Cranial Nerves: Function, Anatomy and Location

The article will explore the functions of a very important nerve group. It is undoubtedly, the Cranial nerves.

What Do Cranial Nerves Mean?

Cranial nerves do quite a justice to their names. Their functions are as complicated as their names. These perform the function of spreading information from the brain at light's speed. This information is received in no time by the other parts of the body like the head, trunk, and neck portions. This set of nerves works as a joint family. Every nerve needs to work in coordination with the other. Otherwise, the system collapses. Doesn't it sound a little mechanical? Yes, the functions they perform are quite mechanical. If this order falters, our system will too!

It is worth mentioning that our system has 12 important cranial nerves. All of them perform important functions. So, it would be fruitful to know the amazing jobs they perform. Their jobs are divided accordingly. They either perform sensory or motor functions. If you are wondering what these are, read on. 

As the name depicts, sensory nerves are related to the functions of the senses. They regulate our senses such as hearing, touch, and smell. Motor nerves, on the other hand, perform the job that requires the handling of glands and muscles. Isn't it interesting? All the nerves are like stock characters. 

These are named according to their functions. So, their functions will not be a tough task to remember. Scientists use a very helpful technique to categorize these 12 fibers. They rank them in roman numbers. This makes it simple for us to memorize their functions and teach about these to others with ease.

The table below simplifies the role of all these nerves. So, get a glimpse at it while sipping your tea. 

After You Know the Gist of Their Functions, Let Us Get into The Depths

Let us go according to the roman numbers to make things easy-peasy.

Olfactory Nerve

The olfactory nerve is a very significant sensory nerve. The first and foremost specialty of this nerve is its length. It is termed the shortest nerve of the cranial family. If we delve a bit more into Biology, we get to know an interesting fact. This nerve is a derivation of the olfactory placode. What is olfactory placode? In simple terms, it's a sensory placode. But, we are going to stick to the details of the Olfactory nerve. 

So, whenever you smell something nice or smell anything, the receptors of these nerves perform the magic. These send signals to the cranial cavity. And these signals reach in no time the olfactory bulb. This olfactory bulb has special nerve cells. These processes take place after the molecules of the aroma spread on the lining of the nasal cavity. 

Towards the end, the nerves contained in the olfactory bulb pass through the olfactory passage, located in the frontal lobe of the brain. This long journey involving so many complicated procedures is made at light's speed. Our systems are better than a computer!

Optic Nerve

Here comes a sensory nerve, the Optic nerve. The nerve name is true to its work. It's related to the eyes. The nerve helps us to relate the information of the light to the brain. Let us get to know the process.

Rods and cones play a significant role here. These are photoreceptor cells and are pretty sensitive to light. But, the rods are much more sensitive than the cones. They are present in larger quantities too. However, both are important in the reception of light. So, these cells receive the light and pass it on to the optic nerve. 

After this, the optic never forms the optic chiasm. What is optic chiasm? In simple terms, it's an X-shaped area present in the forebrain. From this space, the optic nerve fibers divide into two optic tracts. Now, through the paths of these optic tracts, the impulse of the light reaches the visual cortex. This is the matter that is ultimately received as information by the brain's visual cortex. So, now you know how advanced our cranial nerves are!

Oculomotor Nerve

First of all, this is a motor nerve. But, this is a special one. It performs double motor functions, which are pupil response and muscle activity.

The function related to the response of the pupil is worth-mentioning. It assists in modulating the size of your pupil. On the other side, the nerve also looks after muscle activity. There are six muscles near your eyes. The oculomotor nerve helps the movement of four muscles out of the 6. These muscles help you to focus on something. If someone has difficulty focusing on objects, then it gives rise to a condition. The condition is popularly called Ophthalmoplegia. 

The nerve is pretty useful as it operates the sphincter pupillae, a muscle around the eye. This muscle helps the pupil to constrict and let less light get in. But, the nerve also helps the pupil relax when more light is required in the eyes. The nerve also manages the ciliary muscles. These muscles help in adjusting long and short-range vision. These are the involuntary features that are managed by this unique nerve.

Another thing to be noted is that this nerve has its origin in the frontal area of the midbrain. This part is called the brainstem. 

Trochlear Nerve

Yes, this is yet another nerve that is noticed for controlling eye movement. This, too is a motor nerve and has its roots in the mid-brain. It assists the contralateral superior oblique muscle. Now, that's a long name. But, do not fret. The function is short! It helps in the inward and downward movements of the eye. Even though the function is short, its significance is not.

This nerve moves on till it gets to the eye sockets. Here it helps in stimulating this oblique muscle. 

