L14 cranial nerves VII-XII

Question 1

what are the 2 main origins of the cranial nerves?

Answer 1

• cerebrum
• brain stem

Question 2

where do cranial nerve 1 and 2 originate from?

Answer 2

the cerebrum

Question 3

RECAP- where does the oculomotor nerve originate from?

Answer 3

the midbrain pontine junction

Question 4

RECAP - where does the trochlear nerve originate from?

Answer 4

the posterior side of the midbrain

Question 5

where does the trigeminal nerve originate from?

Answer 5

the pons

Question 6

where do the abducens nerve, facial nerve and vestibulocochlear nerve originate from?

Answer 6

the pontine medulla junction

Question 7

what cranial nerves originate in the medulla?

Answer 7

• glossopharyngeal
• vagus
• hypoglossal

Question 8

where does cranial nerve 11 originate from?

Answer 8

the lateral cervical spinal cord

Question 9

Where does the facial nerve exit the cranial cavity?

Answer 9

the stylomastoid foramen

Question 10

what are the main functions of the facial nerve (CN VII)?

Answer 10

• special visceral efferent - controls muscles of facial expression
• general visceral efferent - parasympathetic innervation to lacrimal gland, submandibular & sublingual salivary glands and mucous glands of mouth and nose
• special visceral afferent -** taste sensations to anterior 2/3 of tongue** through chorda tympani branch

Question 11

does the facial nerve innervate the parotid gland? If not, what cranial nerve innervates this gland?

Answer 11

• No, it passes through it but does not innervate it
• the glossopharyngeal nerve (CN IX) innervates it

Question 12

what causes bells palsy?

Answer 12

a lesion in the facial nerve

Question 13

What are the 5 branches of the facial nerve?

T.Z.B.MM.C

Answer 13

• temporal
• zygomatic
• buccal
• marginal mandibular
• cervical

Question 14

Describe the course of the facial nerve

Answer 14

• CN VII arises from the pontomedullary junction
• traverses to the internal acoustic meatus and follows the facial canal to the stylomastoid foramen
• it exits the cranial cavity via the stylomastoid foramen and enters the parotid gland to form the parotid plexus
• it then divides into 5 branches

Question 15

what is the sensory ganglion of CNVII called?

Answer 15

the geniculate ganglion

Question 16

How is the motor function of the facial nerve tested on a patient?

Answer 16

• test the motor function by asking patients to show teeth and smile, raise eyebrows, frown, close eyes tightly, puff out cheeks etc
• observations are recorded
• all the facial muscles should be bilateral and equal in strength

Question 17

how is the sensory function of the facial nerve tested on a patient?

Answer 17

• test for sensory function of facial nerve by using drops of taste strips on either half of the anterior 2/3 of tomgue
• ensure to rinse mouth between tests and record results

Question 18

what is a complete lack of gustation called?

Answer 18

ageusia

Question 19

what is a reduced gustation called?

Answer 19

hypogeusia

Question 20

what are the main functons of the vestibulocochlear nerve?

Answer 20

• special somatic afferent - axons carry modalities of hearing and balance

Question 21

what are the 2 divisions of the vestibulocochlear nerve?

Answer 21

1. cochlear nerve
2. vestibular nerve

Question 22

Describe the cochlear nerve

Answer 22

• composed of central process of bipolar neurons in spiral ganglion
• the peripheral processes of the neurons extend to the organ of corti for sense of hearing

Question 23

Describe the vestibular nerve

ie what ganglion called, what organs do the processes supply?

Answer 23

• composed of central processes of bipolar neurons in the vestibular ganglion
• the vestibular ganglion houses cell bodies of bipolar neurons and extend processes to** supply 5 sensory organs**
• 4 cristae - located in semicircular canals
• 2 maculae of the saccule and utricle

Question 24

what is conduction deafness?

Answer 24

when sound is impaired from reaching the receptors in the inner ear
* ie deafness in apparatus that allows sound to reach inner ear

Question 25

what is **sensorineural deafness**?

