Eyes

Question 1

What receptors are found in the eye?

Answer 1

Photoreceptors.

Question 2

Which area of the brain processes visual information?

Answer 2

The Occipital lobe.

Question 3

What is the function of the Lacrimal apparatus?

Answer 3

Production of Lacrimal fluid/tears.

Question 4

State the flow of Lacrimal passage from the apparatus to the nasal cavity.

Answer 4

Lacrimal apparatus,
Lacrimal gland,
Lacrimal ducts to canal,
Lacrimal sac,
Nasolacrimal duct,
Nasal cavity.

Question 5

What is the function of Lacrimal fluid?

Answer 5

Contains lysozyme which protects and cleanses the eyes.

Question 6

What are the THREE tunics of the eye?

Answer 6

Fibrous tunic,
Vascular tunic,
Retina.

Question 7

What does the fibrous tunic consist of?

Answer 7

Cornea & Sclera.

Question 8

What does the Vascular tunic consist of?

Answer 8

Choroid, Ciliary body, Iris & Pupil.

Question 9

What does the Retina consist of?

Answer 9

Photoreceptors- Rods & cones,
Optic disc,
Macula lutea,
Fovea Centralis

Question 10

What is the function of the Cornea?

Answer 10

The transparent layer over the iris, protects the eye and has a curved shape to focus light. Accounts for 75% of refraction.

Question 11

What is the function of the Sclera?

Answer 11

The white of the eyes,
Covers the entire eye except the cornea,
Provides shape & support.

Question 12

What is the function of the Choroid?

Answer 12

Contains Melanocytes which produce melanin to absorb light.
Highly vascular.

Question 13

What is the function of the Ciliary body?

Answer 13

Secretes aqueous humor,
ciliary muscles alter shape of the lens to focus image - Accomodation.

Question 14

What is the function of the Iris?

Answer 14

The coloured portion of the eye - determined by melanin count.
Regulates the amount of light entering the eye.
Contains circular and radial smooth muscle.

Question 15

What is the function of the Pupil?

Answer 15

The hole in the centre of the iris,
Point where light enters the eye.

Question 16

What is the function of the Retina?

Answer 16

Forms the beginning of the visual pathway, Contains photoreceptors.
Contains the optic disc which is the location where the optic nerve exists the eye.

Question 17

What is the function of the Macula Lutea?

Answer 17

The exact centre of the posterior retina, contains the Fovea Centralis which contains only cones - highest area of visual activity.

Question 18

What is the difference between rods & cones?

Answer 18

Rods are specialised for black and white vision, aswell as shapes and movement. 120million in each eye.
Cones are specialised for colour vision. 6 million in each eye.

Question 19

What are the TWO cavities of the eye?

Answer 19

Anterior cavity,
Posterior cavity.

Question 20

What is the Anterior cavity?

Answer 20

Anterior to the lens,
Contains two chambers- Anterior chamber: between cornea & iris.
Posterior chamber: between iris & lens - contains aqueous humor which nourishes the lens and cornea.

Question 21

What is the Posterior cavity?

Answer 21

Lies between the lens and retina,
contains the vitreous body- a jelly like substance which maintains the shape of the eye.

Question 22

What is Intraocular pressure?

Answer 22

The pressure from Aqueous humor and Vitreous body.

Question 23

What are the FOUR steps of image formation?

Answer 23

Refraction,
Accomodation,
Pupil Constriction,
Convergence of the eyes.

Question 24

What is Refraction?

Answer 24

The Cornea & Lens bend light rays to focus an image on the Central fovea.

Question 25

What is Accomodation?

Answer 25

The change in shape of the Lens to allow sharp focusing of light into the Retina.

Question 26

What is Pupil constriction?

Answer 26

The smooth muscle of the Iris controls the amount of light entering the eye & helps prevent light scattering.

Question 27

What is Convergence of the eyes?

Answer 27

Medial movement of both eyes to focus on an object.

Question 28

What is the definition of Refraction?

Answer 28

A bending of light as it passes from one substance into another with a different density.

Question 29

Where does Refraction occur? and at what percent?

Answer 29

75% of Refraction occurs in the Cornea, 25% of Refraction occurs in the Lens.

Question 30

What is a potential abnormality that affects Refraction?

Answer 30

Presbyopia: Loss of lens elasticity which results in a decreased ability to focus on near objects.

Question 31

What is the process for focusing on a DISTANT object?

Answer 31

Ciliary muscles relax - pulls on suspensory ligament - which pulls on the Lens. Flat lens = reduced refraction.

Question 32

What is the process for focusing on a NEAR object?

Answer 32

Ciliary muscles contract - lessens tension on suspensory ligaments - lens thickens - increased curvature of lens= increased refraction.

Question 33

What is meant by Binocular vision?

Answer 33

Both eyes focus on the same object.

Question 34

What is the first step of vision transduction?

Answer 34

Absorption of light by photopigments in rods & cones. This initiates an action potential.

Question 35

What is the flow of Visual pathway?

Answer 35

Visual info in the Optic nerve travels to the: Hypothalamus - establishes sleep patterns based on circadian rhythm. Midbrain: Contains some visual reflex centres that control movement of the head, eyes & trunk in response to visual stimuli. Primary Visual area: Location in which visual imagery is processed and associated.

Question 36

What are the THREE cranial nerves involved in the movement of Extrinsic eye muscles.

Answer 36

Oculomotor, Abducens, Trochlear.

Question 37

What are the accessory structures of the eye?

Answer 37

Eyelid, Eyebrow, Eyelash, Canthus, Lacrimal Caruncle.