CRANIAL NERVES

There room lots of an excellent pictures the cranial nerves in any kind of internet search. CLICK right here to load photo search of cranial nerves and also check several of the thumbnails out to assist you acquire an idea of where these nerves are at. You will likewise study the location and anatomy of these nerves in Bio 264 lab.

Remember the friend the you required to the emergency room ~ she gained hurt sledding. When the physician shined a light right into her eye to check her reflexes the was in reality performing a small component of a cranial nerve examination. Act an examination of the cranial nerves have the right to provide valuable clinical information around the state and condition of the worried system. There are twelve pairs of cranial nerves that originate in the mind and lug information to and from the brain. The cranial nerves space designated by roman inn numerals (I - XII) and also by names. The numbering starts with those most superior and anterior and also progresses posteriorly and also inferiorly. The names usually correspond to either the duty or the structure of the nerve, hence, the Optic nerve is associated with vision and also the Trigeminal nerve has 3 branches. This nerves can lug both sensory and motor information, simply as we have actually seen v spinal nerves. We have the right to subdivide the sensory information more into 1) unique senses and 2) basic senses. The motor info can likewise be subdivided right into 1) somatic motor and also 2) parasympathetic. In comparison to the spinal nerves, however, not all cranial nerves bring both sensory and also motor information. In fact, three cranial nerves lug purely sensory information and four cranial nerves carry nearly entirely somatic engine information. The staying cranial nerves lug some mix of sensory, somatic motor and also parasympathetic information. Because of the clinical importance of the cranial nerves we will comment on further the major functions of each one and also some the the usual symptoms observed when the nerves space damaged.

You are watching: You suspect your friend has damage to cranial nerve i when he is unable to

Cranial Nerve 1 (CN I): Olfactory

Major Function: Sensory - odor (olfaction)

Lesion: lose of odor on the affected side

*Note: lose of odor doesn"t necessarily confirm a CN i lesion together an top respiratory tract infection etc. Could also decrease olfaction.

Cranial Nerve 2 (CN II): Optic

Major Function: Sensory - Vision

Lesion: blindness on affected side and loss the pupillary light reflex (Described Later)

Cranial Nerve 3 (CN III): Oculomotor

Major Function: Somatic engine to 4 of the six extrinsic muscle that move the eye

ANS Innervation: Parasympathetic come sphincter pupillae muscle because that constriction the the pupil

Lesion: Eye deviation causing dual vision, pupil dilation and loss the pupillary irradiate reflex

Cranial Nerve 4 (CN IV): Trochlear

Major Function: Somatic engine to premium oblique eye muscle

Lesion: Eye deviation causing dual vision

Cranial Nerve 5 (CN V): Trigeminal

Major Function: Sensory - general sense native the face and also forehead (including emotion of much of the mouth and anterior 2/3 the the tongue)

Motor: Somatic engine to muscle of mastication (chewing muscles)

Lesion: ns of sensation in face and also forehead or enhanced sensitivity come pain well-known as Trigeminal neuralgia. (Described Later). Also, muscle weakness of the muscle of mastication

Cranial Nerve 6 (CN VI): Abducens

Major Function: Somatic motor to lateral rectus eye muscle

Lesion: Medial deviation that the eye causing dual vision

Cranial Nerve 7 (CN VII): Facial

Major Function: Sensory - Taste from the anterior 2/3 of the tongue and Motor - Somatic motor to the muscles of face expression

ANS Innervation: Parasympathetic to salivary glands and also lacrimal glands

Lesion: Facial paralysis often dubbed Facial or Bell"s palsy. (Described Later). Decreased ability to taste (particularly ~ above the anterior 2/3 the the tongue). Diminished salivation and also lacrimation (tearing)

Cranial Nerve 8 (CN VIII): Vestibulocochlear

This nerve is created of yarn from two branches: the vestibular nerve and the cochlear nerve, every with particular functions

Major Function: Sensory - Vestibular branch senses balance. Cochlear branch if for hearing.

Lesion: Vestibular-If only the vestibular branch is damaged the would an outcome in ns of balance and dizziness (vertigo). Cochlear-If just the cochlear branch is damaged that would result in ns of hearing. If the lesion occurs after the 2 branches converge then you can have a combination of the above symptoms.

Cranial Nerve 9 (CN IX): Glossopharyngeal

Major Function: Somatic engine to swallowing muscle of the throat and also Sensory - Taste come the posterior 1/3 of the tongue and also Sensory native the pharynx, carotid body and carotid sinus

ANS Innervation: Parasympathetic come salivary glands

Lesion: Trouble swallowing, lose of taste (particularly come posterior 1/3 of tongue), decreased capacity to sense and also respond to blood press changes and also decreased salivation

Cranial Nerve 10 (CN X): Vagus

Major Function: Motor - Somatic engine to neck muscles associated in swallowing and speech and also Sensory - Taste from posterior tongue. Also, sensory native throat, thoracic and abdominal organs

ANS Innervation: Parasympathetic to thoracic and abdominal organs regulating things such as heart and respiratory rate and also gastrointestinal peristalsis etc.

Lesion: Trouble swallowing and also hoarse speech uvula deviation far from next of lesion

Cranial Nerve 11 (CN XI): Accessory

Major Function: Somatic motor to sternocleidomastoid and trapezius muscles

Lesion: Muscle weakness and also trouble turning the head and also elevating the scapula

Cranial Nerve 12 (CN XII): Hypoglossal

Major Function: engine - Somatic motor to tongue and throat muscles

Lesion: Tongue deviation towards the next of lesion; trouble manipulating food through tongue and trouble swallowing.

