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A wave of contraction spreads from the S...

A wave of contraction spreads from the S-A node across the walls of the atria to the _______, which transmits impulses to the ventricles via _______.

A

atrio-ventricular node, a bundle of branching fibers

B

A-V node, bundle of His

C

Atrio-ventricular node, bundle of His

D

All of the above

Text Solution

AI Generated Solution

The correct Answer is:
To answer the question, we need to understand the sequence of electrical conduction in the heart, particularly how impulses travel from the sinoatrial (S-A) node to the ventricles. ### Step-by-Step Solution: 1. **Identify the Starting Point**: The electrical impulse begins at the sinoatrial (S-A) node, which is located in the right atrium of the heart. This node is often referred to as the natural pacemaker of the heart. 2. **Contraction of Atria**: The wave of contraction spreads from the S-A node across the walls of the atria, causing them to contract and push blood into the ventricles. 3. **Next Structure**: After the atria contract, the impulse travels to the atrioventricular (AV) node. The AV node is located at the junction between the atria and ventricles and serves as a critical relay point for the electrical signals. 4. **Transmission to Ventricles**: From the AV node, the impulse is transmitted to the ventricles through the bundle of His (also known as the atrioventricular bundle). The bundle of His then branches into the right and left bundle branches. 5. **Final Pathway**: The electrical impulses further spread through the Purkinje fibers, which are specialized fibers that distribute the impulse throughout the ventricles, leading to their contraction. ### Final Answer: A wave of contraction spreads from the S-A node across the walls of the atria to the **AV node**, which transmits impulses to the ventricles via the **bundle of His**.
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