What triggers the action potential in the SA node?


What triggers the action potential in the SA node?

The SA nodal cells have an unstable resting membrane potential that spontaneously depolarizes due to a pacemaker potential. This is caused by the “funny” Na+ current and a decrease in the conductance of the inward rectifier K+ channel.

How is the SA node activated?

Most members in the superfamily are activated by depolarization. In contrast, HCN channels are activated by hyperpolarization due to some unknown mechanism (Männikkö et al., 2002). The currents through HCN channels in the SA node are called If.

What controls the SA node?

The autonomic nervous system, the same part of the nervous system as controls the blood pressure, controls the firing of the SA node to trigger the start of the cardiac cycle.

How the SA node action potential is generated spontaneously to maintain your heart rate?

The action potential generated by the SA node passes down the electrical conduction system of the heart, and depolarizes the other potential pacemaker cells (AV node) to initiate action potentials before these other cells have had a chance to generate their own spontaneous action potential, thus they contract and …

What are the three parts of action potential in a SA nodal cell?

SA Node Action Potential; also AV Node

  • Phase 0, upstroke. action potential opens L-type voltage-gated Ca2+ channels.
  • Phase 1 and 2 are absent in SA node action potential.
  • Phase 3: repolarization.
  • Phase 4: diastolic depolarization.
  • Heart rate.

What causes the rapid depolarization phase of a contractile cell action potential?

In nerve and muscle cells, the depolarization phase of the action potential is caused by an opening of fast sodium channels. This also occurs in non-pacemaker cardiac cells; however, in cardiac pacemaker cells, calcium ions are involved in the initial depolarization phase of the action potential.

How is action potential produced in the heart?

The cardiac action potential is a brief change in voltage (membrane potential) across the cell membrane of heart cells. This is caused by the movement of charged atoms (called ions) between the inside and outside of the cell, through proteins called ion channels.

What nerve stimulates the SA node?

right vagus nerve
The right vagus nerve primarily innervates the SA node. The left vagus primarily innervates the atrial–ventricular (AV) node.

What actions of the heart are controlled by the SAN?

The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles. The lower heart chambers (ventricles) contract or pump.

Why does the SA node spontaneously depolarize?

Another mechanism as important as the funny current (through HCN channels) is forward mode sodium-calcium exchanger (NCX) current. The currents thought to be responsible for spontaneous depolarization in the SA node are the funny current, T-type calcium current, forward mode NCX, and finally the L-type calcium current.

What is the SA node made of?

The SA node, also known as the sinus node, represents a crescent-like shaped cluster of myocytes divided by connective tissue, spreading over a few square millimeters. It is located at the junction of the crista terminalis in the upper wall of the right atrium and the opening of the superior vena cava.

How long is SA node action potential?

approximately 200 ms.
The action potential duration (APD) is approximately 200 ms. Reproduced with permission from Stanley and Carlsson. The action potentials of pacemaker cells in the sinoatrial (SA) and atrioventricular (AV) nodes are significantly different from those in working myocardium.