Q2: Receptors, The Eye

Question 1

Two main types of light receptors in the mammalian eye

Answer 1

Rod cell and cone cells

Question 2

Rod cells and cone cells act as …

Answer 2

Transducers

Question 3

Transducers

Rod and cone cells

Answer 3

Conserve light energy into the electrical energy of a nerve impulse.

Question 4

Greater number of rod cells or cone cells?

Answer 4

More rod cells

Question 5

Many or a single rod cell connected to a single sensory neurone in the optic nerve?

Answer 5

Many rod cells are connected to a single sensory neurone in the optic nerve.

Question 6

Rod cells function

Answer 6

Rod cells are used to detect light of very low intensity.

Question 7

What happens before a generator potential is created in bipolar cells that lots of rod cells are connected to?

Answer 7

A certain threshold value must be exceeded

Question 8

Retinal convergence

Answer 8

Lots of rod cells connected to a single bipolar cell.

Question 9

Retinal convergence effect on threshold value?

Answer 9

Means that it is likely to be exceeded

Question 10

Why do rod cells only show images in black and white?

Answer 10

They cannot distinguish between different wavelengths of light.

Question 11

Pigment in rod cells

Answer 11

Rhodopsin

Question 12

Rhodopsin in rod cells must be broken down…

Answer 12

In order to create a generator potential

Question 13

Low intensity light has enough energy to…

Answer 13

Cause breakdown of rhodopsin

Question 14

How many types of rod cells

Answer 14

One

Question 15

Why can’t the brain distinguish between separate sources of light that has stimulated rod cells?

Answer 15

The light received by rod cells sharing the same neurone will only generate one impulse which travels to the brain.

Question 16

Visual acuity of rod cells?

Answer 16

Low visual acuity

Question 17

How many types of cone cells?

Answer 17

Three

Question 18

Each of the three types of cone cells responds to…

Answer 18

A different wavelength of light

Question 19

Often cone cells are connected to

Answer 19

Their own bipolar cell connected to a sensory neurone in the optic nerve

Question 20

Why do cone cells only respond to a high intensity of light?

Answer 20

Their stimulation cannot combine to exceed the threshold value and create a generator potential

Question 21

Pigment in cone cells

Answer 21

Iodopsin

Question 22

Iodopsin vs rhodopsin

Light intensity for breakdown

Answer 22

Iodopsin requires a higher light intensity for its breakdown than rhodopsin

Question 23

Each type of cone cell contains…

So?

Answer 23

A specific type of iodopsin.

So each cone cells is sensitive to a different range of wavelengths of light.

Question 24

Why do cone cells have good visual acuity?

Answer 24

Each cone cell has its connection to a single bipolar cell so eg: if two were stimulated, the brain would receive two separate impulses.

Question 25

Distribution of rod and cone cells on the retina

Answer 25

Uneven

Question 26

Fovea

Answer 26

Part of the retina which is opposite the pupil where light is focussed by the lens.

Question 27

Fovea receives …

Answer 27

The highest intensity of light

Question 28

Rod cells or cone cells found at the fovea

Answer 28

Cone cells

Question 29

Further away from the fovea, the concentration of cone cells…

Answer 29

Decreases

Question 30

Where is light intensity the lowest in the retina?

Answer 30

The peripheries of the retina

Question 31

Are rod cells or cone cells found at the peripheries of the retina?

Answer 31

Rod cells