Chapter 2: Beginning Of The Perceptual Process Flashcards
FIrst step of the process
Light reflected from an object into the eye
Virtual Process first four steps
1) The distal stimulus (aika the tree)
2) Light is reflected from the tree and enters the eye to create the proximal stimulus on the vision receptor
3) Receptors transform light into electrical signals
4) Electrical signals are ‘processed” as they travel through a network of neurons
Visible light
The energy within the electromagnetic spectrum that humans can perceive, has wavelength from 400nm-700nm
Electromagnetic spectrum
A continuum of electromagnetic energy that is produced by electric charges and is radiated as waves
Wavelength
The distance between the peaks of the electromagnetic waves
The eye (how it works)
Light reflected from objects in the environment enters the eye through the pupil and is focussed by the cornea and lens to form sharp images of the objects on the retina, the network of neurons that covers the back of the eye and that contains the receptors for vision
2 types of visual receptors
Rods
Cones
Outer segments
Part of the receptor that contains light-sensitive chemicals called visual pigments that react to light and trigger electrical signals
Fovea
Only contains cones (when we look at an object, the objects image falls on the fovea)
Peripheral retina
Includes all of the retina outside of the fovea, contains both rods and cones
Macular degeneration
Common in older people
Destroys the cone rich fovea and a small area surrounding it, which creates a blind spot when seeing an object (loses sight of the object)
Retina pigmentosa
Degeneration of the retina that is passed from one generation to the next, attacks peripheral rod receptors and results in poor vision in the peripheral vision field
Blind spot
A spot where there is an absence of receptors where the nerve fibers leave the eye
2-element optical system
cornea and lens
Cornea
Transparent covering of the front of the eye
-accounts for 80 percent of the eye’s focussing power
Lens
supplies remaining 20% of focussing power
-can change it shapes to adjust focus for objects at various distances
Accommodation
Change in the len’s shape that occurs when the ciliary muscles at the front of the eye tighten and increase the curvature of the lens so it gets thicker
Presbyopia
Unable to accommodate enough to see objects (due to hardening of lens and weakening of muscles)
myopia (nearsightnedness)
an inability to see distant objects clearly (light rays come to focus in front of the retina)
Refractive myopia
the cornea and or the lns bends the light too much
Axial myopia
In which the eyeball is too long
Hyperopia (farsightedness)
Can see distant objects clearly but have trouble seeing nearby objects because the focus point for parallel rays of light is located behind the retina, usually due to too small of an eyeball
Transduction
The transformation of one form of energy into another form of energy
Visual pigments have two parts
Long protein called Opsin
Small light sensitive component called retinal
Isomerization
The retinal changing shape due to the pigment molecule absorbing light