Which structure at the base of the brainstem controls heartbeat and breathing?

The structure at the base of the brainstem that is primarily responsible for regulating vital functions such as heartbeat and breathing is the medulla. The medulla oblongata contains the cardiovascular center, which manages the heart rate and blood pressure, as well as the respiratory centers that control the rhythm and rate of breathing. This part of the brainstem acts as a critical hub for autonomic functions, ensuring that these involuntary processes maintain homeostasis and support life.

The thalamus serves as a relay station for sensory information and is not directly involved in the control of autonomic functions such as heartbeat and breathing. The cerebellum is primarily responsible for coordination and movement, contributing to balance and motor control but not autonomic functions. The reticular formation plays a role in arousal and the sleep-wake cycle rather than directly regulating cardiovascular or respiratory functions. Therefore, the medulla is the correct answer, as it directly governs the life-supporting processes critical to survival.