Vision Flashcards
Light
the stimulus
detected they eye, where the initial stages of processing are taken care of, then the result is sent to the brain for further processing
Variations in light waves
Amplitude
Wavelength
Purity
Amplitude
height of each wave
- variations affect brightness
- the bigger it is, the more light is being reflected or emitted
Wavelength
distance between peaks of successive waves
- variations affect perceptions of colour
- measured in nanometers
- larger = lower frequency; smaller = higher frequency
Visible Spectrum
the tiny position of the total range of wavelengths of the electromagnetic radiation that humans are sensitive to (360nm-750nm)
-some animals see other spectrums
Purity
affects perception of saturation
-light that is made up of a single wavelength is pure. We typically see a mixture of wavelengths and they are less intense than pure colour
Cornea
begins focusing process when light passes through
-transparent window out front of eye
Sclera
tougher membrane that covers rest of eye
Pupil
processes light after cornea
-round window (black dot)
Iris
controls size of pupil
- coloured part of the eye
- consists of a band of muscles controlled by the brain
- dilate pupil to allow more light
- constrict pupil to restrict light
Lens
processes light after pupil
- final focusing
- curvature causes images to land on the retina upside down and reversed left to right (the brain corrects this)
- flexible piece of tissue whose shape can be altered by surrounding muscles
Lens Accomodation
the lens can change shape to focus on object that vary in distance
- fatter/rounder for close objects
- flatter/elongated for far away objects
Vitreous Humor
light passes through after lens
-clear, jelly-like substance that comprises the main chamber inside the eyeball
Retina
light finally lands here
- natural tissue that lines back of eye
- made up of complex network that neural cells arranged in 3 layers
3 Layers of Retina
Ordered in an inside out fashion based on nutrition requirements of different cells
Photoreceptors
Bipolar Cells
Ganglion Cells
Photoreceptors
translate the physical stimulus of light into a neural signal that the brain can understand
-light must pass through other layers first
Retinal Pigment Epithelium (RPE)
provide nutrients for photoreceptors and located at back of eye (which is why the layers are arranged backwards)
Rods
125 Million
lower light intensities
night vision
no colour, poor visual acuity, concentrated surrounding fovea/periphery
Cones
6 Million
day vision
colour, good visual acuity, concentrated in fovea
Ganglion Cells
collect info from larger segment of retina
- axons of these cells converge at optic disk
- leave optic nerve which travels to brain
Blind Spot
area of the eye where the optic nerve leaves - there are no photoreceptors
Bipolar Cells
receive info from photoreceptors and send it to ganglion cells
Horizontal and Amacrine Cells
cells in the retina that allow areas in the retinal layer to communicate with each other
-allow info from adjacent photoreceptors to combine their info - cones and rods converge to travel along only one million
Receptive Field
collection of rods and cones in the retina that, when stimulated, affects the firing of a particular ganglion cell
-photoreceptors get divided into groups that get assimilated into one signal that affects a ganglion cell down the line