chapter 3 Biological foundations

Transmission

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Unformatted text preview: onsout,whichbringsthe membraneintoarefractoryperiod ApumprestorestheK+andNa+ratiosbacktoitsoriginalstate Duringtherefractoryperiod,themembranecannotdischargeanotheractionpotential Thenervoussystemdifferentiatesbetweendifferentstimulusthroughthenumberofneurons firingaswellastherateoffiring Psych 1000 My Notes Page 14  ­  ­  ­  ­  ­ firingaswellastherateoffiring TheMyelinSheath Themyelinsheathcoverstheaxons Itisafatty,whitishinsulationlayerderivedfromglialcells ItisinterruptedbythenodesofRanvier wherethemyliniseitherextremelythinorabsent Inmyelinatedaxons,electricalconductioncanskipfromnodetonodetoaccountforhigh conductionspeedsofmorethan300kmperhour Multiplesclerosis How Neurons Communicate: Synaptic Transmission  ­ Theneuronsarenotinphysicalcontact,butcommunicatedatasynapse  ­ Theneuronsrelasedchemicalsfromoneneurontothenext  ­ Thereisagapcalledthesynapticcleftbetweentheneuronandthedendriteofthenextneuron Neurotransmitters  ­ Neuronsproduceneurotransmitterswhicharechemicalsubstancesthatcarrymessagesacross thesynapsetoeitherexciteotherneuronsorinhibittheirfiring  ­ Thishappensin5steps 1. Synthesis:chemicalmoleculesareformedinsidetheneuron 2. Storage: moleculesarestoredinchamberscalledsynapticvesicleswithintheaxon terminals 3. Release:themoleculesarereleasedinthesending(presynaptic)neuron 4. Binding: themoleculesbindatthereceiving(postsynaptic)neuron 5. Deactivation: Excitation,Inhibition,andDeactivation  ­ Thebindingofatransmittermoleculecaneitherexcitethepostsynapticneuron(through depolarization)orinhibititthroughhyperpolarizationbyallowingpotassiumionstoflowoutof theneuronornegativeionssuchaschloridetoflowintotheneuron  ­ Neuronsareconstantlybombardedbyexcitatoryandinhibitoryneurotransmittersfromother neuronsandtheirinterplaydetermineswhethertheactionpotentialfires  ­ Aneurotransmittercontinuestoinhibitorinhibit...
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This document was uploaded on 02/26/2014 for the course PSYCHO 1000 at UWO.

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