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 cardiac muscle consists of specialized cells that are responsible for generating and conducting action potentials rhythmically, ensuring coordinated contractions of the heart. One of the key components of this system is the sino-atrial node (S-A node), also known as the natural pacemaker of the heart.
Here is a simplified diagram illustrating the conductive system and the spread of action potentials throughout the cardiac muscle:
1. Sino-Atrial (S-A) Node: The S-A node is located at the junction of the superior vena cava and right atrium. It is a small group of specialized cells that initiate the electrical impulses in the heart. These cells possess an intrinsic ability to spontaneously depolarize and generate action potentials.
S-A node
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Right atrium Superior vena cava
2. Internodal Pathways: The action potentials generated by the S-A node radiate in all directions through specialized conduction pathways called internodal pathways. These pathways conduct the electrical impulses from the S-A node to the atria, stimulating their contraction.
Internodal Pathways
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Anterior path Middle path Posterior path
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Left atrium S-A Node Right atrium
3. Atrioventricular (A-V) Node: After the electrical impulses reach the atria, they travel towards the atrioventricular (A-V) node, located at the bottom of the right atrium. The A-V node serves as a gatekeeper, delaying the transmission of the electrical impulses from the atria to the ventricles. This delay allows the atria to complete their contraction before the ventricles contract.
Left atrium A-V Node Right atrium
4. Bundle of His: Beyond the A-V node, the action potentials continue their journey through the bundle of His, a bundle of specialized muscle fibers that conducts the impulses towards the ventricles.
Bundle of His
5. Purkinje Fibers: The bundle of His divides into smaller branches called Purkinje fibers, which spread throughout the ventricles. These fibers rapidly distribute the action potentials to the ventricular muscles, triggering their contraction in a synchronized manner.
Purkinje Fibers
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Left Ventricle Right Ventricle
Overall, this specialized conductive system ensures that the action potentials originating from the S-A node are transmitted efficiently and uniformly, leading to the coordinated contraction of the atria and ventricles, ultimately facilitating proper heart function.