Impulse Transmission within Nerve Fibers

  1. The relatively static membrane potential of quiescent cells is called the resting membrane potential, as opposed to the specific dynamic electrochemical phenomena called action potential and graded membrane potential.
  2. Graded potentials are changes in membrane potential that vary in size, as opposed to being all-or-none.
  3. The threshold potential is the critical level to which the membrane potential must be depolarized in order to initiate an action potential.
  4. An action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory.
  5. The refractory period is the amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitation.
A. Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. B. An actual action potential (blue trace) recorded from a mouse hippocampal pyramidal neuron. In this case, the action potential was stimulated by a prolonged pulse of current (brown trace; approx. 2 micro Amps)passed into the cell through the recording electrode. This method of stimulation distorts the AP compared to the schematic, in that the

Examples of graded potentials.