12 Cranial Nerves And Their Functions Pdf

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Cranial nerves are the nerves that emerge directly from the brain including the brainstem. In contrast, spinal nerves emerge from segments of the spinal cord. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck. Spinal nerves emerge sequentially from the spinal cord with the spinal nerve closest to the head C1 emerging in the space above the first cervical vertebra.

How to Assess the Cranial Nerves

It has been known for over a century that these cranial nerves exist, and that they are not typographical errors nor a sensational event reported in the medical literature. A number of scientific articles on anatomy highlight how textbooks on descriptive anatomy do not always consider variables such as differences related to the geographical areas where people live, and these differences do exist.

This is an important concept not only for surgeons, but also for all medical professionals who use manual techniques when treating their patients, ie, osteopaths, chiropractors, physiotherapists, and other manual therapists. This paper highlights the latest developments regarding these cranial nerves, offering at the same time some ideas for further reflection when looking at clinical scenarios that appear to bear little relationship to each other.

Inclusion of these concepts in everyday anamnesis is encouraged. First discovered in in sharks and other types of fish, it was initially referred to as the nerve of pinkus. In , it became classified as terminal because, in other animal species, it was observed to extend into the region of the lamina terminalis delineating the anterior wall of the third ventricle and, in its lower section, before the optic chiasma, forming the optic recess.

Recent textbooks, published after , have classified cranial nerve XIII as the zero nerve, given that it is more rostral than the other cranial nerves. Although first formally mentioned in a paper on human anatomy in , 1 it has rarely been mentioned in the medical literature since. The probable reason for this is that, during anatomical dissection, when taking off the dura mater, this nerve is torn off and cannot be found on subsequent examination.

However, as long as the pia mater remains intact, the nerve can be located between the olfactory stalk and the rostral section of the optic chiasma. Cranial nerve XIV was first identified in , but it was not until that it was mentioned in a textbook as the nerve of Wrisberg. This confirms that this nerve is an independent entity and not a mere ramification of cranial nerve VII. Anatomy is still a field rich in findings, and as regards the data collected so far, nothing can be taken for granted.

There are many reference texts on anatomical dissection that demonstrate numerous variations in the human body. Unlike the other cranial nerves, nerve N lies in the most rostral area where the brainstem and olfactory bulb are located. Finally, it passes through the cribriform plate of the ethmoid bone more medially and deeply than do the tracts of the olfactory nerve.

As demonstrated by research in other species, the nerve is linked with the olfactory nerve 11 in terms of its location and probably also its function. From an embryological perspective, it seems to have developed from the area of the olfactory cells, although some have hypothesized that it may originate from the neural crest. It is important to remember that, at the level of the nose, there is the nasopalatine nerve which innervates the nasal cavity and belongs to the maxillary section of the trigeminal nerve.

At the same level there is the ethmoidal nerve, which supplies the anterior nasal mucosa, and develops from the ophthalmic division of the trigeminal nerve.

Furthermore, in some animal species, nerve N supplies the retina, indicating that this nerve may be responsive to light. So far, there are still differing opinions about the function of this nerve. However, these are only hypotheses and suggestions, none of which is definitely based on incontrovertible evidence. According to the numerous studies carried out to date, nerve N could somehow be connected with reproductive function.

In several animal species, nerve N secretes or stimulates the secretion of luteinizing hormone-releasing hormone, also known as gonadotropin-releasing hormone. In humans, particularly in females, this group of neurons can be identified as being mainly in the preoptic area and in the infundibular nucleus of the mediobasal hypothalamus.

We still do not know. Generally speaking, stimulation of a hormonal response in men can be linked with the nasal epithelium through chemosensitive receptors or unidentified bonds with pheromones.

The current view is that nerve N has the ability to affect sexual behavior, but the extent to which it does this is unknown as yet. It is believed to act by stimulating luteinizing hormone-releasing hormone on contact with pheromones, improving olfaction and identifying odors, and this series of events will affect sexual behavior.

Finally, the trigeminal system can be stimulated by odors. In addition, we could link certain sexual behavioral disorders to trigeminal pain. Many other hypotheses might be formulated, but what is certain is that the human body is a sole entity. In order for the body to maintain homeostasis, each and every part needs to be in harmonious and tensegritive collaboration, with regard to not only fascial but also immunological, neuroendocrine, and psychological functioning. Recent research on the olfactory system theorizes a correlation between olfactory changes and certain psychiatric and behavioral disorders, and other neurological pathologies.

However, we are again awaiting further research on this relationship. The intermediary nerve has always been considered a ramification of the facial nerve, which is complex 37 , 38 and all its connections have not been clearly revealed as yet. However, the intermediary nerve is actually a separate and independent nervous entity.

It is a short nerve, measuring no more than 21 mm in length. In contrast, the afferents of the intermediary nerve derive from receptors known as the concha auriculae located in a small area behind the ear, from the external layer of the membrana tympani, and from part of the wall of the external auditory meatus. This has further confirmed its separation from the facial nerve.

From an anatomical perspective, which involves taking into consideration its direct connections with the geniculate nucleus, the pterygopalatine ganglion, and the brainstem, and from an electrophysiological point of view, the intermediary nerve is now regarded as a nervous structure in its own right. First, the intermediary nerve is connected indirectly to the trigeminal system.

