Cranial Nerves - Sensorimotor Function Flashcards
1
Q
How many cranial nerves are there and where do they arise from?
A
12 pairs of cranial nerves arise from the cerebrum or brain stem
2
Q
How is the nuclei of the cranial nerves laid out?
A
Their nuclei are essentially laid out from medial to lateral in the brainstem and sequentially, longitudinally in the midbrain, pons and medulla
3
Q
What are the motor modalities of the cranial nerves?
A
somatic efferent, special visceral efferent to muscles derived from brachial arch, general visceral efferent (parasympathetic)
4
Q
What are the sensory modalities of the cranial nerves?
A
somatic efferent, special visceral afferent (smell and taste), general visceral afferent, special somatic afferent (sight, hearing and balance)
5
Q
What do the cranial nerves pass through?
A
foramina on cranial bones
6
Q
What is the function of the cranial nerves? And what nerve is the exception to this?
A
With the exception of vagus, all cranial nerves innervate structures of the head and neck
7
Q
A
8
Q
What area is referred to as the olfactory region?
A
The upper third of the nasal cavity (superior nasal concha, roof od the nasal cavity and nasal septum)
9
Q
Where do the olfactory nerves pass through? And what is it anchored by?
A
Olfactory nerves pass through the cribriform plate, where they are anchored by dura mater and synapse at the olfactory bulb
10
Q
What do axons of the neurons in the olfactory bulb form?
A
olfactory tract
11
Q
Where does the olfactory tract project to?
A
Projects to the olfactory cortex FIRST and then to the limbic system, hypothalamus and reticular formation for visceral and behavioural responses to odours
12
Q
What is Anosmia? And what is likely to cause this clinical condition?
A
- Olfactory neuropathy caused by upper respiratory tract infections (loss of sense of smell)
- Trauma, causing the brain and olfactory bulb to move may tear the olfactory nerves
- Fractures of the cribriform plate may cause CSF rhinorrhoea (blood stained CSF leaking from the nose)
13
Q
What is unqiue about the basal cells of the olfactory region?
A
- Basal cells can differentiate to bipolar (olfactory neurons)
- Regeneration in adult humans
14
Q
What is unique about the special sense olfaction?
A
Only sense that travels to the cortical field prior to thalamus
15
Q
What is the largest cranial nerve and what are its main divisions?
A
- The largest cranial nerve = Trigeminal Nerve
- Has three divisions: V1, V2 and V3
- V1 and V2 are afferent only
- V3 is both afferent and efferent
16
Q
What is the function of the trigeminal nerve?
A
Supplies general, conscious sensation to much of the face, head and associated orbital, nasal and oral cavities
17
Q
How many nuclei does the trigeminal nerve have?
A
- Has 4 nuclei (and 2 roots)
- Sensory roots: to mesencephalic nucleus, principle (pontine) nucleus, spinal nucleus
- Motor root: from motor nucleus
18
Q
Where do the sensory and motor roots of the trigeminal nerve emerge?
A
the mid-pons and run towards the trigeminal ganglion
19
Q
What emerges from the trigeminal ganglion?
A
- Three divisions of the trigeminal nerve
- V1 = opthalmic division
- V2 = maxillary division
- V3 = mandibular division
20
Q
What is the course of CN V1
A
lateral wall of the cavernous sinus –> superior orbital fissure –> orbit
21
Q
What is the course of CN V2
A
Lateral wall of cavernous sinus –> foramen rotundum –>
pterygopalatine fossa
22
Q
What is the course of CN V3
A
foramen ovale –> infratemporal fossa
23
Q
Describe the opthalmic nerve
A
- Sensory division only
- Picks up sympathetic fibres from the carotid plexus
- Gives off meningeal branch near trigeminal ganglion that supplies dura
24
Q
What are the three branches of the opthalmic nerve?
A
o Lacrimal
o Frontal
o Nasocillary
25
What is the function of the lacrimal branch of the opthalmic nerve?
- Supplies general sensation to the lacrimal gland, conjunctive and upper eyelid in the vicinity of Lacrimal gland
- Also carries parasympathetic fibres of facial nerve (VII) to the lacrimal gland
26
What is the largest branch of the opthalmic nerve and what does it divide into?
Frontal Nerve
- Divides into supra-orbital and supra-trochlear nerves
27
What is the function of the frontal nerve?
- Supplies the upper eyelid and conjunctiva, frontal sinus and scalp as far back as vertex
28
What branches does the nasocillary nerve give off?
