22. Choose the correct sequence of action potential conduction along the conductive tissues of the heart:...

22. Choose the correct sequence of action potential conduction along the conductive tissues of the heart:

a. SA node → AV node → Bundle of His → Purkinje fibers → Bundle branches

b. SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

c. SA node → AV node → Bundle branches → Bundle of His → Purkinje fibers

d. SA node → AV node → Purkinje fibers → Bundle of His → Bundle branches

e. AV node → SA node → Bundle of His → Bundle branches → Purkinje fibers

Expert Solution

22. Choose the correct sequence of action potential conduction along the conductive tissues of the heart:

Answer: b) SA node --> AV node --> Bundle of His --> Bundle branches --> Purkinje fibers

Explanation: The electrical impulse in the heart originates in sinoatrial node (SA node) which is a group of specialised cardiac muscle cells located in the wall of the right atrium of the heart. SA node constantly generates electrical signals (action potential) which travels through the conductive system of the heart causing the rhythmic contraction and relaxation of the heart. Thus, SA node is called as the natural pacemaker of the heart as it sets the rate and rhythm of the heart beat.

From the SA node, action potential is transmitted to both the atria causing their contraction. After the atria, the signal reaches atrioventricular node (AV node) which is located in the interatrial septum. From AV node, action potential is transmitted to Bundle of His which later divides into left and right bundle branches. Both left and right bundle branches are located in the interventricular septum. The action potential from left and right bundle branches are spread across the ventricular wall by finer branches called Purkinje fibers that innervate entire ventricular wall.

The action potential generated by SA node is spread across the entire heart through a network of specialised cardiac cells which constitutes the conductive system of the heart. Thus, the action potential is transmitted along the entire conductive system of the heart causing the rhythmic contraction and relaxation of the heart.

Sydney Mullin answered 1 year ago

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