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ANAT3022 > cranial nerves > Flashcards

cranial nerves Flashcards

1
Q

list the four pairs of cranial nerves and their location

A

TELENCEPHALON (forebrain):
• olfactory, I

DIENCEPHALON (epithalamus, hypothalamus, thalamus):
• optic, II

MESENCEPHALON (midbrain):
• oculomotor, III
• trochlear, IV

RHOMBENCEPHALON (hind brain):
• trigeminal, V
• abducens, VI
• facial, VII
• vestibulocochlear, VIII
• glossopharyngeal, IX
• vagus, X
• accessory, XI
• hypoglossal, XII
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2
Q

which are the only two cranial nerves which don’t arise from the brainstem?

A

olfactory (I) and optic (II)

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3
Q

which is the only cranial nerve which does not arise from the basal surface of the brain?

A

trochlear (III)

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4
Q

classify four types of afferent sensory fibres

A
  1. General Somatic Afferent (GSA):
    • similar to information carried in dorsal roots of the spinal cord => touch, pain, temperature, itch
    • CN V
  2. Special Somatic Afferent (SSA):
    • special senses => vision, hearing and balance
    • CN II, VIII
  3. General Visceral Afferent (GVA):
    • sensory feedback (usually pain but also tissue stretch and pressure) from e.g. organs or glands
    • CN IX, X
  4. Special Visceral Afferent (SVA):
    • found in organs of special chemical sensing
    => taste and olfaction
    • CN I, VII, IX and X
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5
Q

classify three types of efferent motor fibres

A
  1. General Somatic Efferent (GSE):
    • like ventral roots; motor fibres that innervate the skeletal muscles of the head and neck, e.g. eye muscles, trapezius
    • CN III, IV, VI, XII
  2. General Visceral Efferent (GVE):
    • fibres that belong to the autonomic nervous system and supply parasympathetic ganglia (e.g. smooth muscle around blood vessels and glands)
    • CN III, VII, IX, X
  3. Special Visceral Efferent (SVE):
    • motor fibres that supply muscles of the pharyngeal arches; also referred to sometimes as ‘branchial efferents’ (BE)
    • CN V, VII, IX, X and XI
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6
Q

which sulcus divides the alar (sensory) and basal (motor) plates during development?

A

sulcus limitans

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7
Q

which four cranial nerves contain parasympathetic fibres?

which ganglia do they synapse onto?

A
  1. oculomotor (III) → ciliary ganglion
  2. facial (VII) → pterygopalatine + submandibular ganglion
  3. glossopharyngeal (IX) → otic ganglion
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8
Q

oculomotor nerve (III):
– fibre type?
– origin and track?
– innervation?

A
  • GSE and GVE fibres
  • originates in midbrain (nuclei are medial)
  • passes through superior orbital fissure
  • innervates sup., med. + inf. rectus and inferior oblique
  • innervates superior levator palpeprae (upper eyelid)
  • innervates ciliary muscle and sphincter pupillae (GVE)
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9
Q

how does the eye respond to light?

A

PUPILLARY LIGHT REFLEX

when bright light enters one eye, the pupils of both eyes become smaller due to pupillary light reflex

  • light enters through only one pupil
  • optic nerve and optic tract transport the light signal
  • collaterals from the optic tract synapse on neurones of the pretectal area
  • neurones of the pretectal area project bilaterally to the Edinger-Westphal nuclei of the oculomotor nerve
  • pretectal fibres cross contralaterally at the posterior commissure
  • parasympathetic oculomotor fibres from the Edinger-Westphal nuclei innervate the sphincter pupillae muscle
  • results in constriction of pupil
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10
Q

what is uncal herniation and what are the consequences?

A

herniation of the uncus due to high intercranial pressure

puts pressure on oculomotor nerve = pupil dilation

puts pressure on posterior cerebral artery = ischemia of the ipsilateral primary visual cortex

the tentorium can put pressure on the midbrain = lesion of pyramidal and sensory pathways

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11
Q

what occurs in oculomotor nerve palsy

A

downward and outward gaze for the affected (right) eye

dilated pupil and ptosis (drooping of the eyelid)

diplopia (double vision)

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12
Q

trochlear nerve (IV):
– fibre type?
– origin and track?
– innervation?

A
  • GSE fibres
  • only nerve to originate from dorsal part of midbrain
  • innervates the superior oblique muscle of the eye
  • tendon of the superior oblique muscle passes through a ottilaginous pulley, called trochlea (trochlear = “pulley”)
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13
Q

what is the consequence of a trochlear nerve lesion?

A
  • Inability to rotate eye infero-laterally
  • Gaze deviates upward and also slightly inward for the affected (right) eye;
  • Diplopia (double vision)
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14
Q

abducens nerve (VI):
– fibre type?
– origin and track?
– innervation?

A
  • GSE fibres
  • originates from the anterior border of the pons and medulla oblongata (facial colliculus)
  • passes through the superior orbital fissure to enter the orbit
  • innervates the lateral rectus muscle of the eye which abducts the eye
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15
Q

what is the consequence of n abducens nerve lesion?

