Swallowing Centers In the Brain
The voluntary initiation of swallowing takes place in special areas of the cerebral cortex of the brain, which is the area that commands the brain’s functions. The regions of the cerebral cortex that command swallowing are located in the precentral, posterior-inferior, and frontal- gyri.
These structures of the cerebral cortex send orders via nerve axons that travel through a nerve pathway called the corticobulbar tract to a swallowing center in the medulla, which is part of the brainstem.
Nerve signals originating in the mouth receive input about the food we are chewing. Several sensory nerves in the mouth, pharynx, and larynx bring information to the brain that allows us to know what type of material is in the mouth and throat. For instance, they “tell” the brain about the size, temperature, and texture of food.
This information is sent to the sensory cortex of the brain, and the medulla integrates with the sensory information in order to direct the efforts of the muscles of chewing, which work together to chew the food.
Nerves Involved in Swallowing
The act of chewing changes the food into a softer and more slippery food bolus that is suitable and safe for swallowing. As the swallowing reflex advances through its different phases, the nerves involved in swallowing trigger the reflexive closing of the larynx and the epiglottis. This closing off of the ‘windpipe’ prevents food and liquid particles from entering the lungs.
If the windpipe dies not properly close off, or if swallowing is not well coordinated, problems such as choking can occur. Another complication of swallowing problems, aspiration pneumonia, can happen if food enters the lungs. This may happen as the result of a stroke or other neurological disorders.
The following sensory nerves are involved in swallowing:
Trigeminal (cranial nerve V)
Facial (cranial nerve VII)
Glossopharyngeal (cranial nerve IX)
Vagus (cranial nerve X)
The muscles of swallowing are controlled by several cranial nerves These are:
The nucleus ambiguous (of the vagus and glossopharyngeal nerves)
The dorsal motor nucleus (of the vagus nerve)
The hypoglossal nucleus (of the hypoglossal nerve)