Retina- 9

Question 1

What is vision?

Answer 1

The transduction of visible light into neural signals so we have perception of what is where

Question 2

What wavelength spectrum is visible light?

Answer 2

400-700nm

Question 3

What are the structures of the external eye?

Answer 3

The sclera, cornea and limbus

Question 4

What is the main part of the intermediate eye?

Answer 4

Uvea

Question 5

What structures are in the anterior uvea?

Answer 5

iris, ciliary body, pupil, lens

Question 6

What structures are in the posterior uvea?

Answer 6

Choroid- blood vessels

Question 7

What structures are the internal eye?

Answer 7

Retina and retinal pigment epithelium

Question 8

What is the sclera?

Answer 8

Dense connective tissue- rubbery- functions to protect the eye.

Question 9

What does the episclera contain?

Answer 9

Blood vessels

Question 10

Describe the cornea

Answer 10

Transparent cover of 1/6 of the anterior eye. Merges with sclera with lots of stem cells.

Question 11

Where is the densest sensory innervation?

Answer 11

The superficial layer of the cornea epithelium

Question 12

What is the iris?

Answer 12

Pigmented diaphragm muscle

Question 13

What are some constrictors of the iris?

Answer 13

alcohol and opiods

Question 14

What are some dilators?

Answer 14

Atropine, LSD, cocaine

Question 15

What controls the shape of the pupil?

Answer 15

Iris

Question 16

What are the ciliary bodies?

Answer 16

Dark irregular ring around the iris. Contains ciliary muscles which control the shape of the lens via suspensory ligaments

Question 17

What controls the shape of the lens?

Answer 17

Ciliary body

Question 18

What is the choroid?

Answer 18

Goes all around the eye and provides blood and nutrients and oxygen

Question 19

What is the lens?

Answer 19

A biconvex translucent lens directly behind the iris and pupil

Question 20

What fraction is refractive power provided by the cornea?

Answer 20

2/3

Question 21

How many dioptres refractive power does the cornea have?

Answer 21

42

Question 22

What changes shape to accomodate for objects at different distances to change the refractive power?

Answer 22

Lens via the ciliary body contracting and suspensory ligaments

Question 23

What shape is the lens with far vision?

Answer 23

Flat

Question 24

What shape is the lens with near vision?

Answer 24

Fatter/rounder

Question 25

What name is given to normal eye vision?

Answer 25

Emmetropia

Question 26

What is myopia?

Answer 26

Longer eye

Question 27

Where do light rays focus in myopia?

Answer 27

Infront of the retina

Question 28

What is myopia?

Answer 28

Shortsightedness

Question 29

What is hyperopia?

Answer 29

Farsightedness- light focuses behind the retina because the eye is shorter from aging and the lens is less elastic.

Question 30

What is antistigmatism?

Answer 30

Either the lens or cornea or both have an irregular shape so there is errors of refraction

Question 31

What is the distance on the retina which represents the visual angle?

Answer 31

300 micrometres

Question 32

What diameter is covered by the whole retina?

Answer 32

200 degrees

Question 33

What is phototransduction?

Answer 33

The conversion of light into electrical signals

Question 34

What is the output cell of the retina?

Answer 34

The retinal ganglion cell

Question 35

What do the axons of retinal ganglion cells bundle together the make?

Answer 35

The optic nerve

Question 36

Starting with the choroid at the bottom, go up and state the layers of the retina

Answer 36

Choroid, Bruch's membrane, retinal pigment epithelium, photoreceptor outer then inner segment, outer limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, nerve fibre layer, inner limiting membrane

Question 37

What is in the outer nuclear layer?

Answer 37

The cell bodies of photoreceptors

Question 38

What is in the outer plexiform layer?

Answer 38

Synapses from photoreceptors to bipolar and horizontal cells

Question 39

What is in the inner nuclear layer?

Answer 39

Cell bodies of horizontal, bipolar and amacrine cells

Question 40

What is in the inner plexiform layer?

Answer 40

Synapses between bipolar and amacrine cells onto ganglion cells

Question 41

What is in the ganglion cell layer?

Answer 41

Cell bodies of ganglion cells

Question 42

Describe the retinal pigment epithelium

Answer 42

It is there to protect the photoreceptors. Black to absorb light and reduce light scatter

Question 43

What are Muller cells and where are they?

Answer 43

They have their cell bodies in the inner nuclear layer and span the entire thickness of the retina. They provide physical and metabolic support to the retina

Question 44

What is the primary path of retinal connections?

Answer 44

Vertical- photoreceptor to bipolar cell to ganglion cell

Question 45

What neurotransmitters is mainly used in the vertical path?

Answer 45

Glutamate

Question 46

Which neurotransmitter is used by horizontal cells?

Answer 46

GABA

Question 47

Which neurotransmitter do some amacrine cells use?

Answer 47

Glycine

Question 48

What is a starburst amacrine cell?

Answer 48

An excitatory amacrine cell which uses Ach

Question 49

What type of potentials do all retinal cells produce (except ganglion cells)

Answer 49

Slow graded potentials

Question 50

Why is the retina inverted?

Answer 50

Because photoreceptors are very metabolically active cells, they require lots of ATP and oxygen to be provided by blood vessels. Blood vessels however are not transparent, so would not let light through to the photoreceptors if the retina was arranged the other way around