The rate of heartbeat is regulated by the integrated activity of inhibiting and accelerating effects occuring in which part of the brain ?

Options

A. Cerebellum
B. Diencephalon
C. Medula oblongata
D. Pons Varolii

Explanation

To answer the question regarding the regulation of the heartbeat by the integrated activity of inhibiting and accelerating effects in the brain, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Heartbeat Regulation**: The heartbeat is regulated by the brain through neural centers that manage both the acceleration and inhibition of heart rate.

2. **Identifying the Brain Regions**: The question provides four options: cerebellum, diencephalon, medulla oblongata, and pons varolii. We need to identify which of these is responsible for regulating the heartbeat.

3. **Role of the Medulla Oblongata**: The medulla oblongata is a part of the brainstem and is known to control various autonomic functions, including the regulation of heart rate. It contains the cardiac control center.

4. **Autonomic Nervous System**: The medulla oblongata regulates the heart rate through the autonomic nervous system, which consists of two main components: the sympathetic and parasympathetic nervous systems.

5. **Sympathetic Nervous System**: The sympathetic nervous system is responsible for accelerating the heart rate. It sends neural signals that increase heart rate and the strength of ventricular contractions.

6. **Parasympathetic Nervous System**: Conversely, the parasympathetic nervous system decreases the heart rate. It sends signals that reduce the heart rate and the strength of ventricular contractions.

7. **Conclusion**: The integrated activity of these two systems (sympathetic and parasympathetic) in the medulla oblongata regulates the heartbeat effectively.

### Final Answer:
The rate of heartbeat is regulated by the integrated activity of inhibiting and accelerating effects occurring in the **medulla oblongata**.

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