Pacemaker potential

In the pacemaking cells of the heart (e.g., the sinoatrial node), the pacemaker potential (also called the pacemaker current) is the slow, positive increase in voltage across the cell's membrane, that occurs between the end of one action potential and the beginning of the next. It is responsible for the self-generated rhythmic firing (automaticity) of pacemaker cells.

In the pacemaking cells of the heart (e.g., the sinoatrial node), the pacemaker potential (also called the pacemaker current) is the slow, positive increase in voltage across the cell's membrane, that occurs between the end of one action potential and the beginning of the next. It is responsible for the self-generated rhythmic firing (automaticity) of pacemaker cells. ==Pacemakers== The heart has several pacemakers, each which fires at its own intrinsic rate: SA node: 60–100 bpm Atrioventricular node(AVN): 40–60 bpm Purkinje fibres: 20–40 bpm The potentials will normally travel in order SA node → Atrioventricular node → Purkinje fibres Normally, all the foci will end up firing at the SA node rate, not their intrinsic rate in a phenomenon known as overdrive-suppression. Thus, in the normal, healthy heart, only the SA node intrinsic rate is observable. ==Pathology== However, in pathological conditions, the intrinsic rate becomes apparent. Consider a heart attack which damages the region of the heart between the SA node and the AV node. SA node → |block| AV node → Purkinje fibres The other foci will not see the SA node firing; however, they will see the atrial foci. The heart will now beat at the intrinsic rate of the AV node. ==Induction== The firing of the pacemaker cells is induced electrically by reaching the threshold potential of the cell membrane. The threshold potential is the potential an excitable cell membrane, such as a myocyte, must reach in order to induce an action potential. This depolarization is caused by very small net inward currents of calcium ions across the cell membrane, which gives rise to the action potential. ==Bio-pacemakers== Bio-pacemakers are the outcome of a rapidly emerging field of research into a replacement for the electronic pacemaker. The bio-pacemaker turns quiescent myocardial cells (e.g. atrial cells) into pacemaker cells. This is achieved by making the cells express a gene which creates a pacemaker current. ==See also== Pacemaker action potential Graded potential ==References==

Text derived from https://en.wikipedia.org/w/index.php?oldid=1340645856 under CC BY-SA 4.0; modifications have been made.