Glossary of CRANIAL NERVES V AND VII - 44
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- Distinguish btw:
A. Central Nervous System
B. Peripheral Nervous System
- A. Central Nervous System
2. Spinal Cord
B. Peripheral Nervous System
1. Spinal Nerves (31 pairs)
2. Cranial Nerves (12 pairs)
- Describe the nerves of the Peripheral Nervous System?
- They contain hundreds to millions of nerve fibers or axons and the function of each fiber in a nerve may differ, so lesions of the nerve may produce a range of motor and/or sensory symptoms.
- Describe lesions of nerves?
- Lesions of nerve produce different symptoms depending on the site of damage
- Distinguish btw:
1. General somatic afferent (GSA) fibers
2. General visceral afferent (GVA) fibers
3. General somatic efferent (GSE) fibers
4. General visceral efferent (GVE) fibers
- 1. General somatic afferent (GSA) fibers: convey sensory input from skin, muscle, bone, and joints, to the CNS
2. General visceral afferent (GVA) fibers: Convey sensory input from visceral organs to the CNS
3. General somatic efferent (GSE) fibers: Convey motor outputs from ventral horn motor neurons to skeletal muscle
4. General visceral efferent (GVE) fibers: Convey motor outputs from intermediolateral cell column neurons, via prevertebral ganglia to glands, smooth muscle, and visceral organs
- Describe the lingual nerve?
- It is a branch of CN V3 and it originates as sensory nerve, but is then joined by the chorda tympani nerve carrying autonomic and taste fibers so now the lingual nereve has those two added components to it.
- What happens if there is a lesion to the lingual nerve at the position where it joins with chorda tympani nerve?
- A lesion at this position would result in loss of touch/pain/temp, as well as autonomic and taste senses
- What are the 2 classifications of every axon in the PNS?
- 1. Efferent fiber
2. Afferent fiber
Every axon may be classified as an efferent or afferent fiber in the PNS; but it cannot be both
- What are the 2 classifications of efferent fibers of an axon in the PNS?
- Efferent = motor
Its classification are?
- Distinguish between:
- 1. Somatic– axons going to the body wall
2. Visceral– internal innervation
1. Efferent somatic fibers
2. Efferent visceral fibers
3. Afferent somatic fibers
4. Afferent visceral fibers
- 1. Efferent somatic fibers
2. Efferent visceral fibers
3. Afferent somatic fibers
4. Afferent visceral fibers
- What is the difference btw spinal and cranial nerves?
- General functions are those you will find BOTH in spinal and cranial nerves (throughout the CNS). Special functions are those carried only by cranial nerves and they carry information, sometimes carried by a single cranial nerve. For ex: vision is carried only by CNII. At most the special sense information is carried by three CNs.
- Delineate between the 7 diff classifications of functional components of peripheral nerves?
- 1. GSE = somotic, skeletal muscle
2. GVE = smooth and cardiac muscles, and glands
3. SVE = branchio-meric
4. GSA = pain, touch, temperature, and proprioreception
5. SSA = vision hearing and balance
6. GVA = pain stretch and distention
7. SVA = smell and taste
- Where is the Somitic derived from?
- SOMITES (swellings giving rise to myotomes and dermatomes). Skeletal muscle derived from somites or mesoderm gets this innervation.
- Describe SVE and its derivation?
- They are fibers that innervate skeletal muscle and they are derived from PHARYNGEAL or BRANCHIAL arches = different embryology from the GSE. Is SVE because the branchial arches are originally gill arches and thus visceral structures in fish.
Still have some visceral characteristics because muscles of the pharynx and eosophagus are still involuntary, not voluntary, even though they are striated muscle
- What is the significance of SSA?
- CN only and for indicated functions (CNs II and VIII). Information related to environmental perception and body relationship to that = somatic type of function.
- Difference btw GVA and GSA is?
- GVA are sensory going to the body cavities! They innervate organs and glands within the body cavities. They provide sensory feedback for CNS. They do not do proprioception quite so much.
- SVA is important for?
- Smell and taste– investigation of food to swallow to take into viscera = connection to viscera
- What are the 2 functional component divisions of CNS Development and what do they give rise to?
