lecture 3 Flashcards
there is a high concentration of which ion inside the cell?
K+
There is a high concentration of what 3 ions outside of the cell?
Cl-, Na+, Ca2+
The resting membrane potential (RMP)=
the net difference between the intracellular fluid and the extracellular fluid at rest
the equilibrium potential (Ex)=
the potential at which the electrical gradient exactly opposes the concentration gradient and there is no net movement of the ion
what does the movement of an ion across its membrane depend on?
its net electrochemical gradient
(there is a chemical driving force and an electrical driving force)
what is the conventional when you set the membrane potential?
the outside of the cell is set to 0 and the membrane potential is measured INSIDE the cell relative to the outside
describe the equilibrium potential under physiological conditions using K+
The K+ concentration gradient “drives” K+ out of the cell
(chemical driving force)
then the excess negative charge in the cell “pulls” K+ back in
(electrical driving force)
Permeable ions will move down their electrochemical gradient until —– and equilibrium is achieved
Vm= Ex
What is the Nernst Equation used for?
to calculate the equilibrium potential
(if the membrane was only permeable to one type of ion, the membrane potential would be the Nernst potential for that ion)
What is the Nernst equation?
E(ion)= 61/z*log([ion]out/[ion]in)
Na+: ICF (mM) and ECF (mM) concentration
ICF= 15.0 mM
ECF= 145.0 mM
K+: ICF (mM) and ECF (mM) concentration
ICF= 140.0 mM
ECF= 4.0 mM
What does the Goldman-Hodgkin-Katz equation predict?
predicts the membrane potential (Vm) that results from the contribution of all ions that can cross the membrane
-based on membrane permeability and concentration gradients for each
Cl-: ICF (mM) and ECF (mM) concentration
ICF= 4.0 mM
ECF= 115.0 mM
what ion is the primary contributor to resting membrane potentil in cells
K+
most cells are about 40 times more permeable to K+ than Na+!!!
