12 cranial nerves – Humans, who are living things, have the characteristic of moving, starting from moving the upper limbs to the lower limbs. Every limb that is moved by humans originates from brain commands. With orders from the brain, the limbs will run according to their function. For example, when the brain orders the members to see, the eye parts of the body will move.
Therefore, it can be said that the brain is the center of all activities carried out by humans every day. If the brain does not function properly, there will be several limbs that cannot be moved optimally. In addition, because the brain is the most important part for moving the limbs, the brain is protected by strong skull bones.
The human brain weighs approximately 1,400 grams or 1.4 kg. The human brain is composed of many neurons or approximately 100 billion neurons in the brain. Each brain neuron has 1,000 to 10,000 synaptic connections with nerve cells in the rest of the body.
The tissue in the brain can be said to have a rubbery consistency and is located inside the skull bone. The size of the skull bones in humans will get bigger as the humans themselves get older. In other words, the more mature humans are, the larger the size of the skull bones will be.
Every tissue in the brain is also protected by several protectors. In this case, the protective tissue of the brain, such as the scalp, lining of the brain, hair, cerebrospinal fluid, and skull. Each protective brain tissue is still divided into several more parts.
The brain which is a very important part of the body because it can move the limbs to the maximum indicates that the brain has nerves that are connected to the other members of the body. Each of these nerves has its own function.
Of the many nerves connected to the brain, one of them is the cranial nerves which consist of 12 pairs. The 12 cranial nerves are a nervous system that has a very important function. For more details, we will discuss the 12 cranial nerves and their functions and locations. So, consider the following reviews, Sinaumed’s.
Definition of Cranial Nerves
In the Big Indonesian Dictionary (KBBI), cranial nerves are the nerves that connect the brain to other organs of the body, totaling 12 pairs, having the function of carrying information from the five senses to the brain.
Cranial nerves or also known as cranial nerves are nerves that are located at the bottom of the brain and play a very important role in the nervous system, why is it important? Because this cranial nerve is connected to the sensory organs, head organs, organs in the neck, chest organs, muscles, without having to go through the spinal cord. Therefore, these cranial nerves can send sensory and motor signals to all parts of the body directly.
With the sensory information to the mouth, nose, ears and eyes through the cranial nerves, it allows humans to carry out activities, such as feeling, smelling, hearing and seeing. In addition, the movements of the limbs that are passed by the cranial nerves allow humans to carry out daily activities, such as the nose to smell something, the mouth to eat or talk, and so on.
Not only that, cranial nerves also have other functions in the form of being able to receive various kinds of motor and sensory information. In fact, cranial nerves can help control various internal organs, such as the lungs and heart.
The cranial nerves themselves originate from two parts of the brain, namely the cerebrum and the brainstem. 10 cranial nerves are in the brainstem, while the other two nerves are in the cerebrum. In the brainstem, these cranial nerves can be seen in certain areas, such as the pons, midbrain, or medulla. However, cranial nerves may also be seen at the junction of each of these divisions.
As previously explained that the cranial nerves consist of 12 pairs, so in the following discussion, we will discuss the function and location of the 12 cranial nerves.
12 Cranial Nerves and Their Functions and Locations
Quoted from a book entitled Neurosurgery, Edition V by Prof. Dr. dr. satyanegara. Sp.BS, here are the 12 cranial nerves and their functions and locations.
1. Olfactory (Cranial 1)
The olfactory nerve is the first cranial nerve. The olfactory nerve is related to or related to human activity on aroma, or more precisely, with the olfactory system or sense of smell. So, the olfactory nerve functions to smell certain odors or aromas. In addition, the olfactory nerve is one of the cranial nerves located in the big brain (cerebrum).
The way the olfactory nerve works starts when a person smells an aroma or smell from the nose, such as the smell of food, the smell of garbage, and so on. Then, after that, the olfactory nerve or olfactory nerve will work to send the smell or aroma information to the brain. After arriving at the brain it will be identified, what smell is this, so that humans can recognize the aroma or smell.