- 1. Alar plate: gives rise to the sensory nuclei
2. Basal plate: give rise to motor nuclei
- Compare dorsal and ventral structures in CNS?
- Dorsal structures in CNS are usually sensory and ventral structures are usually motor.
- Describe the organization of:
1. GSE column
2. SVE column
- 1. GSE column: are motor nuclei innervating muscles derived from somites. Nuclei for specific nerves are lined up in this column and then they break off to form specific CNs
2. SVE column: are nuclei for branchiomeric muscles and it runs parallel to the GSE column. This organization is conserved in the CNS.
NOTE: Looking at nucleus– an oval shaped structure; but it actually forms a column of cells
- What do we need to know about CNS?
- ORIGIN FROM BRAIN
(NUCLEI IN CNS)
GANGLIA (type and location)
- What is the clinical relevance of Foramen of nerves?
- It is a site of potential injury and Cranial Nerves are often damaged as such ex:stenosis of the foramen, fracture of the foramen, etc
- What is a ganglion and what are its 2 divisions?
- Ganglion is somas in CNS,and their 2 divisions are:
1. dorsal root ganglion: sensory
2. sympathetic chain ganglion: autonomic with sympathetic and parasympathetic functions
- What is the trochlear nerve?
- Either of the 4th pair of cranial nerves that arise from the dorsal aspect of the brainstem just below the inferior colliculus and supply the superior oblique muscle of the eye with motor fibers.
- What is the trigeminal nerve?
- Either of the 5th pair of cranial nerves that are mixed nerves in humans and are the largest of the cramial nerves. They arise by a small mottor and a larger sensory root which both emerge from the side of the pons
- What happens to the sensory root of the trigeminal nerve?
- The sensory root bears the trigeminal ganglion which divides into opthalmic, maxillary, and mandibular nerves.
- Where does the motor root of the trigeminal nerve supply?
- It supplies fibers to the mandibular nerve and through this to the muscles of mastication.
- What are tested in a physical examination?
- Deficits as a result of lesions
Tests to use and in what order in a physical examination
- Why is the foramen important?
- Fracture lines often go through foramen, crushing or severing cranial nerves
- What will happen if there is a swollen artery in a foramen with other veins and nerves as a result of aneurysm, phylibitis, or tumor?
- It will not damage the bone but it will damage soft nerve structures going through the foramina
- What should a clinician look for when testing cranial nerve function?
- The clinician always notes sensory/ motor asymmetries, thus using the patient has his/her own control. Since there is a lot of anatomical and physiological variation in human beings, you test right and left hand sides for symmetry and the threshold for sensory stimulation should be symmetrical
- What are muscles tested against to unmask weakness?
- Muscles are tested against resistance to unmask weakness. So, testing the trapezius to see if shrugging is symmetrical; ask patients to contract muscle against pressure/ resistance. Resistance is also good because there are many muscles contributing to muscle shrugging and they would use all those. The weakness would then only be seen with resistance against movement.
- What is paresis?
- This is muscle weakness and this may result instead of paralysis in things like a stroke. Asymmetry suggests pathological change.
- How is cranial nerve function evaluated?
- It is evaluated through the testing of reflexes.
- What are the 5 basic components of a reflex?
1) Sensory receptor
2) Afferent nerve
3) Central integration
4) Efferent nerve
- 1) Sensory receptor
2) Afferent nerve
3) Central integration
4) Efferent nerve
- Why is the reflex arc important and what does it need?
- It is the most fundamental circuit of the Nervous System and it needs:
1. motor limb
2. sensory limb
- What do you do if you get no reflex or a hyperreflex?
- This indicates a change along the pathway so you test further to see what kind of loss it is.
- What are the 3 sensory cranial nerves?
A. CN I
B. CN II
C. CN VIII
- What are the 5 motor cranial nerves?
A. CN III
B. CN IV
C. CN VI
D. CN XI*
E. CN XII
- What are the 4 mixed cranial nerves?
A. CN V
B. CN VII
C. CN IX
D. CN X
- What are the special seenses for?
