Endocrine System

Three functions
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Pathway of formation of T3Thyroglobulin (protein) recreated by principal cells under the influence of thyrotropin or thyroid-stimulating hormone (TSH) --> Tyrosine incorporated to form T4 --> T4 goes into circulation --> degrade or converted to more active T3 form4 Major functions of TGMetabolism, Growth and metamorphosis, Molt, reproductionTG Metabolismelevate oxygen consumption and heat production by tissues (increase basal metabolic rate) do this through increase in plasma membrane (especially in mitochondria) and by increase in molecular activities of membrane proteinsTG Growth and Metamorphosis What happens in humans if there is too much or too littleHYPOthyroidism: underproduction of hormones; stunted growth and mental retardation in human infants called CRETINISM HYPERthyroidism: overproduction of hormones; heightened activity, nervousness, bulging eyes, rapid weight loss (GRAVE'S disease)TG MoltMolt: loss and subsequent replacement of hair or feathers in mammals an birdsTG ReproductionElevated levels of thyroid hormones= gonad maturation and oogenesis and spermatogenesis EXCEPT in amphibians: thyroid hormones arrest thisUltimobranchial body and Parathyroid Gland What is the difference between the two?both centered on Ca2+ metabolism Ultimobranchial body --> secretes Calcitonin (thyrocalcitonin), LOWERS blood levels of calcium Parathyroid Gland --> secretes parathryoid hormone (parathormone), ELEVATED levels of blood calciumWhere are Ultimobranchial body found?Not in cyclostomes Parafollicular cells (C Cells): incorporated directly into the thyroid, form a small, dispersed population of C cells scattered amongst the principal cells in the walls of the thyroid folliclesParathyroidlocated on the thyroid or dispersed along the major veins in the neck Absent in fish Chief Cells: the most abundant cell type, source of parathormone Oxyphil cells: present in humans, unknown functionWhy calcium is importanteggshells, antlers, bone strength, prevent muscle spasming, etc.Adrenal Gland...what is important about it?Composite gland derived from two phylogenetic sources 1) Adrenocortical tissue: produces corticosteroid hormones 2) Chromaffin tissue (chromaffin bodies): produces catecholaminesWhat are corticosteroid hormones? CateogriesBelong to class of steroids (3 Categories) 1) mineralocorticoids: water reabsorption and sodium transport by the kidney 2) Glucocorticoids: metabolism of carbohydrates 3) Reproduction: estrogens, androgens, progesterones3 reproductive steroidsEstrogen: stimulates development and vascularization of female reproductive tract Androgens: masculizing agents and promote development of secondary sex characteristics Progesterone: maintain pregnancy and uterine wallWhat do the Chromatin tissue produce?Produce catecholamines epinephrine (adrenaline) and norepinephrineMain points of Phylogeny of Adrenal GlandAmniotes: forms a distinct structure located on or close to the kidneys Reptiles: adrenocortical tissue receives its own arterial and venous blood supply, does not rely on kidney for distribution Mammals: combine tissues form a cortex (from adrenocortical tissue) and a medulla (from chromatin) to create a composite adrenal gland (suprarenal)Adrenal Gland Function: Outer most zoneZona glomerulosa --> kidney secretes RENIN --> stimulates release of mineralocorticoids (aldosterone) --> reabsorption of sodium --> increase concentration gradient --> restore fluid volume in blood and tissueAdrenal Gland Function: middle zoneZona Fasciculate --> Adrenocorticotropic hormone (ACTH) released by pituitary --> stimulates secretion of glucocorticoidsAdrenal gland funtion: inner zoneZona Reticularis: controlled by the pituitary to secret androgens and additional glucocorticoidsAdrenal Gland...what special thing do mammals have?Fetal zone: occupies the periphery of the adrenal cortex prior to birth produces precursor to estrogen in placenta failure to fetal zone to function terminates pregnancy --> premature birthWhat is the most important function of the adrenal gland? Definition/vocab wordCoordinate response to stress Emergency life history state: takes minutes or hours to develop, triggered by unexpected environmental stressors that are not immediate threats Primarily adrenal glucocorticoidsPancreas...what kind of structure? Composed of?Composite structure consisting of exocrine an endocrine portions Exocrine portion: consists of acini: secrete digestive enzymes into ducts Endocrine: pancreatic islets (islets of Langerhorns): masses of endocrine cells embedded within exocrine pancreasPancreatic Islets: Cyclostomes, Teleosts, other vertsBony fishes: isolates masses of pancreatic tissue scattered along the liver, gall bladder, bile ducts, abdominal blood vessels, and surface of the intestines Principal islets: separate islets are gathered into a single mass (few bony fish) Most tetrapods: endocrine islets distributed in small clumpsWhat are the four cells of the pancreas?1) B cells: produces insulin, controls metabolism of carbohydrates, fats, proteins 2) A cells: produce glucagon, breaks down fats (more important that insulin in birds and lizards) 3) D cells: produce somatostatin, inhibits