supply: McKinley and Michael, Anatomy and physiology: An blanketed approach , Maloine, 2014
Excitation Threshold : beginning of slow voltage-gated Na + channels under the repolarization effect of the preceding cycle. The inflow into the ion cell varies the ability of the membrane from -60 to -40mV.
Depolarization : beginning of speedy voltage-gated Ca2 + channels. The influx into the ion mobile varies the membrane ability from -forty to barely greater than zero.