Finally, looking more closely at the intermediary nerve, there are minute anastomoses with nerves VII and VIII at the level of their origin. The recent medical literature cites the intermediary nerve in terms of the problems it may cause, although these do not occur frequently. For example, paroxysmal otalgia lasting seconds or minutes , found in combination with alterations in lacrimation, salivation, and taste perception, is known as geniculate neuralgia, neuralgia of the intermediary nerve, or Tolosa-Hunt syndrome.

As osteopaths, we know that anomalous drainage of the cranial venous system may cause dysfunction in the cranial nerves. In the light of the information currently available in the medical literature, the nomenclature for the cranial nerves should be revised. Further studies are needed to improve our knowledge of the clinical scenarios that may arise from physiological alteration of their function, as well as a more detailed anatomical description of medical strategies which may be helpful in treating related problems.

National Center for Biotechnology Information , U. Journal List J Multidiscip Healthc v. J Multidiscip Healthc. Published online Mar Bruno Bordoni 1 and Emiliano Zanier 2. Author information Copyright and License information Disclaimer. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.

This article has been cited by other articles in PMC. Abstract It has been known for over a century that these cranial nerves exist, and that they are not typographical errors nor a sensational event reported in the medical literature. Keywords: cranial nerve, facial nerve, trigeminal system, Tolosa-Hunt syndrome. Nerve N Anatomy is still a field rich in findings, and as regards the data collected so far, nothing can be taken for granted.

Intermediary nerve The intermediary nerve has always been considered a ramification of the facial nerve, which is complex 37 , 38 and all its connections have not been clearly revealed as yet. Conclusion In the light of the information currently available in the medical literature, the nomenclature for the cranial nerves should be revised. Acknowledgment In memory of Erio Mossi; osteopath, teacher, and writer. Footnotes Disclosure The authors report no conflicts of interest in this work.

References 1. Vilensky JA. The neglected cranial nerve: nervus terminalis cranial nerve N Clin Anat. Jul 26, Cranial Osteopathy Principles and Practice. History of the nervus intermedius of Wrisberg. Ann Anat. The nervus intermedius: a review of its anatomy, function, pathology, and role in neurosurgery. World Neurosurg. Apr 3, Bilateral asymmetric supernumerary heads of biceps brachii.

Anat Cell Biol. Supernumerary peronei in the leg musculature — utility for reconstruction. Chang Gung Med J. J Plast Surg Hand Surg. Anomalous fascicle of triceps brachii muscle and its clinical importance in relation to radial nerve entrapment.

Clin Ter. Nervus terminalis cranial nerve zero in the adult human. Clin Neuropathol. The microsurgical anatomy of the gyrus rectus area and its neurosurgical implications. Arq Neuropsiquiatr. Whitlock KE. Development of the nervus terminalis: origin and migration. Microsc Res Tech. Von Bartheld CS. Nervus terminalis derived from the neural crest?

A surprising new turn in a century-old debate. Anat Rec B New Anat. The anatomical and electrophysiological basis of peripheral nasal trigeminal chemoreception. Ann N Y Acad Sci.

Wirsig-Wiechmann CR. Introduction to the anatomy and function of the nervus terminalis. What defines the nervus terminalis? Neurochemical, developmental, and anatomical criteria.

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It has been known for over a century that these cranial nerves exist, and that they are not typographical errors nor a sensational event reported in the medical literature. A number of scientific articles on anatomy highlight how textbooks on descriptive anatomy do not always consider variables such as differences related to the geographical areas where people live, and these differences do exist. This is an important concept not only for surgeons, but also for all medical professionals who use manual techniques when treating their patients, ie, osteopaths, chiropractors, physiotherapists, and other manual therapists. This paper highlights the latest developments regarding these cranial nerves, offering at the same time some ideas for further reflection when looking at clinical scenarios that appear to bear little relationship to each other. Inclusion of these concepts in everyday anamnesis is encouraged. First discovered in in sharks and other types of fish, it was initially referred to as the nerve of pinkus.


Cranial nerves and their functions (Table ). Cranial nerves arise from the brain as twelve pairs. They pass through or into the cranial bones (thus cranial.


The Names, Functions, and Locations of Cranial Nerves

The cranial nerves are nerves that arise from the brain and exit the skull through holes cranial foramina at its base rather than through the spinal cord. Peripheral nervous system connections with various organs and structures of the body are established through cranial nerves and spinal nerves. While some cranial nerves contain only sensory neurons, most cranial nerves and all spinal nerves contain both motor and sensory neurons. Cranial nerves are responsible for the control of a number of functions in the body.

Cranial nerves are the nerves that emerge directly from the brain including the brainstem , of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck , including the special senses of vision , taste , smell , and hearing.

Your cranial nerves are pairs of nerves that connect your brain to different parts of your head, neck, and trunk. There are 12 of them, each named for their function or structure. This is based off their location from front to back.

Smell, a function of the 1st olfactory cranial nerve, is usually evaluated only after head trauma or when lesions of the anterior fossa eg, meningioma are suspected or patients report abnormal smell or taste. The patient is asked to identify odors eg, soap, coffee, cloves presented to each nostril while the other nostril is occluded. Alcohol, ammonia, and other irritants, which test the nociceptive receptors of the 5th trigeminal cranial nerve, are used only when malingering is suspected. For the 2nd optic cranial nerve, visual acuity is tested using a Snellen chart for distance vision or a handheld chart for near vision; each eye is assessed individually, with the other eye covered. Color perception is tested using standard pseudoisochromatic Ishihara or Hardy-Rand-Ritter plates that have numbers or figures embedded in a field of specifically colored dots.

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