Gives off long ciliary nerve(s), anterior and posterior ethmoidal nerves, before continuing as infratrochlear nerve
29
What does the nasocillary nerve supply?
- Supplies the skin of medial, upper eyelid and root of nose
- Sensation to the cornea of the eye afferent limb of cornea reflex
- The tip of the nose
30
Describe the maxillary division of the trigeminal nerve
Sensory only division
31
What are the major branches of the maxillary division of the trigeminal nerve?
* Sends zygomatic and infra-orbital branches into the orbit via the inferior orbital fissure
* Infra-orbital nerve exits the orbit via infra-orbital canal infra-orbital foramen
* Sends palatine and superior alveolar branches to the palate and upper teeth
32
What does the maxillary nerve (CN V2) supply?
* Lateral forehead
* Zygomatic region
* Lower lid
* Side of nose
* Cheek (anteriorly)
* Upper lip
33
What type of fibres does the mandibular branch of the trigeminal nerve contain?
Contains both sensory and motor fibres
34
What branches does the mandibular nerve give off?
Gives off auriculotemporal, buccal, lingual and inferior alveolar branches
35
What does the mandibular nerve provide sensation to?
o Skin of auricle and temple
o Cheek, posteriorly
o Lower lip and chin
o General sensation to the anterior 2/3 of the tongue, and the floor of the mouth
o The lower gums and teeth
36
What does the mandibular nerve provide motor function to?
o Muscles of mastication: lateral pterygoid, medial pyerygoid, masseter and temporalis
o Tensor tymapni
o Tensor veli palatini
o Mylohyoid
o The anterior belly of digastric
37
What is Jaw Jerk and what is its function?
Tests the mandibular division of the trigeminal nerve (CN V3) and nuclei
38
Where is the oculomotor nerve nucleus located?
midbrain
39
What is the course of the oculmotor nerve?
- Passes between the posterior cerebral and superior cerebellar arteries, before lying close to the posterior communicating artery
- Runs anteriorly on the lateral wall of the cavernous sinus
- Passes through superior orbital fissure and enters the orbit
40
What does the oculomotor nerve divide into?
Divides into superior and inferior divisions (rami)
* Through common tendinous ring of Zinn
41
What type of nerve is the oculomotor nerve?
Motor and parasympathetic
42
What does the superior branch of the oculomotor nerve supply?
* Levator palpabrae superiosis
* Superior rectus
43
What does the inferior branch of the oculomotor nerve supply?
* Inferior rectus
* Inferior oblique
* Medial rectus
* ciliary ganglion
44
What type of nerve is the trochlear nerve?
Motor only
45
Where is the nucleus of the trochlear nerve?
the midbrain
46
What is the course of the trochlear nerve?
- Runs anteriorly around cerebral peduncle
- Enters cavernous sinus
- Passes through superior orbital fissure
47
What does the trochlear nerve supply?
- Supplies superior oblique
48
What occurs in injury of the trochlear nerve?
- Injury to the trochlear nerve results in the patient not being able to look medially and inferiorly
- Patient experiences diplopia while walking downstairs or reading a book
49
What type of nerve is the abducent nerve?
Motor only
50
Where is the nucleus of the abducent nerve located?
the pons
51
What is the course of the abducent nerve?
- Nerve exits brainstem medially, between pons and medulla
- Enters cavernous sinus
- Enters orbit through superior orbital fissure
52
What muscle does the abducent nerve supply?
Lateral rectus
53
What would occur due to injury to the right abducent nerve?
diplopia when looking right – the right eye would not abduct
fully
54
What type of nerve is the facial nerve?
Mixed nerve
55
Where is the nucleus of the facial nerve?
in Pons
56
What is the motor nucleus of the facial nerve and what divisions does it have?
- Motor nucleus – Nucleus solitarius (sensory)
- Motor nucleus has superior and inferior divisions which innervate the upper and lower facial musclesrespectively
57
What is the superior division of the motor root of the facial nerve connected to?
- The superior division is connected to the ipsilateral and contralateral motor cortices
58
What is the inferior division of the motor root of the facial nerve connected to?
- The inferior division is connected to contralateral cortex only
59
What is the course of the motor root of the facial nerve?
- The motor root emerges in the angle between the lower pons and the cerebellum – the cerebellopontine angle
- Enters the temporal bone at the internal acoustic meatus, with VIII and the labyrinthine artery
60
Where does the facial nerve eneter the facial canal?
within the temporal bone
61
Where are the cell bodies for taste fibres located?
geniculate ganglion (sensory ganglion of the facial nerve)
62
Where does the facial nerve exit the facial canal?
