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<title>Pacemaker potential</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Pacemaker potential</span></span>

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<p>In the <a href="Pacemaker_cells" class="mw-redirect" title="Pacemaker cells">pacemaking cells</a> of the <a href="Heart" title="Heart">heart</a> (e.g., the <a href="Sinoatrial_node" title="Sinoatrial node">sinoatrial node</a>), the <b>pacemaker potential</b> (also called the <b>pacemaker current</b>) is the slow, positive increase in voltage across the <a href="Cardiac_myocyte" class="mw-redirect" title="Cardiac myocyte">cell</a>'s membrane, that occurs between the end of one <a href="Action_potential" title="Action potential">action potential</a> and the beginning of the next. It is responsible for the self-generated rhythmic firing (<a href="Cardiac_automaticity" class="mw-redirect" title="Cardiac automaticity">automaticity</a>) of pacemaker cells.

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<div class="mw-heading mw-heading2"><h2 id="Background">Background</h2></div>

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</style><div role="note" class="hatnote navigation-not-searchable">See also: <a href="Cardiac_pacemaker" title="Cardiac pacemaker">Cardiac pacemaker</a></div>

<p>The <b>cardiac pacemaker</b> is the <a href="Heart" title="Heart">heart</a>'s natural rhythm generator. It employs pacemaker <a href="Cell_(biology)" title="Cell (biology)">cells</a> that generate electrical impulses, known as <a href="Cardiac_action_potential" title="Cardiac action potential">cardiac action potentials</a>. These potentials cause the <a href="Cardiac_muscle" title="Cardiac muscle">cardiac muscle</a> to contract, and the rate of which these muscles contract determines the <a href="Heart_rate" title="Heart rate">heart rate</a>.

</p><p>As with any other cells, pacemaker cells have an electrical charge on their membranes. This electrical charge is called the <a href="Membrane_potential" title="Membrane potential">membrane potential</a>. After the firing of an action potential, the pacemaking cell's membrane <a href="Repolarization" title="Repolarization">repolarizes</a> (decreases in voltage) to its <a href="Resting_potential" title="Resting potential">resting potential</a> of -60 mV. From here, the membrane gradually <a href="Depolarization" title="Depolarization">depolarizes</a> (increases in voltage) to the <a href="Threshold_potential" title="Threshold potential">threshold potential</a> of -40 mV,<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> upon which the cell would go on to fire the next action potential. The rate of depolarization is the slope: the faster voltage increases, the steeper the slopes are in graphs. The slope determines the time taken to reach the threshold potential, and thus the timing of the next action potential.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>In a healthy sinoatrial node (SAN, a complex tissue within the right atrium containing pacemaker cells that normally determine the intrinsic firing rate for the entire heart<sup id="cite_ref-pmid17823213_3-0" class="reference"><a href="#cite_note-pmid17823213-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>), the pacemaker potential is the main determinant of the heart rate. Because the pacemaker potential represents the non-contracting time between heart beats (<a href="Diastole" title="Diastole">diastole</a>), it is also called the <b><a href="Diastolic_depolarization" title="Diastolic depolarization">diastolic depolarization</a></b>.

The amount of net inward current required to move the cell membrane potential during the pacemaker phase is extremely small, in the order of few pAs, but this net flux arises from time to time changing contribution of several currents that flow with different voltage and time dependence. Evidence in support of the active presence of K<sup>+</sup>, Ca<sup>2+</sup>, Na<sup>+</sup> channels and Na<sup>+</sup>/K<sup>+</sup> exchanger during the pacemaker phase have been variously reported in the literature, but several indications point to the “funny”(I<sub>f</sub>) current as one of the most important.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> (see <a href="Funny_current" class="mw-redirect" title="Funny current">funny current</a>). There is now substantial evidence that also sarcoplasmic reticulum (SR) Ca<sup>2+</sup>-transients participate to the generation of the diastolic depolarization via a process involving the Na–Ca exchanger.

