action potential and LA Flashcards
resting membrane potential
-70mV
ICF or ECF more negative?
ICF
sodium potassium poump
3 sodium out
2 potassium in
1 atp
Resting membrane potential is mainly driven by what
K+ diffusing out through K+ channels
resting membrane is very permeable to K+
what does sodium potassium pump do
it also maintians the resting membrane potential at -70
electrogenic
means generates a charge.
Na-K pump generates a charge
upstroke caused by
sodium diffusing in
downstroke
cause by potassium diffusing out
ion channel gates are controlled by?
ligands
voltage
3 states of sodium channels
open, resting, inactivated
m gate vs h gate when the channels are open, closed and in refractory
close -> m gate close h gate open
open -> both open
refractory -> m gate open h gate close
when does sodium channel open?
when it reaches threshold of -55
when does h gate close?
when membrane potential reaches +35 ie the peak
no more sodium can pass
when does potassium channel gate open
opens at the peak ie +35mV
what is the purpose of the refractory period
- ensure AP is in one direction
- limits maximum firing frequency
- prevents summation of AP
