Cranial Nerves I-VI 21.02.23

Question 1

Are the cranial nerves part of the CNS or PNS?

Answer 1

• PNS
• 12 pairs of cranial nerves: head and neck (except vagus which is odd one as it innervates thorax and abdomen etc)
• 31 pairs of spinal nerves

Question 2

What is the function cranial nerves?

Answer 2

• Carry sensory/motor/autonomic information between the brain and the head and the neck
• Contain different combinations of fibre types (motor, general, sensory)

Question 3

What are the 12 cranial nerves (names)?

Answer 3

I Olfactory
II Optic
III Oculomotor
IV Trochlear
V Trigeminal
VI Abducens
VII Facial
VIII Vestibulocochlear
IX Glossopharyngeal
X Vagus
XI Accessory
XII Hypoglossal

Question 4

Are the 12 cranial nerves sensory, motor or both?

Answer 4

I Olfactory Some
II Optic Say
III Oculomotor Money
IV Trochlear Matters
V Trigeminal But
VI Abducens My
VII Facial Brother
VIII Vestibulocochlear Says
IX Glossopharyngeal Big
X Vagus Brains
XI Accessory Matter
XII Hypoglossal Most

Question 5

Which four cranial nerves carry parasympathetic fibres?

Answer 5

III - Oculomotor
VII - Facial
IX - Glossopharyngeal
X - Vagus

Question 6

How are sympathetic fibres carried?

Answer 6

Start in the spinal chord then they form a trunk and then innervate the head and neck. They are carried alongside the arteries entering the brain. They are not carried in cranial nerves

Question 7

Which cranial nerves are found in the brainstem?

Answer 7

III - XII

Question 8

What does carrying sensory or motor signals mean?

Answer 8

• Either receive sensory/ afferent input from the periphery
• Contain cells whose axons convey motor/ efferent signals to the periphery
• Some nerves with motor and sensory components have two separate nuclei

Question 9

Where is the first cranial nerve connected to the brain?

Answer 9

• Not in the brainstem
• On the cerebrum

Question 10

What is the function of the first cranial nerve?

Answer 10

Smell

Question 11

what is the connection to the skull foramen of the first CN?

Answer 11

The cribriform plate

Question 12

Where are the receptors for the first CN?

Answer 12

The nasal cavity
- Then axons travel through the cribriform plate to the olfactory bulb to the tracts then to the temporal lobe

Question 13

What is the brain connection, function and skull foramen of the second CN?

Answer 13

Brain connection: Cerebrum (not brainstem)
Function: sight
Skull foramen: Optic canal

Question 14

Where do the fibres of the second CN travel?

Answer 14

From the retina to the primary visual cortex. giving meaning to the images we see

Question 15

How can we test the second CN?

Answer 15

1. visual acuity (chart of letters)
2. Visual fields
3. Pupillary light reflex
4. Fundoscopy (looking at retina when light shone into their eye)

Question 16

What is the brain connection, function and skull foramen of the third CN?

Answer 16

Brain connection: Midbrain
Function: eye movements, eyelid opening, pupil constriction, accommodation
Skull foramen: superior orbital fissure

Question 17

How does the pupillary light reflex work (direct and consensual response)?

Answer 17

When light is shone into one eye
- Ipsilateral pupil constricts (direct response)
- Contralateral pupil constricts (consensual response)

Question 18

Is Pupil constriction parasympathetic or sympathetic?

Answer 18

parasympathetic - constriction so if that doesn’t work pupil will be dilated and vice versa for sympathetic

Question 19

What is the brain connection, function and skull foramen of the fourth CN?

Answer 19

Brain Connection: midbrain
Function: eye movement (Superior oblique only)
Skull foramen: Superior orbital fissure

Question 20

What would a deficit of this nerve result in?

Answer 20

Diplopia on looking down. inability to depress an adducted eye
- Only CN to leave brainstem posteriorly

Question 21

What is the brain connection, function and skull foramen of the sixth CN?

Answer 21

Brain connection: pons
Function: eye movement (lateral rectus muscle only)
Skull foramen: superior orbital fissure
A deficit in this nerve would result in an inability to abduct the eye

Question 22

How do we test the sixth cranial nerve?

Answer 22

able to look right but unable to look left

Question 23

What are the three branches of the fifth CN?

Answer 23

The trigeminal nerve is split into:
V1. Ophthalmic
V2. Maxillary
V3. Mandibular

Question 24

What is the brain connection, function and skull foramen of the fifth CN?

Answer 24

Brain connection: pons
Function: sensation to the anterior head and face AND motor to the muscles of mastication (chewing)
Skull foramen: V1 - superior orbital fissure, V2 - foramen rotundum, V3 - foramen ovale

Question 25

What are the functions of the three branches of the trigeminal CN?

Answer 25

V1 - sensation from the anterior head (superior 1/3)and face including scalp, forehead, cornea and tip of the nose
V2 - Sensation from the face (middle 1/3) including cheek, nose and upper lip, upper teeth and palate
V3 - sensation from the face (inferior 1/3) including lower lip, lower teeth, chin, jaw, anterior 2/3 of the tongue and muscles of chewing

Question 26

How do we test sensation of the fifth cranial nerve?

Answer 26

Test the general sensation over the face (compare the left and right) by touch and the three sections of the face

Question 27

What does injury to the fifth nerve cause?

Answer 27

• Paralysis of muscles of mastication
• Pain in the face (trigeminal neuralgia)