Exits through the temporal bone through stylomastoid foramen
63
What branches does the facial nerve give off/recieve?
- Sends a branch to stapedius
- Receives (gives off) chorda tympani
- Sends branches to supply occipitalis and the auricular muscles
64
What occurs when the facial nerve enters the parotid gland?
- Enters the parotid gland and divides to form a plexus within (superficial to the external carotid artery
and retromandibular vein)
- 5 nerves branch off and supply the muscles of facial expression, posterior belly of digastric and stylohyoid
65
What are the 5 branches of the facial nerve beyond the parotid gland?
* Temporal
* Zygomatic
* Buccal
* Mandibular
* Cervical
66
What occurs when there is a facial nerve injury ay the cerebellopontine angle?
* Balance and hearing problems
* Ipsilateral facial muscle paralysis
* Hyperacusis (pain on loud sounds)
* Taste disturbances
* Reduced lacrimal secretion
67
What occurs when the is a facial nerve injury within the petrous temporal bone?
```
o Reduced lacrimal secretion
o Hyperacusis (pain on loud sounds)
```
o Taste disturbances
o Ipsilateral facial muscle paralysis
68
What occurs when there is a facial nerve injurt distal to the stylomastoid foramen?
o Ipsilateral facial muscle paralysis
o Dry eye, drooling
69
Describe cental facial palsy
70
Describe peripheral facial palsy
71
What type of nerve is the glossophayrngeal nerve and where are its nuclei located?
Mixed nerve; nuclei in medulla
72
What are the motor and sensory nucleus of the glossopharyngeal nerve?
Motor nucleus is nucleus ambiguus, sensory nucleus is nucleus solitarius
73
What branch of the glossopharyngeal nerve goes to the middle ear?
Tympanic branch to middle ear, tympanic membrane and mastoid air cell
74
What sensory input does the glossopharyngeal nerve recieve?
o General sensation from middle ear, oropharynx, palatine tonsil, inferior aspect of soft palate, posterior 1/3 tongue
o General visceral sensation from carotid sinus and carotid body
o Special visceral sensation (taste) from posterior 1/3 tongue
75
What is the motor supply of the glossophayrngeal nerve?
- Motor supply to stylopharyngeal muscle
76
What type of nerve is the vagus nerve and where are its nuclei located?
- Mixed nerve; nuclei in medulla
77
What is the course of the vagus nerve?
- Leaves brainstem, passes through jugular foramen with IX and XI
78
What are the different nuclei of the vagus nerve?
- Motor nucleus is nucleus ambiguus, sensory nucleus is nucleus solitarius (taste and general visceral)
79
What is the general somatic sensation of the vagus nerve?
General somatic sensation from deep auricle and parts of the external acoustic meatus
80
What is the general visceral sensation of the vagus nerve?
- General visceral sensation from the laryngopharynx and larynx
81
What is the motor supply of the vagus nerve?
straited muscles of the pharynx and larynx
82
What type of nerve is the accessory nerve and where are its roots located?
Motor only
- Spinal root: from C1-C5
- Cranial root: from nucleus ambiguous
83
What is the course of the accessory nerve?
* Spinal root enters cranial cavity through foramen magnum
* Joins with cranial root
* Both roots exit skull via jugular foramen as accessory nerve
* Crosses the posterior triangle in the investing layer of fascia, surrounded by lymph nodes
84
What does the accessory nerve supply?
- Spinal accessory supplies trapezius and sternocleidomastoid
85
What type of nerve is the hypoglossal nerve and where is its nucleus located?
- Motor only
- Hypoglossal nucleus in medulla
86
Describe the course of the hypoglossal nerve
Exits the brainstem anterior to olive
- Emerges from hypoglossal (anterior condylar) canal
- Descends the neck, passing lateral to both the internal and external carotid arteries and associated with
a loop of Cx nerves that supply the strap muscles of the neck
- Enters oral cavity under the tongue between the hyoglossus
87
What is the function of the hypoglossal nerve?
supply all the tongue muscles except palatoglossus
88
What occurs if the hypoglossal muscle is injured?
If injured, ipsilateral tongue weakness, therefore tongue deviates to the side of the lesion
89
Describe the innervation of the anterior 1/3 of the tongue
* Taste by glossopharyngeal nerve
* General sensation by glossopharyngeal
90
Describe the innervation of the posterior 2/3 of the tongue
* Taste by chorda tympani of Nervus Intermedius (facial)
* General sensation by lingual nerve of V2
