Action potentials are generated at maximum frequency by

Options

A. Bundle of His
B. Purkinje fibres
C. SAN
D. Ventricles

Answer

To solve the question "Action potentials are generated at maximum frequency by," we will analyze the options provided and understand the role of different cardiac tissues in generating action potentials.

### Step-by-Step Solution:

1. **Understanding Action Potentials**: Action potentials are electrical impulses that trigger heart contractions. They are generated by specialized tissues in the heart.

2. **Identify the Cardiac Tissues**: The options given are:
- Bundle of His
- Purkinje fibers
- Senoatrial node (S.A.N.)
- Ventricles

3. **Role of Each Tissue**:
- **Bundle of His**: This tissue conducts impulses from the atria to the ventricles but does not generate impulses at a high frequency.
- **Purkinje Fibers**: These fibers distribute the action potentials throughout the ventricles but have a lower frequency of impulse generation compared to the S.A.N.
- **Ventricles**: The ventricles contract in response to impulses but are not the primary generators of action potentials.
- **Senoatrial Node (S.A.N.)**: This is known as the pacemaker of the heart. It generates action potentials at the highest frequency, typically around 70 to 75 times per minute.

4. **Conclusion**: Since the S.A.N. generates action potentials at the highest frequency compared to the other options, it is responsible for initiating the heartbeat.

5. **Final Answer**: The correct answer is **Senoatrial Node (S.A.N.)**.