The medulla oblongata, a structure comprising the lower section of the brain stem, is responsible for a number of tasks essential to human life. There is no single function of the medulla, but most of the processes it controls are related to one another. These involuntary functions include the regulation of heart rate, blood pressure, breathing, and digestion. Sleep and arousal, some motor control, and sensory relay to the cortex are all other significant duties of this structure. The exact role of some parts of the medulla have not yet been identified, and as research continues, more functions could be revealed.
The medulla is influenced by several types of unique receptors throughout the body that react to environmental changes. Chemoreceptors in the lungs send information back to the medulla, signalling when a different rate of respiration is needed. Baroreceptors in the blood vessels monitor blood pressure, and sends this information to the nucleus tractus solitarius in the medulla. This structure then can send signals via the autonomic nervous system to effect changes in heart rate and vascular resistance.
Another important function of the medulla is to regulate reflex actions involving the face and throat. This allows such actions to be performed without time consuming cognitive processing. Certain stimuli cause the medulla to send signals through the cranial nerves to execute actions like sneezing, swallowing, or coughing. While not always a reflex, the neurons that initiate vomiting are also found here. If these actions had to be initiated in higher cortical areas, there is the chance they could not be performed in time to be helpful.
The inferior olivary nucleus located in this region shares connections with the cerebellum, and is involved in physical movement. Although this function of the medulla is not to initiate movements, it helps with their control and refinement. This area also helps to ensure the coordination of movements with cognition and sensory processes. This task may be accomplished by the nucleus encoding the timing of the arrival of sensory information.
Several nuclei exist in the medulla that receive sensory information from the nerves of the peripheral nervous system. These reveal another important function of the medulla, which is to relay sensations of touch, pain, balance, and limb position to the cortex. The gracile nucleus and fasciculus are the largest nuclei that accomplish these activities, and damage to them can result in a loss of sensation.