</p><p>The rhythmic activity of some <a href="Neurons" class="mw-redirect" title="Neurons">neurons</a> like the <a href="Pre-B%C3%B6tzinger_complex" title="Pre-Bötzinger complex">pre-Bötzinger complex</a> is modulated by neurotransmitters and neuropeptides, and such modulatory connectivity gives to the neurons the necessary plasticity to generating distinctive, state-dependent rhythmic patterns that depend on pacemaker potentials.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Pacemakers">Pacemakers</h2></div>

<p>The heart has several pacemakers, each which fires at its own intrinsic rate:

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<li><i>Atrioventricular node(AVN):</i> 40–60 bpm</li>

<li><i>Purkinje fibres:</i> 20–40 bpm</li></ul>

<p>The potentials will normally travel in order<br>

SA node → Atrioventricular node → Purkinje fibres

</p><p>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.

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<div class="mw-heading mw-heading2"><h2 id="Pathology">Pathology</h2></div>

<p>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.

</p><p>SA node → |block| AV node → Purkinje fibres

</p><p>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.

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<div class="mw-heading mw-heading2"><h2 id="Induction">Induction</h2></div>

<p>The firing of the pacemaker cells is induced electrically by reaching the threshold potential of the cell membrane. The <a href="Threshold_potential" title="Threshold potential">threshold potential</a> is the potential an excitable cell membrane, such as a <a href="Myocyte" class="mw-redirect" title="Myocyte">myocyte</a>, must reach in order to induce an action potential.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> This <a href="Depolarization" title="Depolarization">depolarization</a> is caused by very small net inward currents of calcium ions across the cell membrane, which gives rise to the action potential.<sup id="cite_ref-pmid19181406_8-0" class="reference"><a href="#cite_note-pmid19181406-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Bio-pacemakers">Bio-pacemakers</h2></div>

<p>Bio-pacemakers are the outcome of a rapidly emerging field of research into a replacement for the <a href="Electronic_pacemaker" class="mw-redirect" title="Electronic pacemaker">electronic pacemaker</a>. 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.<sup id="cite_ref-pmid19162611_10-0" class="reference"><a href="#cite_note-pmid19162611-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>

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<ul><li><a href="Pacemaker_action_potential" title="Pacemaker action potential">Pacemaker action potential</a></li>

<li><a href="Graded_potential" title="Graded potential">Graded potential</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite id="CITEREFWeiYohannanRichards2025" class="citation book cs1">Wei, Xingyu; Yohannan, Sandesh; Richards, John R. (2025). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/books/NBK537194/">"Physiology, Cardiac Repolarization Dispersion and Reserve"</a>. <i>StatPearls</i>. StatPearls Publishing. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/30725879">30725879</a>. <q>[Depolarization] starts when the membrane potential reaches -40 mV, the threshold potential for pacemaker cells. [...This] results in an upstroke in membrane potential from -40 mV to +10mV. [... Repolarization involves a] rapid decrease of membrane potential from +10 mV to -60 mV.</q></cite></span>

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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite id="CITEREFSokolovGrechenko1981" class="citation book cs1">Sokolov, E.N.; Grechenko, T.N. (1981). "Pacemaker Plasticity in Isolated Neuron". <i>Brain and Behaviour</i>. pp. <span class="nowrap">7–</span>12. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2FB978-0-08-027338-9.50007-4">10.1016/B978-0-08-027338-9.50007-4</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-08-027338-9</bdi>. <q>[When the pacemaker potential] reaches threshold (approximately –40mV in nodal cells) it triggers an action potential, which sparks off the next heart beat. The slope of the pacemaker potential determines the time taken to reach the threshold value, so the slope governs heart rate; the steeper the slope the sooner threshold is reached and the shorter the time between beats. Since the pacemaker slope is steeper in SA node cells than elsewhere in the electrical system, the SA node has the fastest intrinsic firing rate and initiates each heart beat.</q></cite></span>

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</style><div id="Physiology_of_the_cardiovascular_system139" style="font-size:114%;margin:0 4em"><a href="Cardiovascular_physiology" title="Cardiovascular physiology">Physiology of the cardiovascular system</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Heart" title="Heart">Heart</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Cardiac_output" title="Cardiac output">Cardiac output</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Cardiac_cycle" title="Cardiac cycle">Cardiac cycle</a></li>