Trigeminal Nerve

This nerve has a combination of both sensory and motor functions. It is what makes this nerve unique. Another feature that makes this nerve special is its length. This nerve is the longest among all!

The three divisions of the nerve are worth-noting. Ophthalmic, Mandibular, and Maxillary are three significant divisions. So, let us get into the roots of its functions.

The origin of this nerve is also important to know. Why? Because its roots are from a cluster of nuclei present in the mid-brain. Consequently, these create a different motor root and sensory root. 

Abducens Nerve

This is another well-known motor nerve. So, let us get going!

Here comes the sixth nerve. This is greatly known for assisting the lateral rectus muscle. You need this nerve to help your eye to look sideways. This nerve takes the direction towards the facial nerve when the medulla and pons unite together. 

It enters through a variety of regions. It proceeds from the subarachnoid area, gets to the cavernous sinus, and then the orbital fissure. Here, the nerve controls the popular muscle called the lateral rectus. 

If the nerve functioning doesn't go well, serious conditions can occur. Double vision is one of them. So, care should be taken to not injure this part of the eye. The nerve, once damaged, would lead to considerable loss. This damage takes place due to tumor growth and infections such as Meningitis. Diabetic neuropathy occurs more often and leads to this damage. So take care of your blood sugar levels to protect your nerves. 

Facial Nerve

How can we forget this nerve? It is worth the highlight. 

It is to be mentioned that the nerve provides both motor and sensory facilities. Some motor functions that the nerve operates are the motion of facial muscles like those present in the jaw. The nerve also assists your taste buds. It also helps in distributing glands to the portions of the neck and head. Two of the most important glands are the tear glands and the salivary glands.

Now, let us know about the way through which this nerve operates. As mentioned, it has its root in the pons section. Here, it already has a sensory and motor root. Ultimately, these two meet and lead to the creation of this facial nerve. 

An interesting thing is about the extension of this nerve. This nerve divides into minute nerve fibers. These help to provide sensory impulses inside and outside of the skull.

Vestibulocochlear Nerve 

This is the eighth in the list of the cranial family.

Firstly, this is a sensory nerve. Secondly, it has only two functions. But, these functions are the most significant ones. It also has two divisions: The vestibular and the cochlea.

These are the two important organs that are necessary for the good functioning of this nerve. Cochlear division which consists of special cells in the ear, helps in maintaining equilibrium while hearing. The vestibular division, on the other hand, is important for assisting the rotational and linear motion of the head. The signal is sent by the vestibular nerve to the brain to maintain the needed balance around the head. 

These two organs have their origin in different portions of the brain. The cochlea begins in the inferior cerebellar peduncle. While the other begins in the medulla and pons portion. Two of these divisions unite to create the popular vestibulocochlear nerve. 

It is to be noted that damage to this nerve might lead to complications. These complications take a serious turn. The ringing of the ears, loss of hearing, and Vertigo are some serious outcomes of the damage. So, take special care of its wellbeing. 

Glossopharyngeal Nerve

First thing first. This has the qualities of motor and sensory functions. 

It assists in transferring sensory impulses to the inner ear, back of the tongue, and throat. The nerve is also important to enhance the taste of the tongue. It also improves the voluntary functioning of a muscle called the stylopharyngeus. 

The origin of this nerve is to be noted. It has its roots in a portion of the brainstem. This part is called the medulla oblongata. Yes, the portion that you learned about in your class 10 Biology books. Ultimately, the nerve stretches to the part of the throat. 

Now, let us have a look at the complications that might occur if the nerve suffers damage due to the pressure of a blood vessel on the nerve due to tumors.

 It might lead to loss of hearing. So, take special care. One of the most common complications is throat pain. This is also known by the name of glossopharyngeal neuralgia. Often the pain caused by the damage of this nerve is like that of trigeminal neuralgia. So, take the advice of a neurosurgeon who deals with the problems of facial pain. He can make out a difference.

Vagus Nerve

This is one of those unique nerves that performs both the features of sensory and motor nerves. 

So, let us list those functions down. 

This nerve transfers the sensation in the areas of the throat. It also provides sensory impulses from different organs to the chest portion that consists of the intestines and heart. Just like the Glossopharyngeal nerve, this nerve provides a sense of taste to the tongue. It also accelerates the functioning of the peristalsis. 

We have got to know about the smallest nerve and the largest nerve of the cranial family. Now, it's your turn to know the nerve that has the longest route. It stretches from the portion of the head to the abdomen. Isn't this an amazing fact too?

