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Cards In This Set
| Front | Back |
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Action Potentials
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Bursting, accommodating, single spiking
frequency and patterns |
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Action Potentials
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Threshold potential = - 45mV
Rising phase - depolarization Overshoot - positive inside Falling phase - repolarization Undershoot - after hyperpolarization |
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Greater current
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Greater depolarization, more and faster AP firing
no increase in AP amplitude |
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Depolarization
Repolarization and hyperpolarization |
Influx of Na+
efflux of K+ |
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Action Potential in Theory
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At Vm huge driving force of Na+
Rising phase - inward of Na+ Falling phase - outward of K+ |
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Voltage Gated Sodium Channels
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Four homologous domains 1-4
1 continuous polypeptide with 6 transmembrane a-helices 1pore loop/domain 1 voltage sensor/domain (S4) each pore loop contributes to 1/4th of selectivity filter 1 activation gate/domain 1 inactivation loop/domain |
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Sodium Channel
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Open when threshhold is reached, open with little delay, open for 1msec and inactivate, cannot be opened until Vm returns to rest
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Asolute refractory period rule
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Time period between channel inactivation and time it takes for the Vm to repolarize and Na+ channels to deinactivate takes 1.5msec
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K+ vs Na+ Channels
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Both open in response to depolarization, Na+ open fast .2msec, K+ open slower 1msec
Na+ undergo voltage dependent inaction, K+ does not Takes 1-2msec to return to activatable state |
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Tetrodotoxin
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Puffer fish
Bind to Na+ channel and block its pore Block Na+ conductance |
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Anesthetics
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Cocaine
Lidocaine - bind inside sodium channel pore reduce Na+ influx, only inhibit when channel are open |
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Spike-Initiation Zones
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Sensory nerve ending, and axon hillock
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Propagation of Action Potential
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Orthodromic - AP travels down axon to terminal
antidromic - backward propagation of AP |
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Nodes of Ranvier
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Diameter constricted packed with NFs and MTs
voltage-gated na+ channels in axon membrane at nodes K+ located adjacent to nodes under myelin sheath Saltatory conduction |
