Which part of the brainstem is responsible for controlling heartbeat and breathing?

The medulla is a crucial part of the brainstem that plays a vital role in regulating autonomic functions such as heartbeat and breathing. It contains vital centers that monitor and adjust these functions to maintain homeostasis in the body. The medulla oblongata specifically houses the cardiac center, which influences heart rate, and the respiratory center, which controls the rhythm and depth of breathing. This control is essential for survival, as it ensures that oxygen levels are regulated and waste gases like carbon dioxide are properly expelled from the body.

The thalamus acts primarily as a relay station for sensory and motor signals but does not directly regulate autonomic functions like heartbeat and breathing. The cerebellum is mainly involved in coordination and fine-tuning of voluntary movements and balance, rather than the automatic regulation of respiratory and cardiac functions. The reticular formation plays a role in regulating wakefulness and attention and has some involvement in autonomic control but is not as central to the direct regulation of heart rate and breathing as the medulla. Thus, the medulla's specific functions make it the correct answer to the question.