2. CN II
3. CN VIII
- 1. CN1 = olfactory;smell
2. CN II = visual
3. CN VIII = hearing, balance (vestibulochochlear)
- What is CN XI in relation to vagus nerve?
- 2 D is a pure motor nerve. It has to be emphasized in relationship to the vagus.
- The motor nerves innervate muscles derived from where?
- occipital somites (branchiomeric = SVE)
- What is CN V?
NERVE OF THE 1ST BRANCHIAL ARCH
- What is the origin of CN V?
- What are the 3 divisions of CN V and their associated foramen?
- 1. V1 (opthalmic division) = Superior Orbital Fissure
2. V2 (maxillary division) = Foramen Rotundum
3. V3 (mandibular division) = Foramen Ovale
- What is the ganglion of CN V?
- What are the 2 components of CN V?
- 1. GSA
- Name 4 clinical cases related to CN V?
- 1. Herpes
2. Tic Douloureux
3. Jaw Jerk Reflex
4. Pupillary Reflex
- Where does CN V :
- 1. originate: Begins as a single nerve coming off the pons
2. terminate: Short stalk which terminates in trigeminal or semilunar ganglion (like dorsal root ganglion)
- What are the 2 components of the semilinar ganglion?
- 1) sensory ganglion
2) contains pseudo-unipolar neurons
- The three major branches of CN V originate from where?
- Semilunar ganglion
- Describe the middle cranial fossa and its importance to CN V?
- It contains the foramen for the branches of CN V and the three divisions of CN V exit the middle cranial fossa. In the middle cranial fossa, from before backward in the sphenoid bone is the superior orbital fissure,location for VI, foramen rotundum, for V2, foramen ovale for V3 and foramen spinosum
The anterior and middle fossae are separated by the lesser wing of sphenoid bone, and the middle and posterior fossae are separated by petrous part of temporal bone
- Where do these 3 divisions of CN V enter into?
1. V1 – Orbit
2. V2– Pterygopalatine Fossa
3. V3 - Infratemporal Fossa
- 1. V1 – Orbit
2. V2– Pterygopalatine Fossa
3. V3 - Infratemporal Fossa
- What does CN V carry and what is unique about V1 and V2?
- CN V carries fibers from the face and note the boundaries at corners of eye and mouth. V1 and V2 BOTH innervate the outer nose.
- What division of CN V is involved in herpes zoster?
- 1. Describe herpes zoster infection.
2. What could herpes zoster infection lead to?
- 1. herpes zoster infection resides in the ganglia and they may become activated at which point they go to nerve endings and cause trouble like blisters there
This is very clearly a problem of V1. it is the sensory innervation to the cornea;
2. This infection could spread and lead to problems on the cornea of the eye which could lead to blindness
- What are the specific areas that the 3 divisions of CN V innervate?
- CN V Carries GSA Sensations from Cavities of the Head and Territories extend to inside of the face but its three divisions innervate:
1. V1: orbit & upper 1/2 of
2. V2: lower 1/2 of nasal cavity upper 1/2 of oral cavity (Hard and soft palate )
3.V3: lower 1/2 of oral cavity
- What happens if there is Herpes of V2?
- There will be involvement of Palate so in her oral cavity, hard palate has blisters as well and causes pain in eating and in the mouth in general
- 1. What does CN V innervate in the brain?
2. V2 innervates what in the brain?
3. V1 innervates what in the brain?
- 1. The dura.
2. Middle cranial fossa on greater wing of sphenoid = V2
3. Tentorium cerebelli, a cleft of dura that covers the upper surface of the cerebellum and supports the occipital lobes of the cerebrum is innervated by V1.
- Why do headaches occur?
- Inflamed Blood Vessels Stimulate Pain Fibers in the Meninges so the swelling of blood vessels and consequently irritation of the nerve causes the headache. Therefore with headache don’t take drugs causing vessel dilation
- What is Tic Doulourex?
- It is also called trigeminal neuralgia and it is an intense paroxysmal neuralgia involving one or more branches of the trigeminal nerve.
- What are 4 characteristics of Tic Neuralgia?
