Anatomy + Physiology 2

Question 1

Describe the sensory innervation of the face?

Answer 1

CN V1 (ophthalmic nerve)

• upper eyelid
• cornea
• conjunctiva

CN V2 (maxillary nerve)

• skin of lower eyelid
• skin over the maxilla

CN V3 (mandibular nerve)

• skin over mandible and TMJ
• except angle of mandible

Question 2

Which nerve is responsible for the sensory (afferent) limb of the corneal blink reflex?

Answer 2

CN V1 (ophthalmic branch of trigeminal)

Question 3

Which nerve is responsible for the motor (efferent) limb of the corneal blink reflex?

Answer 3

CN VII (facial) - eyelid part of orbicularis oculi

Question 4

What is the function of the vestibulo-ocular reflex?

Answer 4

Turns the eyes in the opposite direction to a head movement

Stabilises gaze on an object during head movement

Question 5

Which nerves are involved in the vestibulo-ocular reflex?

Answer 5

CNS connection between CNVIII + CNs III, IV + VI

Question 6

What is the oculocardiac reflex?

Answer 6

Reflex bradycardia in response to tension on extra ocular muscles or pressure on eye

Question 7

Which nerves are involved in the oculocardiac reflex?

Answer 7

CNS connections between CN V1 + CN X

Question 8

Which structures of the eye have an autonomic nerve supply?

Answer 8

Smooth muscle of iris (pupil diameter)
Smooth muscle of ciliary body associated with lens (focussing)
Lacrimal glands

Question 9

What is the affect of sympathetic supply to the eye?

Answer 9

Eyes open wider
Pupils increased in diameter (let more light in)
Focus on far objects

Question 10

What is the affect of parasympathetic supply to the eye?

Answer 10

Pupils narrow (less light into eyes)
Focus on near objects

Question 11

How is a non-physiological constricted pupil described?

Answer 11

Miotic pupil (miosis)

Question 12

Pathology affecting which nerve might cause a fixed-dilated (blown) pupil?

Answer 12

CNIII (oculomotor)

Question 13

Which muscle fibres constrict the pupil?

Answer 13

Sphincter pupillae

Question 14

How is a non-physiological enlarged pupil described?

Answer 14

Mydriatic pupil

Question 15

Which muscle fibres dilate the pupil?

Answer 15

Dilator pupillae

Question 16

Describe the afferent and efferent limbs of the pupillary light reflex

Answer 16

Afferent (special sensory) - ipsilateral CN II
CNS connections in midbrain
Efferent (motor) - bilateral CNs III

Question 17

What is the difference between the direct light reflex and the consensual light reflex?

Answer 17

Direct - occurs in stimulated eye

Consensual - occurs in the other (non-stimulated) eye

Question 18

What is the function of the suspensory ligament?

Answer 18

Connects the circumference of the lens and the ciliary body to facilitate the accommodation reflex

Question 19

Describe the mechanism of accommodation for far vision?

Answer 19

Ciliary muscle relaxes (no parasympathetics)

Suspensory ligament tightens + lens flattens to focus on an object in the distance

Question 20

Describe the mechanism of accommodation for near vision?

Answer 20

Ciliary muscle contracts (parasympathetic)

Ligament relaxes + lens becomes spherical to focus on near objects

Question 21

What are you assessing when checking the lens accommodation reflex?

Answer 21

Response to ‘near’ - 3 components:

• bilateral pupillary constriction (parasympathetic constriction of sphincter pupillae)
• bilateral convergence of both eyes towards midline (medial rectus)
• bilateral relaxation of the lens (lens becomes spherical due to contraction of ciliary muscles)

–> All CN III

Question 22

Why does a raised ICP cause papilloedema?

Answer 22

Optic nerve is covered by meninges so raised ICP will be transmitted along the subarachnoid space in the optic nerve sheath
–> compression of optic nerve (and central artery and vein of retina)

Question 23

Why might CNIII be affected in raised ICP?

Answer 23

Susceptible to damage due to compression from tentorial herniation –> medial temporal lobe herniates through tentorial notch

Question 24

What would be the effect of a damaged/compressed CN III?

Answer 24

Paralysis of 4 extra-ocular muscles + parasympathetic innervation of sphincter pupillae

Question 25

How would CN III damage present clinically?

Answer 25

Loss/slowness of pupillary light reflex
Dilated pupil
Ptosis
Eye turned inferolaterally –> down and out

Question 26

What would be the effect of CN IV damage/compression?

Answer 26

Paralysis of superior oblique –> inferior oblique unopposed

• eye cannot move inferomedially
• diplopia when looking down

Question 27

What would be the effect of CN VI damage/compression?

Answer 27

Paralysis of lateral rectus –> eye cannot mover laterally in horizontal plane
- medial deviation of the eye