What is the primary function of the brain stem?

The primary function of the brain stem is to serve as a critical connection between the brain and the spinal cord. This structure coordinates many essential functions needed for survival, including regulating involuntary processes like breathing and heart rate, but its most fundamental role is maintaining the pathway for signals traveling between the brain and the rest of the body via the spinal cord. It acts as a relay station for information, ensuring that signals can be transmitted efficiently, allowing for communication between the central nervous system and the peripheral nervous system.

While regulating body temperature, controlling voluntary movements, and filtering air in the lungs are all important bodily functions, they are not the primary responsibilities of the brain stem. Other parts of the nervous system or different organs oversee those functions. For example, the hypothalamus plays a vital role in temperature regulation, the motor cortex is involved in voluntary movements, and the respiratory system, particularly the lungs and diaphragm, deals with air filtration during the process of breathing.