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ANATOMY4: Cranial nerves > Facial nerve > Flashcards

Facial nerve Flashcards

1
Q

What are the 3 main functional components of the facial nerve (CNVII)?

A
  1. special visceral (branchiomotor - facial expression) efferents: facial nerve proper
  2. general visceral efferent (secretomotor / parasympathetic): nervus intermedius
  3. special visceral afferents (taste)
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2
Q

What is the facial nerve proper?

A

contains branchiomotor or special visceral efferents

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3
Q

What are 4 things supplied by the facial nerve proper?

A
  1. muscles of facial expression
  2. stapedius (small muscle in middle ear)
  3. stylohyoid
  4. posterior belly of the digastric
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4
Q

What type of fibres are in the nervus intermedius?

A

secretomotor or parasympathetic fibres (general visceral efferent)

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5
Q

What is the course of the secretomotor parasympathetic fibres of the nervus intermedius?

A

synapse in the ptergyopalatine ganglion, travel to lacrimal gland/choroid

also transmits fibres from anterior two-thirds of tongue

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6
Q

What structures are supplied by the nervus intermedius? 2 key things

A
  1. supply the lacrimal gland and choroid in addition to other glands in and around the nose and mouth.
  2. the nerve also transmits taste fibres (special visceral afferents) from the anterior two-thirds of the tongue.
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7
Q

What are the 7 different functional components of the cranial nerve?

A
  1. Somatic efferent (general motor)
  2. Somatic afferent (general sensory)
  3. General visceral efferents (parasympathetic)
  4. General visceral afferents
  5. Special visceral efferents (branchiomotor)
  6. Special somatic afferent (special senses concerned with body position, excluding vision)
  7. Special visceal afferent (special viscceral senses, taste and smell)
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8
Q

What is the fucntion of the somatic efferent (general motor) component of the cranial nerves and which 4 cranial nerves is this role present in?

A
  • supplies skeletal muscle of somatic origin (preotic somites: extraocular muscles, occipital somites, tongue musculature)
  • III, IV, VI, XII
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9
Q

What is the fucntion of the somatic afferent (general sensory) component of the cranial nerves and which 4 cranial nerves is this role present in?

A
  • pain, temperature and touch. supplies skin and mucous membranes of head and neck
  • predominantly V
  • minor elements in VII, IX and X
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10
Q

What is the function of the general visceral efferent (parasympathetic) component of the cranial nerves and which 5 cranial nerves is this role present in?

A
  • supplies smooth muscle (viscera), cardia muscle, glands, blood vessels and intrinsic eye muscles (ciliary muscle and sphincter pupillae)
  • III, VII, IX, X, XI (X is largest parasympathetic nerve in body)
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11
Q

What is the function of the general visceral afferents component of the cranial nerves and which 3 cranial nerves is this role present in?

A
  • pain and sensibility of the viscera
  • VII, IX, X
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12
Q

What is the function of the special visceral efferents (branchiomotor) component of the cranial nerves and which 5 cranial nerves is this role present in?

A
  • skeletal muscles of mastication and facial expresion (i.e. pharyngeal arch or visceral evolutionary origin)
  • V, VII, IX, X, XI
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13
Q

What are the origins of the skeletal muscles of mastication and facial expression?

A

pharyngeal arch or visceral evolutionary origin

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14
Q

What is the function of the special somatic afferent (special senses concerned with body position) component of the cranial nerves and which cranial nerve is this role present in?

A

CN VII

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15
Q

What is the fucntion of the special visceral afferent (special visceal senses, taste and smell) component of the cranial nerves and which 4 cranial nerves is this role present in?

A
  • olfactory epithelium in nasal cavity and taste receptors in tongue and palate
  • I (olfaction); VII, IX, X (taste)
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16
Q

What is the main motor nucleus for CNVII?

A

branchiomotor or special visceral efferent nucleus

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17
Q

Whatis the anatomical position of the main motor nucleus (branchiomotor or SVE) for the CNVII?

