week 2 notes
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This 10 page Class Notes was uploaded by Alexandra Votaw on Saturday January 24, 2015. The Class Notes belongs to BIO282 at Arizona State University taught by Dr.Bang, Dr. Michel, Dr. Orchinik in Winter2015. Since its upload, it has received 138 views. For similar materials see BIO 282- ConceptualApproachBioMajorsII in Biology at Arizona State University.
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Date Created: 01/24/15
BIO 282 Notes week ofJanuary 20 2015 TEXTBOOK NOTES Chapter 42 Animal Form and Function 425 How Do Animals Regulate Body Temperature Heat ows from hotcold regions similar concept to gradients MECHANISMS OF HEAT CONTROL Can exchange heat with environment in four ways Conduction direct transfer of heat between two physical bodies that are in contact with each other 0 Rate of conduction depends on surface area of transfer steepness of temp diff and how well each body conducts heat Convection heat exchange between solid and a moving liquidgas type of conducUon 0 rate of convection increases as speed of gasliquid increases radiation transfer of heat between two bodies that are not in direct physical contact all objects radiate heat evaporation phase change when liquid water turns to gas 0 leads only to heat loss breaking Hbonds requires heat absorption need to regulate body temp 0 heat stroke overheatinngenatured proteinstehydrationDdeath o hypothermia too codslow enzyme function energy productionljdeath VARIATION IN TH ERMOREGULATION thermoregulation control body temp ability varies endotherm produces adequate heat to warm its own tissues ectotherm relies on heat gained from environment to warm its tissues most animals are something between endotherms and ectotherms homeotherms keep body temp constant heterotherms allow body temp to risefall depending on environmental conditions endothermic homeotherms species produces on heat and maintains constant body temp 0 ie birds and mammals ectothermic heterotherms body temp changes throughout dayseasons 0 ie freshwaterterrestrial invertebrates sh amphibians and reptiles torpor reducing metabolic rate and allowing body temp to drop hibernation when torpor persists for weeks or months at a time torporhibernation allow survival in extreme weather ENDOTHERMS AND ECTOTHERMS A CLOSER LOOK endotherms can warm themselves bc of large amount of heat given off by high rate of chemical reactions high basal metabolic rate 0 retain heat through insulation feathersfur ectotherms have low metabolic rates so they make less heat 0 heat gained by radiationconduction endotherms need more energy rich food TEMPERATURE HOMEOSTASIS IN ECTOTHERMS hypothalamus has separate centers that sense and integrate increasesdecreases in body temp 0 controls blood temp o if mammal is cold sends signals to induce shivering uffing fur or feathers o if mammal is hot sends signals to induce sweatingpanting heat shock proteins speed refolding of proteins after activation caused by dramatic temp spikes that denature proteins in cells 0 negative feedback is used to return to regular body temp Sensor records temperature skin spinal cord hypothalamus Effectors return body tel J 1 B d vessels Integrator compares sensor D39IateDbIOOd ow Wheat loss on input with set point Instructs skin surface effector ConstrictDblood ow lessentheat loss from skin surface decreases hypothalamus 2 Seat glandsshivering StimulatedDevaporationDheat loss on skin Generates heat in muscles 3 Respiration Chemical signals respiratory centers stimulatedljpanting heat loss chemical signals arrive cellsDincrease cellular respirationheat production W COUNTE RCURRENT H EAT EXCHANGERS water conducts heat and easily takes metabolic heat insulate with blubber or fur or specially arranged blood vessels AN EXAMPLE GRAY WALE TONGUES tongue contains bundles of arteriesveins one artery carries warm oxygenated blood from core encircled by smaller veins that bring cold bloochore antiparallel arrangement counter current exchanger uids flow through adjacent pipes in opposite directions 0 heat exchange occurs between oldwarm blood 0 warmertocooler gradient maintained whole timeefficient A MULTIPLIER EFFECT large difference in temperature from one side of the pipe to the other but small difference between two solutions at any point along pipe 0 longer systemgreater difference 0 small difference in heat along pope sum to create overall temp difference Pages 10001001 and 10041005 HOW DO HORMONES COORDINATE RESPONSES TO STRESSORS hormones play a part in short term and long term responses to stress SHORT TERM RESPONSES TO STRESS ght or ight response short term reaction triggered by the sympathetic nervous system epinephrine adrenaline hormone released by adrenal medulla stimulated by sympathetic nerves 0 leads to heightened alertness and increased energy use to prepare body for rapid intense action ie eeing ghting LONG TERM RESPONSES TO STRESS cristol produced in adrenal cortex and ensures continuing availability of glucose for use by the brain during long