Resting Membrane Potential Flashcards
What factors contribute to RMP
Intracellular anions, Na+/K+ pump, equilibrium potentials of permeable ions
What forces act on an ion
net force= [ ]chemical+ electrical forces
netforce = membrane potential (Vm) - equilibrium potential (Ex)
How do you find the equilibrium potential of an ion
nernst equation
Membrane potential develops due to the concentration and permeability of what ions
Ca2+ Na+ K+ and Cl-
what is meant by equilibrium or steady state
no net ion flow across membrane
RMP is expressed in relation to intracell or extracell
intracellular potential to extracellular
what contributes to the overall negative intracellular charge
impermeable molecules that are retained in the cell
movement of Na+/K+ pump
3 Na+ out, 2K+ in
what are the direct and indirect contributions the Na/K pump gives to RMP
indirect: [ ] gradients promote passive ion diffusion
direct: active electrogenic pump i.e moving 1+ charge out of the cell
What is a diffusion potential
potential difference across cell membrane due to [ ] difference of an ion
what are the trends of K, Na, Ca, and Cl relative to concentration extracellulary
K tiny extracellular, huge intra
Na huge extra cell, tiny intra
Ca2 more out than in
Cl huge out, tiny in
Relative comparison of 4 key ions [extra]/[intra]
K .026 because more inside
Na 12 because more outside
Ca2 10,000 much more out than in. tiny overall
Cl 29 because more outside
how does force relate to concentration in chemical force
increase gradient, increase force
describe the magnitude and direction of electrical force
magnitude depends on membrane potential
direction depends on ion charge
how do you find the net force if the concentration and electrical forces are in same direction
its the sum
how do you find the net force if the concentration and the electrical forces are in opposite direction
subtract
how do you find the net force if the concentration and electrical forces are equal but in opposite directions
no net force
what is the electrochemical equilibrium
no net diffusion of ions when chemical and electrical forces acting on ion are equal and opposite
What is the goal of each permeable ion on RMP
to drive it toward its own equilibrium potential
equation for nernst
the Eq potential equals= 60mv/ z log10 [Xout]/[Xin}
z= valences of ion
log 10 (10)= ? log 10 (.1) =?
log10(10) = 1 log10(.1) = -1
If membrane potential is given in Vm and the nernst eq was used for equilibrium potential (Ex) then what can be concluded?
the difference between Ex and Vm= net force
if Ex=Vm ion is at equilibrium
what is the K+ and Na+ Ex in most cells
K+ -105mV
Na+ +45mV
What is the Ex of Cl
most cells -47mV
skeletal is -89mV
What is the Ex for Na and K and Ca in muscle cells
Na +67 mV
Ca2 +123mV
K -95mV
If the Vm is more negative than the ions Ex what direction will ions go
Inward current of cations, anions are repelled
If Vm is more positive vs ions Ex what direction will it go
outward current of cations, inwards for anion
general direction of ion flow
K+ goes extracellular
Na+, Ca2+, Cl- goes intracellular
what determines membrane conductance
number of open channels
what are the molecular conductors in cells
the ion channels because bilayer is a poor conductor of electricity
how do you know if conductance is increasing
channels are opening
What are the major types of ion channels
ungated (leak), voltage-gated
Desribe the flow of K+ in cell
high intracell concentration but cell is negative. Slow leak of K+ out of cell via leak channels
If you decrease the ECF fluid of K+ what happens to flow
more K+ efflux
as K+ conductance increases what happens to K+
efflux
What is the reversal potential
voltage at which current direction is reversed= nernst potential
what is the reversal potential of K+
-95mV
what is a major determinant of RMP
K+ equilibrium potential
if you increase or decrease the [Na] ECF what happends to RMP
little effect because NA+ channels closed at RMP
what is the reversal potential of Na
+67mV
What is the very average range of RMP
-50 to -90 mV
