Anatomy - Eye Reflexes

Question 1

For each of the following branches of the trigeminal nerve. Name them and match there area of sensory innervation

They are all sensory nerves but one also has motor, name it?

Answer 1

V1 - ophthalmic

• upper eyelid
• cornea
• conjunctiva

V2 - maxillary

• skin of lower eyelid
• skin over maxilla

V3 - mandibular (also motor)
- skin over mandible and TMJ (except angle of the mandible)

Question 2

What is the purpose of the corneal reflex?

Answer 2

To protect the eye from foreign bodies

Question 3

How is the corneal reflex tested clinically?

Answer 3

Cotton wall brushed against sclera (not cornea - don’t want to risk any damage)

Question 4

Describe the neural pathway of the corneal reflex

Answer 4

CN V1 - sense something on cornea/sclera

Travel to CNS

CN VII (facial nerve) - eyelid part of orbicularis oculi contract

Question 5

Describe how the pupil size changes with sympathetic and parasympathetic innervation

Answer 5

Sympathetic - increases pupil size (want to be able to see danger coming)

Parasympathetic - decreases pupil size

Question 6

The levator palpebrae superioris contains skeletal muscle (controlled by CN III) and smooth muscle (AKA mueller’s muscle). When these contract what happens?

Answer 6

Autonomic response -> causes eyes to open more widely

Question 7

For each of the following muscles state whether sympathetic or parasympathetic innervation is
responsible and what the action is:
- sphincter pupillae
- dilator pupillae

Answer 7

Sphincter pupillae

• parasympathetic
• contract the pupil

Dilator pupillae

• sympathetic
• dilate the pupil

Question 8

In a sick patient are you more likely to see dilated or constricted pupils?

Answer 8

Dilated (“fight” off sickness)

Question 9

What is meant when using the terms:

• mydriatic pupil
• miotic pupil

Answer 9

Mydriatic pupil = non-physiological dilated pupil

Miotic pupil = non-physiological constricted pupil

Question 10

Each of the following clinical signs are indicative of serious pathology:

• “pin-point” pupil
• “fixed-dilated” pupil

Give a reason for each

Answer 10

Pin-point pupil - opiate drugs

Fixed-dilated - CN III, CNS disease and raised ICP

Question 11

What is meant by consensual light reflex?

Answer 11

When light is shone in one eye and the non-stimulated eye has the same response as the stimulated

Question 12

When light is shone in an eye, what nerve is responsible for the IPSILATERAL sensory reflex?

What nerve is responsible for the BILATREAL motor reflex?

Answer 12

CN II - optic nerve - sensory

CN III - oculomotor - motor

Question 13

Describe the changes in the lens when viewing a near object.

Is it sympathetic or parasympathetic that is responsible for this?

Answer 13

Lens becomes more spherical

Parasympathetic

Question 14

How does the lens change shape?

Go to onenote and look at task 1

Answer 14

Parasympathetic control of the ciliary body via CN III

Stimulation causes the muscle to contract and the suspensory muscles to relax = more spherical lens

No stimulation causes the muscle to relax and suspensory muscles to contract = more flat lens = view far away objects

(think of this like an accordian -> hands out flat and relaxed - inside is stretched and visa versa)

Question 15

What 3 reflexes are you testing when bringing finger close towards nose.

Answer 15

1. Bilateral pupillary constriction
   - parasympathetic constriction of sphincter pupillae
2. Bilateral convergence of eyeballs towards midline
   - medial rectus muscle
3. Bilateral relaxation of the lens
   - parasympathetic contraction of the ciliary body

Question 16

What nerves are responsible for efferent (sensory) and afferent (motor) control of reflex tears to mechanical or chemical stimulation?

Answer 16

Efferent - CN V1

Afferent - CN VII

(VII provides parasympathetic innervation to lacrimal glands)

Question 17

Sympathetic or parasympathetic responsible for reflex tears?

Answer 17

Parasympathetic