Does the brain have nerves?

In this post we are going to answer the question ‘’Does the brain have nerves?’’  We will learn what the nerves are, where they are and their main functions.

Does the brain have nerves?

Yes, the brain has nerves that come directly from the brain to the brain, these are called cranial nerves.

Nerves are structures made up of bundles of neuronal fibers (nerve extensions and axons), located outside the central nervous system, which are responsible for conducting nerve impulses and communicating the nerve centers of the brain and spinal cord with the rest of the organs of the body, and vice versa.

These fiber bundles are surrounded by a thin membrane, the perineurium, which surrounds the bundle of nerve fibers; and in turn, the complete nerve formed by the union of several fascicles is covered by another structure, called the epineurium.

As we will see later, some nerves originate from the spinal cord, while others originate from the brain. There are different types of nerves, being able to be sensitive, motor or mixed, and this will depend on the function that each one of them fulfills within our nervous system.

But before delving into it, we will briefly see how the human nervous system works and what its characteristics are.

The human nervous system

The human nervous system functions as a great system in charge of managing and coordinating the activities and bodily functions through its network of wiring, which communicates all the parts of our body.

The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord, command control and nerve impulse transmission center, respectively.

The PNS is made up of several types of nerves that exit or enter the CNS. The SNP is in charge of sending the information and, after being evaluated, the brain sends the appropriate responses to the necessary parts of the body, such as muscles or other types of organs.

The main function of the PNS is thus to connect the CNS with the organs, limbs and skin. Its nerves extend from the CNS to the outermost areas of our body. And it is the SNP that is in charge of helping us react to stimuli in our environment.

Types of nerves and classification

As we mentioned earlier, the nerves of the peripheral nervous system connect the central nervous system with the rest of the body. And they do it in different ways, and with different functions. Next, we will classify these nerves according to the following criteria:

1. According to the direction in which the nerve impulse is transmitted

Nerves can be classified in 3 ways, depending on the direction in which they transmit the nerve impulse.

Motor nerves

The motor nerves are responsible for all voluntary skeletal and somatic movement (such as moving a leg or an arm), they conduct the nerve impulse to the muscles and glands.

Sensitive nerves

The sensitive nerves are responsible for conducting the nervous impulse towards the central nervous system, that is, from the receptors to the coordination centers

Mixed nerves

Mixed nerves conduct nerve impulses in both directions and have both sensory and motor axons.

2. According to the origin from where the nerves come out

Nerves can also be classified based on where they start from in our body. In this case, two types of nerves are differentiated:

Cranial nerves

There are 12 pairs of nerves (12 on the left and 12 on the right) that arise from the brain or at the level of the brainstem. Some are sensitive, others motor and also mixed.

These nerves basically control the muscles of the head and neck, except for one of them, the vagus nerve, which also acts on structures in the thorax and abdomen.

Spinal nerves

There are 31 to 33 pairs of nerves and they are all mixed. They originate in the spinal cord and cross the vertebral muscles to distribute themselves in various areas of the body.

All of them have a dorsal or sensitive root, made up of bodies of neurons that receive information from the skin and organs; and another ventral or motor, which transmits the information to the skin and organs.

3. According to their role in coordinating voluntary or involuntary acts

Another of the criteria with which we can classify various types of nerves is their involvement in the coordination of voluntary or involuntary acts; that is, if they innervate the autonomic nervous system or the somatic or voluntary nervous system.

Somatic nervous system nerves

The somatic or voluntary nervous system is the one that fully or partially manages the actions and activities of our body, which can be conscious (such as picking up or manipulating an object) or unconscious (putting the left leg forward when walking, for example).

Your nerves are made up entirely of myelinated fibers (an insulating layer that forms around the nerve to make transmission more efficient).

Nerves of the autonomic nervous system

The autonomic nervous system, for its part, responds mainly to nerve impulses in the spinal cord, brain stem, and hypothalamus. The nerves of this system are made up of efferent fibers that leave the central nervous system, except for those that innervate skeletal muscle.

The afferent nerves, which transmit information from the periphery to the central nervous system, are in charge of transmitting visceral sensation and regulating vasomotor and respiratory reflexes (control of heart rate or blood pressure).

In the autonomic nervous system, two types of nerves can be differentiated. On one side are the nerves of the parasympathetic nervous system; this system predominates in moments of relaxation, and is made up of the vagus cranial nerve. It also shares the spinal nerves of the sacral region (lower part of the spine).

