The correct answer is option 'C', the Medulla Oblongata.

The Medulla Oblongata is a part of the brainstem, located at the base of the brain. It is responsible for controlling many involuntary actions in the body, including the movement of the lungs in breathing and the contraction of the heart.

Here's a detailed explanation of how the Medulla Oblongata controls these functions:

1. Overview of the Medulla Oblongata:
The Medulla Oblongata is a crucial structure in the brainstem that connects the brain to the spinal cord. It plays a vital role in controlling various autonomic functions, such as regulating heart rate, blood pressure, and respiratory rhythm.

2. Control of Breathing:
Breathing is an essential process that ensures the supply of oxygen and removal of carbon dioxide in the body. The Medulla Oblongata contains specialized cells called respiratory centers, which regulate the rate and depth of breathing.

- The primary respiratory centers in the Medulla Oblongata are the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). These centers receive information from sensors in the body and adjust the breathing rate accordingly.
- The DRG is responsible for generating the basic rhythm of breathing, while the VRG helps in controlling the force and depth of breathing.
- The Medulla Oblongata also receives feedback from chemoreceptors in the blood vessels that detect changes in oxygen and carbon dioxide levels. This feedback helps in fine-tuning the respiratory rate to maintain the body's homeostasis.

3. Control of Heartbeat:
The Medulla Oblongata also plays a crucial role in regulating the heartbeat and maintaining blood pressure.

- It contains the cardiac center, which controls the rate and force of the heartbeat. The cardiac center receives inputs from various receptors, such as baroreceptors (detect changes in blood pressure) and chemoreceptors (detect changes in blood oxygen and carbon dioxide levels).
- Based on the inputs received, the Medulla Oblongata sends signals to the heart through the autonomic nervous system, specifically the sympathetic and parasympathetic branches. These signals adjust the heart rate and contraction strength to meet the body's requirements.

In conclusion, the Medulla Oblongata, located in the brainstem, is responsible for controlling involuntary actions like breathing and heartbeat. It contains specialized centers that regulate the respiratory rhythm and adjust the heart rate and force of contraction. These functions are crucial for maintaining homeostasis and ensuring the body's proper functioning.