Final answer:
The brain stem consists of the midbrain, medulla oblongata, and the pons. It controls unconscious functions such as heart rate and breathing, and regulates basic survival functions like breathing, heartbeat, and blood pressure.
Step-by-step explanation:
The brain stem is the lowest part of the brain that connects the brain with the spinal cord. It consists of the midbrain, medulla oblongata, and the pons, and controls unconscious functions such as heart rate and breathing. Clusters of cells in the brain stem regulate basic survival functions like breathing, heartbeat, and blood pressure.