Session 3 - Cranial Nerves Flashcards Preview

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Flashcards in Session 3 - Cranial Nerves Deck (43)
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0
Q

How are the connective tissue bindings in the CNS and PNS different?

A

In CNS layers are: endoneurium, perineurium, and epineurium

In PNS layers are, pia mater, arachnoid mater and dura mater.

1
Q

What is a cranial nerve?

A

A nerve bundle that issues direct from the brain and supply or innervate tissues of the head and neck region. (They also supply some viscera outside of Head and neck region)

2
Q

Cranial nerves are numbered I to XII what relevance does this have?

A

CN I is most rostral (anterior/superior) CN XI is most caudal. CNXII is the exception and is just in front of CNXII

3
Q

Name the cranial nerves:

A
I - olfactory nerve 
II - optic nerve 
III - oculomotor nerve 
IV - Trochlear nerve 
V - trigeminal nerve 
VI - Abducens nerve 
VII - facial nerve 
VIII - Vestibulocochlear nerve 
IX - glossopharyngeal 
X - vagus nerve 
XI - accessory nerve 
XII - hypoglossal nerve
4
Q

Describe CN I

A

Olfactory nerve - supplies sense of smell
Is not a true cranial nerve - more of a brain tract
Exits the cranium via the cribiform plate (susceptible to damage here) and then forms the olfactory bulb.
Left and right nasal cavities are supplied by separate left and righ olfactory nerves.
Loss of smell is called anosmia

5
Q

What are some causes of anosmia?

A

Upper respiratory tract infections

Fracture of cribiform plate

6
Q

Describe CN II

A

Optic nerve - is a sensory nerve
Actually a brain tract.
Central retinal artery and vein pass through the nerve.

7
Q

Describe CNIII

A

Oculomotor nerve
Mixed nerve - motor and autonomic fibres
Supplies all extraocular muscles except superior oblique and lateral rectus so supplies: superior, inferior and medial rectus and inferior oblique. It also supplies levator palpaebrae superioris.
Autonomic - parasympathetic - controls constrictor pupillae
Pre-ganglionic parasympathetic fibres - ciliary ganglion - post ganglionic neurones (short- ciliary nerves) - to ciliary and sphincter pupillae muscles causing constriction of pupil and curvature of lens (accomodation)

8
Q

Describe the clinical features of a complete CNIII palsy.

A

At rest the eye assumes a down and out position.
Complete ptosis of the upper eyelid (denervation of the levator palpaebrae superioris muscle)
Pupil is fixed and dilated

9
Q

Describe CN IV

A

Trochlear nerve

Supplies superior oblique only

10
Q

Describe the clinical features seen if there was CNIV damage.

A

Patient would get diplopia when looking Medially and downwards e.g. When going downstairs.
To test ask patient to look Medially and downwards. Able to look Medially (medial rectus) but not downwards.

11
Q

Describe CNVI

A

Abducens nerve
Supplies lateral rectus
Has a long intercranial course and runs through the cavernous sinus so is susceptible to damage if there is increased inter cranial pressure.

12
Q

What clinical signs are seen in CNVI damage?

A

Patient is unable to look laterally

Squint on looking outwards.

13
Q

Describe CNV

A

Trigeminal nerve
Has motor and sensory functions.
Splits into three branches: Vi - opthalmic, Vii - maxillary, Viii - Mandibular
Vi - sensory function only - forehead, canthus of eye, bridge of nose. Sensation to cornea and conjunctiva
Vii - sensory function only cheeks also mucosa of nasal cavity, mucosal lining of paranasal sinuses, mucosal lining palate, roots of upper teeth.
Viii - sensory and motor function - rest of face including mucosa of inner cheek, anterior 2/3rds of tongue (sensation only) and roots of lower teeth. Motor function to muscles of mastication - masseter, temporalis, medial and lateral pterygoids, anterior belly of digastric.

14
Q

Describe CNVII

A

Facial nerve
Motor, sensory and autonomic divisions
Motor - facial nerve
Sensory - Nervus intermedius
Autonomic - part of the Nervus intermedius - greater petrosal nerve is its largest branch
Motor division - muscles of facial expression and muscle to stapedius
Sensory - general sensation of the concha of auricle and behind ear.
Special sensory - taste to anterior 2/3rd of tongue (chordae tympani)
Autonomic - supplies lacrimal, submandibular, sublingual glands, also supplies glands of mucous membranes of nasopharynx, paranasal sinuses, hard and soft palate.

15
Q

Describe the clinical features or CNVII damage

A
Loss of facial expression 
Loss of sphincter function 
Loss of naso-labial fold
Hyperacusis 
(Forehead sparing) 
If damage posterior wall (chordi tympani) can have an affect on taste,salivation and lacrimation.
16
Q

Describe CNVIII

A

Vestibulocochlear nerve
Special sense
Vestibular - balance
Cochlear - hearing

17
Q

What are the two types of hearing loss? And what test can be used to differentiate between the two?

A

Sensori-neural - nerve damage
Conductive - blockage
Rinnes and webers test.

18
Q

What are the clinical features of damage to vestibular nerve?

A
Loss of balance 
Vertigo 
Nausea 
Nystagmus 
Impairment of caloric response.
19
Q

Describe CNIX

A

Glossopharyngeal nerve
Mixed sensory and motor nerve
Motor - brachiomotor - stylopharyngeus, viscera motor - parotid gland.
Sensory - viscerosensory - carotid body and sinus, pharynx and middle ear, special sensory - posterior 1/3rd of tongue.

20
Q

How can you test the glossopharyngeal nerve?

