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11 Cards in this Set
- Front
- Back
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Char. of Propagated Action Potential
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1. transient voltage change
2. travels along axon in single dir. (=propagation) 3. electrical currents flow (ions, not wire) |
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Nernst Potential eqtn.
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Body temp (T=37 deg):
Ex=(61mV/Z)log([x]o)/([x]i) Room Temp(T=20 deg): Ex=(58mV/Z)log([x]o)/([x]i) |
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Membrane permeability to common cell ions
resting cell potential why? |
K>>>Na
-90mV: closer to K (-97mV) b/c cell is more permeable to K ions |
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How steady state is maintained in resting cells
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Na wants in and K wants out
active transport counteracts |
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threshold potential
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where 1/2 of depolarizations will lead to complete depol. and reversal of memb. potential to positive-> transient hyperpolarization-> repolarization
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subthreshold depolarizations
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stationary
and graded: "not all-or-nothing" and non-propagated: |
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cable properties of cell
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causes stationary potentials with sub-threshold depol.
b/c memb allows current to flow thru it: not a perfect insulator & current is dissipated |
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action potential: permeabilities
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membrane permeability:
-mostly to K+ in resting state -mostly to Na+ durig action potential therefore: perm. of memb. dep. on transmemb. potential |
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refractory period
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Pk/Pna ^ than resting and Pna can't be increased by depol.-> can't gen. action potential
limits the # of impulses/sec. of axon |
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causes:
Upswing Downswing of action potential |
up: Na ions rushing in
down: K ions moving in -pump only there to equalize excesses -would work 10^6 times w/o it! |
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Hodgkin Cycle
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hypopolarization-> ^GNa-> entry o Na-> more hypopolarization
-> spontaneous vGNa =Na Inactivation Gk>>GNa |