secretion of both insulin and glucagon 4) PP cells: secretes pancreatic polypeptide after a protien-rich or protein fat mealDiabetes mellitus Related to..insulin production is too low, glucose is unable to enter cells, build up in blood, eliminated in urineHypoglycemia vs. hyperglycemiaHypoglycemia: blood levels of glucose fall, and intracellular levels rise Hyperglycemia: elevated blood levels of glucoseAnother name for the pituitary gland Found in which organisms?Hypophysis (hypo-under; physic-growth). Beneath the brain Found in ALL vertebratesWhere are pituitary hormones produced? Stimulated by?In the hypothalamus (specifically, the axons of neurosecretory neurons) I think this is wrong the neurohypophysis is supported by the pituicytes ""cells of the adenohypophysis synthesize pituitary hormones" Neurohormones from the hypothalamus (releasing hormones or release-inhibiting hormones) stimulate itNeurophysis (what does this mean????) Two hormones synthesized by neurosecretory cells of the hypothalamus1) Vasopressin: acts on smooth muscle in the walls of peripheral arterioles, causing them to restrict; also called ADH; resistance to blood flow --> increased blood pressure; makes walls of renal collecting duct more permeable --> concentrated urine; diabetes insipidus 2) Oxytocin: targets myometrium (smooth muscle layer of the uterus) and mammory glands; rhythmic smooth muscle contractions (think birth and suckling baby)Adenohypophysis: 6 major hormonesGrowth hormone, prolactin, thyrotropin, gonadotropin, corticotropin/adrenocorticotropic hormone (ACTH), Melanophore-stimulating hormone (MSH)Growth HormoneTargets the liver, increased protein synthesis, mobilization of fatty acids, decreased glucose utilization Pituitary dwarfism in young: deficient levels Pituitary giantism: excess levels in young Acromegaly: in adults, disproportionate proliferation of cartilage from excess GHProlactinpromotes development of the mammary glands and lactation during pregnancy Birds: stimulates lipid synthesis during pre migratory fattening and supports brooding behavior Stimulates appearance of Brood patch: defeathered, highly vascularized region of breast skin placed against incubating eggs Crop milk: nutritional fluid produced in the crop and fed to fledglingsGonadotropins1) FSH: induce development of selected ovarian follicles/ initiate & maintain spermatogenesis 2) Luteinizing hormone: finalize maturation of ovarian folliclesCorticotropin/Adrenocorticotropic hormone (ACTH)stimulates cortex of the adrenal gland to release glucocorticoidsMelanophore-stimulating hormone (MSH) Lots of vocab what is actual hormone calledtargets melanophores (pigment cells of the skin) stimulation --> pigment melanin disperse into fixed cytoplasmic pseudopods of the melanophores to darken skin melatonin: actual hormone that affect melanophoresGondads: Males & FemalesMales -->Interstitial cells (Leydig cells): cluster between seminiferous tubules, produce androgens Females --> principle hormones are estrogen and progesteronePineal Rhythmsdorsal invagination of midbrain involved in detecting seasonal or daily light schedules regulate reproductive cycles circadian rhythms: daily rhythmsWhat are the secondary endocrine glands? two types?play a central role in activities other than endocrine regulation; release chemicals carried by the vascular system to responsive tissues GI & kidneysGI List the hormonesProduce chemicals that stimulate or inhibit target tissues in the GI tract or related digestive organs (liver, pancreas) **** recreated directly rather than through ducts. This is what makes them secondary **** Gastrin, secretin, enterogastrone, CCKGastrin released by what? does what?released by gastric mucosa when food enters stomach enters blood --> transported to stomach --> stimulates secretion of gastric juiceSecretin released by? stimulates? Does?released by intestinal mucosa when the stomach empties the churned and acidified food into the duodenum stimulates pancreas release alkaline pancreatic juice that buffers the acidic chyme from stomachEnterogastrone released by? Does?released by intestinal mucosa, inhibits further gastric secretion and mobilityCholecystokinin (CCK) or CCK-PZ What stimulates its release from where?fats, proteins, and acids stimulate the secretion from the intestinal mucosa stimulates a much of stuff related to gallbladder --> ejection of bile stimulates pancreas to secrete pancreatic juice containing digestive enzymesEnterocrininreleased by intestinal mucosa, increases the production of intestinal juiceKidneys..what secondary glands?Juxtaglomerular cells Renin Angtiotensin IIJuxtaglomerular cellsBP drops, cells wrapped around renal arterioles release the hormone reninreninsets in motion a cascade of changes that eventually result in elevating the blood pressure angtiotensiongen -->angiotensin 1 --> angtiotensin IIAngiotensin IIvasoconstrictor, also increases blood volume by stimulation of the release of aldosterone from the adrenal gland more reabsorption of sodium --> increased water reabsorption --> rise in blood volumeErythropoietinstimulates red bloods cells when there are reduced oxygen levels passing through kidneys elite athletes take artificial levels to increase preformance