A pacemaker potential is a spontaneous depolarization of the resting membrane potential of certain specialized cells in the heart, which initiates the electrical impulse that triggers the heartbeat. These cells are located in the sinoatrial (SA) node, which is known as the natural pacemaker of the heart.
During the pacemaker potential, the membrane potential of the SA node cells gradually becomes less negative, eventually reaching a threshold level that triggers an action potential. This action potential then spreads throughout the heart, causing the atria and ventricles to contract and pump blood.
The pacemaker potential is a key component of the normal electrical activity of the heart, and it helps to ensure that the heart beats at a regular rhythm. However, certain factors such as disease or medication can disrupt the pacemaker potential and lead to abnormal heart rhythms or arrhythmias.
Pacemaker cells have a unique combination of ion channels that allow them to spontaneously depolarize and generate the pacemaker potential. These cells also have a slower depolarization rate and a lower threshold for firing an action potential compared to other cardiac cells. This specialized electrical activity of pacemaker cells is what enables the heart to maintain a steady rhythm and ensures that it beats effectively to pump blood throughout the body.