The Cranial Nerves and Their Functions

Why does pressure on the meninges cause a variety of symptoms?

To recap, pressure or a tug on the membrane system (meninges), which envelops the brain and spinal cord (CNS) as one unit, anywhere from the top of the head to the bottom of the spine may produce a myriad of symptoms, such as impaired vision, headaches, difficulty with hearing and balance, nausea, digestive upset, impaired speech, difficulty breathing, and many more. So will trauma to the head as well as the spine.

Trauma to the head or spine may shift the skull bones and irritate the cranial nerves.

The cranium has many openings called foramina through which the 12 cranial nerves, numbered one through twelve in Roman numerals (I-XII), exit the skull.  A shifting of the skull bones may change the shape and size of the foramina and distort the meninges lining the inside of the skull, thus compressing or stretching the cranial nerves as they pass through these openings.  Know that the cranial nerves have to pass through the membrane, as well as the foramina of the cranium.

We all know that tight muscles or dislocated vertebrae parking on our nerves may produce tremendous pain, as well as dysfunction in the structures that the nerves innervate.  The same is true regarding the cranial nerves.  Any trauma to these 12 cranial nerves will result in dysfunction of the structures that they innervate, as well as pain or discomfort.

The functions of the 12 cranial nerves

There are 12 cranial nerves. These nerves transmit information between the brain and the various regions of the body. Each nerve controls a specific type of function, such as sight, hearing, or smell.

The 12 cranial nerves have various names but are also assigned Roman numerals for ease of reference. Here is a list of the cranial nerves and their functions, ordered by their assigned Roman numeral:

  • I – (olfactory nerve):  allows us to smell.
  • II – (optic nerve):  allows us to see.
  • III, IV, VI – (oculomotor, trochlear, and abducens nerves): supply the muscles that move the eyes.
  • V – (trigeminal nerve): supplies the sensory nerves of the face, as well as the muscles involved in chewing (mastication).
  • VII – (facial nerve): primarily supplies the muscles of expression in our face.
  • VIII – (vestibulocochlear nerve): allows us to hear and maintain balance.
  • IX – (glossopharyngeal nerve): gives sensation to the posterior one third of the tongue, the tonsils, pharynx, and middle ear, as well as allows us to swallow and produce saliva.
  • X – (the famous vagus nerve): innervates the larynx,  trachea, bronchi, lungs, heart, digestive tract (from the mouth to the first one third of the large intestine), as well as the external ear.
  • XI – (accessory nerve): allows us to turn our head and tilt it to the side, as well as raise and lower our shoulders.
  • XII – (hypoglossal nerve): primarily supplies the tongue muscles for speech and moving food to the back of the mouth for swallowing.

In conclusion, trauma to your head can cause symptoms in different parts of your body

So, there you have it in a nutshell:  If your brain gets hurt, you will hurt, too, although not always the way you would expect it.  However, knowing that these 12 cranial nerves are extensions of the brain that find their way into the body through the bony labyrinth of your skull helps to understand why we feel the way we do when we sustain injury to the face or head.

The spinal nerves are extensions of the brain as well.  They leave the cranium via the spinal cord.  Pressure on these nerves can, like with cranial nerves, cause symptoms in various parts of one’s body.

In the next post, we will explore the functions of the spinal nerves.