenger must be released Must be exocytosed packed into secretory vesicles can then be processed into active endocrine lose pro prefix Stored in vesicles until signal releases them only release when needed like NTs Released on demand Examples Insulin regulates blood sugar Hypothalamic releasing hormones Pituitary endocrines Gastrointestinal endocrines digestive system 3 Steroid Endocrines NONpolar Synthesized from cholesterol amphipathic everyone has cholesterol needed in body All have same chemical structure multiple rings Relaxed to sex Lipophilic hydrophobic needs binding protein to move through plasma Intracellular receptors bind inside the cell Alters DNA transcription Produced released by gonads adrenal cortex and placenta Production requires steroidogenic enzymes making steroids If not wanted in system can go after enzyme that creates the endocrine Mechanism of Action Endocrines are ligands that go and bind to receptors Hydrophilic bind to membrane bound receptors activate 2nd messenger system Hydrophobic activate DNA transcription Spots for disruption of ligand receptor communication up regulate or down regulate 1 Endocrine ligand synthesis or release 2 Receptor expression can hide them or put out more 3 Alter clearing how long is it present in blood after its released Send out agent to catabolize endocrines and or excrete them peeing to get rid of or to communicate Endocrine levels can be tested in blood AND urine Ex dogs sniffing other dog s buts to determine endocrine communication in body Ex pregnancy tests measure endocrine levels Regulation of Secretion Concentration of substances in plasma monitors chemosensory levels homeostasis Ions like Na K Ca2 Nutrients like glucose needed for energy Neurotransmitters trigger endocrine release ACh stimulates adrenal medulla to release epinephrine norepinephrine NOTE interface between nervous endocrine system hypothalamus Hypothalamic neurons receive input from NTs to release endocrines Other endocrines often cause release of other endocrines to get final response Ex pituitary endocrines stimulate other glands to release other endocrines Structure Components Hypothalamus surrounds 3rd ventricle 4 total part of the brain Contains neurons that release endocrines Master Gland NOT pituitary 2 ways to release endocrines to pituitary anterior posterior Pituitary gland Hypophysis Infundibulum tissue connects bottom of brain to pituitary 2 divisions Anterior adenohypophysis Endocrines released by hypothalamus reach it via portal vasculature 7 endocrines hypophysiotrophic Posterior neurohypophysis Talk of it becoming part of pituitary Via terminals of hypothalamic neurons extension of hypothalamus Doesn t make any endocrines of its own 2 endocrines released this way Communication Overview Stress activates it Hypothalamus releases endocrine 1 anterior pituitary endocrine binds to receptors and releases endocrine 2 gland releases endocrine 3 effector target organs cells response NOTE gland endocrine 3 has 3 jobs create response and negative feedback on E1 and E2 production keeps us from overshooting once endocrine is in system Why do we need 3 groupings So complex Benefits Many opportunities to regulate more opportunity to make adjustments Amplification begins in brain to hypothalamus To have more endocrine made need more production space more cells But can t increase size of hypothalamus much b c in brain Bigger production area out in body where space less limited ex thyroid Few E2s can cause many E3s directly Few E1s can indirectly cause many E3s E1 from hypothalamus hypophysiotropic endocrines 7 impact pituitary gland 5 stimulate it pituitary releases endocrines Released by hypothalamus 1 Corticotropin releasing hormone CRH cortex area in outer adrenal gland Causes anterior pituitary gland to release adrenocorticotropic hormone ACTH E2 in adrenal gland 2 Thyrotropin releasing hormone TRH Thyroid stimulating hormone TSH E2 in thyroid gland 3 Growth hormone releasing hormone GHRH Growth hormone GH E2 4 Gonadotropin releasing hormone GnRH releases 2 E2s Luteinizing hormone LH and follicle stimulating hormone FSH 5 Prolactin releasing factor PRF Prolactin released by pituitary impacts mammary glands NOTE 1 4 release hormones 5 is a recent edition new version of name 2 inhibit it 1 Somatostatin SS opposite of growth hormone releasing hormones 2 Dopamine DA inhibits pituitary s release of prolactin Transmission for all through vasculature system E1 travels to anterior pituitary glands via portal vasculature system binds causes release of E2 anterior pituitary hormones E3 Anterior Pituitary Hormones E2 gland in ACTH adrenal cortex cortisol TSH thyroid T3 and T4 GH GH is a unique E2 doesn t just go to liver to release endocrine can impacts many organs tissues directly Athletes get injections to try to enhance performance liver plus IGF 1 insulin like growth factor 1 Need more proteins to grow enzymes for processes base for many ligands Need bigger muscles for bigger loads Channel energy for protein synthesis via carb lipid metabolism Converts fat carbs into proteins Like rolie polie kid sprouting during growth spurt GH kicks in and fat used to fuel upward growth FSH LH gonads sex hormones Prolactin mammary glands increase breast tissue milk NOTE For following hormones E1 is UNKNOWN Present in humans but don t know action Beta lipotropin In
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