Biological Bases of Behavior

About -70 mV, with the inside of the cell negative relative to the outside.

Voltage-gated sodium (Na+) channels open and Na+ rushes into the cell.

Voltage-gated potassium (K+) channels open and K+ exits the cell.

Once threshold is reached, an action potential fires at full amplitude; a stronger stimulus does not produce a larger spike.

A brief interval after firing when the neuron cannot (absolute) or has difficulty (relative) firing again.