The Membrane Potential That Exactly Offsets an Ion's Concentration Gradient

Question

The membrane potential that exactly offsets an ion's concentration gradient is called the
A) graded potential.
B) threshold potential.
C) equilibrium potential.
D) action potential.
E) inhibitory postsynaptic potential.

Accepted Answer

The equilibrium potential is the point at which the electrical potential across the cell membrane exactly offsets the concentration gradient of an ion. This means that there is no net movement of that ion across the membrane because the electrochemical forces are balanced. Choice A is incorrect because a graded potential is a change in the membrane potential that varies with the strength of the stimulus. Choice B is incorrect because the threshold potential is the level of depolarization needed to initiate an action potential. Choice D is incorrect because an action potential is a rapid and coordinated electrical signal that travels down the length of a neuron. Choice E is incorrect because an inhibitory postsynaptic potential is a hyperpolarization of the postsynaptic membrane that makes it less likely for an action potential to occur.