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Given these structures of the conduction...

Given these structures of the conduction system of the heart
1. Bundles of His 2. AV node
3. Bundle branches
4. Purkinje fibres
5. SA node
Choose the arrangement that lists the structures in an order of an action potential passes through them.

A

2,5,3,1,4

B

5,2,1,3,4

C

2,5,1,3,4

D

5,2,4,1,3

Text Solution

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The correct Answer is:
To determine the correct order of structures in the conduction system of the heart through which an action potential passes, we can follow these steps: ### Step-by-Step Solution: 1. **Identify the Starting Point**: The conduction system of the heart begins at the **SA node** (Sinoatrial node), which is known as the natural pacemaker of the heart. It generates electrical impulses that initiate the heartbeat. 2. **Next Structure**: After the SA node, the electrical impulses travel to the **AV node** (Atrioventricular node). The AV node acts as a gatekeeper, slowing down the impulse before it moves to the ventricles, allowing the atria to contract and pump blood into the ventricles. 3. **Proceed to the Bundle of His**: From the AV node, the action potential moves to the **Bundle of His**. This structure is a pathway that conducts the impulses from the AV node down into the ventricles. 4. **Continue to the Bundle Branches**: The Bundle of His splits into two pathways known as the **Bundle branches** (right and left). These branches carry the electrical impulses towards the apex of the heart. 5. **Final Destination - Purkinje Fibres**: Finally, the impulses reach the **Purkinje fibres**, which spread throughout the ventricles, causing them to contract and pump blood out of the heart. ### Correct Order: Thus, the correct sequence in which the action potential passes through the conduction system of the heart is: 1. SA node 2. AV node 3. Bundle of His 4. Bundle branches 5. Purkinje fibres ### Answer: The correct arrangement is: **5 (SA node) → 2 (AV node) → 1 (Bundle of His) → 3 (Bundle branches) → 4 (Purkinje fibres)**.
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