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Action Potential Refectory Periods

  • After an action potential starts, the membrane is typically unresponsive to new stimuli until the resting potential is re-established. This time span is called the refractory period.
  • The first phase of the refractory period is the image descriptionabsolute refractory period. It extends from the start of the action potential until the K+ channels begin to close.
An image showing a diagram of action potential measured (mv) through time
An image showing the Absolute refractory period (pink) using diagram of action potential measured (mv) through time
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  • During this time, the Na+ channels are already image descriptionopen (active) or image descriptioninactive, so the membrane will not respond to¬†any stimulus, regardless of strength.
An image showing the Absolute refractory period (pink) using diagram of action potential measured (mv) through time
An image showing the active Na+ channel (open) during Absolute refractory period (pink) using diagram of action potential measured (mv) through time
An image showing the inactive (closed) and active (open) Na+ channel during Absolute refractory period (pink) using diagram of action potential measured (mv) through time
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  • The second phase of the refractory period is referred to as the image descriptionrelative refractory period. It immediately follows the absolute refractory period and lasts until the membrane returns to the resting state.
An image showing the inactive (closed) and active (open) Na+ channel during Absolute refractory period (pink) using diagram of action potential measured (mv) through time
An image showing the Relative refractory period , inactive (closed) and active (open) Na+ channel during Absolute refractory period (pink) using diagram of action potential measured (mv) through time
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  • The Na+ channels image descriptionare closing (deinactivating) while the membrane potential changes. As long as the membrane is hyperpolarized, a greater than normal stimulus is needed to open the channels that have closed.
An image showing the Relative refractory period , inactive (closed) and active (open) Na+ channel during Absolute refractory period (pink) using diagram of action potential measured (mv) through time
An image showing the inactive (closed) during Relative refractory period , inactive (closed) and active (open) Na+ channel during Absolute refractory period (pink) using diagram of action potential measured (mv) through time
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