chapter 3 Flashcards
1
Q
vision is the sensory system that allows us to perceive….
A
light
2
Q
light
A
- electromagnetic energy
- made up of photons
- wavelength
3
Q
electromagnetic energy
A
- form of energy that includes light, both a wave and a particle
4
Q
wavelength
A
- distance between two adjacent peaks in a repeating wave, different forms of electromagnetic energy are classified by their wavelengths
5
Q
intensity in reference to waves
A
- height of a wave
6
Q
frequency
A
- number of waves per unit of time, frequency is the inverse of wavelength
7
Q
the shorter the wavelength is…
A
the higher the energy is
8
Q
electromagnetic spectrum
A
- the complete range of wavelengths of light and other electromagnetic energy
9
Q
photon
A
- a single particle of light
10
Q
how humans see light
A
- light emanates from a light source
- light falls on objects in an environment
- those wavelengths reflected by the objects
- reflected light enters the eye through the pupil, focused on the retina by the cornea and lebns
- rods and cones in the retina transduce light energy into an electrochemical signal
- sent to the brain processing through the optic nerve
11
Q
cornea
A
- clear front surface of the eye that allows light in
- major focusing element
12
Q
sclera
A
- outside surface of the eye
- protective membrane covering the eye
13
Q
anterior chamber
A
- fluid filled space between the cornea and the iris
14
Q
iris
A
- muscle that controls the amount of light entering through the pupil
- colored part of the eye
15
Q
pupil
A
- an opening in the middle of the iris
16
Q
pupillary reflex
A
- automatic process by which the iris contratcs or relaxes in response to the amount of light entering the eye
- the reflex controls the size of the pupil
17
Q
heterochromia
A
- one person has irises of 2 different colors
18
Q
posterior chamber
A
- space between the iris and the lens, filled with aqueous humor
19
Q
the lens
A
- located behind the iris
- adjustable focusing element of the eye
20
Q
accommodation
A
- process of adjusting the lens of the eye so that you can see near and far objects clearly
- controlled by ciliary muscles
21
Q
ciliary muscles
A
- work with zonule fibers connecting the lens to the choroid membrane
- contract, increasing curvature of the lens, lens thickens, focus close
22
Q
presbyopia
A
- incoming light focuses behind the retina
- difficulty close up objects
- lens becoming less flexible as you age
23
Q
retinal image
A
- light projected onto the retina
24
Q
- retina
A
- innermost of the three membranes in the eye
- paper thin layer of cells at the back of the eye where transduction takes place
- designed to help photoreceptors capture light
- starts the process of transmitting visual information to the brain
25
Q
- photoreceptors
A
- cells at the back of the eye
- photoreceptors synapse ( connect) with two types of cells, horizontal and bipolar
26
Q
- bipolar cells
A
- biopolar cells synapse with amacrine and ganglion cells
- receive information from photoreceptors
27
Q
- ganglion cells
A
- send their axons to the optic disc where they exit the eye
- axons then become the optic nerve carrying the signals from the retina to the brain
28
Q
function:
receptors
A
- transduce light into a neural signal
28
Q
function
rods
A
- night vision, light detection, grayscale vision
29
Q
function
cones
A
- color vision, daytime vision
30
Q
function
horizontal cells
A
- receive information from photoreceptors and other horizontal cells
- cross talk across photoreceptors
31
Q
function
amacrine cells
A
- receive information from bipolar,ganglion cells and other amacrine cells
32
Q
function
retinal ganglia
A
- recieve information from bipolar cells, send signals to the brain via the optic nerve`
33
Q
rods
A
- photoreceptors at the periphery of the retina, sensitive to light
34
Q
fovea
A
- an area on the retina that is dense in cones but lacks rods
- rods more common at the periphery
35
Q
cones
A
- photoreceptors in the fovea of the retina, responsible for color
36
Q
macula
A
- direct center of the retina
- holds the fovea but is larger than it
37
Q
optic disc
A
