Cranial nerves

Question 1

how many pairs of cranial nerves are there

Answer 1

12 pains

Question 2

what are the 5 types of cranial nerves

Answer 2

1. somatic motor fibres
2. visceral motor fibres
3. visceral sensory
4. general sensory
5. special sensory

Question 3

what do somatic motor fibres do

Answer 3

supply striated muscle

Question 4

what do visceral motor fibres do

Answer 4

supply smooth muscle and glands (cranial division of parasympathetic)

Question 5

what do visceral sensory fibres do

Answer 5

afferent inputs from pharynx, larynx, heart, lung, gut, etc - i.e. not normally conscious

Question 6

what do general sensory fibres do

Answer 6

afferent inputs from skin and much membranes e.g. touch, temperature, pain

Question 7

what do special sensory fibres do

Answer 7

special sense - taste, smell, vision, hearing and balance

Question 8

where is parasympathetic outflow

Answer 8

cranial, sacral

Question 9

where is sympathetic outflow

Answer 9

thoracic

Question 10

where is visceral sensory input

Answer 10

baroreceptor, chemoreceptor

Question 11

where are the cell bodies of sensory (afferent) fibres

Answer 11

dorsal root ganglion - outside the CNS

Question 12

where are the cell bodies of somatic motor (efferent) fibres

Answer 12

in the CNS - continuous until terminal axon

Question 13

where are the cell bodies of autonomic (efferent) fibres

Answer 13

in the CNS - as well as along the chain to terminal

Question 14

what is the first cranial nerve

Answer 14

olfactory

Question 15

what is the CNI pathway

Answer 15

receptors in olfactory epithelium of nasal cavity - passes through foraminifera in cribriform plate of ethmoid bone - enters olfactory bulb in anterior cranial fossa

Question 16

what are the CNI components

Answer 16

special sensory - smell

Question 17

what are the clinical aspects of CNI

Answer 17

fractured cribriform plate may tear olfactory nerve fibres causing anosmia

Question 18

what is the second cranial nerve

Answer 18

optic

Question 19

what is the CNII pathway

Answer 19

enter via optic canal - join to form the optic chiasm - fibres from medial (nasal) half of each retina cross to form the optic tract

Question 20

what are the CNII components

Answer 20

special sensory - vision

Question 21

what are the clinical aspects of CNII

Answer 21

increase in CSF pressure can cause papilloedema - section of right optic nerve causes blindness through right eye - section of optic chiasm causes loss of peripheral vision (bitemporal hemianopia) = section of right optic tract causes blindness in left temporal and right nasal fields (left homonymous hemianopsia)

Question 22

what is the third cranial nerve

Answer 22

oculomotor

Question 23

what is the pathway of CNIII

Answer 23

emerges from midbrain and exits via superior orbital fissure

Question 24

what are the CNIII components

Answer 24

somatic motor - extraocular muscles and eyelid

visceral/autonomic motor - parasympathetic to pupil causing constriction and to ciliary muscle casuign accommodation of the lens

Question 25

what are the clinical aspects of CNIII

Answer 25

drooping of upper eyelid (ptosis) eyeball abducted and pointing down no pupillary reflex no accommodation of the lens

Question 26

what is the fourth cranial nerve

Answer 26

trochlear

Question 27

what is the pathway of CNIV

Answer 27

emerges from dorsal surface of the mid brain and exits via the superior orbital fissure

Question 28

what are the components of CNIV

Answer 28

somatic motor - extraocular muscle - SUPERIOR OBLIQUE - turns eye downwards

Question 29

what is the clinical application of CNIV

Answer 29

diplopia when looking down

Question 30

what is the fifth cranial nerve (and what are its three branches)

Answer 30

trigeminal: V1 - opthalamic V2 - maxillary V3 - mandibular

Question 31

what is the pathway of CNV1

Answer 31

emerges from the pons - travels through the bigeminal ganglion and exits via the superior orbital fissure

Question 32

what are the components of CNV1

Answer 32

general sensory - from cornea, forehead, scale, eyelids, nose and mucosa of nasal cavity and sinuses

Question 33

what is the pathway of CNV2

Answer 33

emerges from the pons - travels through the trigeminal ganglion - exits via the foramen rotundum

Question 34

what are the components of CNV2

Answer 34

general sensory - from face over maxilla, maxillary teeth, temperomandibular joint, mucosa of nose, maxillary sinuses and palate

Question 35

what is the pathway of CNV3

Answer 35

emerges from the pons - travels through the trigeminal ganglion and exits via the foramen ovale

Question 36

what are the components of the CNV3

Answer 36

general sensory - from the face over the mandible, mandibular teeth, temperomandibular joint, mucosa of mouth and anterior 2/3rds of tongue sensory motor - muscles of mastication, part of digastric, tensor veli palatinin and tensor tympani

Question 37

what are the clinical aspects of CNV1,2,3

Answer 37

paralysis of muscles of mastication, loss of corneal or sneezing reflex, loss of sensation in the face, trigeminal neuralgia (light touch is perceived as painful)

Question 38

what is is the sixth cranial nerve

Answer 38

abducent

Question 39

what is the pathway of CNVI

Answer 39

emerges between the pons and medulla and exits via the superior orbital fissure

Question 40

what are the components of CNVI

Answer 40

somatic motor - extraocular muscle (LATERAL RECTUS - abducts the eye)

Question 41

what are the clinical aspects of CNVI

Answer 41

medial deviation of the affected eye causing diplopia

Question 42

what is the seventh cranial nerve

Answer 42

facial

Question 43

what is the pathway of CNVII

Answer 43

emerges between the pons and medulla dn exits via internal acoustic meatus, cranial stylomastoid foramen

Question 44

what are the components of CNVII

Answer 44

somatic motor - muscles of facial expression and scalp, stapedius of middle ear, part of digastric muscle visceral motor - parasympathetic innervation of submandibular and sublingual glands, lacrimal glands, glands of nose and palate special sensory - taste from anterior 2/3rds of tongue and soft palate general sensory - from external acoustic meatus

Question 45

what are the clinical aspects of CNVII

Answer 45

most frequently injured - due to long pathway through bone Bells palsy - cannot frown, close eyelid or bare teeth