The 12 Cranial Nerves And Their Functions

The complexity of the nervous system is great. Its multiple connections make this system one of the most important in our body. In this article we will talk about several of its most important pathways: the cranial nerves.

The cranial nerves or pairs arise from the base of the skull and reach their destination areas through holes distributed in it. Thus, they communicate with peripheral areas. Its name is due to the fact that there is a nerve on both one side and the other of the brain. So there are twelve nerves in the right hemisphere and twelve nerves in the left.

Classification of the cranial nerves

The cranial nerves can be classified in different ways:

• According to its function.
  • Motor cranial nerves . There are the cranial nerves that are related to eye movements: three, four and five; and the cranial nerves related to the movements of the tongue and neck: ten and twelve.
  • Sensitive cranial nerves : one, two, and eight.
  • Mixed cranial nerves : five, seven, nine and ten.
  • Parasympathetic cranial nerves : three, seven.
• According to your position. Those found above the brainstem (pairs one and two); those found in the upper part of the brainstem (pairs three and four); those near the bridge (pairs five, six, seven and eight); those that are in the lowest part of the medulla oblongata (pairs nine, ten, eleven and twelve).

Now, according to Bear, Connors and Paradiso, authors of the book  Neuroscience. Brain exploration suggests that the first two cranial nerves are part of the central nervous system and the others are like spinal nerves, “in the sense that they contain axons of the peripheral nervous system.” Although, each nerve has fibers that perform various functions.

Cranial nerves and their functions

Cranial nerve one

Types of axons : special sensory.

It is the shortest cranial nerve, since its destination area is close to the area from which it arises in the brain. It is also called the olfactory nerve. In addition, as its other name indicates, it is responsible for carrying nervous information related to smell.

Cranial nerve two

Types of axons : special sensory.

It originates from the diencephalon. And, like the previous one, it has afferent fibers, that is, they carry nerve impulses from the sensory organs to the central nervous system. Its function is to convey visual information.

Cranial nerve three

Types of axons : somatic motor and visceral motor.

It is called by two other names: oculomotor nerve or common ocular motor. It is responsible for the movement of the eyes and eyelids. In addition, the parasympathetic control of the size of the pupils.

Cranial nerve four

Types of axons : somatic motor.

The fourth pair originates from the midbrain. It is called both the trochlear nerve and the pathetic nerve. It also takes care of eye movement. Specifically, it sends signals to the superior oblique muscle of the eye.

Fifth cranial nerve

Types of axons : somatic sensory and somatic motor.

Known as the trigeminal nerve. It has motor and sensory functions. At the motor level, it sends orders to the muscles in charge of chewing and at the sensory level, it collects tactile, pain, proprioceptive information from the mouth and face.

6th cranial nerve

Types of axons : somatic motor.

It is called the Abducens Nerve. It is responsible for the abductor movements of the eye, that is, it is what makes the eye move to the opposite side of the nose. Incredible true?

Seventh cranial nerve

Types of axons : somatic sensory, and somatic motor.

Also known as a facial pair. It is responsible for the movements of the muscles of facial expression. In addition, the sense of taste in the previous two thirds of the language. Also, it sends orders to the lacrimal and salivary glands.

Eighth cranial nerve

Types of axon : special sensory.

It is the vestibulocochlear nerve. It is responsible for the sense of hearing and balance. Therefore, it receives information about what we hear and the position in which we find ourselves.

Cranial nerve nine

Axon types: somatic motor, visceral motor, special sensory and visceral sensory.

Called the glossopharyngeal nerve. It is a mixed nerve, from its name we could deduce some of its functions.

Let’s see what they are:

• Movement of the throat muscles.
• Parasympathetic control of the salivary glands.
• Detection of changes in blood pressure in the aorta.
• Sense of taste, in the posterior third of the tongue.

Cranial nerve ten

Types of axons : visceral motor.

It is called the vagus nerve. It is responsible for the parasympathetic control of the heart, lungs and abdominal organs, as well as the sensation of visceral pain, the movement of the throat muscles and receives taste information.

Cranial nerve eleven

Types of axons : somatic motor.

It’s called the spinal accessory nerve. It is responsible for the movements of the muscles of the throat and neck. 

Twelfth cranial nerve

Types of axons : somatic motor.

Called hypoglossal. Participate in the action of swallowing. In addition, it is responsible for the movement of the tongue, working hand in hand with the ninth and tenth cranial nerve. Thanks to this pair, swallowing is performed optimally.

Now, any damage to the cranial nerves can mean a problem for our survival or for the functioning of our body. Above all, neurological disorders may be evident. We hope that thanks to this journey that we have taken you will get to know this essential part of our body a little better.