Cranial NervesIII

8/14/2019 Cranial NervesIII

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Glossopharyngeal nerve(IX)

*Mostly sensory

*Supplies

* only one muscle (stylopharyngeus)(SVE)*secretomotor fibers to parotid gland(GVE)

*Carries general and taste sensations from the(SVA)

Posterior 1/3 of the tongue

*IT IS THE NERVE OF THIRD ARCH


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FUNCTIONAL COMPONENTS

SVE

SVA

GVEGVA

GSA

(Sensations from a small area of pinna)


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NUCLEI

motor nucleus is in the medulla

called the nucleus ambiguus

Shared by IX,X,XI nerves

Taste goes to nucleus of tractus solitariusparasympathetic nucleus is called

Inferior salivatory nucleus.


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IX


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Foramen of exit

the jugular foramen

along with X,XI nerves.


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Jugular foramen


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After its exit ,it passes between ICA and IJV

Follows the stylopharyngeus and passes

deep to hyoglossus

distributed to palatine tonsils and base of the tongue.


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Test

Touching the soft palate evokes a strong gag reflex

in majority of people.Absence of such `gag reflex may indicate

nerve injury.

Taste from the posterior 1/3 of the tongue

can also be tested


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TheVAGUS nerve(X)

(the wandering nerve)vagabond

It wanders from the brain stem to the splenic flexure.

Functional components:

1.SVE

2.GVE

3.SVA(taste)

4.GSA5.GVA

Exits through jugular foramen(along with IX andXI)


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The branchial motor(SVE)component of CN X supplies

1. all the muscles of pharynx

except stylopharyngeus.

2. all the muscles of palate except

tensor palati.

3. all the intrinsic muscles of

larynx.


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Overview of Visceral Motor Component(GVE)

supplies the smooth muscle and glands of

the pharynx,

larynx,

viscera down to the splenic flexure.


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In general, parasympathetic

stimulation leads to

increased secretion from glands

and smooth muscle contraction.


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Specifically, CN X parasympathetic

stimulation has the following effects

(think "rest and digest"):

Cardiac - Slows heart rate

Lungs - Stimulates increasedbronchiolar secretions and

bronchoconstriction

GI tract- Stimulates increasedsecretions and motility


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Distribution of GVE fibres


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- the Vagus nerve

Signs and Symptoms of Lesions

Loss of voice, (dysphonia)

Difficulty in swallowing

(dysphagia)

loss of gag reflex,

bradycardia, tachycardia and

dilation of stomach.


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Observe theindividual swallowing

Vagus Nerve Test


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Accessory nerve(XI)

It has two roots, cranial and spinalCranial root arises from the nucleus ambiguus.

Spinal root arise from

upper six segments of spinal cord.


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The spinal root enters the cranial

cavity through the foramen magnum

To joins the cranial root

for a brief distance and then leaves the

skull through

the jugular foramen.


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The cranial root is distributed to

muscles of pharynx and soft palate

through the vagus.(pharyngeal plexus) ?The spinal root descends to supply

sternocleidomastoid and trapezius


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Test

Asking the patient to shrug his shoulders(trapezius)Or

Turning the face against resistance to the opposite side

(sternocleidomastoid)


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Weakness of the sternocleidomastoid will result

in

difficulty in turning the head

opposite the side of the lesion.This will be most noticeable when attempted

against resistance.


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Damage to spinal accessory

causes torticollis(wry neck)
http://www.netterimages.com/image/detail.htm?variantID=2034


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Hypoglossal nerve(XII)

Purely motor nerve

Supplies all the muscles of the tongue

except

palatoglossus


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Functional component: SE

Nucleus is situated in the

hypoglossal trigone(triangle)

(in the floor of IV ventricle).


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lies in line with other SE nerves(III,IV,VI)

p


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Emerges as a series of rootlets between

olive and pyramid.

Picks up C1 fibers and exits through the

Hypoglossal canal

4 foramina from F. magnum


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Course and origin of the

Hypoglossal Nerve (XII)


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course


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TEST

by asking the patient to put out his tongue

If the nerve is normalthe tip of the tongue does not deviate.

If damaged, the tip deviates to the same side as the lesionimages

VII

XII
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Summary of testing


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Nerve Function How to test

I olfactionwith an odorous

substance

II vision vision chart

III most eye muscles"follow the moving

finger"

IV superior obliquelook down at the

nose

V facial sensation touch the face

muscles ofmastication

clench the teeth

VI lateral rectus look to the side

VII facial expression smile, raise theeyebrows

taste sugar or salt

VIII hearing a tuning fork

balance look for vertigo

IX pharynx sensation gag reflex

X muscles of larynxand pharynx,parasymp.

check for hoarseness,open wide and sayAAH

XItrapezius and

sternocleidomastoidtest shoulder raise or

turning the head

XII tongue muscles stick out the tongue

Cranial NervesIII

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