The intrinsic ability and of cardiac muscle to generate action potentials (APs) rhythmically is achieved by the normal pace maker, the sino-atrial node (S-A node). The S-A node is part of the special excitatory and conductive system of cardiac muscle. With the help of a diagram, describe this conductive system how the AP spreads throughout the muscle.
Apologies, but I can't generate a diagram for you. However, I can describe the conductive system and the spread of action potentials (APs) throughout the cardiac muscle.
The conductive system of the cardiac muscle consists of specialized cells that generate and conduct electrical impulses. These cells are interconnected through gap junctions, allowing for rapid transmission of electrical signals.
The Sino-Atrial (S-A) node, located in the right atrium near the entrance of the superior vena cava, is the natural pacemaker of the heart. It initiates the electrical impulses that regulate the heartbeat. From the S-A node, the electrical impulses spread through the following pathway:
1. Sino-Atrial (S-A) node: This node initiates the electrical impulses and serves as the natural pacemaker. It generates action potentials spontaneously at a regular rate.
2. Internodal Pathways: The electrical impulses from the S-A node spread through specialized pathways within the right atrium called internodal pathways. These pathways consist of the anterior, middle, and posterior internodal tracts.
3. Atrioventricular (A-V) node: The electrical impulses reach the A-V node, located at the junction between the atria and ventricles near the tricuspid valve. The function of the A-V node is to delay the transmission of the impulses, allowing the atria to contract before the ventricles.
4. Bundle of His: After the delay in the A-V node, the electrical impulses enter the Bundle of His, a specialized bundle of conducting fibers. It is located in the interventricular septum, which separates the ventricles.
5. Purkinje Fibers: The bundle of His divides into left and right bundle branches that spread throughout the ventricular walls. These branches further divide into Purkinje fibers, which rapidly conduct the electrical impulses to all parts of the ventricular myocardium.
The action potential spreads through the cardiac muscle cells via gap junctions, allowing for coordinated contraction of the atria and ventricles. This synchronized contraction ensures an efficient pumping of blood by the heart.
Please note that cardiac muscle cells are capable of generating action potentials on their own, but the natural pacemaker (S-A node) sets the pace and coordinates the rhythmical firing of action potentials within the heart.