A

Test gag reflex
Sensory limb of the reflex
As sensory supply to pharynx

21
Q

Describe CNX

A

Vagus nerve
Mixed sensory and motor nerve
Motor - intrinsic muscles of the larynx and pharynx
Muscles of the palate
Smooth muscle - bronchi and digestive tract
Secretomotor - thoracic and abdominal viscera

Sensory - external ear, auditory canal and eardrum
Pharynx and larynx
Visceral sensation - thorax and abdomen

22
Q

What are the symptoms of right recurrent laryngeal nerve damage?

A

Symptoms are hoarse voice, weak cough, risk or aspiration of fluids

23
Q

How might damage to the left recurrent laryngeal arch occur?

A

Bronchial or oesophageal carcinoma
Enlarged mediastinal lymph nodes
Stretched over an aneurysm of the aortic arch.

24
Q

Describe CNXI

A

Accessory nerve
Has both cranial and spinal divisions which join in the cranium and exit the brain together.
Motor function
Supplies sternocleidomastoid and trapezius

25
Q

Describe CNXII

A

Hypoglossal nerve
Motor nerve
Supplies muscles of the tongue

26
Q

What clinical features are seen in CNXII damage?

A

Dysarthria
Tongue wasting
Tongue deviates towards side of weakness

27
Q

What are the four general classes of spinal nerve fibres?

A

General somatic efferents - supply skeletal muscle
General somatic afferents - General sensation
General visceral afferents - visceral sensation
General autonomic efferents - autonomic fibres innervating visceral structures.

28
Q

What are the general classifications of cranial nerves?

A

General somatic afferents
General visceral afferents
General somatic efferents
General autonomic efferents
Special visceral efferents - muscles derived from brachial arches
Special somatic afferents - equilibrium, hearing, sight
Special visceral afferents - taste

29
Q

Which cranial nerves are sources of autonomic fibres?

A

CNIII
CN VIII
CN IX
CN X

30
Q

Which nerve is involved in the distribution of autonomic fibres but is not a source of them?

A

CNV

31
Q

Where are the somata of pre-ganglionic neurones of PNS located?

A

Brain stem

32
Q

Where do the pre-ganglionic neurones terminate and synapse?

A

Either four discrete ganglia
Or
Parasympathetic ganglia in walls of target organs (CNX)

33
Q

Name the four ganglia where pre-ganglionic PNS neurons synapse:

A
Ciliary ganglion 
Pterygopalatine ganglion
Submandibular ganglion
Optic ganglion 
These ganglia are all in association with the branches of the trigeminal nerve.
34
Q

Where does the PNS branch of oculomotor nerve synapse?

A

Ciliary ganglion

In association with the opthalmic division of trigeminal nerve

35
Q

Where do the PNS fibres of the facial nerve synapse?

A

Pterygopalatine or submandibular ganglion.

These are related to the maxillary and Mandibular divisions of trigeminal nerve respectively.

36
Q

Where do the PNS fibres of the glossopharyngeal nerve terminate?

A

In the otic ganglion

In relation to the Mandibular division of the trigeminal nerve.

37
Q

Describe the course of the autonomic fibres of CNIII

A

Originate from the Edinger-Westphal nucleus
Pre-ganglionic fibres travel with the optic nerve to the ciliary ganglion.
Post-ganglionic fibres travel with the short ciliary nerves to supply:
Sphincter pupillae
Ciliary muscles (accomodation)

38
Q

Describe the course of the autonomic fibres of CNVII

A

Originate from the superior salivatory nucleus.
Pre-ganglionic fibres run along greater petrosal nerve to terminate in the pterygopalatine ganglion. It supplies the lacrimal gland, mucous glands of the nose, mucous glands of the palate.
OR
Pre-ganglionic fibres run along the chordi tympani nerve to the submandibular ganglion. This supplies the submandibular, sublingual and mucous glands of the palate.

39
Q

Describe the course of the autonomic fibres of the glossopharyngeal nerve.

A

Originate in the inferior salivatory nucleus.
Pre-ganglionic neurones run along the lesser petrosal nerve.
Terminate in the otic ganglion.
Post ganglionic fibres supply by the auriculotemporal nerve the parotid gland and oropharynx.

40
Q

Describe the course of the PNS output of the vagus nerve.

A

Originate in the dorsal vagal motor nucleus.
Do not synapse on discrete autonomic ganglia.
Pre-ganglionic fibres travel with vagus nerve to reach their targets In the neck. They then synapse with specific post ganglionic cells in the wall of the target organ rather than in specific ganglia. Post ganglionic fibres supply the laryngophayrnx, larynx, oesophagus, trachea

41
Q

Where does sympathetic outflow to the head and neck come from?

A
T1-L2/3 
Then there are three cervical ganglia of the pre-vertebral chain. 
Superior cervical ganglion 
Middle cervical ganglion 
Inferior cervical ganglion
The internal carotid nerve ascends with the internal carotid artery to form the internal carotid plexus. They hitchhike using the walls of the common carotids and the internal and external carotids. Sympathetics then pass to: 
Pterygopalatine ganglion 
Abducens nerve 
Glossopharyngeal nerve 
Trochlear 
Oculomotor 
Opthalmic nerves 
Vessels derived from the internal carotid artery.
42
Q

Describe the location of the superior, middle and inferior cervical ganglion.

A

Superior - located anterior to C1,2,3,4
Middle - small and often absent, lies anterior to C6 and anterior to infer thyroid artery
Inferior - sometimes fused with first thoracic ganglion to form cervicothoracic ganglion (stellate ganglion) located anterior to C7