A

ventrolateral aspect of the tegmentum in th elower pons (most medial of the three nuclei)

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18
Q

What is the course taken by efferent fibres from the main motor nucleus (branchiomotor) of CNVII to emerging from the brainstem?

A
  • pass dorsomedially around abducent nucleus creating small elevation (Facial colliculus) in floor of fourth ventricle
  • pass laterally to abducens nucleus
  • course ventrally and caudally through body of pons
  • emerge at ponotmedullary junction lateral to abducent nerve
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19
Q

What is the course taken by efferent fibres from the main motor nucleus (branchiomotor) of CNVII after emerging from the brainstem?

A
  • pass through internal acoustic meatus
  • pass through petrous temporal bone in facial canal
  • fibres of CNVII exit skull through stylomastoid foramen
  • pierce parotid gland
  • emerge at anterior border of gland and radiate on face
  • supply muscles of facial expression
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20
Q

Which foramen do GVE fibres of CNVII exit the skull via?

A

stylomastoid foramen

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21
Q

What muscles are supplied by the main motor nucleus fibres of CNVII?

A

muscles of facial expression

22
Q

Where does the parasympethatic nucleus (GVE) of CNVII lie?

A

lateral to themain motor nucleus

23
Q

What are the 2 components of the parasympethatic / GVE nucleus of CNVII?

A
  1. superior salivatory nucleus (SSN)
  2. lacrimal nucleus (LN)
24
Q

What is the pathway of the CNVII fibres from the superior salivatory nculeus to their target organs?

A
  • SSN i slocated in reticular formation of lower pons
  • fibres pass ventrolaterally in the pons from SSN and emerge as the nervus intermedius
  • preganglionic fibres terminate in the submandibular ganglion
  • postganglionic parasympathetic fibres supply the submandibular and sublingual glands
25
Q

Where is the SSN located (pat of the GVE / parasympathetic nucleus of CNVII)?

A

reticular formation of lower pons

26
Q

Where do preganglionic fibres from the parasympathetic SSN terminate?

A

submandibular ganglion

27
Q

What is the target organ of parasympathetic fibres of CNVII from SSN?

A

submandibular and sublingual glands

28
Q

Where is the lacrimal nucleus located in relation to the SSN (other part of the GVE nucleus)?

A

LN is located more rostrally

29
Q

In which ganglion to preganglionic fibres from the lacrimal nucleus terminate?

A

ptergyopalatine ganglion

30
Q

In which nerve do fibres from the lacrimal nucleus travel to reach the ptergyopalatine ganglion?

A

petrosal nerve

31
Q

What organs are supplied by the postganglionic parasympathetic fibres from the LN via the ptergyopalatine ganglion (3 things)?

A
  • lacrimal glands
  • nasal glands
  • palatine glands
32
Q

What is the path of parsympathetic fibres from GVE nucleus, lacrimal nucleus, to the target organs?

A
  • fibres travel in petrosal nerve to pterygopalatine ganglion
  • postganglionic fibres supply lacrimal, nasal and palatine glands
33
Q

What are 2 structures that the lacrimal nucleus has higher input from? What purposes does each serve?

A
  1. hypothalamus - emotional responses
  2. sensory nucleus of trigeminal - reflex lacrimation in response to irritatino f cornea and conjunctiva
34
Q

Where is the sensory nucleus (special visceral afferents) of CNVII?

A

lies close to motor nucleus (in ventrolateral aspect of tegmentum in lower pons)

35
Q

What does the sensory nucleus (SVA) of CNVII receive input from?

A

sensory neurons located in the geniculate ganglion in the facial nerve, which subserve sensation from the anterior 2/3 of the tongue

36
Q

Where do efferent nerves from the sensory visceral afferent nucleus of CNVII travel?

A
  • efferents from the nucleus decussate and ascend to the thalamus
  • signals are relayed from there to the postcentral gyrus of the cerebral cortex
37
Q

What are 3 important locations of lesions of the facial nerve to be aware of as clinical correlates?

A
  1. supranuclear lesions
  2. nuclear lesions
  3. infranuclear lesions
38
Q

What causes supranuclear lesions of CNVII and what structures are damaged?

