The Visual System

Question 1

Name the following muscles of the eye

Answer 1

a) Superior levator
b) Superior oblique
c) Lateral rectus
d) Inferior oblique
e) Inferior rectus

Question 2

Which part of the eye is being decribed?

White capsule that is the insertion point for muscles.

Answer 2

Sclera

Dense fibrous connective tissue and elastic fibres.

Contains small vessels and nerves

Question 3

Name the 3 structures that are in the uvea layer of the eye

Answer 3

Uvea = middle layer.

Iris, cillary body & choroid

Question 4

Dercribe the cornea

Answer 4

Cornea

2/3rds the focusing power of the eye.

Continuous with the sclera corneal limbus

Most richly innervated part of the body - numerous free nerve endings.

Endothelium - single layer that never replaces

Question 5

Where is aqueous humour found?

Answer 5

Aqueous humour is clear fluid that fills the anterior chamber (between the iris and the cornea)

Question 6

Where are the smooth muscles found that determine the size of the pupil?

Answer 6

Iris

This is the colourful part of your eye

Question 7

What features can you see through an opthalmoscope?

Answer 7

Macular lutea- blood vessel free region at the centre of the retina

Fovea centralis- central shallow pit within the macula- high density of cones.

Optic disc

Blood vessels

Question 8

Give the 2 structures which refract light as it enter the eye

Answer 8

The cornea and lens

Question 9

What structures, other than the eye, can be found in the orbit?

Answer 9

Extrinsic eye muscles

The lacriminal gland

The cranial nerves

Blood vessels

Question 10

Name and describe the fluid found in the posterior cavity

Answer 10

Vitreous humor

Thick gelatinous fluid - jelly like viscous substance

Question 11

Give the functions of the vascular layer

Answer 11

Vascular layer = iris, cillary body and the choroid

• Route for vessels and lymphatics
• Regulates the amount of light entering the eye
• Secretes and reabsorbs aqueous humour
• Controls the shape of the lens (focusing power)

Question 12

Describe the pupillary muscles including their innervation and response to stimulus

Answer 12

Bright light - parasympathetic - pupillary constrictors (concentric circles around the pupil) = smaller pupils

Dim light - sympathetic - pupillary dilators = larger pupils

• Sympathetic ‘fight or flight’ need to see to do this with more light, therefore dilation

Question 13

Describe the pupillary reflex

Answer 13

Reflex in response to light intensity - adaption

Ganglion cells project bilaterally to the pretectal nuclei

Pretectal passes crossed and uncrossed fibres to the Edinger-Westphal nuclei which gives the preganglionic parasympathetic fibers - CN III

Question 14

Give and describe the 2 parts of the retina

Answer 14

Pigmented part - absorbs light

Neural part - Light receptors, supporting cells & neurons that do the preliminary processing and intergration of visual image

Question 15

Decribe the photoreceptors

Answer 15

Rods - don’t distinguish colour - highly sensitive (can see in a dim room)

Cones - 3: Red, Green and Blue - colour - sharper but need more light - high conc in fovea

Question 16

Describe the role of amacrine and horizontal cells

Answer 16

Amacrine and horizontal cells facilitate/inhibit the communication between the photoreceptors and glanglion cells, altering the sensitivity of the retina

Question 17

Give the 4 other cells found in the retina which aren’t the photo receptors

Answer 17

Amacrine

Horizontal

Bipolar

Ganglion

Question 18

What is conjuctiva?

Answer 18

a delicate membrane that lines the eyelids and covers part of the outer surface of the eye - loosely adherent to allow free movement of the eye

The fornix prevents anything going behind the eye

Question 19

Give the movement of tears from the lacriminal gland to the nasal cavity

Answer 19

Produced: Lacriminal gland

Lacriminal puncta - lacriminal canals - lacriminal sac - nasolacriminal duct - nasal cavity (inferior meatus)

Question 20

What are conjugate eye movements?

Answer 20

• refers to the motor coordination of the ocular muscles to allow the bilateral fixation on a single object.