effective vs absolute refractory period

[westernmed007]

what exactly is the difference in terms of cardiac phys, I have asked several of my friends and none of them seem to know exactly.

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[westernmed007]

shoulda added this but it really doesn't clarify at all:
(from BRS phys)

absolute- no action potential can be initiated
effective - no conducted action potential can be elicited

Where would that come into play? Are they not the same thing?

 

[analgold09]

shoulda added this but it really doesn't clarify at all:
(from BRS phys)

absolute- no action potential can be initiated
effective - no conducted action potential can be elicited

Where would that come into play? Are they not the same thing?

It's my understanding that in ARP absolutely no action potential can be initiated, as all the Na channels are closed. In the ERP, a small fraction of channels are open, so that a large enough stimulus can cause an action potential. However, this fraction of available Na channels is so small that the elicited potential cannot be conducted to surrounding tissue. It remains locally, or to be more specific, it is an electrotonic potential.

 

[pikappa]

10 years late to the thread, but here's a peer reviewed source about this topic:

• Absolute refractory period (ARP): the cell is completely unexcitable to a new stimulus.
• Effective refractory period (ERP): ARP + short segment of phase 3 during which a stimulus may cause the cell to depolarize minimally but will not result in a propagated action potential (i.e. neighbouring cells will not depolarize).
• Relative refractory period (RRP): a greater than normal stimulus will depolarize the cell and cause an action potential.
  
  
  

 

[Treebeard]

I found this thread while looking the same thing up myself. The clinical importance of this information seems extremely low.