Cranial nerves – Anatomy and Functions

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What are the cranial nerves?

Cranial nerves are a type of nerves that send electrical signals between the brain and different parts of the body, including the neck, eyes and head. These signals help to sense smell, taste, hear and move the facial muscles.

The cranial nerves start from the back of the brain and extend to the spinal cord. These nerves play a crucial part in the operation of the nervous system.

How many cranial nerves are there?

There are 12 types of cranial nerve pairs. Each nerve pair splits to serve both sides of the brain and body.

What are the types of cranial nerves?

Cranial nerves are divided into 12 pairs based on their individual function. Experts categorise the cranial nerves based on different functions.

1. Olfactory nerve: Sense of smell.

2. Optic nerve: Ability to see.

3. Oculomotor nerve: Ability to move and blink your eyes.

4. Trochlear nerve: Ability to move your eyes up and down or back and forth.

5. Trigeminal nerve: Ability to move face and cheeks, taste and jaw movements.

6. Abducens nerve: Ability to move your eyes.

7. Facial nerve: Facial expressions and sense of taste.

8. Auditory/vestibular nerve: Sense of hearing and balance.

9. Glossopharyngeal nerve: Ability to taste and swallow.

10. Vagus nerve: Digestion and heart rate.

11. Accessory nerve (or spinal accessory nerve): Shoulder and neck muscle movement.

12. Hypoglossal nerve: Ability to move your tongue.

What is the main purpose of the cranial nerves?

The following are some of the essential functions of cranial nerves. They play a significant role in controlling sensation and motor skills. Cranial nerves help you to feel, touch, hear, taste, smell and see.

Motor nerves play a role in managing the glands and facial muscles. Some cranial nerves have both motor and sensory functions.

Where is the location of the cranial nerves?

Cranial nerves first originate in the cerebrum. The cerebrum is the most significant portion of the brain that resides above the brainstem. Cranial nerves are sub-divided into two pairs.

· Olfactory nerves – Responsible for detecting the sense of smell.

· Optic nerves – Affects the ability to see. The other ten pairs of cranial nerves commence in the brainstem. The brainstem connects the spinal cord and the brain.

What is the longest cranial nerve?

The longest cranial nerve known as the vagus nerve, which has both motor and sensory functions. It runs through many body parts, including the heart, throat, tongue and digestive system.

What conditions affect cranial nerves?

Some conditions may damage different brain parts where cranial nerves are located. In some instances, a condition may damage only one cranial nerve. Trauma or surgery may injure any of the nerves.

Disorders that affect the cranial nerves includes the following.

Amyotrophic lateral sclerosis (ALS): A disorder where nerve cells break down, and the muscle becomes weak.

Bell’s palsy: Sudden drooping and muscle weakness on either side of the face.

Hemifacial spasm: Involuntary face contractions on any one side of the face.

Internuclear ophthalmoplegia: Inability to move eyes in sync when you look to the side.

Oculomotor palsy: Injury to the third cranial nerve that causes any of your eyes to stay immobile despite going down and out to the side.

Stroke: Hindrance to the blood supply in the brain because of a blood clot blood vessel.

Traumatic brain injury: Disruption to the brain function due to a sudden blow to the head.

Trigeminal neuralgia: Chronic pain in the fifth cranial nerve runs through your cheek.

What are the common signs or symptoms of cranial nerve disorders?

In general, cranial nerves affect many functions and sensations of the body. Due to this, different cranial nerve disorders occur with different symptoms. A cranial nerve disorder might affect any of the following.

  • Balance
  • Facial expressions
  • Hearing
  • Sense of smell
  • Swallowing
  • Taste
  • Vision

When should I call my doctor?

The symptoms of cranial nerve injuries vary depending on the type of nerve being affected. Try to seek help from your doctor if you experience any of the following.

  • Drooling with no known cause
  • Drooping in one side of your face
  • Facial pain
  • Muscle weakness or paralysis
  • Slurred speech
  • Tingling anywhere in your body
  • Vision loss

Summing up

Cranial nerves are nerve pairs that help in connecting the brain to parts of the body and play a vital role in the movement and sensation of the body.

If a condition or injury affects your cranial nerves, you may have problems with taste, smell and Vision. It predominantly affects the ability to make facial expressions.

Your entire nervous system becomes healthier by eating nutritious foods, exercising and managing health conditions.

FAQs

What is the structure and function of the cranial nerve?

The cranial nerves combine 12 paired nerves in the back of your brain. They are responsible for sending electrical signals from the brain to the face, neck and torso. They help you taste, smell, hear and feel sensations.

Which is the largest cranial nerve?

The vagus nerve is the longest cranial nerve in the body.

Which is the smallest cranial nerve?

The trochlear nerve is the smallest cranial nerve in terms of the number of axons it contains.

Which is the thickest nerve?

The sciatic nerve is the thickest and longest nerve in the body. It’s made up of five nerve roots.


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