How Your Brain Controls Swallowing

old woman drinking water
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Believe it or not, swallowing is one of the most complicated tasks that your body performs, as it requires a delicate coordination between your brain, and certain nerves and muscles. 

Cranial Nerves and Muscles Involved in Swallowing

Swallowing occurs in three sequential phases, all requiring the careful coordination of muscles in the mouth, pharynx (your throat), larynx (your voicebox), and esophagus (a hollow tube that carries food from your throat to your stomach).

These muscles are all under the control of a group of nerves called your cranial nerves.

The cranial nerves are 12 pairs of nerves that emerge from the brainstem, located at the base of your brain. Your cranial nerves control functions such as smelling, tasting, swallowing, seeing, moving your face and eyes, and shrugging your shoulders. Several of the cranial nerves are involved with controlling the coordination and movements involved in chewing and swallowing.

The following cranial nerves are involved in swallowing:

  • Trigeminal (cranial nerve V)
  • Facial (cranial nerve VII)
  • Glossopharyngeal (cranial nerve IX)
  • Vagus (cranial nerve X)
  • Hypoglossal nerve (cranial nerve XII)

In turn, cranial nerves are controlled by “processing centers” in the brain where information related to swallowing is processed. These centers include areas located in the cerebral cortex, the medulla oblongata, and the cranial nerve nuclei.

Swallowing Centers In the Brain

The voluntary initiation of swallowing takes place in special areas of the cerebral cortex of the brain, called the precentral gyrus (also called the primary motor area), posterior-inferior gyrus and the frontal gyrus. Information from these areas converge in the swallowing center in the medulla, which is part of the brainstem.

 

Apart from the brain, 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 eventually the medulla, which uses the sensory information to direct the efforts of the muscles of chewing.

Potential Complications of Swallowing Problems

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 does 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 disorder.

Lastly, malnutrition and dehydration may occur as a result of swallowing difficulties.

How Swallowing Is Affected by Stroke

As you can see, there are multiple areas of the central nervous system which, if affected by a stroke or another neurological condition like multiple sclerosis, Parkinson's disease, or dementia, could disrupt the ability to swallow.

Even more so, the medulla is a relatively small area of the brainstem that contains multiple structures that are critical in carrying out the swallowing reflex—so strokes that involve the medulla are especially likely to cause swallowing problems.

In fact, people with medullary strokes may require temporary or permanent feeding tube placement to prevent choking and aspiration pneumonia.

A Word From Verywell

While living with swallowing problems certainly adds a complication to your life, know that there are well-designed techniques that can help you or your loved one safely adapt to these difficulties. For instance, a speech and swallow therapist can help you make adjustments to the types of food and liquids that you consume in order to make it easier for you to safely swallow. 

In addition, swallowing exercises like the supraglottic swallow or Mendelsohn's maneuver can help strengthen your muscles involved in swallowing. These oral movement exercises and others strategies like using a cup, straw, or spoon can further be helpful. 

Sources:

Alali D, Ballard K, Bogaardt H. Treatment effects for dysphagia in adults with multiple sclerosis: A systematic review. Dysphagia. 2016 Oct;31(5):610-8.

Lembo AJ. (2017). Oropharyngeal dysphagia. Talley NJ, ed. UpToDate. Waltham, MA: UpToDate Inc.

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