Endocrine Part 1
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This 5 page Study Guide was uploaded by De Vs on Wednesday February 25, 2015. The Study Guide belongs to BIL360 at University of Miami taught by Dr. DuBois in Spring2014. Since its upload, it has received 148 views.
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Date Created: 02/25/15
Chapter 16 Endocrine and Neuroendocrine Physiology Hormone carried thru bloodstream has far reaching effects with low conc longerterm effect Can in uence many target cells unlike for neurons A chemical produced and released by nonneural endocrine cells or neurons Get secreted into extracellular uid which diffuses into capillaries Paracrine don39t enter bloodstream In uences nearby cells Autocrine don39t enter blood stream In uence same cell that secretes them endocrine gland organs of secretory cells discrete endocrine cells grouped together into distinct glands diffuse scattered endocrine cells in the tissues of organs that are nonendocrine mammalian ut intermediate glands structure is btwn discrete and diffuse glands islets of Iangerhaans two classes of endocrine cells epithelial nonneural cells release hormones Usually stimulated by other hormones Neurosecretory cells Always signaled to secrete by synaptic input from neurons neurohormones are the secretions Release products by exocytosis into the blood Cell bodies are in the CNS but axons are outside Neurohormones are synthesized in cell body and released at the end of axons neurohemal organ where the axon terminals are contained and neurohormones get released In both invertebrate and vertebrate target cell cell that responds to a chemical signaling molecules May express receptors for more than one signaling molecules Sensitivity depends on number of receptors present and can be changed by upregulation and downregulation sensitivity how a target cell reacts to a hormone Depends on the number of functional receptor molecules the target cell expresses for that hormone biological halflife how long a hormone remains active peripheral activation conversion of hormone after secretion to a more potent form steroid hormone made from cholesterol Secreted by gonads skin and adrenal cortex Alos molting hormones in arthropods Lipid soluble peptide hormone made from chains of AA Antidiuretic hormones insulin growth hormone Vary in size Watersoluble amine hormone modi ed AA Melatonin dopeamine epinephrine preprohormone large precursor molecules are modi ed by posttranslational processing to make it a prohormone and then a mature hormone lipoprotein carrier steroid hormones need help moving through the blood stream LDLs and HDLs cholesterol pregnenolone steroid hormone made by the brain that is a defense against effects of weed Prevents THC from fully activating its brain receptor hypothalamus links the brain to the endocrine system and in uences the pituitary gland anterior amp posterior pituitary anterior adenohypophysis and posterior neurohypophysis Posterior hormones are vasopression and oxytocin which are secreted in response to neural activation Anterior hormones are controlled by releasing hormones RHs and inhibiting hormones IHs from the hypothalamus that are transported into the anterior via the hypothalamo hypophysial portal system The pars nervosa is part of the posterior pituitary gland median eminence part of the hypothalamus where hormones are released and is important for the portal system that connects hypothalamus and pituitary gland The pars nervosa is continuous with the median eminence via the infunidbular stalk The median eminence collect the secretions from hypothalamus before they enter the portal system infundibulum the pituitary stalk Connection of hypothalamus and posterior pituitary that carries axons from the Neurosecretory cells of the hypo down to the posterior pituitary where oxytocin and vasopressin get released releasing and inhibitory hormones is secreted by neuroendocrine cells in the hypothalamus that stimulates secretion of a hormone Inhibitory inhibits the release of a hormone from anterior pituitary adrenal gland cortex medulla endocrine glands above the kidneys Responds to stress hormones glucocorticoids class of steroid hormones cortisone cortisol corticosterone that promote an increase in blood glucose Secreted at adrenal cortex HPA axis Hypothalamus circadian rhythms sends signals to pituitary Pituitary Adrenal Gland An axis is a system where secretions of endocrine gand act on another in a sequence HPA controls glucocorticoid secretion hormonal neural and feedback mechanisms modulate the HPA axis negative feedback hormonal modulation where hormones causes changes in pathway that suppress its own secretion synergism when one hormone ampli es the effect of another Makes enhanced response permissiveness presence of one hormone is required for the other to work antagonism one hormone opposes the action of another mammalian stress response adaptive response to stressful stimuli Suppressing reproduction Glucose conc in blood increases to make energy supply for muscles stressor turns on components of the stress response sympathetic nervous system gets activated in the stress response as well as the HPA axis It releases catecholamines catecholamine epinephrine and norepinephrine Hormones You are responsible for understanding the general function and location of the following hormones discussed in class For a quick summary of each without digging through the text see Appendix K in your book Hypothaamus corticotropinreleasing hormone CRH acts on anterior pituitary Posteriorpituitary vasopressinantidiuretic hormone ADH Anterior pituitary adrenocorticotropic hormone ACTH Adrenal cortex cortisol corticosterone bird Adrenal medulla epinephrine norepinephrine Islets of Langerhans pancreas insulin glucagon 1 Compare and contrast the control systems of the nervous system and endocrine system 0 Both use chemical signals nervous system neurotransmitters released from axon terminals diffuse SHORT distances with pinpointed control The signal is quickly terminated Responses start quickly endocrine hormones travel is blood long distances and in uence large populations of target cells Responses are initiated slowly Responses can be short or last days 2 What is a hormone What criteria distinguish hormones from other chemical messengers A hormone is a chemical produced and