Anatomy: Reflexes of the Eye

Question 1

Name the muscle fibres responsible for pupillary dilation in response to sympathetic stimulation

Answer 1

Dilator pupillae fibres

Question 2

What is the oculocardiac reflex?

Answer 2

Reflex bradycardia in response to tension on extraocular muscles or pressure on the eye

Question 3

Name the muscle fibres responsible for pupillary constriction in response to parasympathetic stimulation

Answer 3

Sphincter pupillae fibres

Question 4

In the corneal (blink) reflex, the central CNS connections are between CN V and CN ____

Answer 4

CN VII

Question 5

Name the cranial nerve which is responsible for sensory innervation of the face

Answer 5

Branches of CN V (trigeminal nerve)

Question 6

What is the function of basal tears?

Answer 6

Involved in corneal health - clean/nourish and hydrate cornea, involved in corneal health

Question 7

Name the muscle which alters the change of the lens in the lens accommodation reflex

Answer 7

Ciliary body

Question 8

What is the function of the lens accommodation reflex?

Answer 8

Change in the shape of the lens to focus on a near or further away object

Question 9

What is the vestibulo-ocular reflex?

Answer 9

Turns the eyes in the opposite direction to a head movement to stabilise gaze on an object during head movement

Question 10

What is the function of reflex tears?

Answer 10

Extra tears in response to mechanical or chemical stimulation

Question 11

Where do CNS connections occur in the pupillary light reflex?

Answer 11

Midbrain in a 4 neurone chain

Question 12

In ‘far vision’, how does the shape of the lens change?

Answer 12

Ciliary muscle relaxes, ligament tightens and lens flattens

Question 13

Which cranial nerve is responsible for the motor (efferent) limb of the pupillary light reflex?

Answer 13

Bilateral via CN III → bilateral constriction

Question 14

What is a ‘fixed-dilated (‘blown’) pupil?

Answer 14

Often a serious pathological sign (e.g. of CN III pathology)

Question 15

In the pupillary light reflex, a _____ light reflex occurs in the non-stimulated eye

Answer 15

Consensual

Question 16

Name the muscle responsible for the wide eye opening of fight or flight

Answer 16

Mueller’s muscle of LPS (involuntary - sympathetic innervation)

Question 17

How would you clinically assess the lens accommodation reflex?

Answer 17

Clinically assess all 3 components of the reflex:

• 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 the ciliary muscles)

Question 18

Describe the effect of parasympathetic stimulation on the eye

Answer 18

Get less light into into eyes (to protect the retina from bright light or when asleep), focus on near objects, reflex lacrimation (to wash away stimulant foreign body and clean the cornea)

Question 19

What is a mydriatic pupil?

Answer 19

A non-physiologically enlarged pupil (e.g. from mydriatic drugs which induce dilation of the pupil)

Question 20

Which cranial nerve is responsible for the sensory (afferent) limb of the pupillary light reflex?

Answer 20

Ipsilateral CN II

Question 21

The ciliary muscle ____ in ‘near vision’

Answer 21

Contracts

Question 22

Which regions of the face are given sensory innervation by CN V2 (maxillary nerve)?

Answer 22

Skin of the lower eyelid, skin over the maxilla

Question 23

Describe the pathway of postsynaptic sympathetic fibres from the superior cervical sympathetic ganglion to the orbit

Answer 23

Superior cervical sympathetic ganglion → internal carotid nerve → internal carotid plexus → axons carried on ophthalmic artery and on its branches to orbital structures

Question 24

What is the function of the corneal (blink) reflex?

Answer 24

Protective function - protects the eyes from foreign bodies and bright lights

Question 25

In the pupillary light reflex, a _____ light reflex occurs in the stimulated eye

Answer 25

Direct

Question 26

In 'near vision', how does the shape of the lens change?

Answer 26

Ciliary muscle contracts, ligament relaxes and lens becomes spherical

Question 27

Which cranial nerves are responsible for the sensory (afferent) limb of the corneal (blink) reflex?

Answer 27

Action potentials conducted from cornea via CN V1 branches To trigenimal ganglion, then along CN V to pons

Question 28

What is the corneal (blink) reflex?

Answer 28

Involuntary blinking of the eyelids elicited by stimulation of the cornea

Question 29

Name the nerves involved in the oculocardiac reflex

Answer 29

CN V1 and CN X

Question 30

Which regions of the face are given sensory innervation by CN V3 (mandibular nerve)

Answer 30

Skin over mandible and TMJ, except over angle of mandible

Question 31

What is a miotic pupil?

Answer 31

Non-physiologically constricted pupil (e.g. a component of Horner's syndrome)

Question 32

Describe the effect of sympathetic stimulation on the eye

Answer 32

Eyes open wider to get more light into eyes, may help focus on far objects, emotional lacrimation

Question 33

Which cranial nerves are responsible for the motor (efferent) limb of the corneal (blink) reflex?

Answer 33

Action potentials conducted via CN VII to eyelid part of orbicularis oculi

Question 34

What is a fixed 'pin point' pupil?

Answer 34

Often a serious pathological sign (e.g. opiate drugs)

Question 35

Describe the arrangement of the sphincter pupillae fibres

Answer 35

Encircle pupil around the internal cicumference of iris

Question 36

The ciliary muscle ______ in 'far vision'

Answer 36

Relaxes

Question 37

Which regions of the face are given sensory innervation by CN V1 (ophthalmic nerve)?

Answer 37

Upper eyelid, cornea, conjunctiva

Question 38

The ___________ division of the ANS is responsible for contraction of the ciliary muscle to accommodate the lens in near vision

Answer 38

Parasympathetic

Question 39

Which branch of the ANS is responsible for emotional tears?

Answer 39

Sympathetic

Question 40

Describe the arrangement of the dilator pupillae fibres

Answer 40

Radially arranged - fixed origin around external circumference of iris, mobile insertion around internal circumference

Question 41

Name the cranial nerves responsible for the efferent limb of the lacrimation reflex

Answer 41

Parasympathetic axons originating from CN VII

Question 42

Name the cranial nerves responsible for the afferent limb of the lacrimation reflex

Answer 42

CN V1 from cornea/conjunctiva

Question 43

Name the nerves involved in the vestibulo-ocular reflex

Answer 43

CN VIII and CNs III, IV and VI