Brainstem, artwork. At bottom is the medulla oblongata, which controls automatic functions and relays messages from the brain to the spinal cord. Above at centre is the 4th ventricle, which is filled with cerebrospinal fluid. At bottom right and left are the pons, which are involved in the control of sleep and arousal. Copies of muscle movement signals from the cerebellum are passed to the pons by the middle peduncles (flat), fibrous bundles above the pons. At top is the thalamus (bilobed), which processes sensory signals. At top centre is the pineal gland, which regulates circadian (daily) rhythms. Below this are the superior (upper) and inferior (lower) colliculi that receive visual and auditory input.