Here's a breakdown of their key functions:
* Generate electrical impulses: Unlike regular muscle cells, pacesetter cells have an unstable resting membrane potential that allows them to spontaneously depolarize and generate action potentials. This depolarization triggers a chain reaction throughout the heart, leading to muscle contraction.
* Set the heart rate: The rate at which pacesetter cells fire determines the heart rate. This rate can be influenced by various factors like the autonomic nervous system (sympathetic and parasympathetic) and hormones.
* Coordinate heart contractions: The electrical impulses generated by pacesetter cells spread throughout the heart, ensuring that the atria and ventricles contract in a coordinated manner, pumping blood efficiently.
Location and types of pacesetter cells:
* Sinoatrial (SA) node: Located in the right atrium, the SA node is the primary pacemaker of the heart. It generates the fastest rhythm, typically around 60-100 beats per minute, establishing the normal heart rate.
* Atrioventricular (AV) node: Located in the interatrial septum, the AV node acts as a secondary pacemaker in case the SA node malfunctions. It has a slower intrinsic rate than the SA node, around 40-60 beats per minute.
* Bundle of His and Purkinje fibers: These specialized fibers conduct the electrical impulses from the AV node to the ventricles, ensuring coordinated ventricular contraction.
In summary, pacesetter cells are crucial for maintaining a regular heartbeat by initiating and regulating the electrical impulses that drive the heart's rhythmic contractions.