However, for some people, they may experience obstacles in smelling certain odors or odors or also known as anosmia. Anosmia itself can occur due to several things, such as a person experiencing flu, colds, smoking habits, sinusitis, and so on.
If someone experiences anosmia, it can interfere with their health because it will be difficult to smell food, so that their appetite is lost. Therefore, it’s best if you experience disturbances in smell, you should immediately see a doctor so you can get even better treatment.
2. Optics (Cranial II)
The optic nerve is the nerve associated with the sense of sight. Therefore, this optic nerve has a sensory function related to the eye or human activity in seeing. The location of the optic nerve lies in the organs of the eye, such as the cornea, pupil, anterior chamber, vitreous body, and so on. With the optic nerve, humans can tell what they are seeing.
The optic nerve works starting from the entry of light from the front of the eye or the cornea which then continues to the eye lens. After the light is processed by the cornea and lens, the light will enter the back of the eye, namely the retina. It is from these retinal cells that they absorb incoming light and then convert the light into electrochemical impulses. After that, it will continue again to the optic nerve and then get to the brain.
In simple terms, the function of the optic nerve is to transmit stimulus information in the form of light to the brain, where this information will be brought to the brain to be identified, what object is being seen or what color is being seen at the moment. Therefore, it can be said that the way the eye works when viewed at a glance is almost the same as how the camera works.
3. Oculomotor (Cranial III)
The third cranial nerve is the oculomotor nerve. The location of the oculomotor nerve is at the front of the midbrain. Then, this nerve moves to the eye socket, so that the oculomotor nerve can move the muscles in the eye.
The oculomotor nerve has a motor function in the form of helping eye movement. In this case, the eye movement in question is the eye moves in the specified direction and the eye blinks. So, it can be said that the human eye can move because of the function of the oculomotor nerve. In fact, the oculomotor nerve also helps the eye focus on an object it sees.
In addition, the oculomotor nerve also functions to help the eye control the pupil against incoming light. With the oculomotor nerve, the pupil can respond to incoming light, so that the eye does not receive excessive light.
4. Trochlear (Cranial IV)
The trochlear nerve is a cranial nerve that has a motor function that is almost the same as the oculomotor nerve, which is to move the eye muscles. However, in the tochlear nerve, the eye muscle that will be moved is the superior oblique muscle. With the trochlear nerve moving the superior oblique muscle, the moving part of the eye is the bottom. In addition, the trochlear nerve also functions to make the eyes bulge and return to normal.
In addition, the trochlear nerve can also move forward up to the eye socket. This trochlear nerve lies ventral to the periaqueductal gray matter and lies directly beneath the oculomotor nerve nucleus complex at the level of the lower colloculi.
5. Trigeminal (Cranial V)
The trigeminal nerve is located on the side of the face. In addition, the trigeminal nerve is further divided into three parts, namely the ophthalmic, maxillary, and mandibular. The three parts have different functions, such as the ophthalmic function of providing sensory information from the scalp, upper eyelids, and forehead. The maxilla has the function of providing sensory information from the cheeks, nasal cavities, lower eyelids, and upper lip. The mandible has the function of providing sensory and motor information starting from the lower lip, jaw, chin, and tongue.
The trigeminal nerve is a cranial nerve that has motor and sensory functions. In this case, the sensory function of the trigeminal nerve, such as being able to feel touch or sensation on the face, upper neck, and scalp. Meanwhile, the motor function of the trigeminal nerve, such as having a role in controlling every movement of the muscles in the mouth, ears and jaw.
6. Abducens (Cranial VI)
The sixth cranial nerve is the abducens nerve. The abducens nerve is related to motor function in the eye. With the abducens nerve, the human eye can move to look sideways and can move the eye outward. It can also occur because the cranial nerves can control the lateral rectus muscles.
