Cranial pairs: What are they? Types, Classification and Function of Each Cranial Pair

They are twelve pairs of nerves that arise directly from the brain.

They allow the information acquired daily to be sent to the various muscles and viscera through the brain so that the daily actions or routines that the individual deserves or desires can be executed.

They are also known as cranial nerves.

Types of cranial pairs

There are 12 types of nerves or cranial nerves that pass through a hole in the base of the skull to carry out its primary function, which is to connect the brain with the muscles, sensory organs, and others. Execute the commands or actions requested by the individual, thus achieving good motor and sensory performance.

For this process to work perfectly, there is an essential factor: the spinal cord, since it is connected to the nerves of the brain and the nervous system in general.

For example, suppose a person is chewing something they like. In that case, the nerves of the face, tongue, and throat emit signals to the spinal cord, and this is responsible for issuing them to the brain so that one of the cranial nerves decodes and emits new orders, whether the individual continues chewing or on the contrary stops that activity and starts another.

What distinguishes or makes the cranial nerves unique is that they form part of the peripheral nervous system that connects the brain with the cervical, the sensory, motor, and vegetative systems, together with an efferent direction.


Classification of cranial nerve pairs

The cranial pairs, as the name implies, are paired and are located at both ends of the brain, that is, in the left hemisphere and the right hemisphere, in total there are 12 pairs with different functions and are located as follows :

  • In the brainstem, couples I and II are found.
  • In the mesencephalon, teams III and IV are found.
  • At the Varolius point, pairs V, VI, VII, and VIII are found.
  • The cranial nerves IX, X, XI, and XII, are found in the medulla.

Cranial nerve functions

The 12 pairs have different assignments in the nervous system of which the following can be mentioned:

  • The pairs I, II, VI, and VIII are in charge of the sensitive functions of the organism.
  • Pairs III, IV, and VI are linked to ocular and eyelid mobility.
  • The pairs V, VII, IX, and X have mixed functions.
  • The pairs III, VII, IX, and X are the faces of the correct functioning of the parasympathetic fibers.
  • The XI and XII are related to the tongue and neck muscle activities.

Although they can be grouped according to the activities they must perform, each pair has a unique and specific function, such as:

Pair I: olfactory nerve

This pair of nerves is responsible for the sensory part. Therefore they must transmit certain olfactory stimuli from the nose to the brain.

Pair II: optic nerve

This pair generates visual stimuli taking the information from the eyes to the brain, where it will be interpreted, emitting a response later.

Par III: oculomotor

These two nerves control the movement of the eyes and the size of the pupil.

Part IV: Trochlear

The fourth pair of nerves have bodily functions, which is why they are connected to the superior oblique muscle of the eye, thus making the eyeball rotate and move.

Part V: trigeminal

This pair has several functions since it is responsible for the face’s sensory, motor, and sensitive part. They are the ones that make the chewing process possible; they also emit pain, touch, and temperature through the sensory fibers.

A pair of 6: abducens

This pair is known as the nerve responsible for the ocular motor. It is responsible for sending stimuli to the external visual muscle.

Part VII: facial o Intermedio

This couple also has varied or diverse functions because it is made up of fibers that emit orders to the muscles of the face to generate facial expressions and send signals to the lacrimal and salivary glands.

A pair of 8: vestibuloclear

They are the two nerves responsible for hearing, which is responsible for balance and orientation within space and time and audio.

By IX: glosofaríngeo

This pair of nerves are responsible for the tongue and pharynx, collecting information on what would be the taste buds, along with the sensory data of the pharynx, helping in the process of swallowing. It also monitors blood pressure.

By X: neumogástrico

It supplies the nerves found in the esophagus, pharynx, larynx, bronchi, trachea, heart, liver, and stomach. It helps to control or reduce stress and send signals to the sympathetic system.

Pair XI: accessory

This pair of nerves are responsible for the movements made by the head and shoulders.

Part XII: hypoglossal

This pair is responsible for the tongue muscles, speech, and swallowing.