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11 Cards in this Set

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Char. of Propagated Action Potential
1. transient voltage change

2. travels along axon in single dir. (=propagation)

3. electrical currents flow (ions, not wire)
Nernst Potential eqtn.
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)
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
How steady state is maintained in resting cells
Na wants in and K wants out

active transport counteracts
threshold potential
where 1/2 of depolarizations will lead to complete depol. and reversal of memb. potential to positive-> transient hyperpolarization-> repolarization
subthreshold depolarizations
stationary
and
graded: "not all-or-nothing"
and
non-propagated:
cable properties of cell
causes stationary potentials with sub-threshold depol.

b/c memb allows current to flow thru it: not a perfect insulator & current is dissipated
action potential: permeabilities
membrane permeability:
-mostly to K+ in resting state
-mostly to Na+ durig action potential
therefore: perm. of memb. dep. on transmemb. potential
refractory period
Pk/Pna ^ than resting and Pna can't be increased by depol.-> can't gen. action potential

limits the # of impulses/sec. of axon
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!
Hodgkin Cycle
hypopolarization-> ^GNa-> entry o Na-> more hypopolarization

-> spontaneous vGNa
=Na Inactivation
Gk>>GNa