- 1) Intense Pain
3) Short Duration
4) Trigger Zone (often distinct from pain locus)
NOTE: paroxysmal means it comes on in periods (spasms of pain that come and go). Also, this pain lasts for short periods of time.
If you touch a portion of their body it sets off the spasm (trigger zone); but it may not be in the same area as the location of the pain sensation (sometimes it is)
It is unique to each neuralgia
- What is the specific source of Tic Douloureux?
- Compression of Root of CN V by the Anterior Superior Cerebellar Artery is
Often the Source of Tic Douloureux.
People go to extremes to control pain which often has a vascular origin
Here the artery is touching and irritating the nerve, causing the neuralgia. Answer is to separate the artery from the nerve thus allowing regrowth and resumed function of the nerve.
- What is the role of SVE in CN V and where are they derived from?
- SVE fibers in V3 innervate skeletal muscles
derived from the 1st branchial arch.
- What 4 muscles derived from the 1st branchial arch are innervateed by SVE fibers in V3?
- 1) Muscles of mastication
2) Ant. belly of diagastric
3) Tensor tympani
4) Tensor veli palatini (muscle of soft palate)
- How do you test the SVE component of V3 in order to find out if there is a lesion?
- When protruded, jaw deviates to side of lesion instead of the jaw normally protuding straight out. This is because, if paralysed it protrudes to the side of the paralysis or lesion
- What method is used to test for sensory and motor components of CN V?
- The jaw-jerk reflex
This is routine in neurological exams and the jaw should shut immediately
when you tap your own finger NOT the jaw.
- Describe CN VII?
- It is called facial nerve and it is a Nerve of second branchial arch
It is involved in facial movements, taste, salivation, and lacrimation
- What are the 2 roots of the facial nerve?
- 1) motor root: This is the larger root and it contains the SVE that innervate muscles of facial expression
2) nervus intermedius: It is the smaller sensory division and it has GSA, SVA, and GVE fibers, which are all first order neurons that are found in the geniculate ganglion within the temporal bone.
- What is the origin of CNVII?
- Pontomedullary junction : Line where medulla comes into the pons
- What are the 2 foramen of CN VII?
- 1) internal acoustic meatus (enters the internal auditory canal meatus and facial canal)
2) stylomastoid foramen (exits the facial canal and skull via the stylomastoid foramen)
- What are the 3 ganglia for CN VII?
- 1) submandibular: autonomic 2) pterygopalatine: autonomic
3) geniculate: sensory
- What are 5 Components of CNVII?
- 1. SVE
- What are 5 Clinical problems associated with CN VII?
- 1) Bell’s palsy
2) blink reflex
3) syndrome of crocodile tears
4) Ramsay Hunt Syndrome
- How does CN VII Exit the Posterior Cranial Fossa?
Through the Internal Auditory Meatus (Arrow)
- Where does CN VII exit the skull through?
- CN VII Exits Skull Through the Stylomastoid Foramen
- Where is facial canal located and what does it do?
- The facial canal, in the petrous portion of the temporal bone,
connects the internal auditory meatus & stylomastoid foramen
- Why is the facial canal very important?
- It is a potential site for compression injuries if CN VII becomes inflamed (eg., herpes infection) so if the nerve swells in here it will be damaged as the bone will not give way and aneurysms of blood vessels could also damage the nerve here
- CN VII: SVE is important for?
- Muscles of Facial Expression
- What are 4 Muscles of Facial Expression controlled by CN VII: SVE?
- 1. stapedius
3. posterior belly of digastic
- How is CN VII clinical testing conducted?
- You ask patient to demonstrate a range of facial expressions including smiling, frowning, & puffing out of cheeks and the tests are performed against resistance. By asking for different expressions, you look for asymmetry; then add resistance for example try to raise eyelids with fingers (cannot do so in healthy person)or puff out cheeks and try to delfate it by poking cheeks (will only happen with paresis)
Important in testing for stroke vs. a lesion
- What is Bell's palsy?
- It is an idiopathic paralysis of muscles of
facial expression. As facial nerve courses through the facial canal, it is vulnerable to inflammatory processes and enlargement of companion vessels.
