The two types of cardiac cells are myocardial contractile cells and myocardial conducting cells (pacemaker cells).
Let's explore these two types of cells in more detail:
Myocardial Contractile Cells
- Function: These cells are responsible for the mechanical contractions that pump blood throughout the body. They constitute approximately 99% of the cardiac cells in the atria and ventricles.
- Mechanism: Myocardial contractile cells contract in response to electrical signals, which causes the heart muscle to shorten and generate force, thus pushing blood out of the heart chambers.
- Characteristics:
- Striated muscle tissue (similar to skeletal muscle).
- Contain actin and myosin filaments that slide past each other during contraction.
- Connected by intercalated discs, which allow for rapid spread of electrical signals.
Myocardial Conducting Cells (Pacemaker Cells)
- Function: These specialized cells initiate and conduct electrical impulses throughout the heart, coordinating the contractions of the atria and ventricles. They make up approximately 1% of cardiac cells.
- Mechanism: Pacemaker cells have the unique ability to spontaneously depolarize, generating action potentials without external stimulation. This inherent rhythmicity sets the heart rate.
- Location: Key components of the heart's conduction system, including the sinoatrial (SA) node (the primary pacemaker) and the atrioventricular (AV) node.
- Characteristics:
- Fewer contractile filaments than contractile cells.
- Specialized ion channels that allow for spontaneous depolarization.
- Form the intrinsic conduction system of the heart, ensuring coordinated and efficient contractions.
In summary, while myocardial contractile cells perform the actual pumping action of the heart, the myocardial conducting cells orchestrate this action by generating and transmitting the electrical signals that trigger the contractions. Both cell types are essential for proper cardiac function.
