4.2 The visual system Flashcards Preview

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Flashcards in 4.2 The visual system Deck (56)
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1

eyes rely on light energy

eyes take in light information and convert it into neural signals that the brain can interpret

2

eyes

tool for collecting light energy

3

light

travels through space in the forms of waves

4

wavelength

the distance b/w two waves

5

amplitude

range
distance b/w the lowest and highest points
high amplitude is brighter than low amplitude

6

the visual light spectrum is just a small part

gamma rays (too short to see ex, used for tanning)
x-rays
ultraviolet rays

visible light

infrared rays
radar
radio waves (too long for us to see)
ac circuits

7

shortest waves lengths we can see are

blue or purple

8

longest visible wave lengths is the colour

red

9

intermediate visible wave lengths are the colours

yellow and green

10

saturation

*light that consists of a mixture of different wavelengths have low saturation (faint colour)
# of wavelengths they receive from a single region in space
complex mixtures of wavelengths are perceived as white
*light waves that consists of mostly one wavelength have high saturation

11

what we perceive as colour represents the ...

wavelengths that bounce off of objects

12

structure of the eye

designed to let light enter but also to direct light to the right spot of the inside of the eye
-sclera
-cornea

13

sclera

white surface of the eyes

14

cornea

clear part in the front of the eye
-shape of cornea helps direct light to right area of the eye by suspending the light waves toward the point that it needs to strike at the back of the eye

15

pupil

the dark opening part
-after traveling through the cornea, light then travels through the pupil
-size of pupil varies depending on how much light is available
-in bright context pupil is smaller to reduce the amount of light that can enter
-in dim context pupil is larger to allow more light to enter

16

iris

difference in pupil size depends on the iris
-the part around the pupil that has a colour
-it is a muscle that tightens around the pupil constricting it
-when the muscle relaxes the pupil dilates

17

the lens

behind the pupil
-the clear part that changes shape
-bends light more or less
-accommodation reflex

18

accommodation

refers to the lens changing shape to bend light that enters the eye, so that it strikes the right spot at the back of the eye
-close objects need the lens to be more spherical because the light from those objects must be bent more significantly to bring them into focus
-bringing far objects into focus requires the lens to be flat since light energy does not need need to be bent as much to direct them to the proper spot at the back of the eye

19

the retina

after passing through the lens the light will travel through the liquid contents of the eye and strike a structure at the back called the retina
-photoreceptors
-ganglion cells
-optic nerve

20

photoreceptors

pair of light receptors designed to absorb light
-transduce light energy into neural signals
*rods and cones are two types of photoreceptors

21

ganglion cells

take signals from photoreceptors and relay that info to the brain

22

optic nerve

where the axons of ganglion cells get bundled together
fibres going to the brain
blind spot

23

rods

are more sensitive to light and they do not provide as fine-grained an image as the cones
-they can detect light at very low intensities so we rely on them more in dim lighting
-grey, black, white
-yellow dots dominate outside of the fovea which represents the periphery of the visual field (not as defined as cones )

24

cones

are less sensitive to light so we don't rely on the as much in the dark
-different cones respond to different wavelengths, so we rely on them for colour vision
(the blue green and red dots dominate in the fovea which represents the centre of the visual field

25

dark adaptation

the process of rods and cones adjusting their sensitivity to dark lighting conditions
this is why dark environments feel less dark as we spend more time there

26

tri-chromatic (or young-Helmholtz) theory

colour vision depends on three types of cones that are each sensitive to different wavelengths of light that correspond to the colours blue, green and red.

27

colour blindness

people missing one or more of the cones

28

negative afterimage

starting at one colour and the afterimage is a different colour

29

opponent-process theory

colour vision depends on patterns of neural signals that put pairs of colour in opposition
red vs green
blue vs yellow
black vs white
individual ganglion cells respond most vigorously to one colour (red) but their activity is inhibited when presented with the opposing colour (green),
this explains negative afterimages, cells that responds to (green) get exhausted over time when presented with something green and viewing green inhibits cells that respond to red
tired green ganglion cells cant compete with a rebound effect from the previously inhibited red ganglion cells, once we stop viewing something green. instead of a return to a neutral state, we end up experiencing an illusion of red after staring at green

30

nearsightedness (or myopia)

prevents bringing far scenes into focus
this occurs when the eye is slightly too long
the light needs to bent less

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