The brain can be easily recognized as the most important organ of the human being, since it is the one that is responsible for carrying out all the important functions that are required, not only to get ahead, but also to exist. With our brain we not only think, but we also regulate the actions we take. Something as simple as breathing, walking, or raising your hands It can be a sample of the importance of our brain, since without it, none of that we could do it in any way.
When we speak of the brain, we can think of the continuous synapses that this organ carries out; in the neurons that allow us to think and perform tasks, whether they are easy or complicated.
However, on many occasions we would like to know a few more things about its operation, and about all those important elements that, within it, allow this work to continue. The cranial nervesFor example, they fulfill an important nerve function within the brain, and are a series of nerves that arise from the lower part of the brain and continue to the neck and abdomen. In this post we will delve into the brain and discover the functions these nerves perform within it.
What are these pairs?
The cranial nerves, which are also known as cranial nerves, are a series of twelve nerves that leave the brain at the level of the brainstem, and are located distributed across the head; We can find them at the base of the skull, neck, trunk and thorax.
The International Anatomical Nomenclature has given the terminal nerve the definition of a cranial nerve, despite being atrophic in humans, and closely related to the olfactory system.
The cranial nerves have an apparent origin, which refers to the place where the nerve leaves or enters the brain. Their real origin is different according to the function they fulfill within the body; the fibers of the cranial nerves with motor function have their point of origin in cell groups that are found in the deepest part of the brainstem, and are homologous to the cells of the anterior horn of the spinal cord.
The fibers of the cranial nerves that exert sensory or sensory functions have their cells of origin outside the brainstem. Usually in ganglia that are homologous to those of the dorsal root of the spinal nerves.
Characteristics of the cranial nerves
There are many characteristics that these nerves can share within the human body. However, the most interesting characteristic that they share, and that makes them unique and special, is the fact that they come directly from the brain, bypassing the spinal cord. That is, these nerves go from the lower part of the brain, passing through holes located at the base of the skull to reach their destination. Interestingly, these nerves not only go to areas such as the head, but also They also end up being directed towards parts such as the neck or the area of the thorax and abdomen.
In this way we can say that the cranial nerves constitutes that part of the nervous system that relates the brain with the cranial and cervical structures. The rest of the afferent and efferent nervous stimuli of the Central Nervous System are carried out through the spinal nerves.
Classification of cranial nerves
When we talk about the cranial nerves we can say that they are divided into pairs, since when leaving the right hemisphere of the brain, there will be another cranial nerve that will leave the right hemisphere, symmetrically.
When we go to classify cranial nerves we must group or classify them according to two known criteria. These are: the place from which they start and the function they fulfill.
According to your position
The cranial nerves always have an associated Roman numeral, as it is the way they are designated by the International Anatomical Nomenclature. These numbers range from 1 to 12, corresponding, in each case, to the pair in question.
The cranial nerves that originate:
- Above the brainstem they are known as pair I and pair II.
- From the midbrain they are pairs III and IV.
- From the brainstem bridge (or Varolio Bridge) they are known as cranial nerves V, VI, VII and VIII.
- From the Medulla oblongata, they are called pairs IX, X, XI and XII.
According to its function
- When they are part of the sensory function, it is made up of cranial nerves I, II and VIII.
- If they are associated with ocular mobility and the eyelids: III, IV and VI.
- When they have elation with the activation of the muscles of parts of the neck and tongue: cranial nerves XI and XII.
- Those that are considered with mixed function: pairs V, VII, IX and X.
- When they function as fibers of parasympathetic function: III, VII, IX and X.
The types of cranial nerves and what they do
The cranial nerves have a specific function and we can find them functioning and working in various parts of the body. They are not limited only to the head and neck, but they continue to work even lower. Here is a list of the cranial nerves, what they do, and where they are located.
Olfactory nerve:
It is a sensory nerve, which is responsible for transmitting the olfactory stimuli from the nose to the brain. Its real origin is given by the cells of the olfactory bulbs. It is cranial nerve I and is considered the shortest cranial nerve of all.
Optic nerve:
This, as you can imagine, is the nerve that is responsible for directing stimuli from the eye to the brain. It is made up of axons of the retinal ganglion cells, and carry information to photoreceptors in the brain. It originates in the diecephalon and corresponds to cranial nerve II.
Oculomotor nerve
This cranial pair is in charge of eye movement; it is also responsible for the size of the pupil. It originates in the midbrain and corresponds to cranial nerve III.
Trochlear nerve
It is a nerve with motor and somatic functions, and it is connected to the superior oblique muscle of the eye, causing it to rotate or come out of the eyeball. The nucleus originates, as in the previous one, in the midbrain, y corresponds to pair IV.
Trigeminal nerve
It is the largest nerve among the cranial nerves, and it is multifunctional (sensory, motor and sensory). Its function is to bring sensitive information to the face, conduct information from the masticatory muscles, tighten the eardrum, among other functions. It is the pair V.
Abducens nerve
This cranial nerve is connected to the eye and is responsible for transmitting stimuli to the external muscle of the eye. In this way the eye can move to the opposite side of where we have the nose. Corresponds to pair VI.
Facial nerve
This pair is also considered mixed. He is in charge of send various stimuli to the face so that, in this way, you can be able to produce and create facial expressions. It also sends signals to the lacrimal and salivary glands. Corresponds to pair VII.
Vestibulocochlear nerve
It is also known as the cranial nerve of the auditory and vestibular nerve, thus forming the vestibulocochlear. It is responsible for balance and orientation in space, as well as auditory function. Its cranial nerve is the VIII.
Glossopharyngeal nerve
The influence of this nerve it resides in the pharynx and on the tongue. It receives information from the taste buds and sensory information from the pharynx. At the same time it conducts orders to the salivary glands and the neck, facilitating the action of swallowing and swallowing. Corresponds to cranial nerve IX.
Vagus nerve
This nerve is also known as the pneumogastric. It originates from the medulla oblongata and innervates the pharynx, esophagus, larynx, trachea, bronchi, heart, stomach, and liver.
Like the anterior nerve, it influences the action of swallowing but also in terms of sending and transmitting signals to our autonomic system, and can even help in what is refers to the regulation of our activation and also to be able to control stress levels, or send signals directly to our sympathetic system, and this, in turn, to our viscera. Its cranial nerve is the X.
Accessory nerve
It is known as one of the "purest". It is a spinal and motor nerve. It innervates the sternocleidomastoid and thus causes the neck to rotate to the opposite side, while tilting the head to its side. This nerve also allows us to throw the head back, so we can say that it intervenes in the movement of the neck and shoulders. Its cranial nerve is the XI.
Hypoglossal nerve
It is a motor nerve, and like the vagus and the glossopharyngeal nerve, it is involved in the action of swallowing and in the muscles of the tongue.