Answer 25

damage to the inner ear receptors, cochlear nerve or the auditory pathways within the brain

Question 26

what is the rinne test?

Answer 26

* a test that compares the perception of sounds transmitted by air conduction to those transmitted by bone conduction * screening for **conductive hearing loss**

Question 27

what is the weber test?

Answer 27

* this test can** detect unilateral conductive hearing loss** (one sided middle ear hearing loss) and** unilateral sensorineural hearing loss** ( one sided inner ear hearing loss) * if both ears are normal the subject will hear the sound equally in both ears * for the unilateral sensorineural deafness, the subject will hear the sound with good ear but not affected ear

Question 28

What are the functions of the glossopharyngeal nerve?

Answer 28

* elevation of the pharynx - stylopharyngeus muscle * salvation through parotid gland * taste for the posterior 1/3 of tongue

Question 29

Describe the **course of the glossopharyngeal nerve**

Answer 29

* emerges from the medulla oblongata * leaves cranium through the jugular foramen * then follows and supplies the stylopharyngeus muscle, passes etween the superior and middle pharyngeal constrictor muscles to reach oropharynx and tongue

Question 30

what are the** functions of the vagus nerve (CN X)**?

Answer 30

* movements of the larynx, pharynx and soft palate * parasympathetic innervation to the thorax and abdomen * general visceral afferent from aortic baroreceptors pulmonary stretch receptor, abdominal - visceral sensations etc

Question 31

Describe the course of the vagus nerve

Answer 31

* nerve emerge from the **medulla oblongata ** * the rootlets merge and **leave the cranium via the jugular foramen**, which contains th**e superior **(general sensory) and **inferior **(visceral and special sensory) ganglia * the vagus nerve continues inferiorly in the carotid sheath * they give rise to the **right and left laryngeal nerves**, before forming the** oesophageal plexus **and **reforming the anterior and posterior vagal trunks **which continue to the abdomen

Question 32

what are the main branches of the vagus nerve?

Answer 32

1. **the neck ** * **pharyngeal branches** - motor innervation to the muscles of the pharynx and soft palate * recurrent laryngeal nerve (right side) - innervates the intrinsic laryngeal muscles 2. **Thorax** * cardiac branches - heart 3. **Abdomen** * vagal trunks terminate by dividing into branches that supply the oesophagus, stomach and large intestines

Question 33

how can you test the sensory function of CN IX and the motor function of CNX?

Answer 33

testing for the gag reflex * if there is an absence of the gag reflex, this may be due to a lesion of either CN IX or CN X on the same side as loss * if abnormality is suspected, test CN IX specifically for taste on each side of the posterior 1/3 of tongue

Question 34

what is the **function of the spinal accessory nerve**?

Answer 34

* controls movement of the **SCM muscle and trapezius muscle** of neck and shoulder

Question 35

Describe the course of the spinal accessory nerve

Answer 35

* fibres originate from **lateral cervical spinal cord (C1-C5)** * the fibres** enter the skull through the foramen magnum **before curving around to exit **via the jugular foramen ** * only cranial nerve to enter and exit the skull * the nerve then desends along internal carotid artery to** innervate the SCM muscle** * nerve** crosses the cervical region** to **supply trapezius muscle** via multiple branches

Question 36

What is the **function of the hypoglossal nerve **(CN XII)?

Answer 36

* innervates all of the **intrinsic and extrinsic muscles of the tongue** EXCEPT PALATOGLOSSUS - VAGUS INNERVATES THIS * controls tongue movements associated with speech, swallowing etc

Question 37

Describe the** course of the hypoglossal nerve**

Answer 37

* nerve arises from the medulla oblongata * nerve exits cranium via the hypoglossal canal - beside the foramen magnum * C1, C2, C3 spinal nerves from cervical plexus hitch hike with CN XII to reach hyoid muscles * hypoglossal nerve curves anteriorly to enter toongue

Question 38

what does a lesion of the hypoglossal nerve result in?

Answer 38

ipsilateral (same side of body) atrophy (muscle wasting) of tongue muscles - especially genioglossus muscles