*Pupillary light Reflex: The pupil diameter is closely regulated and also responds to the lot of irradiate available. The pupil will dilate in a dark atmosphere to permit in an ext light and constrict in a light setting to limit the lot of irradiate entering the eye. This dynamic manage has 2 branches. The afferent (sensory) limb of the reflex is regulation via CN II, i beg your pardon sends action potentials come the control facility in the midbrain about light intensity. The midbrain then sends out signals with the efferent (motor) body of the reflex, i beg your pardon is CN III, to constrict the pupil. Dilation the the pupil is achieved via a forgiveness nerve which is exit the CNS in the spinal chord and is not mediated by a cranial nerve. Clinical Manifestation: when you bright a light into a patient"s left eye the optic nerve should rise signals to the midbrain which will then cause the oculomotor nerve to wake up the constrictor pupillae muscle come contract, for this reason constricting the pupil that the left eye. This is referred to as the straight light reflex. In addition to pupil constriction in the left eye, the pupil of the best eye will also constrict, i m sorry is known as the consensual light reflex. Any kind of deviation from this sample represents a pathological condition that would certainly warrant further investigation.

*Trigeminal Neuralgia (tic douloreux): CN V it s okay its name from the fact that it has three branches, trigeminal way "three twins." The 3 branches (V1, V2, and also V3) room responsible for giving innervation to certain regions that the anterior head. V1 (ophthalmic) supplies sensory innervation come the forehead under to the nose. V2 (maxillary) gives sensory innervation to the maxillary region inferior come the nose and also superior to the reduced jaw. V3 (mandibular) offers sensory innervation come the mandibular region or the lower jaw and also anterior come the ear, and somatic engine innervation come the muscles connected in chewing. The maxillary and mandibular branches of the trigeminal nerve are additionally responsible for providing sensory innervation to the teeth.

When friend "visit" the dentist to to fill a cavity the dentist make the efforts to minimize the trauma by anesthetizing the area the he is going to ultimately abuse with various power tools! The many common method this is excellent is through performing a "nerve block" in i beg your pardon inject lidocaine, or some other local anesthetic is injected right into the area bordering either the maxillary nerve, if they should work on your upper teeth, or the mandibular nerve, if they space working top top your lower teeth. This "nerve block" literally blocks or prevents action potentials indigenous being sent to your brain.

Trigeminal neuralgia involves intense episodic pains in any, or all 3 facial locations supplied by CN V. It has actually been explained as one of the many intensely painful conditions known come man! it is defined by hypersensitivity that the nerve to the allude where a light touch on the face or even a gentle breeze can reason intense, debilitating pain. Those with trigeminal neuralgia often define the pain together burning, electrical, stabbing, crushing, or even exploding pain. And if that doesn"t sound negative enough the is likewise quite difficult to control. Happily there are several pharmacologic therapies to help manage the pain.

The leading theory to define the reason of this problem involves compression the the myelin sheath around the nerve, likely as result of an enlarged artery or aneurysm. This compression deserve to lead to damage of the myelin sheath, bring about the nerve to become hypersensitive to the little stimulation. Likewise, this can also make it difficult for the trigeminal nerve to protect against the afferent pains signals when they have actually begun.

*Facial Palsy (Bell"s Palsy): Bell"s palsy is a condition that outcomes in partial or finish facial paralysis ~ above one next of the face, although some situations can manifest bilaterally. This is a an outcome of a lesion of the facial Nerve (CN VII), most likely as result of inflammation although the specific cause is unknown. The leading explanation is the a dormant herpes viral epidemic becomes reactivated causing the face nerve inflammation. Stress, trauma, environmental and also other components may precipitate the reactivation of the virus. There room other reasons of face paralysis, the most usual being mind tumor or stroke.

See more: How Long Is The Wizard Of Oz Beyond The Yellow Brick Road ? The Wizard Of Oz: Beyond The Yellow Brick Road

Treatment: The symptoms of Bell"s palsy typically resolve ~ above their own over the course of days to weeks, but corticosteroids administered early on after beginning of symptoms have been displayed to improve recovery. Since the impacted eyelid is often unable to close, the is essential to protect against drying the the cornea by making use of eye fall and/or physically closing the eye! (Taping the eye closed and also using an eye patch can be helpful and also who doesn"t love a pirate, arrrrrr!)

Speaking of pirates, it has been rumored the pirates wore eye patches so that together they walk from the deck wherein it was an extremely bright to the rooms listed below deck where it was fairly dim they might remove the patch and maintain their capacity to see. Based upon the consensual light reflex described above, the is unlikely that pupil constriction/dilation would be the mechanism enabling pirates to see as they move from light to dark environments. Save this in mind together you learn about vision in succeeding modules and, in particular, the rhodopsin cycle.

A cranial nerve check is an important part of any physical examination wherein you doubt that there might be some level of mind trauma, but specifically when there space no clear symptoms that suggest mind injury. Since of their relationships with assorted parts that the brainstem and also cerebrum, functional deficits associated to one of the cranial nerves deserve to provide an important insight into the location and also severity that damage. Often a medical provider can perform a short cranial nerve exam at the very same time the they space performing their regimen physical exam. Because that example, when they watch at your throat and also you say "ahhhhhh" they are not only searching for redness and inflammation etc. Linked with famous or bacterial infection. After all, execute you think your neck would automatically become red by act this? The answer is no. The medical professional is really in search of elevation of the palate or deviation that the uvula, which would signal a cranial nerve problem. The adhering to is a attach to a YouTube video clip of a short cranial nerve examination. Https://www.youtube.com/watch?v=a0vtkXMr7qQ (Video Transcriptions Available)

**You might use the buttons below to walk to the next or previous analysis in this Module**
*
print this web page