Fundamentals of neuroscience: cells, axons, and synapses

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Electrotonic Potential SpreadACTION POTENTIALTHRESHOLDCurrentPotential (V)CurrentElectrotonicPotential+20mV0Overshoot-60mVUpstroke0 100 time (ms)-20Threshold-40UpstrokeRepolarisationCurrent-60-80Resting Pot’lThreshold-80Current Pulses2.5 mm0 ms 50 ms 5Voltage-dependent Na + ChannelsSodium Channel StructureDEPOLARISATION“Positive Feedback”or “Regeneration”Na + EntersCellVoltagedependentNa +Channels OPENNote: Voltage-dependent Na + ChannelsINACTIVATEThe Refractory PeriodPERMEABILITY CHANGES DURING THE ACTION POTENTIAL+20+20 V m 0V m0-20Na + K +-20-40mV-60-800 ms 5300MembranePermeabilityorConductancemS/cm 2-40mV-60-80Threshold0Absolute Relative5 msREFRACTORY PERIOD4
PROPAGATION OF THE ACTION POTENTIAL - 1Unmyelinated nerve membranePROPAGATION OF THE ACTION POTENTIAL - 1Unmyelinated nerve membraneExtracellular+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -IntracellularNa +Extracellular+ + - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +- + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - -IntracellularNote• No significant change in ionic concentrations during the action potential.• No change in Na + Pump activity during the action potential.PROPAGATION OF THE ACTION POTENTIAL - 1Unmyelinated nerve membranePROPAGATION OF THE ACTION POTENTIAL - 2Unmyelinated nerve membraneNa +Extracellular+ + - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +- + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Local Circuit CurrentsIntracellularNa +Extracellular+ + + + + + - - + + + + + + + + + + + + + + + + + + + + + + + + + +- - - - - - + + - - - - - - - - - - - - - - - - - - - - - - - -K +IntracellularPROPAGATION OF THE ACTION POTENTIAL - 3Unmyelinated nerve membranePROPAGATION OF THE ACTION POTENTIAL - 3Unmyelinated nerve membraneNa +Extracellular+ + + + + + + + + + + + + - - + + + + + + + + + + + + + + + + + + + + +Na +Extracellular+ + + + + + + + + + + + + + + + + - - + + + + + + + + + + + + + + + +- - - - - - - - - - - - + + - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - + + - - - - - - - - - - - - - - -and so forthK + IntracellularK +IntracellularNote• An action potential is triggered in each portion of the membrane• The action potential can travel in all directions from the initial triggering point.• The action potential cannot immediately reinvade a portion of membrane,because of the refractory period.5
Page 1 and 2: ANAT 3045 Visual NeuroscienceBIOS 3
Page 3: Nernst EquationRTE K =__ZFWhereln__
Page 7 and 8: Action Potential Propagation in Mye

Fundamentals of neuroscience: cells, axons, and synapses

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