A
  • vascular stroke
  • descending corticonuclear and corticospinal fibres are damaged in the internal capsule
39
Q

How are supranuclear lesions of CNVII related to its function?

A
  • corticonuclear and corticospinal fibres are damaged by stroke in the internal capsule
  • the upper facial motor nucleus (supplying upper half of facial muscles) receives input from ‘face’ areas of both ipsilateral and contralateral motor cortices
  • lower part of facial nucleus has only contralateral input
40
Q

What is the effect of a stroke on the supranucleus course of CNVII?

A

contralateral paralysis or weakness of the limbs and lower face

upper face survives because of bilateral supranuclear supplyto upper part of facial nucleus

41
Q

What is an example of a nuclear lesion of CNVII?

A

direct damage to facial nucleus due to thrombosis of the pontine branches of the basilar artery

42
Q

What are the clinical effects of a nuclear lesion of CNVII?

A

complete paralysis of structures supplied by the facial nerve (and abducens nerve) together with motor weakness of limbs on opposite side, owing to pyramidal deussaiton below this level

43
Q

What are 4 examples of an infranuclear CNVII lesion?

A
  1. Bell’s palsy - direct neuritis of facial nerve in bony canal within the temporal bone
  2. Multiple sclerosis
  3. Tumours of the cerebellopontine angle (acoustic neuromas)
  4. Middle ear disease
  5. Tumours of the parotid gland
44
Q

What is the clinical effect of an infranuclear CNVII lesion (e.g. Bell’s palsy)?

A

complete facial paralysis

45
Q

What are 5 effects of complete facial paralysis seen in infranuclear CNVII lesions?

A
  1. unable to move lips (saliva and food drools from corner of mouth)
  2. unable to move eyebrows or close eyelids (lids may be lax, causing epiphora)
  3. suffer hyperacusis (from paralysis of stapedius)
  4. may have reduced lacrimal and salivatory secretions
  5. loss of taste to anterior 2/3 of tongue
46
Q

What are the 2 most important roles of the CNVII in relation to the eye/orbit?

A
  1. Parasympathetic supply to lacrimal gland (and some intraocular branches)
  2. Motor supply to periorbital facial muscles (escecially orbicularis oculi)
47
Q

Why is the facial nerve very clinically prevalent?

A

it is the most paralysed of all peripheral nerves

48
Q

What are the 3 reflex arcts in the brainstem involving the facial nerve?

A
  1. Corneal reflex
  2. Blinking to light or fast-approaching object
  3. Blinking to noise
49
Q

What is the important reflex involving CNVII that can be importantly clinically tested?

A

corneal reflex

50
Q

What is the receptor, afferent pathway, first synapse, second synape and efferent pathway, and effector muscle, of the corneal reflex?

A
  • receptor: sensory ending in corneal epithelium
  • afferent pathway: long ciliary nerves, nasociliary nerve, ophthalmic nerve
  • first synapse: spinal nucleus of trigeminal
  • second synapse: facial nucleus
  • efferent pathway: temporal and zygomatic branches of CNVII
  • effector muscle: orbicularis oculi
51
Q

What is the receptor, afferent pathway, first synapse, second synape and efferent pathway, and effector muscle, of the blinking to light/fast-approaching object reflex?

A
  • receptor: retina
  • afferent pathway: optic nerve
  • first synapse: superior colliculus
  • second synapse: facial nucleus
  • efferent pathway: temporal and zygomatic branches of facial nerve
  • effector muscle: orbicularis oculi
52
Q

What is the receptor, afferent pathway, first synapse, second synape and efferent pathway, and effector muscle, of the blinking to noise reflex?

A
  • receptor: cochlea
  • afferent pahway: vestibulocochlear nerve
  • first synapse: inferior colliculus
  • second synapse: facial nucleus
  • efferent pathway: temporal and zygomatic branches of facial nerve
  • effector muscle: orbicularis oculi

ANATOMY4: Cranial nerves (6 decks)

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