The part of the brain comprising the medulla oblongata, the midbrain, and the pons. Superficially it resembles and is continuous with the spinal cord. The midbrain controls and integrates reflex activities (such as breathing and swallowing) that originate in higher centres of the brain. The reticular formation (sometimes called the reticular activating system) is a network of neural fibres and cell bodies that extends the length of the brainstem. It receives sensory inputs of all kinds and regulates how much attention we give to them by acting as a sensory filter. It also influences muscle tone, and is thus a crucial part of the system governing arousal, wakefulness, and sleep. Ascending fibres of the reticular formation connect with neurons in the adjacent thalamus and hypothalamus, which in turn influence the cerebral cortex.