The Visual System Flashcards
how does light affect our perception
wavelength and intensity of a light affects COLOUR and BRIGHTNESS
iris
donut shaped bands of contraticle tissue that affect the amount of light entering the retina
pupil
hole in lens where light enters which adjusts in size to changes in light (sensitivity and acuity)
lens
focuses light on retina; adjusted by cillary muscles
sensitivity
ability to detect presence of an object in dim light
actuity
abilitiy to see details of an object
accomodation
adjusting configuration of lenses to bring images into focus on the retina
label an eye diagram
x
what have verebrates evolved to have
bilateral vision
stereoscopic vision (3D perspection)
bincoular disparity
colour vision
convergence
eyes coordinate so poitns in visual world correspond to the retina
binocular disparity
difference in position of the same image on 2 retinas
label the cells in the retina
x
amacrine and horizontal cells
specialized for lateral communication
fovea
indentation of ceter of retina for ‘high acuity’ vision
this thin layer dilutes incoming light
blind spot
where optic nerve connects= hence no visual processining occurs here
how does the visual system cope with the blindspot
visual information by periperhal receports fill in the ‘gaps’ (completion)
types of photoreceports
rods and cons
cones
phototrophicv vision colour perecpetion high lighting high actuity 1 cone to 1 bipolar cell 3 types (RGB) in centre of the retina few cones converege to each ganglion cell
rods
scotopic vision sensitive vision (shape/detail, etc) dim lighting low acuity several rods converge to 1 ganglion cell (multiple rods: 1 bipolar cell) 1 type peripheray of retina
visual perception
summation of recent visual information
temporal integration
how visual system fills in time-lags during processes
involuntary fixational eye movement
eyes are contionusly moving to allow us to see even duraction fixation
this results in tremors, drifts and saccades
visual transduction
conversion of one form of energy to another: in terms of visual transduction this referes to the conversion of light to neural signals
how does visual transduction occur
rhodopsin absorbs light in visual receptors; this is a G-Protein that responds to LIGHT instead of neurotransmitters which activates chemical events
it acts by INHIBITION
in dark light, rhodopsin… (3 steps)
- rhodopsin is inactive
- sodium channels open
- sodium ions flow into rods= slight depolarization of them
in bright light, rhodopsin… (3 steps)
1, light reaches rhodopsin
- sodium channels close
- sodium ions can’t enter= hyperpolarizes rods
after passing through the retina, what happens to visual information
it is transported vis the retina-geliculate striate pathways to the primary visual cortex
signals from LEFT visual field are transported to RIGHT primary visual cortex
retina reliculate striate pathways mechansims
carry signals from retina to primary visual cortex via the lateral geniculai nuclei in the thalamus using left and right pathways
RGS pathways
6 layers; each layer of each nucleus has different input from all the convulaed visual fields on an eye
retinotopic organization
RGS is retinotopic as each level is organized as a map in the retina
disproportionate amount of each system is dedicaed to analyzing the fovea
what is an edge
perception of a contrast between 1 adjacent areas of a visual field; yields information information about an object
how do we see an edge
- contrast
2. brightness