Final answer:
The brain stem connects the lower and upper parts of the brain, with the pons and medulla playing critical roles in regulating sleep, breathing, heart rate, and other autonomic functions.
Step-by-step explanation:
The part of the brain that connects the lower and upper parts is known as the brain stem. This includes the midbrain, the pons, and the medulla oblongata.
As the name suggests, the pons serves to connect the hindbrain to the rest of the brain, playing a pivotal role in regulating brain activity during sleep and in various autonomic functions. Both the pons and the medulla are involved in important processes such as breathing, heart rate, and blood pressure.
In detail, the brain stem is composed of the midbrain, the pons, and the medulla oblongata. Together, these structures support basic life functions, coordinate motor control signals, and integrate sensory and motor information.
The pons facilitates the relay of messages between different parts of the brain and plays a role in respiratory regulation and may be involved in the dreaming phase of sleep. The medulla, alongside the pons, controls subconscious functions including cardiovascular and respiratory systems' regulation.
The midbrain is part of the brain stem that handles auditory and visual sensory input and has a role in the reticular formation, which is critical for sleep and arousal. The cerebellum, attached to the brain stem but considered a separate region, helps in coordinating movement and is connected to the pons.