In general, it can be said that the human brain communicates with almost all the nerves of the brain through the spinal cord.
Thus, for example, the information that reaches us about what we touch with our hands is collected by nerves that run through the arm until they reach the spinal cord, and from there to the brain, from where the order will be issued to continue examining the object. This efferent order will also leave the brain through the spinal cord, and will reach the corresponding arm through the nerve fibers that leave it.
However, this is not a rule that is always followed, since there are also some nerves that leave directly from the brain, without being born in the spinal cord. These are the cranial nerves, or cranial nerves , which arise from the lower part of the brain and reach their destination areas through small holes distributed throughout the base of the skull. From these openings, the cranial nerves communicate with peripheral areas.
Furthermore, although it may seem strange, not all of these cranial nerves have the function of reaching areas and organs found in the head. Some extend to the neck and even the abdomen area.
How are the cranial nerves classified and distributed?
The cranial nerves They are called that because they are counted in pairs, as there is one on both the right and left sides of the brain Thus, there are twelve cranial nerves pointing towards the right hemisphere and another twelve pointing towards the left, symmetrically.
Each pair is numbered with a Roman numeral depending on whether the position from which they emerge from the brain is more or less close to the frontal area. In fact, The cranial nerves can be grouped and classified into categories according to two criteria : the place from which they start and their function.
Cranial pairs classified according to their position
Cranial pairs classified according to their function
What are the cranial nerves?
Below we will learn what the cranial nerves are one by one, and their main functions.
1. Olfactory nerve (cranial nerve I)
As its name indicates, This cranial nerve is dedicated to specifically transmitting nervous information about what is detected through the sense of smell , and therefore it is an afferent fiber. It is the shortest of the cranial nerves, since its destination is very close to the area of ​​the brain from which it arises.
2. Optic nerve (cranial nerve II)
It is also part of the afferent fibers, and It is responsible for transmitting the visual information collected from the eye to the brain Arises from the diencephalon.
Also know as oculomotor nervethis cranial nerve sends orders to most of the muscles involved in eye movement and causes the pupil to dilate or contract.
4. Trochlear, or pathetic nerve (cranial nerve IV)
Like the oculomotor nerve, this cranial nerve deals with eye movement Specifically, it sends signals to the superior oblique muscle of the eye. The place from which this pair of nerves arise is the midbrain.
5. Trigeminal nerve (cranial nerve V)
It is one of the mixed cranial pairs, because has both motor and sensory functions In its role as a motor nerve, it sends orders to muscles responsible for carrying out chewing movements, while as a sensory cranial nerve it collects tactile, proprioceptive and pain information from various areas of the face and mouth.
6. Abducent nerve (cranial nerve VI)
This is another of the cranial nerves responsible for making the eye move Specifically, it is responsible for producing abduction, that is, moving the eye to the opposite side to where the nose is.
7. Facial nerve (cranial nerve VII)
It is one of the mixed cranial pairs. It is responsible for sending orders to facial muscles dedicated to creating facial expressions (thus allowing you to socialize and communicate correctly) as well as the tear and salivary glands. It also collects taste data from the tongue.
8. Vestibulocochlear nerve (cranial nerve VIII)
It is one of the sensory cranial nerves, and collects information from the auditory area Specifically, it receives data related to what is heard and the position we are in with respect to the center of gravity, which allows us to maintain balance.
It is both a sensory and motor nerve and, as its name indicates, it has an influence on both the tongue and the pharynx (the tube that connects the mouth with the stomach). It receives information from the taste buds of the tongue, but also sends orders to both the parotid (salivary) gland and neck muscles that facilitate the action of swallowing.
10. Vagus nerve (cranial nerve
This cranial pair carries orders to most of the pharyngeal and laryngeal muscles , sends nerve fibers from the sympathetic system to viscera found in the area of ​​our abdomen and receives gustatory information that comes from the epiglottis. Like the glossopharyngeal nerve, it is involved in the action of swallowing, so it is very relevant given the importance of this vital function.
11. Accessory nerve (XI cranial nerve)
This cranial nerve too It is known as the spinal nerve
It is one of the pure cranial pairs, and activates the trapezius and sternocleidomastoid muscles , which intervene in the movement of the head and shoulders, so that their signals are noticeable in part of the upper area of ​​the thorax. Specifically, it allows the head to be tilted to one side and can be tilted backwards.
12. Hypoglossal nerve (cranial nerve XII)
Like the vagus and glossopharyngeal nerves, activates tongue muscles and participates in the action of swallowing Thus, it works together with the IX and X cranial nerves to allow swallowing to be carried out correctly, something essential for the good condition of the body.
