Potential Chart

Potential Chart - and it is still strong enough to reach...

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Re sti ng M em bra ne Po ten tial Local Potential Dentrites and Soma Action Potential axon
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Random Facts * Betw een 40mv and 90mv (usua lly 70mv ) * cell mem brane more perm eable to K+ than Na+ * large cytop lasmi c anion s make ICF more negat ive SHORT DISTANCES (short lived local distances) Graded Decremental Reversible Exitatory or Inhibitory LONG DISTANCES (self propagating) All or none Nondecremental irreversible *many more voltage regulated gates on axon than on dendrite *Way neurons communicate *ONLY excitable membranes
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Na+ And K+ DEPOLARIZATION Chemical (ligand) binds to receptor on neuron and stimulates opening of Na+ gates Na+ flows in and makes cell voltage closer to 0 Na+ pushes for short distances among plasma membrane toward trigger zone Not enough Na+ gates on dentrites to reach threshold, once it gets to axon hillock there are many more voltage-regulated gates (allowing threshold to be reached) HYPERPOLARIZATION Opposite and makes cell less likely to produce action potential If Na+ reaches trigger zone (axon hillock)
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Unformatted text preview: and it is still strong enough to reach threshold then neuron fires DEPOLARIZATION Na+ gates open faster than K+ gates and Na+ is rushed into cell, as Na+ enters more Na+ gates open (positive feedback). action potential goes from -70mv to +35mV (peak membrane potential) REPLOARIZATION Na+ gates close as K+ gates are all open by time membrane potential peaks. K+ is repelled by positive ICF and leaves cell Resting potential is restored but not ionic distribution HYPERPOLARIZATION K+ gates stay open longer than Na+ gates Result is even though membrane potential is restored, there is more Na+ in cell and more K+ outside cell than normal Corrected by Na+-K+ pump THEN: Opens Ca++ channels in axons synaptic knobs *action potentials spread down axon like a wave *action potential itself does not travel down axon, rather it stimulates new action potential in membrane ahead of it...
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Potential Chart - and it is still strong enough to reach...

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