term stress WHAT DOES CORTISOL DO Manages three main processes lnduces synthesis of liver enzymes that make glucose from amino acidschemical precursors Makes adipose tissue resting muscle resistant to insulin 0 Adipose and resting muscle can39t take sugar out of blood stream Promotes release of fatty acidsfor use by heart and muscle Glucocorticoid regulates blood glucose aka cortisol 0 Causes a decrease in muscle massDweakness o lmpairs wound healingrepresses immune system 493 How is the Production of Hormones Regulated Hormone production is often directlyindirectly controlled by nervous system THE HYPOTHALAMUS AND PITUITARY GLAND Pituitary gland located on the base of the brain and directly connected to the hypothalamus 0 Basis of connection between CNSendocrine system 0 Has 2 parts hypothalanterior pituitaryposterior pituitary o Secretes growth hormones and hormones that regulate production of others CONTOLLING THE RELEASE OF GLUCOCORTICOIDS Adrenocorticotropic hormone ATCH molecule from pituitary gland that affects the adrenal gland 0 Regulatory hormone o lnduces the release if glucocorticoids Corticotropin releasing hormone CRH released by hypothalamus and induces release of ACTH by the pituitary FEEDBACK INHIBITION BY GLUCOCORTICOIDS Glucocorticoids use feedback inhibition suppress their own production Glucocorticoid levels to highDACTH levels decrease Glucocorticoid levels to lowlj ACTH levels increase Cushing39s disease unrelenting stress response that drains the body s protein reserves fatal if not treated PROTEINS IN GLUCOCORTICOID RELEASE Usually CHR productiondaiy rhythm highest level in early morning 0 Allows you to wake up 0 Response to painanxiety l higher CRH and ACTH and cortisol level in blood THE HYPOTHALAMICPITUITARY AXIS AN OVERVIEW Hypothalamicpituitary axis forms 2 anatomically distinct systems Neurosecretory cells release neurohormones under control of brain Posterior pituitary stores hormones Anterior pituitary secretes regulatory hormones CLASS NOTES12115 WHEN DO MAMMALS quotDEFENDquot HOMEOSTASIS Cannon originally proposed regulation of limited number of controlled variables 0 Ie body temp water levels carbon dioxide and oxygen levels NaCL Ca cation sugar and proteins 0 Best example partial pressure of C02 and therefore pH in blood Tropic hormone hormone whose target is an endocrine gland ie all released from hypothalamus Hypothalamusrelease hormoneanterior pituitaryDrelease a hormone target glandDrelease 3rCI hormone TWO COMPONENETS TO STRESS RESPONSE 1 Activation of sympathetic NSrelease of neurotransmitter norepinephrine NE at target tissue a Release of hormone epinephrineadrenaline from adrenal glands medulla 2 Neuroendocrine cascade response leading to release of stress hormone cortisol into blood stream a Hypothalamicpituitary TEXTBOOK NOTES Chapter 49 Chemical Signals in Animals Endocrine system collection of organs and cells that secrete chemical signals into the blood stream Hormone a chemical signal that circulates through body uids and affects distant target cells 491 Cellto Cell Signaling An Overview 0 Chemical signals have longlasting effect while electrical impulses are shorter MAJOR CATEGORIES OF CHEMICAL SIGNALS Chemical signals released from cells separate 0 5 classes of chemical messengers do not coincide with 5 structurally distinct classes of molecules 0 Can be amino acids or lipids etc Peptides or lipids steroids can function as endocrine autocrine and paracrine signals AUTOCRINE SIGNALS ACT ON THE SAME CELL THAT SECRETES THEM Autocrine signals affect same cell that releases them Cytokines amplify response of a cell to stimuli 0 best studied interleukin 2 cytokine synthesizedreleased by Tcell type of white blood cell that is ghting off an infection 0 activates T call to help eliminate infection 0 causes cell to divide repeatedly to increase amount PARACRINE SIGNALS ACT ON NEIGHBORING CELLS paracrine signals diffuse locally and act on target cells near the source cell 0 cytokines can also act as paracrine signals insulin glucagon and somatostatin cross categories too 0 produced in islets of Langerhans 3 distinct populations of cells in pancreas o react as paracrine signals in pancreatic cells to ensure response to changing bloodglucose levels 0 can act as hormones if released into body ENDOCRINE SIGNALS ARE HORMONES endocrine signals carried to distant cells by blood or other body uids glands cells that are organized together to produce endocrine signals 0 can also have cells dispersed throughout an organ NEURAL SIGNALS ARE NEUROTRANSMITI39ERS neural signaling fast because change in action potential is fast and neurotransmitters only have to diffuse a short distance 0 short lived because signaling molecules are broken down taken up NEUROENDOCRINE SIGNALS AT A DISTANCE neuroendocrine signals neurohormones hormones that act on distant cells but created by neurons antidiuretic hormone ADH neuroendocrine signal produced by neurons in hypothalamus 0 act on cells in collecting ducts in kidney 0 help regulate water excretion HORMONE SIGNALING PATHWAYS