the period of time required so that a neuron can generate another action potential.
•Absolute – from opening of voltage gated Na+ channels until sodium inactivation gates close
–Cannot be stimulated at all during this time
•Relative – period of repolarization (including hyperpolarization)
–Takes a stronger stimulus to depolarize the membrane enough to generate another action potential
–Na+ channels have to reset the activation gates
–K+channels have to close - they close more slowly than Na+ channels