Refractory Period: Difference between revisions
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Refractory periods are a short phase in time following an [[Action potential|action potential]] where another action potential cannot be generated. There are two types of refractory periods: | Refractory periods are a short phase in time following an [[Action potential|action potential]] where another action potential cannot be generated. There are two types of refractory periods: | ||
#The absolute refractory period is a period where it is completely impossible for another action potential to be activated, regardless of the size of the trigger. This is because the [[Sodium channels|sodium channels]] are inactivated and remain that way until hyperpolarization occurs. In cardiovascular mechanism, this refractory period is sometimes called effective refractory period (ERP).<br><ref>http://www.cvpharmacology.com/antiarrhy/ERP</ref> | #The absolute refractory period is a period where it is completely impossible for another action potential to be activated, regardless of the size of the trigger (stimulus). This is because the [[Sodium channels|sodium channels]] are inactivated and remain that way until hyperpolarization occurs. In cardiovascular mechanism, this refractory period is sometimes called effective refractory period (ERP).<br><ref>http://www.cvpharmacology.com/antiarrhy/ERP</ref> | ||
#The relative refractory period is the period | #The relative refractory period is the period that occurs during the undershoot phase; where an action potential can be activated but only if the trigger (stimulus) is large enough. This is because the sodium channels have been reactivated and have recovered but it is a difficult process due to the counter-acting [[Potassium|potassium]] flow as some potassium ion channels are still open <ref>Wayne M. Becker, Lewis J. Kleinsmith, Jeff Hardin. (2006) The World of the Cell, 6th edition, San Francisco:Benjamin Cummings</ref>.<br> | ||
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*The brain will be able to percieve nerve impulses as seperated events since there is a time lag between them. | *The brain will be able to percieve nerve impulses as seperated events since there is a time lag between them. | ||
*The number of generated impulses or repetitive firing rate of a neuron will be limited in a given period of time<ref>Bruce, A, Et al. Molecular biology of the cell. (6th ed.). New York: Garland Science, Taylor &amp;amp;amp;amp; Francis Group, LLC, an informa business; 2015. P622-623</ref>. | *The number of generated impulses or repetitive firing rate of a neuron will be limited in a given period of time<ref>Bruce, A, Et al. Molecular biology of the cell. (6th ed.). New York: Garland Science, Taylor &amp;amp;amp;amp;amp; Francis Group, LLC, an informa business; 2015. P622-623</ref>. | ||
*The nerve impulses will only travel in one direction. This is because, as the [[Action potential|action potential]] is moving forwards along axons, the [[Resting potential|resting potential]] will be re-established behind it. However, not until this happens can a new action potential occur.<br> | *The nerve impulses will only travel in one direction. This is because, as the [[Action potential|action potential]] is moving forwards along axons, the [[Resting potential|resting potential]] will be re-established behind it. However, not until this happens can a new action potential occur.<br> | ||
Revision as of 00:35, 5 December 2016
Refractory periods are a short phase in time following an action potential where another action potential cannot be generated. There are two types of refractory periods:
- The absolute refractory period is a period where it is completely impossible for another action potential to be activated, regardless of the size of the trigger (stimulus). This is because the sodium channels are inactivated and remain that way until hyperpolarization occurs. In cardiovascular mechanism, this refractory period is sometimes called effective refractory period (ERP).
[1] - The relative refractory period is the period that occurs during the undershoot phase; where an action potential can be activated but only if the trigger (stimulus) is large enough. This is because the sodium channels have been reactivated and have recovered but it is a difficult process due to the counter-acting potassium flow as some potassium ion channels are still open [2].
The refratory period causes 3 things to occur.
- The brain will be able to percieve nerve impulses as seperated events since there is a time lag between them.
- The number of generated impulses or repetitive firing rate of a neuron will be limited in a given period of time[3].
- The nerve impulses will only travel in one direction. This is because, as the action potential is moving forwards along axons, the resting potential will be re-established behind it. However, not until this happens can a new action potential occur.
References
- ↑ http://www.cvpharmacology.com/antiarrhy/ERP
- ↑ Wayne M. Becker, Lewis J. Kleinsmith, Jeff Hardin. (2006) The World of the Cell, 6th edition, San Francisco:Benjamin Cummings
- ↑ Bruce, A, Et al. Molecular biology of the cell. (6th ed.). New York: Garland Science, Taylor &amp;amp;amp;amp; Francis Group, LLC, an informa business; 2015. P622-623