The intrinsic ability 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.
The conductive system of the cardiac muscle consists of several specialized components that are responsible for generating and conducting action potentials to ensure coordinated muscle contractions.
One of the key components of this system is the sino-atrial (S-A) node. The S-A node is a small cluster of cells located in the upper right atrium near the entrance of the superior vena cava. It acts as the natural pacemaker of the heart, initiating the generation of action potentials.
Here is a diagram illustrating the conductive system of the cardiac muscle:
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SA Node AV Node
|______| |______|
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Bundle of His
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Purkinje Fibers
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1. Sino-Atrial (S-A) Node: As mentioned, the S-A node is located in the right atrium, near the superior vena cava. It generates spontaneous action potentials at regular intervals, establishing the basic rhythm of the heart.
2. Atrioventricular (AV) Node: The action potentials generated by the S-A node spread through both atria, causing them to contract. From the atria, the electrical impulses reach the AV node, which is situated in the lower part of the interatrial septum. The AV node acts as a gatekeeper, delaying the conduction of electrical signals to allow the atria to contract fully and fill the ventricles.
3. Bundle of His: After passing through the AV node, the action potentials enter the Bundle of His. It is a specialized bundle of conducting fibers located in the interventricular septum, which divides into the left and right bundle branches.
4. Purkinje Fibers: The bundle branches divide into smaller branches known as Purkinje fibers. These fibers spread throughout the ventricles, carrying the action potentials to individual cardiac muscle cells in the ventricular walls.
As the action potentials propagate through the Purkinje fibers, they rapidly spread to the surrounding cardiac muscle cells, resulting in coordinated contraction of the ventricles.
Note: The diagram provided is a simplified representation of the cardiac conductive system and may not include all the intricate details and structures involved.