Absolute refractory period is due to:
Opening of calcium channels
Opening of potassium channals
Closure of Active gates of sodium channals
Closure of inactive gates of sodium channals
Inactivated gates of sodium are closed during depolarization and Remain closed until repolarization no action potential can occure untill inactivated sodium gate are opened Ref:Guyton and Hall textbook of medical physiology 12th edition,page number:70
General physiology