A2 Unit F214 - Communication, Homeostasis and Energy
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Summary OCR A Level Biology A* Neuronal Communication Detailed Notes
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A2 Unit F214 - Communication, Homeostasis and Energy
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OCR
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A2 Unit F214 - Communication, Homeostasis and Energy
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s 3 I neurones
specialisednervoussystem
cents
ie
initialis niiatiifuisesaroundthebody all with along
fibre axon cellbodywithnucleus organelles axonterminalwithnerveendings to allow
connections withmanyothern ewones receiveimpulses toroomnetworks communication
some are myelinated axoninsulated by myelinsheathformedby specialised Schwanncells
thatwraparoundneurone withsmalluninsulatedsections nodesofRanvier forcesimpulses to
jumpbetweennodes speedsuptransmission us uninsulated impulsetravelsalongwholelength
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Fattyimpulsesreceptors cus
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laws
cones inretinadetect lightintensit
photoreceptors light eye lightenergy electrical energy
chemoreceptors chemicals hypothalamus chemicalenergy electrical detectchemicals bodytempinblood
mechanoreceptors stretching bloodvessels kineticenergy electrical detectmusclestretch mechanicalstrain
baroreceptors bloodpressureaortacarotidartery kineticenergy electrical directlevelas stretch ofvascularwalls
osmoreceptors bodytwids hypothalamus chemicalenergy electrical detectwater torrentofblood
auditoryreceptors sound ear soundkinetic electrical detect sound movement andorientation
Pacinian corpuscles Pacinian corpusclesfoundatendof
mechanoreceptors found sensoryneuronaxons madeofmany
deepin skinastingers layersof membraneseparatedbyge
solesofnet joints tendons containing Nations
respond to
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pressurechanges onoutsideof membrane resting
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sodium channelsopen Natentersa
producedbysensory 3 Nat Howsintoneurone establishing
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theaxon membrane generatorpole
s 3 3 Resting potentials
in a resting axon notcurrently transmitting impulses inside theaxon has a Ove electricalpotential vsoutsi
this differente theresting potential potential difference 70mV established maintained by 2 factors
Activetransport of Natand kt carrierproteins sodium potassiumpumps use ATPtoactively
nsport swatout of the axon forevery 2kt they activelytransportin higherconc of
veionsoutsideaxon maninside electrochemical gradient establishedby movement of ionsvia
di in potassiumpump 2 Differentialmembrane permeability selentiveproteinchannelsin cell
racemembraneofneurons allowsodiumand potassiumionstomoveacrossby facilitated
fusion But proteinchannels are less permeable to Nat man kt so kt ions can diffuse
okdowntheirconc gradient outof meaxon at a fasterrate mansodium ions
5 3 4 Action Potentials
nervesignals causedby rapidmovement of Nat and kt acrossmembraneofaxon the
resultantbriefchange in distributionof electri inargeacross thecellsurfacemembrane
voltage gated channel protein open close depending on electrical potential across axon membrane letsionsthro
e SEMI note c animism io e imEtn inroco
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iii iii is n i
morechannelsopen more Nat moredepolarisation positivefeedback actionpotentialreaches potentialof 30mV
ii
3 REPOLARISATION 1msafterpotentialdifferencereaches 30mV all Natchannelsclose AND kt voltagegatedchannel
rokins insectionofaxonmembrane open allows diffusion of kt out downconc gradient returns p.D.tonormal 70m
4 HYPERPOLARISATION K channels areslowto store toomany kt ditureoutofnewore negativereaba
potentialdifference belones brieflymore ve mannormal restingpotential 70mu
S RESTING POTENTIAL when kt channelsclose he sodium potassium pumprestoresrest po ii
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