MEDICAL PHYSIOLOGY

Detailed explanation-1: -The refractory period is the time after an action potential is generated, during which the excitable cell cannot produce another action potential. There are two subphases of this period, absolute and relative refractoriness. Absolute refractoriness overlaps the depolarization and around 2/3 of repolarization phase.

Detailed explanation-2: -Because completion of repolarization is difficult to identify precisely, it is common to measure APD to the point of 90% repolarization. We shall refer to this moment as the repolarization time. Refractory period refers to the interval from depolarization to the recovery of excitability.

Detailed explanation-3: -In its wake, the action potential leaves the Na+ channels inactivated and K+ channels activated for a brief time. These transitory changes make it harder for the axon to produce subsequent action potentials during this interval, which is called the refractory period.

Detailed explanation-4: -A fibre first enters the absolute refractory period directly after an action potential has been fired, then the relative refractory period. The absolute refractory period of a human muscle fibre is typically between 2.2 and 4.6 ms.