NOTE: idiopathic– don’t know the cause. May be inflammation of nerve or artery in the facial canal
- If there a left bell's palsy, what would you notice?
- You notice the facial symettry and see that Eyelids on right would be more open
- What are 3 things you note in patients with bell's palsy?
- 1. lack of wrinkles on the unaffected side
2. mouth drawn to unaffected side
NOTE: Also they grimace when asked to smile
Muscle contraction causes wrinkles and so without it the face is smooth (slide is wrong)
- What is hyperacusia?
- Abnormally acute hearing in which sounds are very loud because muscle that dims sound is gone
- What is tetanus?
- Spasms of jaw, face and neck muscles due to neurotoxins produced by Clostridium tetani. CNVII is involved in this.
- How is CNVII implicated in tetanus?
- It is implicated because the bacteria that causes tetanus or lock jaw grows and releases toxins that causes contraction of muscles of facial expression so ppl
cannot open their mouth, eat, sleep or drink
They are in constant contraction (look scared or happy) and when it spreads to diaphragm they cannot breathe and they can die.
- What are the 2 things involved in blink reflex?
- 1. Sensory Limb: V1
2. Motor Limb: Motor Root of CN VII
NOTE: Try to touch eyeball
- What are the 3 locations where there is a role for the GVE component of CN VII?
- It is a parasympathetic component that sends secromotor to and innervates:
1. lacrimal gland
2. submandibular gland
3. sublingual gland (and glands in the oral and nasal cavities)
So, Autonomic supplies information to the lacrimal gland, mucous glands and salivary glands
- What are the 2 types of autonomic ganglia for CN VII?
- 1. Ptergopalatine ganglion
2. Submandibular ganglion
- What is crocodile tear syndrome?
- This is lacrimation during eating and it is caused by a facial nerve (CN VII) lesion proximal to the geniculate ganglion. Therefore, regenerating preganglionic salivatory fibers are misdirected to the pteryogopalatine ganglion, which projects to the lacrimal gland.
- What is the geniculate ganglion?
- It is a sensory ganglion of CNVII and it contains the soma of the sensory fibers carried by CN VII.
- What is the role of the SVA component of CNVII?
- It has cell bodies located in the geniculate gamglion and it innervates the taste buds from the anterior two-thirds of the tongue.
So, Anterior 2/3rds of the tongue (visceral cos tongue is thought of as taking in food which is processed viscerally)
- In what 2 areas do SVA of CNVII not innervate the tongue?
- 1. circumvallate
2. folliate papillae
The taste buds not included in CNVII: SVA are innervated by CN IX
- What is the role of GSA fibers from VII ?
- They innervate the skin
around the external auditory meatus
- What develops for 1st and 2nd pouches?
- Auricle Develops for 1st & 2nd Pouches
(Thus, the auricle is innervated by CN’s V & VII)
NOTE: don’t have to know this.
Skin of outer ear is from territory of facial nerve
- What is ramsay hunt syndrome?
- It is also known as herpes zoster oticus and it is acute facial paralysis that occurs in association with herpetic blisters of the skin of the ear canal, auricle, or both and it is caused by infection of the geniculate ganglion by human herpesvirus 3 (ie, varicella-zoster virus [VZV]). Due to this,nerves in the facial canal may swell leading to Bell’s palsy
NOTE: Herpes blisters seen here. It is herpes zoster and since GSA is in this area it is possible.
- Describe CN X?
- It is called vagus nerve and it is a nerve of the 4th and 6th branchial arch. It is involved in phonation, swallowing, elevation of palate, and taste.
NOTE: Vagus = wanderer or vagabond
- What is the origin for CN X?
- Medulla; Originates dorsal to the inferior olive of the medulla and Rostral to it is CN IX if you look on a ventral view.
- What is the foramen for CN X?
- Jugular foramen
- What are the 3 ganglion of CN X?
- 1) Superior: Sensory
2) Inferior: Sensory
3) Intramural: Parasymp.
- What are the 5 components of CN X?
- 1. SVE
- What are 3 clinical concerns of CN X?
- 1) Dysphagia
3) Gag Reflex
- What travels along with CN X in the jugular foramen as it exits the skull?
