Absolute Refractory Period (ARP)
Absolute refractory period (ARP) describes the time of dormancy that occurs after a nerve has been fired. Lasting 1-2 minutes, during this phase the neuron can't be stimulated no matter how strong the stimulus is. It is essentially recharging itself in order to be able to fire again. The NA+ channels in the neuron are deactivated during the ARP and are unable to respond to any stimulus. Following the ARP is the relative refractory period (RRP) which is longer in duration and is when the neuron is able to respond to a stimulus but needs a stronger than normal stimulus in order to do so. It is essentially partially recharged and can respond if the stimulus is strong enough. The RRP is like a person still partially asleep who doesn't notice someone quietly trying to get their attention but will respond if someone loudly yells their name.