Phis 206 1nd Edition Exam 3 Study Guide Lectures 29 37 Part 4 Physiology Notes Neural Communication very discrete can stimulate inhibit a single cell local stimuli Instantaneous cut on Instantaneous cut of Endocrine System endocrine ductless secrete directly into circulation exocrine ducts glands cell secrete messengers into blood stream which then goes throughout the body to target Doesn t usually involve cells that are close to each other not anatomically connected Long term regulation Characteristics that differ from Neural Takes much longer to get to target When it gets there it doesn t get there abruptly Takes awhile to reach full amplitude gradual increase decrease in concentration When stop secreting it lasts in blood stream for awhile The message is difused some hormone acts on many diferent cells global simuli Hormones messenger chemicals secreted by endocrine system which is secreted straight into bloodstream therefore the Endocrine Glands are also called ductless glands there are instances when the nervous system neurons releases hormones into bloodstream instead of target cells and they are known as Neuroendocrine cells and the hormones that release are called Neurohormones Basic Principles They are practically important in things that have to be maintained over long periods of time this is important because in Neural System receptor fatigues or adapts so they are not good choices for maintaining things Things that are under endocrine control total body water blood glucose level Things that make up endocrine system consists of glands that are not connected or anatomically disconnected and work as a group because they are held together by circulation there are hormones that are released just to control other secretion of other hormones are called Tropic Hormones Hormones that mainly act on things outside endocrine system called Nontrophic Hormone some endocrine glands have more than one cell in them so they secrete more than one type of hormone Very common for a hormone to have efect on more than one type of cell Hormone Classes work at low concentrations Determined by Chemical Structure 1 Peptides 2 Steroids 3 Amines Useful grouping because each class have similarities in how a they are synthesized b what its stored in if it is c how they get secreted d how they are transported e what it does when it gets there Peptide Hormones basically small proteins chains of amino acids too big to cross cell membranes synthesized for export from cell synthesis happens on ribosomes as in active precursors Get transported through cell in ER When arrive at Golgi they get enclosed in membrane and get stored as vesicles When it is stimulated the packages get released somewhere between last one and here get turned into hormones All water soluble they dissolve in plasma with no trouble and that s how they travel in blood they do not get into cells because large water soluble small enough to difuse in capillaries When they get to target cell there have to be structures on the external surface of the target cells called receptors that the hormone can interact with Secondary messenger carries message into cell any cell that doesn t have receptor won t be efected If gave a peptide orally it would be destroyed in stomach meaning you can t use them orally as therapeutic devices Hormone and receptor is internalized by lysosome and degraded into amino acids Steroid Hormones Unlike peptides they are fat lipid fat soluble meaning they can get into cell can difuse right across There is no way for cell to synthesize and store them so there is not step of storage to wait for stimulus Instead when cell gets stimulated then it starts producing steroid and release them Have specific carrier proteins in plasma which steroid bind tightly to them it behaves as if proteins didn t exist hormones would end up in the walls of gland used like taxies When they get to target cell receptors allow carrier proteins to release steroid then it difuses in get to nucleus get to proteins that bind to steroids to steroid which get in DNA which activate genes Remains tied to proteins until it encounters a place that causes them to release from protein Because steroid cross membrane easily and they are not destroyed in stomach they can be given orally Amines Fairly diverse group so not able to produce a list of properties Characteristics of all Hormones 1 Efective at very low concentrations 10 8M to 10 12M much more potent unlike other systems 10 3 to 10 1 Concentration of hormone in blood stream represents a balance in it bring added of subtracted to blood stream it almost never means that one is acting more than another one goes up the other goes up too if a hormone concentration changes it s usually due to secretion Operate on negative feedback loops Endocrine Disorders include situation in which blood concentrations are pathologically high secrete too muchhypersecretion Plasma levels are low secrete too little hyposecretion Target cell responses abnormal some efects are if concentrations were low When plasma level is too low give them hormone When too high depends on reason why it is too high Tumor is not subject to same regulations as endocrine gland When gland secreting too much have to find out why it is not regulating Down regulation with peptide hormones they bind to surface receptors then they get internalized broken down then resynthesized Down regulation is more are being internalized than being resynthesized Causes desensitivity in target cells to hormone Can be caused by chronic high levels of hormone Hypothalamus secretes tropic hormones have cells that secrete through the posterior Infundibulum connects hypothalamus to pituitary gland hypophysis Pituitary Hormone created by hypothalamus released by pituitary gland Anterior pituitary Adenohypophysis glandular part Posterior pituitary Neurohypophysis consists of axon terminals of hypothalamus neurons An endocrine gland that has function mechanism in brain Many animals have MSH Melonocyte Stimulating Hormone in intermediate lobe has no known function in humans Pathological case in which skin color darkens there is a connection or identity to the posterior pituitary and hypothalamus relationship close hypothalamus is main link between neural and endocrine Blood Flow arteries capillaries hypothalamus Blood in Pituitary have already been in hypothalamus hypothalamohypophisio portal system Hypothalamus in good position to secrete things that influences the