Membrane Electrophysiology: RMP Flashcards
membrane potential
separation of charge across plasma membrane
potential to do work
in millivolts
resting membrane potential
when not sending electrical signals (equilibrium)
-no net ion flow
expressed as intracellular potential relative to extracellular potential
intracellular anions
fixed, so cations balance the charge
impermeable molecules (proteins)
Na+ K+ Pump
electrogenic
ATP dependent ion pump
indirect contribution to RMP maintaining ion [gradient]
what ions have great contribution to RMP?
those with greatest permeability
Exchange rate for Na/K pump
3 Na out and 2 K in
positive outside
more sodium outside/potassium inside
distribution of Na?
greater in ECF
distribution of K?
greater in ICF
electrogenic
sodium/potassium pump that causes a net movement of +1 outside of cell
diffusion potential
due to concentration difference of an ion
-contributes to RMP
distribution of calcium
much more outside cell ECF
distribution of chloride
more outside ECF
-larger concentration difference in skeletal muscles
force acting on an ion?
- concentration (chemical) force
- electrical force
NET force is sum of two
electrical force
depends on membrane potentital and charge on particle
equilibrium potential
unique for each ion
-when chemical and electrical gradients balance out
nernst equation
to predict equilibrium potential for any concentration gradient of an ion
Ex=60/z log10 (Xo/Xi)
log10 (10) = ?
1
log10 (0.1) = ?
-1
net force on ion?
difference between Ex and Vm
potassium equilibrium potential?
-90mV
sodium equilibrium potential?
+60mV
driving force
Vm - Ex
if Vm is more negative?
inward current of cations
if Vm is more positive?
outward current of cations
which ion has greatest driving force?
calcium
at RMP what ways would major ions move?
potassium out
sodium in
calcium in
chloride in
what determines membrane conductance?
number of open channels
-channels are opening, conductance is increasing
rate of ion movement depends on?
external and internal concentrations of ions
transmembrane voltage
permeability of ion
ungated ion channels
leak channels
always open
voltage gated channels
open/close in response to membrane voltage change
ligand gated channels
open/close in response to binding ligand
potassium contribution to RMP?
high K+ inside cell
2 opposing forces - chemical vs electrical
K+ not at EQ
ungated, leak channels always open
NET EFFLUX OF K+
increased K+ conductance?
hyperpolarization
decreased ECF potassium?
hyperpolarization
increased ECF potassium?
depolarization
RMP and K?
very sensitive in change to ECF concentration of potassium
reversal potential
voltage at which current direction is reversed
nernst potential of ion
major determinant of RMP?
potassium
diffusion of K+
concentration - OUT
electrical - INSIDE
RMP and Na?
high sodium outside cell
low permeability to Na+
large force on sodium (far from EQ)
is resting membrane potential sensitive to changes in sodium?
NO
increase or decrease in ECF sodium?
minimal effect on RMP
sodium concentration gradient
INSIDE cell
sodium electrical gradient
INSIDE cell
skeletal muscle, cardiac, and nerve cell RMPs?
-60 to -90mV
Na/K pump
continues to restore gradient by pumping K+ back in