On the other hand, we have the nerves of the sympathetic nervous system. This system predominates in moments of tension, and your nerves share the rest of the spinal nerves.

The nerve fibers that harbors this system are partially separated from the rest of the spinal nerves and form two chains of ganglia, located on both sides of the spinal column.

What are the cranial nerves?

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 it reaches 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, that arise from the lower part of the brain and reach their destination areas through small holes scattered around the base of the skull. From these orifices, the cranial nerves communicate with peripheral areas.

Also, although it may seem strange, not all of these cranial nerves have the function of reaching areas and organs that are in the head. Some extend to the neck and even the abdomen area.

We are going to know below which are the cranial nerves one by one, and their main functions.

1. Olfactory nerve (cranial nerve I)

As its name suggests, 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 is responsible for transmitting the visual information that is collected from the eye to the brain. It arises from the diencephalon.

3. Oculomotor nerve (cranial nerve III)

Also known as the common ocular motor nerve, this cranial nerve commands most of the muscles involved in eye movement, causing the pupil to dilate or contract.

4. Trochlear, or pathetic nerve (IV cranial nerve)

Like the oculomotor nerve, this cranial nerve deals with the movement of the eyes. Specifically, it signals the superior oblique muscle of the eye. The place from which this pair of nerves arises is the midbrain.

5. Trigeminal nerve (cranial nerve V)

It is one of the mixed cranial nerves, because it has both motor and sensory functions. As a motor nerve, it commands the muscles responsible for 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 (VI cranial nerve)

This is another of the cranial nerves responsible for making the eye move. Specifically, it is responsible for producing abduction, that is, the eye moves to the opposite side to where the nose is.

7. Facial nerve (cranial nerve VII)

It is one of the mixed cranial nerves. It is responsible for sending orders to the muscles of the face dedicated to creating facial expressions (thus allowing to socialize and communicate correctly) and to the lacrimal and salivary glands. It also collects taste data from the tongue.

8. Vestibulocochlear nerve (VIII cranial nerve)

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 in which we are in relation to the center of gravity, which allows us to maintain our balance.

9. Glossopharyngeal nerve (IV cranial nerve)

It is both a sensory and a motor nerve and, as its name suggests, 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 it also commands both the parotid (salivary) gland and neck muscles that facilitate swallowing.

10. Vagus nerve (cranial nerve X)

This cranial pair carries orders to most of the pharyngeal and laryngeal muscles, sends nerve fibers from the sympathetic system to the viscera found in the area of ​​our abdomen, and receives taste information that comes from the epiglottis.

11. Accessory nerve (cranial nerve XI)

This cranial nerve is also known as the spinal nerve.

It is one of the pure cranial nerves, and it activates the trapezius and sternocleidomastoid muscles, which are involved in the movement of the head and shoulders, so that their signals are felt in part of the upper chest. Specifically, it allows the head to be tilted to one side and to be tilted back.

12. Hypoglossal nerve (XII cranial nerve)

Like the vagus and glossopharyngeal nerves, it activates muscles of the tongue and participates in the action of swallowing. Thus, it works together with cranial nerves IX and X to allow swallowing to be performed correctly, something essential for the good state of the body.

FAQS: Does the brain have nerves?

Does the brain have nerve endings?

No, the nerve endings are generally found in the skin and the brain has no skin.

Why are there no nerves in the brain?

Yes, there are nerves in the brain. But, there are no nerve endings.

Do we have nerves in your head?

Yes. Cranial nerves are called nerves that link the brain with the eyes, ears, nose and throat and with different parts of the head, neck, and trunk.

What part of the brain makes you feel pain?

The parietal lobe is involved in interpreting pain in the body.

Can the brain heal?

Eventually, the brain repairs itself.

In this post we answered the question ‘’Does the brain have nerves?’’  We have learned what the nerves are, where they are and their main functions.

If you have any questions or comments please let us know!

References

Purves, D. (2001). Neuroscience.

Davis, M. C., Griessenauer, C. J., Bosmia, A. N.; Tubbs, R. S., Shoja, M. M. “The naming of the cranial nerves: A historical review”. Clinical Anatomy. 27 (1): pp. 14 – 19.

Snell, R. S. (2010). Clinical neuroanatomy. Lippincott Williams & Wilkins.