usually sensory info integrator CNSeffectorshormones can go from sensorDeffector ie plants 0 negative feedback feedback inhibition products of a process inhibits its production 0 regulates all 3 types of signaling pathways direct from endocrine cell direct from CNS or CNS to endocrine in endocrine pathway hormone produced by effector cells feeds back on endocrine cellsinhibits production and slows cellular response 0 also feeds back to integrator neuroendocrine to endocrine signaling pathways have extra regulation 0 endocrine signal can inhibit production of neuroendocrine signals nervous system and endocrine system tightly integrated in celltocell signaling feedback inhibition reduces productionsecretion of hormones WHAT MAKES UP THE ENDOCRINE SYSTEM endocrine glands organs that secrete hormones into the blood stream exocrine glands deliver secretion through outlets called ducts into spaces not in circulatory system 0 most digestive glands in pancreas exocrine cells release digestive enzymes into intestine endocrine release glucagoninsulin into blood stream CHEMICAL CHARACTERISTICS OF HORMONE 3 major classes of chemicals that act as hormones in animals polypeptides amino acid derivatives and steroids lipids with 4 ring structure Secretin polypeptide epinephrine amino acid derivative cortisol from steroid cholesterol HORMONE CONCENTRATIONS ARE LOW BUT THEIR EFFECTS ARE LARGE Hormones have large affect despite small concentration 0 Growth hormone GH large effects in small amounts and controlled by pituitary ONLY SOME HORMONES CAN CROSS CELL MEMBRANES Steroids are lipid soluble polypeptideamino acids not Thyroid gland produces thyroid hormones triodothyronine T3 and thyroxine T4 are derivatices of tyrosine amino acid 0 are lipid soluble lipid soluble hormones pass through plasma membrane and bind to receptors inside the cell polypeptidesmost amino acid derivatives bind to receptors outside the cells HOW DO RESEARCHERS IDENTIFY A HORMONE secretin cell to cell signaling molecule from small intestine o induces secretion of alkaline solution by pancreas hormones from adrenal gland regulate bloodsugar and blood pressure BREAK THROUGH IN MEASURING HORMONE LEVELS Need to nd out how much hormone in blood stream hard to do Radioimmunoassay estimates quantity of hormone in a blood sample by adding radioactively labeled hormones that compete with unknown amount of hormone to bind to antibodies 0 Extremely helpful and used everyday 494 How Do Hormones Act on Target Cells 0 Difference in lipid solubility indicates location of receptors STEROID HORMONES BIND TO INTRACELLULAR RECEPTORS Estrogens steroids that direct development of female secondary sex characteristics 0 Estradiolmostimportant IDENTIFYING THE ESTRADIOL RECEPTOR Estradiol receptor protein bc destroyed by proteinase enzymes 0 ln nucleus not associated with its development 0 Only in estradiol target tissues uterus hypothalamus and mammary glands Hormones only act on cells with correct receptor 0 All steroid receptors are descended from 1 ancestral receptor molecule DOCUMENTING CHANGES IN GENE EXPRESSION Estradiolother hormones affect genes transcription after binding Zinc nger proteins that make physical contact with DNA 0 le estradiol receptor changes gene regulation Hormone response elements speci c sites in DNA upstream from target cells that hormone receptor complexes bind 0 Gene expression changes when hormone receptor complexes binds to it 0 Each hormone receptor complex leads to production of many copies of gene product ampli cation HORMONES THAT BIND TO CELL SURFACE RECEPTORS Signal transduction transducing message given by hormone molecule that binds outside of cell 0 Message changed into inactive form inside cell IDENTIFYING EPINEPHRINE RECEPTOR Epinephrine binds to 2 types of receptors alpha and beta 0 Two types of alpha receptors and two types of beta receptors 0 Total of 4 types in different tissues and different responses 0 Some hormone can trigger effects in different cells WHAT ACTS AS THE SECOND MESSENGER Phosphorylase enzyme that catalyzes a reaction cleaving glucose molecules of glucogen o Switches between active and inactive from when dephosphoryated by other enzyme 0 ln liver 0 Increases in amount when epinephrine added 0 Cyclic adenosine monophosphate cyclic AMP cAMP activates phosphorylase Second messenger nonprotein signaling molecules that increase in inside cell in response to received signals A PHOSPHORYLATION CASACADE Epinephrine binds to receptoractivates Gprotein l Activates adenylyl cyclaseD catalyzes reaction that turns ATP cAMPsignal transduction cascade by binding to cAMPdependent protein kinase Al phosphorylating phosphorylase kinaseD phosphorylates phosphorylase Adenylyl cyclase thought to catalyze 100 cAMP molecules Ampli cation occurs bc transduction cascade CA IP3 DAG 3395 cyclic GMP common 2nCI messenger WHY DO DIFFERENT TARGET CELLS RESPOND IN DIFFERENT WAYS Can have same receptor but diff 2nCI messenger Same chemical messengerljdifferent bc diff factors
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