<li><a href="Cardiac_output" title="Cardiac output">Cardiac output</a>

<ul><li><a href="Heart_rate" title="Heart rate">Heart rate</a></li>

<li><a href="Stroke_volume" title="Stroke volume">Stroke volume</a></li></ul></li>

<li><a href="Stroke_volume" title="Stroke volume">Stroke volume</a>

<ul><li><a href="End-diastolic_volume" title="End-diastolic volume">End-diastolic volume</a></li>

<li><a href="End-systolic_volume" title="End-systolic volume">End-systolic volume</a></li></ul></li>

<li><a href="Afterload" title="Afterload">Afterload</a></li>

<li><a href="Preload_(cardiology)" title="Preload (cardiology)">Preload</a></li>

<li><a href="Frank%E2%80%93Starling_law" title="Frank–Starling law">Frank–Starling law</a></li>

<li><a href="Cardiac_function_curve" title="Cardiac function curve">Cardiac function curve</a></li>

<li><a href="Venous_return_curve" class="mw-redirect" title="Venous return curve">Venous return curve</a></li>

<li><a href="Wiggers_diagram" title="Wiggers diagram">Wiggers diagram</a></li>

<li><a href="Pressure%E2%80%93volume_diagram" title="Pressure–volume diagram">Pressure–volume diagram</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Echocardiography" title="Echocardiography">Ultrasound</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Ventricle_(heart)#Dimensions" title="Ventricle (heart)">Fractional shortening</a> = (<a href="End-diastolic_dimension" class="mw-redirect" title="End-diastolic dimension">End-diastolic dimension</a></li>

<li><a href="End-systolic_dimension" class="mw-redirect" title="End-systolic dimension">End-systolic dimension</a>) / End-diastolic dimension</li>

<li><a href="Aortic_valve_area_calculation" title="Aortic valve area calculation">Aortic valve area calculation</a></li>

<li><a href="Ejection_fraction" title="Ejection fraction">Ejection fraction</a></li>

<li><a href="Cardiac_index" title="Cardiac index">Cardiac index</a></li>

<li><a href="Left_atrial_volume" title="Left atrial volume">Left atrial volume</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Heart_rate" title="Heart rate">Heart rate</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Cardiac_pacemaker" title="Cardiac pacemaker">Cardiac pacemaker</a></li>

<li><a href="Chronotropic" title="Chronotropic">Chronotropic</a> (<a href="Heart_rate" title="Heart rate">Heart rate</a>)</li>

<li><a href="Dromotropic" title="Dromotropic">Dromotropic</a> (<a href="Nerve_conduction_velocity" title="Nerve conduction velocity">Conduction velocity</a>)</li>

<li><a href="Inotrope" title="Inotrope">Inotropic</a> (Contractility)</li>

<li><a href="Bathmotropic" title="Bathmotropic">Bathmotropic</a> (Excitability)</li>

<li><a href="Lusitropy" title="Lusitropy">Lusitropic</a> (Relaxation)</li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Conduction</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Cardiac_conduction_system" title="Cardiac conduction system">Conduction system</a></li>

<li><a href="Cardiac_electrophysiology" title="Cardiac electrophysiology">Cardiac electrophysiology</a></li>

<li>Action potential

<ul><li><a href="Cardiac_action_potential" title="Cardiac action potential">cardiac </a></li>

<li><a href="Atrial_action_potential" title="Atrial action potential">atrial</a></li>

<li><a href="Ventricular_action_potential" title="Ventricular action potential">ventricular</a></li></ul></li>

<li><a href="Effective_refractory_period" title="Effective refractory period">Effective refractory period</a></li>

<li><a href="Electrocardiography" title="Electrocardiography">Electrocardiography</a>

<li><a href="PR_interval" title="PR interval">PR interval</a></li>

<li><a href="QRS_complex" title="QRS complex">QRS complex</a></li>

<li><a href="QT_interval" title="QT interval">QT interval</a></li>

<li><a href="ST_segment" title="ST segment">ST segment</a></li>

<li><a href="Hexaxial_reference_system" title="Hexaxial reference system">Hexaxial reference system</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Chamber pressure</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Central_venous_pressure" title="Central venous pressure">Central venous</a></li>

