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Cardiac action potential
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This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2013)
As in other cells, the cardiac action potential is a short-lasting event in which the difference of potential between the interior and the exterior of each cardiac cell rises and falls following a consistent trajectory.[1]
The cardiac action potential differs significantly in different portions of the heart. The heart is provided with a special excitatory system and a contractile system necessary to perform this function.
This differentiation of the action potentials allows the different electrical characteristics of the different portions of the heart. For instance, the specialized excitatory system of the heart has the special property of depolarizing without any external influence with a slow, positive increase in voltage across the cell's membrane (the membrane potential) that occurs between the end of one action potential and the beginning of the next action potential. This increase in membrane potential typically permits the membrane potential to reach the threshold potential at which it fires the next action potential (pacemaker potential). Thus, the pacemaker potential is what drives the self-generated rhythmic firing. This is known as cardiac muscle automaticity.[2]
Pacemaker potentials are fired by sinoatrial node (SAN), but also by the other foci. However, the last ones have firing frequencies slower than the SAN's. When other foci attempt to fire at their intrinsic rate, they can't because they have been discharged by the previous electric impluse coming from the SAN before their pacemaker potential threshold is reached. This is called "overdrive suppression".[3] Rate dependence of action
close
Cardiac action potential
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2013)
As in other cells, the cardiac action potential is a short-lasting event in which the difference of potential between the interior and the exterior of each cardiac cell rises and falls following a consistent trajectory.[1]
The cardiac action potential differs significantly in different portions of the heart. The heart is provided with a special excitatory system and a contractile system necessary to perform this function.
This differentiation of the action potentials allows the different electrical characteristics of the different portions of the heart. For instance, the specialized excitatory system of the heart has the special property of depolarizing without any external influence with a slow, positive increase in voltage across the cell's membrane (the membrane potential) that occurs between the end of one action potential and the beginning of the next action potential. This increase in membrane potential typically permits the membrane potential to reach the threshold potential at which it fires the next action potential (pacemaker potential). Thus, the pacemaker potential is what drives the self-generated rhythmic firing. This is known as cardiac muscle automaticity.[2]
Pacemaker potentials are fired by sinoatrial node (SAN), but also by the other foci. However, the last ones have firing frequencies slower than the SAN's. When other foci attempt to fire at their intrinsic rate, they can't because they have been discharged by the previous electric impluse coming from the SAN before their pacemaker potential threshold is reached. This is called "overdrive suppression".[3] Rate dependence of action