Pathway of impulse or correct route through which pulse making impulse travels in the heart

Options

A. AV node ` to ` Bundle of His ` to ` SA node ` to ` Purkinje fibres ` to ` Heart muscles
B. AV node ` to ` SA node ` to ` Purkinje fibres ` to ` Bundle of His ` to ` Heart muscles
C. SA node ` to ` Purkinje fibres ` to ` Bundle of His ` to ` AV node `to ` Heart muscles
D. SA node ` to ` AV node ` to ` Bundle of His ` to ` Purkinje fibres ` to ` Heart muscles

Explanation

To understand the pathway of impulse in the heart, we need to follow the sequence of structures through which the electrical impulse travels. Here is the step-by-step explanation:

### Step-by-Step Solution:

1. **Sinoatrial Node (SA Node)**: The impulse begins at the SA node, located in the right atrium. This node is known as the pacemaker of the heart because it generates electrical impulses that initiate the heartbeat.

2. **Atrial Contraction**: As the impulse spreads from the SA node, it travels through the atria, causing them to contract (atrial systole). This contraction pushes blood into the ventricles.

3. **Atrioventricular Node (AV Node)**: After the atria contract, the impulse reaches the AV node, which is also located in the right atrium. The AV node serves as a gatekeeper, briefly delaying the impulse before it passes into the ventricles, allowing time for the ventricles to fill with blood.

4. **Bundle of His**: From the AV node, the impulse travels down into the interventricular septum through a bundle of fibers known as the Bundle of His. This structure conducts the impulse into the ventricles.

5. **Right and Left Bundle Branches**: The Bundle of His splits into two branches: the right bundle branch and the left bundle branch. These branches carry the impulse to the respective ventricles.

6. **Purkinje Fibers**: The impulse then travels through the Purkinje fibers, which spread throughout the ventricular myocardium (heart muscle). This ensures that the contraction occurs simultaneously in both ventricles.

7. **Ventricular Contraction**: Finally, the impulse causes the ventricles to contract (ventricular systole), pumping blood out of the heart to the lungs and the rest of the body.

### Final Pathway:
The correct pathway of impulse in the heart is: **SA Node → AV Node → Bundle of His → Right and Left Bundle Branches → Purkinje Fibers → Heart Muscles**.