Accessory Nerve

Now, it's time for the eleventh cranial nerve. It is popularly known as the accessory nerve. It is a motor nerve and assists the programming of the neck muscles. These muscles are the ones that help you in your neck movement. 

The accessory nerve is divided into two portions. One is spinal while the other is cranial. Both these portions have their share of work. The spinal nerve has its root in the spinal cord's upper area, while the latter begins from the medulla oblongata.

Now, these two divisions unite shortly before the spinal nerve proceeds towards the neck muscles, and the cranial portion goes after the vagus nerve.

The Last Nerve of the Cranial Family: Hypoglossal Nerve

This is the last but not the least cranial nerve. Yes, it is the twelfth nerve about which it is mandatory to know. It is the last nerve but performs great functions. 

It is in charge of a lot of muscles present in the tongue. It has its root in the medulla oblongata, from where it proceeds into the jaw muscles and, ultimately, the tongue. 

Some complications lead to the damage of this nerve. Tongue paralysis might occur if the nerve ceases to operate freely. To test the proper functioning of this nerve, one is ought to do what the doctor says. Generally, the doctor asks to point out the tongue. Now, if the tongue suffers from paralysis, it would aim towards the side that is affected. 

The Close Up

Now we know about the functions of all the 12 cranial nerves. We also know about the complications that would lead to their damage. The point of the article is to promote the functions of all these nerves that assist us in our daily voluntary and involuntary activities. If we are kept in the dark regarding this, it would be such a waste. 

So, it is necessary to take proper care of these nerves to assist their functioning in the best way. Some cranial nerve disorder medications include:

• Trigeminal neuralgia
• Microvascular Decompression
• Percutaneous Glycerol Rhizotomy

It would be advisable to talk to the doctor about these medications and take further steps. So, what are you waiting for? Get started with the care.

Frequently Asked Questions

What Is The Specialty Of Cranial Nerves?

The special thing about cranial nerves is that they perform one of the most significant functions in our body. The family of nerves is important for it transmits information from various parts of the body to the brain. Numerous involuntary and voluntary functions are operated by these nerves. The damage to these nerves might lead to serious problems. For example, damage to the Glossopharyngeal nerve leads to throat pain. Glossopharyngeal neuralgia is one of the complications caused by damage to this nerve. So, proper advice from doctors should be taken in these situations.

Is It Possible For Cranial Nerves To Cross?

An important fact to be noticed is that cranial nerves do not cross. Reports presented by the site of the neurologic exam state that no cranial nerves cross except the fourth one. The fourth cranial nerve is the Trochlear nerve. 

How Do Cranial Nerves Exit?

It is to be noted that cranial nerves begin from the brain and is likely to exit through cranial foramina, which are holes that help to lead these nerves through. Certain cracks that are not well girdled by bones shall also be included in this group. 

What Is The Length Of Time That Is Required To Heal Cranial Nerves?

It depends on the condition of the nerve. If the nerve is not slit, then it is likely to heal approximately within six months. A cut nerve will take longer to heal. It usually grows 1 mm every day after a 3 to 4-week period of healing. So, rest is the mantra. 

How Can Facial Nerve Inflammation Be Healed?

Medicines like Corticosteroids help a lot. These medications have anti-inflammatory properties and promote quick healing of the seventh nerve of the cranial family. Also, antiviral medicines are recommended. If these medications are taken orally for 14 days, benefits would be evident. However, some side effects always accompany these medicines. But, do not worry, these are rare.

Proper consultation from a trusted doctor would assist greatly. Using eye drops is of great help too. If the eye on the affected side is moistened with this drop, it will provide some relief to this paralysis. If one suffers from the condition of dry eye, lubricating liquids and gels are always recommended by doctors. 

References

• Schulman. (2019), The 12 Cranial Nerves, health line - https://www.healthline.com/health/12-cranial-nerves
• myPennMedicine - https://www.pennmedicine.org/for-patients-and-visitors/find-a-program-or-service/neurosurgery/cranial-nerve-disorders/cranial-nerve-treatments
• Ayers, R. (2015), Nerve Surgery and Nerve Repair - http://www.rebeccaayers.co.nz/procedures-and-information/hand-surgery/nerve-surgery-and-nerve-repair
• Johal, J. Iwanga, J. (2018), The Accessory Nerve: A Comprehensive Review, The Anatomical Record, Volume 302, Issue 4, p. 620-629 - https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.23823
• Lue, E. (2019), What are the 12 Cranial Nerves, MedicalNewsToday - https://www.medicalnewstoday.com/articles/32662