homeostasis notes

INTRODUCTION · conditionsinourbodiesareconstantlychanging· mechanismsinthebodyhelptoadjustand preventchangeswithinourbodiesfromgoing beyondnormal· thisisknownashomeostasis ⊥themaintenanceofaconstantinternalenvironment inthebody INTERNALCONDITIONSTHATCOULDCHANGE · bloodglucoseconcentration 1)lowbloodglucoseconcentrationleadsto insufficientenergy 2)highbloodglucoseconcentrationcancausedamage tobloodvessels ⊥persistenthighbloodglucoseconcentration isasignofdiabetes waterpotentialofbloodplasma 1)higherwaterpotentialthancells ⊥cellsburst/lyse2)lowerwaterpotentialthancells ⊥cellsshrink/crenate· bodytemperature 1)rateofenzyme-catalysedreactionsaffected

NEGATIVEFEEDBACKLOOP · homeostasisismaintainedbyanegativefeedbackloop achangetothenormalstateactsasastimulus ·stimulusisdetectedbyareceptor,whichwillactivate correctivemechanismstorestoreconditionstonormal · afterconditionsarerestored,thecorrectivemechanisms stop ､ component set-point(norm)thenormalconditiontobe maintained changeininternalorexternal stimulusenvironmentthatthebody reactsto receptordetectsthestimulus triggersappropriateresponses controlcenterbyeffectorstorestore constantinternalenvironment carriesoutresponsesas effectordirectedbythecontrol center correctivemechanismmadeupofresponse(s)that returnconditiontonormal negativefeedbackisaprocessthatbringsabout anoppositeeffecttothechangefromthe normalcondition

' _ _‰ ⾮ θ ਷ ⾮ ⾮ Ψ∅ e ∞ >ร ¤ ⾮¤ θ ǒ⾮ ⾮ = รี ' tσ ¤ৈ '

THERMOREGULATION · receptorthermoreceptors 1)thermoreceptorsintheskindetecttemperaturechanges intheenvironment 2)thermoreceptorsinthehypothalamusdetecttemperature changesintheblood ·controlcentre 1)hypothalamusinthebrain 2)monitorsandregulatesbodytemp. 3)receivesinformationabouttemp.changesfrom: thermoreceptorsintheskin thermoreceptorsinthehypothalamus· correctivemechanisms 1)shivering sudden,uncontrolledmusclecontractions· increasesrespirationinmusclecells,thusincreasing rateofreleaseofheatenergy2)sweating Sweatglandscanbemoreactiveorlessactive moreorlesssweatisproducedfromthesweatgland, throughthesweatductandoutofthesweatpore· heatislostasthewaterinsweatevaporates thisleadstoacoolingeffectontheskin

3)vasoconstrictionandvasodilationofarteriolesintheskinwhenbodytemperaturerisesabovenormal,· vasodilationofarteriolesintheskinallowsmore bloodtoflowthroughthecapillariesnearthesurface oftheskin-aretotherelaxationofmusclesinthewallsofthe arterioles· thisallowsmoreheattobelostthroughthe skinsurface whenbodytemperaturedoorsbelownormal,· vasoconstrictionofarteriolesintheskinleadtolessbloodflowingthroughcapillariesnearthe surfaceoftheskin~ duetocontractionofmusclesinthewallsofthearterioles· thisreducestheheatlostthroughtheskinsurface 4)hairerectormusclescontrast/relax contractwhenexternaltemperatureiscold 1)leadstoproductionofgoosebumps 2)inhairymammals,theraisedskinhairtrapsa layerofairnexttoskintoactasalayerof insulation relaxwhenexternaltemperatureiswarm Forhumans,thisisnotasignificantcorrective mechanisminresponsetotemperaturechangesaswedonothavelongenoughhair