Basis of differentiation | Graded potential | Action potential |
Definition | Is a variable-strength signal that can be conveyed over small distances and could lead to an action potential if it becomes strong enough to meet the threshold value of -55mv | Is a massive depolarization that can be transferred over long distances and is the actual message sent by neurons |
Trigger | May be brought about by:
| Are triggered by membrane depolarization to threshold |
Threshold | No threshold - can occur with any stimulus | Requires threshold to be reached |
Occurrence | May occur in any region of the cell plasma membrane | Occurs in regions of the cell plasma membrane where there is a high concentration of voltage-gated Na+ and K+ channels |
Amplitude | Varies depending on the strength of the stimulus | Is all-or-nothing and does not vary with stimulus strength |
Duration | Varies depending on the duration of the stimulus, generally ranges from a few milliseconds to seconds | Consistent duration, generally relatively short lasting from 3 to 5 milliseconds |
Stimulus strength | Decreases with distance | Does not decrease with distance |
Ion channels | Ion channels responsible may be:
| Ion channels responsible are:
|
Ions involved | Usually Na+, K+, or Cl− | Usually Na+ and K+ |
Refractory period | None | Has absolute and relative refractory periods |
Depolarization | May be depolarizing or hyperpolarizing depending on the stimulus | Always leads to depolarization of membrane and reversal of the membrane potential |