Refractory period

Absolute refractory period

aka Effective refractory period

While h gates are completely closed

• No response to stimulation
• Prevents tetanic contraction
• ARP last till during phase 3 where Vm reaches about -50mV [BL8:p26]

Relative refractory period

During the period between the end of ERP and full repolarisation (phase 4), action potential can be produced, but:

• Stronger stimulus is needed
• Amplitude of the AP produced reduced
• Conduction velocity reduced
• Duration of the AP reduced (??due to incomplete inactivation of ik current)