The abducen nerve is located caudal to the pons tegmentum or just below the floor of the fourth ventricle. The abducens nerve can also move toward the lateral rectus muscle, which is located in the eye socket. Judging from how it works, the abducen nerve starts from the pons of the brainstem, then enters the area of Dorello’s canal, then moves through the cavernous sinus, until it reaches the lateral rectus muscle.
7. Facial (Cranial VII)
The next cranial nerve is the facial nerve. The function of the facial nerve is not far from the facial limbs. The facial nerve has functions, such as storing glands that can produce saliva and can secrete tears, providing sensory information from the tongue so that it can feel various kinds of food tastes, and providing motor information to control every muscle movement related to facial expressions or expressions.
The facial nerve is located inside the parotid salivary gland which has left the stilomastoid foramen. This nerve forms several terminal branches at the anterior border of the parotid gland. Each of these branches will move towards the muscles that can move facial expressions.
8. Vestibulocochlear (Cranial VIII)
There are two sensory functions in the vestibulocochlear nerve, namely functions related to balance and functions related to hearing. Therefore, the vestibulocochlear nerve has two parts, namely the vestibular and the cochlea. Vestibular has a function in the form of collecting any information related to the inner ear and related to balance. Meanwhile, the cochlea has the function of detecting any vibrations originating from the tone of voice and volume.
The vestibulocochlear nerve originates laterally from the angle formed between the cerebellum and the pons. Then it will pass through the facial nerve to lead to the internal acoustic meatus on the temporal bone.
9. Glossopharyngeal (Cranial IX)
The glossopharyngeal nerve has the function of providing sensory information from the outer ear to the cavity of the middle ear. In addition, the glossopharyngeal nerve also functions to provide sensory information at the back of the throat and on the back of the tongue. In other words, the main function of the glossopharyngeal nerve is to provide sensory innervation from the oropharynx and the back of the tongue.
The glossopharyngeal nerve originates in the medulla oblongata and travels toward the neck and throat. The role of the glossopharyngeal nerve is related to the gag reflex, so it can be said that the role of the glossopharyngeal nerve is not that important.
10. Vagus Nerve (Cranial X)
The vagus nerve has several functions related to the human internal organs. The function of the vagus nerve, such as controlling every movement of the heart, lungs, to the vocal cords. In addition, the vagus nerve also has the function of controlling the digestive organs, such as the stomach and intestines. The vagus nerve can also help the process of the body’s metabolic hormones by stimulating the endocrine glands.
The vagus nerve is opposite the parasympathetic nerve. The vagus nerve is the longest nerve of the autonomic nervous system in the human body. The length of the vagus nerve starts from the brain to the tongue, then to the heart, and up to the digestive organs.
11. Accessory (Cranial XI)
The accessory nerves are located above the posterior triangle of the neck, such as the trapezius and sternocleidomastoid. This accessory nerve is the eleventh cranial nerve. This nerve is also known as the accessory spinal nerve. This nerve consists of two parts, first the skull, and second, the spine.
The two halves touch each other for a short time before the spinal cord makes a move to send the neck muscles. Meanwhile, on the cranial side, join the vagus nerve.
This nerve has a function in the form of helping the motor nerves of the neck muscles to work. Therefore, this accessory nerve can control every movement that occurs in the neck muscles, so that the neck can move according to our wishes. In addition, the function of the accessory nerves is also related to every muscle in the shoulders, neck and head.
12. Hypoglossus (Cranial XII)
The twelfth or last cranial nerve is the hypoglossal nerve. This nerve originates from the medulla oblongata which then moves towards the jaw until it reaches the tongue. Therefore, this nerve has a fairly important role in moving the tongue and playing a role in swallowing, speaking and chewing food.
This part of the muscles on the tongue can move because of the hypoglossal nerve. If the hypoglossal nerve is disturbed, it will be difficult for the tongue to move or even paralyzed. Paralysis of the tongue usually occurs on one side only.
This is an explanation of the 12 cranial nerves. Hopefully knowing the 12 cranial nerves will make us more confident in protecting every part of our body so that unwanted things don’t happen and can function properly.