<li>Right

<ul><li><a href="Right_atrial_pressure" title="Right atrial pressure">atrial</a></li>

<li><a href="Right_ventricular_pressure" class="mw-redirect" title="Right ventricular pressure">ventricular</a></li></ul></li>

<li><a href="Pulmonary_artery_pressure" class="mw-redirect" title="Pulmonary artery pressure">pulmonary artery</a>

<ul><li><a href="Pulmonary_wedge_pressure" title="Pulmonary wedge pressure">wedge</a></li></ul></li>

<li>Left

<ul><li><a href="Pulmonary_wedge_pressure" title="Pulmonary wedge pressure">atrial</a></li>

<li><a href="Left_ventricular_pressure" class="mw-redirect" title="Left ventricular pressure">ventricular</a></li></ul></li>

<li><a href="Aortic_pressure" title="Aortic pressure">Aortic</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Ventricular_remodeling" title="Ventricular remodeling">Ventricular remodeling</a></li></ul>

</div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Circulatory_system" title="Circulatory system">Vascular system</a>/<br><a href="Hemodynamics" title="Hemodynamics">hemodynamics</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Hemodynamics" title="Hemodynamics">Blood flow</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Compliance_(physiology)" title="Compliance (physiology)">Compliance</a></li>

<li><a href="Vascular_resistance" title="Vascular resistance">Vascular resistance</a></li>

<li><a href="Pulse" title="Pulse">Pulse</a></li>

<li><a href="Perfusion" title="Perfusion">Perfusion</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Blood_pressure" title="Blood pressure">Blood pressure</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Pulse_pressure" title="Pulse pressure">Pulse pressure</a>

<ul><li><a href="Systole" title="Systole">Systolic</a></li>

<li><a href="Diastole" title="Diastole">Diastolic</a></li></ul></li>

<li><a href="Mean_arterial_pressure" title="Mean arterial pressure">Mean arterial pressure</a></li>

<li><a href="Jugular_venous_pressure" title="Jugular venous pressure">Jugular venous pressure</a></li>

<li><a href="Portal_venous_pressure" title="Portal venous pressure">Portal venous pressure</a></li>

<li><a href="Critical_closing_pressure" title="Critical closing pressure">Critical closing pressure</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Cardiovascular_physiology#Regulation_of_blood_pressure" title="Cardiovascular physiology">Regulation of BP</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Baroreflex" title="Baroreflex">Baroreflex</a></li>

<li><a href="Kinin%E2%80%93kallikrein_system" title="Kinin–kallikrein system">Kinin–kallikrein system</a></li>

<li><a href="Renin%E2%80%93angiotensin_system" title="Renin–angiotensin system">Renin–angiotensin system</a></li>

<li><a href="Vasoconstriction" title="Vasoconstriction">Vasoconstrictors</a></li>

<li><a href="Vasodilation" title="Vasodilation">Vasodilators</a></li>

<li><a href="Autoregulation" title="Autoregulation">Autoregulation</a>

<ul><li><a href="Myogenic_mechanism" title="Myogenic mechanism">Myogenic mechanism</a></li>

<li><a href="Tubuloglomerular_feedback" title="Tubuloglomerular feedback">Tubuloglomerular feedback</a></li>

<li><a href="Cerebral_autoregulation" title="Cerebral autoregulation">Cerebral autoregulation</a></li></ul></li>

<li><a href="Paraganglion" title="Paraganglion">Paraganglia</a>

<ul><li><a href="Aortic_body" title="Aortic body">Aortic body</a></li>

<li><a href="Carotid_body" title="Carotid body">Carotid body</a></li>

<li><a href="Glomus_cell" title="Glomus cell">Glomus cell</a></li></ul></li></ul>

</div></td></tr></tbody></table><div></div></td></tr></tbody></table></div></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-03-23" href="https://en.wikipedia.org/wiki/?title=Pacemaker_potential&oldid=1282043288">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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