- the point of exit for ganglion cell axons (optic nerve) leaving the eye, no receptor cells
38
Q
photo pigments
A
- molecule that absorbs light
- releases an electric potential by altering the voltage in the cell
39
Q
opsin
A
- protein portion of a photopigment that captures the photon of light and begins the process of transduction
- variation in opsin determines the type of visual receptor
40
Q
photopigments are composed of (rods)
A
- opsin in rods
- vitamin a (retinal
- rhodopsin
41
Q
photopigments are composed of (cones)
A
- chromodopsin in cones
- vitamin a (retinal)
- similar to rhodopsin but 3 classes
42
Q
hyperpolarization
A
- change in the voltage of a neuron whereby the inside of the cell becomes more negative than it is in its resting state
43
Q
duplex theory of vison
A
- functionally two distinct ways in which our eyes work, depending on conditions in the environment
- photopic, cones
- scotopic, rods
44
Q
photopic vision
A
- vision associated with cones
- daytime, good acuity in the fovea, color vision
45
Q
scotopic vision
A
- vision associated with rods
- poor acuity, no color ability
- sensitive to light
46
Q
spectral sensitivity
A
- relative sensitivity of a receptor type to all of the wavelengths
47
Q
purkinje shift
A
- difference im spectral sensitivity with rods and cones
- shift towards blue side of color spectrum at night
- as night time conditions appear, longer wavelengths of light will appear darker, shorter wavelengths will appear brighter
48
Q
spatial summation
A
- multiple presynaptic neurons release neurotransmitters onto a single postsynaptic neuron, combining signals, action potential
- ability to pool light across different regions of space
- at night need to detect as much light as possible, a little blurry
49
Q
acuity
A
- ability to see fine details
50
Q
convergence
A
- many rods connect to one retinal ganglion cell where their responses are added together
- allows the scotopic system to pool responses across different rods to maximize sensitivity to light in exchange for less acuity
50
Q
dark adaptation
A
- sensitivity to low light is increased
- first 8 minutes cones do most of the seeing
- dark eyes have concentration of rhodopsin
50
Q
light adaptation
A
- when light returns, dark adaptation in reverse
- 5 minutes or less
- visual systems sensitivity is reduced so that it can operate in higher light levels
50
Q
convergence of photoreceptors onto ganglion cells
A
50
Q
edge detection
A
- process of distinguishing where one object ends and the next begins
50
Q
receptive field
A
- area in the visual world that a particular vision neuron responds to
- array of photoreceptors from which each retinal ganglion cell receives input
50
Q
on center receptive fields
A
- retinal ganglion cells that increase their firing late (excitation) when light is presented in the middle of the receptive field
- decrease their firing rate (inhibition) when light is presented outside of the receptive field
- cells respond to luminance contrast
50
Q
hyperopia
A
- condition causing an inability to focus on near objects
- accommodation cannot make the lens thick enough
50
Q
lateral inhibition
A
- reduction of a response of the eye to light
50
Q
center surround receptive field
A
- a receptive field in which the centre responds opposite to how the surround of the receptive field responds
- eg centre, increase activity, outside, decrease activity
50
Q
off center receptive fields
A
- retinal ganglion cells that decrease their firing late (inhibition) when light is presented in the middle of the receptive field
- increase their firing rate (excitation) when light is presented outside of the receptive field
50
Q
astigmatism
A
- irregular shape of the cornea or lens
- impossible for the lens to accommodate a fully focused image
51
Q
myopia (nearsightedness)
A
- condition causing an inability to focus clearly on far objects
- accommodation can’t make the lens thin enough
51
Q
cataracts
A
- darkening of the lens
51
Q
macular degeneration
A
- disease that destroys the fovea and the area around it
51
Q
retinitis pigmentosa
A
- inherited progressive degenerative disease of the retina
- can lead to blindness`