released by nonneural endocrine cells or by neurons 0 They are effective in low concentrations and enter capillaries Hormones bind to receptor molecules expressed by target cells Hormones only bind to target cells that express receptor molecules for that hormone 3 Know the three major classes of hormones and their basic chemical properties Know how these are synthesized stored and released see table 161 in your text Peptides they are secreted by EXOCYTOSIS from they are synthesized in rough ER and stored in vesicles the are dissolved in plasma or bound to carrier proteins and they activate GPCR or alter membrane channels Steroids secreted by adrenal cortex gonads skin and placenta they are synthesized on demand and are not stored they are secreted by diffusion thru cell membrane and are transported bound to carrier proteins once at target cell they alter gene expression or initiate transcription Amines 4 What is a hormone s halflife What factors into the halflife and why does it matter Longer half life longer effects on the body Halflife vary depending on chemical class Seconds hours or days long 0 Carrier proteins extend half life by protecting the hormone Magnitude of a hormones effect depends on of receptor molecules and its conc in the blood which depends on synthesis rate and degradationexcretion rate which can sometimes depend on another hormone Lipid soluble hormones have longer half lives than peptide hormones since they are bound to carriers Know the types of endocrine glands discrete diffuse intermediate and cells epithelial neurosecretory Know how the latter are controlled Epithelial endocrine cells are controlled by hormones some like pancreas beta cells get neural input Neurosecretory endocrine cells are always controlled by synaptic input from neurons Understand the anatomy and function of the anterior and posterior pituitary and their relationship to the hypothalamus Pituitary gland is below hypothalamus Two parts are anterior and posterior pituitary Posterior is an extension of hypothalamus and anterior is all nonneural tissue Posterior consist of bundles of axon ends that start in hypothalamus Posterior lobe releases vasopression aka antidiuretic hormone which limits urine production And oxytocin that causes uterus contractions and milk ejection All hormones of anterior pituitary are made within its tissues Only makes peptidespretoeins Two groups of hormones rst effects nonendocrine tissues like growth hormone prolactin MSH Second group is hormones that control other endocrine glands like TSH ACTH LH and FSH and they have tropic suffix The secretions of anterior pituitary gland is controlled by neurohormones secreted by hypothalamus What types of hormones are secreted by the adrenal gland Where is it located in the body What are the general physiological effects of hormones secreted by the adrenal gland The adrenal gland secretes glucocorticoids cortisone cortisol and corticosterone which rare steroid hormones that increase glucose blood conc CRH gets released into capillaries and is carried to anterior pituitary where it stimulates ACTH to get secreted and carried to the adrenal cortex where it stimulates glucocorticoid secretion 0 Understand mechanisms of hormonal modulation negative feedback synergism permissiveness antagonism and how these in uence endocrine glands and other target Ussues Negative feedback is when a hormone causes changes in its pathway that suppresses its own secretion Hormones that are ancillary parts of a pathway can alter a target glands response to a particular hormone through synergism to produce an enhanced response Antagonism is when a hormone inhibits another Permissiveness is when a hormone is needed for the other to work Describe the HPA axis Include the in uence of neural control on this axis neural modulation sensory input and circadian clocks affects HPA axis Neurosecretory cells in hypothalamus secrete CRH into the median eminence hormones can be secreted in pulses with brief periods of high hormone blood conc CRH neurons secrete pulses 23 times an hour neuronal biological clocks in uence hormone secretion too Blood levels of cortisol rise and fall daily and are driven by a circadian clock in the b rain that sends input to the CRH secretory cells 10Describe the adaptive function of the mammalian stress response What parts of the nervous system and endocrine system are involved in the stress response How Understand the deleterious effects of chronic stress 0 During stress response heartbreathing rate increase cognition and alertness sharpens metabolic processes release stored energy oxygennutrients are directed to the CNS and sites in the body that are most stressed Feeding and reproduction are curtailed These are to ensure survival in a crisis 0 When the stressor is gone feedback mechanisms turn off response o If a physical or emotional stressor persists for a long time then responses that are adaptive in the 5 short term become damaging in the long term 0 Within seconds sympathetic nervous system releases norepinephrine and epinephrine catecholamines from sympathetic nerve terminals and the adrenal medulla Hypothalamic neurosecretory cells release CRH into the portal system Followed by ACTH from the anterior pituitary The sympathetic ight or ight and the HPA axis are both activated with intermingled functions CRH not only stimulates ACTH but also acts as a neurotransmitter for the sympathetic nervous system in the brain 0 Phase 1 catecholamine trigger heartbreathing rate and BP increase that increases blood ow to muscles and heart and air into the lungs Blood vessels constrict and divert blood from injury sites epinephrine releases glucose into the blood by breakdown of glycogen Catecholamines inhibit insulin ACTH secretion is increased by epinephrine and CRH and this facilitates preparedness and decreases pain perception Phase 2 glucocorticoids are secreted by adrenal cortex Last 1 hour after response Reinforce release of energy and stimulate liver to use AA to make glucose by gluconeogenesis They stimulates catabolism of fats so fatty acids can be used as alternative energy source Also make AA available for tissue repair o If there is a lot of blood loss then catecholamines stimulate heart and blood vessels to maintain blood pressures and kidney to retain water to conserve uid volume
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