A

gaze deviates inwards (adduction)

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16
Q 
trigeminal nerve (V):
– fibre type?
– origin and track?
– innervation?
– branches?
A

GSA + SVE fibres

originates from pons

contains three branches

V1: ophthalmic nerve

  • sensory only
  • supplies forehead, eyelid, eyebrow, nose
  • supplies eye → afferent component for blink reflex (efferent motor part from CN VII)
  • branches into frontal, naso-ciliary and lacrimal nerves

V2: maxillary nerve

  • sensory only
  • supplies skin of middle face
  • major nerve continues as the infraorbital nerve
  • several major branches in the pterygopalatine fossa

V3: mandibular nerve

  • sensory + motor
  • sensory innervation to skin of lower face, teeth of lower jaw and anterior 2/3 tongue
  • motor innervation to muscles of mastication, muscles of middle ear, muscles of oral diaphragm, muscles of palate

thalamic relay for the sensory trigeminal
pathway is the ventral posterior medial nucleus (VPM)

17
Q

what are the consequences of a trigeminal nerve lesion?

A

damage leads to flaccid, ipsilateral paralysis of muscles of mastication

slight deviation of the jaw to the side of injury

jaw-jerk reflex is absent.

with bilateral upper motor neuron lesions (above level of trigeminal nucleus), mandible will hang low, leading to difficulty in producing vowels, labial/lingual sounds

18
Q 
facial nerve (VII):
– fibre type?
– origin and track?
– innervation?
– branches?
A

SVA, SVE and GVE fibres

originates in pons

special visceral afferents:
• taste sensation from anterior 2/3 of the tongue (geniculate ganglion)

parasympathetic component:
• nasal gland, tear gland + salivary glands (submandibular and lingual)

motor component:
• muscles of facial expression
• muscles of scalp
• posterior belly of digastric, stylohyoid and stapedius muscles
• contributes to blink reflex

motor branches (to zanzibar by motor car)

1) temporal
2) zygomatic
3) bucal
4) marginal mandibular
5) cervical

19
Q

what are the consequences of a lesion to the facial nerve

A

lesion to facial nerve = bell’s palsy

paralysis of facial muscles

loss of taste sensation

dry eyes + mouth

hyposalivation

hyperacusis:
lack of innervation of the stapedius muscle; stapedius muscle normally dampens the ear
drum and limits movement of the ossicles = normal sounds become very loud

20
Q

what responds to rotation, gravity and movement?

A

semicircular canals

21
Q 
vestibulocochlear nerve (VIII):
– fibre type?
– origin and track?
– innervation?
– branches?
A

SSA fibres

fibers arise from the vestibular apparatus (balance) and cochlea (hearing) of the inner ear

travels through the internal acoustic meatus to enter the brainstem at the pons-medulla border

vestibular nerve:
• concerned position of head in relation to movement
• receives input from 3 semicircular canals, the utricle, and the saccule
• utricle and saccule detect gravity and linear acceleration
• semicircular ducts detect angular acceleration

cochlear nerve:
• hearing

22
Q

glossopharyngeal nerve (IX):
– fibre type?
– origin and track?
– innervation?

A

SVA, GVA, SVE + GVE fibre types

fibres emerge from medulla and exit via the jugular foramen

special sensation:
• taste sensation from posterior 1/3 of tongue

general sensation:
• intraoral, pharynx and dorsal 1/3 of tongue

motor component:
• supplies stylopharyngeus muscle; from nucleus ambiguus
• motor component of gag reflex

parasympathetic component:
• from inf. salivatory nucleus; to parotid salivary gland via the otic ganglion

23
Q

vagus nerve (X):
– fibre type?
– origin and track?
– innervation?

A

GSA, GVA, GVE, SVA, SVE fibres

general visceral sensory component:
• receptors in walls of viscera

special visceral sensory component:
• taste from he pharyngeal area

motor component:
• muscles of larynx, pharynx, upper esophagus

parasympathetic component:
• all visceral organs of the neck, thorax, upper abdomen, and parts of the intestine that are derived from the foregut and midgut

sensory component of gag reflex

24
Q

what are the consequences of a vagus nerve lesion?

A

impaired reflexes for swallowing, gagging, coughing, sneezing, vomiting, breathing and heart rate

paralysis of the pharynx and soo palate –> swallowing difficulty

unilateral lesions may cause breathy voice and hoarseness, but ability to phonate is only minimally affected

bilateral lesions => aphonia; impaired air flow

25
Q

accessory nerve (XI):
– fibre type?
– origin and track?
– innervation?

A

SVE

cranial part originates from the brain stem and merges with vagus nerve

spinal part emerges from spinal cord and merges with cranial part

innervates trapezius and sternocleidomastoid

26
Q

what are the consequences of an accessory nerve lesion?

A

ipsilateral shoulder sags and cannot be raised (paralysis of trapezius)

movement opposite to side of damage is limited (sternocleidomastoid)

27
Q

hypoglossal nerve (XII):
– fibre type?
– origin and track?
– innervation?

A

GSE

only cranial nerve to exit most anteriorly from the medulla (between pyramids and olives)

innervates muscles of tongue

important for sticking out the tongue

28
Q

what are the consequences of a hypoglossal nerve lesion?

A

when (leo) hypoglossal nerve is damaged, the tip of the tongue is deviated to the affected side

tongue becomes flaccid and wrinkled

muscle atrophy of innervated muscles causes wrinkling of tongue surface

ANAT3022 (14 decks)

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