overshoot

o·ver·shoot

(ō'vĕr-shūt),

1. Generally, any initial change, in response to a sudden step change in some factor, that is greater than the steady-state response to the new level of that factor; common in systems in which inertia or a time lag in negative feedback outweighs any damping that may be present. Changes in a negative direction are sometimes distinguished by the term undershoot, and the two may alternate in an oscillatory fashion, as in the transient oscillations of a pendulum when released from an initial displacement.

2. Momentary reversal of the membrane potential of a cell (inside becoming positive rather than negative relative to the outside) during an action potential; considered a form of overshoot1 because, before discovery of overshoot2, excitation was thought merely to depolarize the membrane to zero transmembrane potential.

o·ver·shoot

(ō'vĕr-shūt)

1. Any response to a step change in some factor that is greater than the steady-state response to the new level of that factor; common in systems in which inertia or a time lag in negative feedback outweighs any damping that may be present.

2. Momentary reversal of the membrane potential of a cell (inside becoming positive rather than negative relative to the outside) during an action potential.

overshoot

the stage of an ACTION POTENTIAL in which the voltage rises from zero to the positive peak.