17. Retinal Function and Visual Perception Flashcards Preview

NSB > 17. Retinal Function and Visual Perception > Flashcards

Flashcards in 17. Retinal Function and Visual Perception Deck (45)
Loading flashcards...
1

What range of electromagnetic wave length is visible to the eye?

400-750 nm

2

What does length of an electromagnetic wave correspond to?

Colour

3

What does amplitude of an electromagnetic wave correspond to?

Brightness

4

What effect does a closer light source have on the focal distance?

Longer focal distance

5

What is accommodation?

Lens alters focal length

6

What are the functions of the pupil?

Control light entering eye
Depth of focus

7

How does the pupil control depth of focus?

Constriction cuts out peripheral light

8

What is the effect of sympathetics on the pupil?

Contract radial muscle of iris
Cause dilation

9

What is the effect of parasympathetics on the pupil?

Contract circular muscle of iris
Cause constriction

10

What is used to test for visual acuity?

Snellen chart

11

What is visual acuity?

Ability to distinguish between 2 nearby points

12

What does each part of 20/20 stand for?

First 20 is distance in feet from Snellen chart
Second is size of the smallest letter read

13

What are the 3 cell types in the retina?

Photoreceptors
Bipolar
Ganglion

14

What do rods detect?

Light intensity

15

Why is visual acuity low in rods?

Many rods converge to the same ganglion

16

What do cones detect?

Colour

17

What is the equation for photon energy?

hv (planck constant x frequency)
hc/ λ (planck constant x speed of light/ wavelength)

18

Which cells are non-image forming photoreceptors?

Retinal Ganglion Cells

19

What do Retinal Ganglion cells control?

Circadian rhythm

20

What light-sensitive pigement is used by retinal ganglion cells?

Melanopsin

21

What is the name for loss of photoreceptor cells?

Macular degeneration

22

What is found in the outer segment of cones?

Discs: specialised receptor region

23

What is found in the inner segment of cones?

Mitochondria and other organelles

24

What is phototransduction?

Converting light to an electrical signal

25

What pigment is used in rods?

Rhodopsin

26

What is rhodopsin composed of?

Retinal and opsin

27

What neurotransmitter is released by rods?

Glutamate

28

What is meant by the dark current?

Na+ enters causing depolarisation
K+ leaves causing repolarisation

29

What happens once light hits rhodopsin?

11-cis retinal converted to 11-trans retinal

30

What does 11-trans retinal activate?

Transducin