- Internal jugular vein travels along with CN IX and XI as they exit the skull via the jugular foramen. Therefore, problems with the vein could compromise this nerve.
- What are 3 roles of CN X: SVE?
- It innervates skeletal muscle of:
1. soft palate (except: tensor veli palatini = (CN V))
2. pharynx (except stylophyngeus (CN IX)
Note: Intrinsic larynx muscle and skeletal muscles of the soft palate and the pharynx
NOTE EXCEPTIONS!!!– soft palate and pharynx (stylopharyngeus (from arch 3))
- Describe gag reflex?
- Motor limb of CN X in a bilateral response is involved and it is a reflex contraction of the muscles of the throat caused especially by stimulation (as by touch) of the pharynx.
Note: - Touching back of oral pharynx and activating the glossopharyngeal nerve (IX); motor limb of the reflex is mediated by X
Sensory = IX and motor = X
- There should be a bilateral response with this regardless of if you touch right or left side
- Based on patients report, name 3 scenarions due to SVE lesions of vagus nerve (CN X)?
- 1) Dysphagia = difficulty swallowing
2) Dysphonia = problems with voice (talk in whisper)
3) Regurgitation (of food into nasal cavity during swallowing)
- What are 2 observations from a physical examination that illustrates that there is SVE lesion of CN X?
- 1. The Uvula deviates contralaterally from the side of the lesion when the patient says “Ahh”.
2.Also, vocal cords may be fixed (does not move)and assymetric i.e. one side only moves and the other does not and this causes problem with voice
NOTE: There is also accumulation of saliva in the pharynx– sign of dysphagia (usually swallowed as a reflex). Is caused by vagus nerve not causing pharynx contraction to bring about swallowing
- How is dysphagia revealed?
- It is revealed by a delay in water entering the stomach so if it takes more than 10 seconds you have problems
- What happens during swallowing?
- The soft palate swings posteriorly & superiorly to seal off the nasopharynx from the oropharynx
- Paralysis of the soft palate results in what?
- Regurgitation of food into the nasal cavity during swallowing. This is how food gets into the nasal cavity
Lazy soft palate allows food into the nasal cavity
- How are Upper motor neuron pathologies expressed?
- By movement disorders
in the skeletal muscles of the pharynx &
- What is Palatal myoclonus (PM)?
- It is characterized by rhythmic involuntary jerky movements of the soft palate of the throat, and also sometimes other muscles related to the throat.
- What 2 places does CNX : GVE send secretomotor innervation to?
- 1) heart
2) foregut & midgut
Note:One of major autonomic nerves
Major Parasympathetic cranial nerves = 3, 7, 9 and 10
2/3rd of digestive system
- From what location does CN X innervate the gut?
- It is from Laryngeal
Pharynx to Left Colic Flexure
NOTE: Esophagus to left colic flexture innervated by CN X
- Name the 2 sensory ganglia of CN X?
- 1. Superior vagal ganglion
2. Inferior vagal ganglion
- What are 2 characteristics of CN X: GVA even though it has the same distribution as GVE?
- 1) visceromotor reflexes
2) sensations do NOT reach consciousness, which means that sensations are not produced to the point where we can feel them ex: pain, etc
- What is a carotid body?
- The carotid body is a small body of vasculature tissue that adjoins the carotid sinus and functions as a chemoreceptor sensitive to change in the oxygen and CO2 content of blood, and mediates reflex changes in respiratory activity
- How is CN X: GVA related to the carotid body?
- It innervates the carotid body (chemoreceptors) via the sinus nerve.
- What is the role of CN X: SVA?
- It innervates the taste buds of the posterior third of the tongue and it is the most important nerve for taste sensation to back of throat.
NOTE: This is the region of the epiglottis and valicular?
- What are 2 characteristics of CN X: GSA?
- 1) It innervates external auditory meatus
2) When stimulated, it may induce nausea or coughing
NOTE: External ear is derived from first, second, third and fourth arches
Otoscope deep in external auditory meatus leads to stimulation of the CNX and causes coughing or nausea
Innervates deep portion of lining of the external auditory meatus
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