Wavelength
-distance between two consecutive crests or troughs of a wave
-color
amplitude
-height of a wave from midpoint of crest or trough
-brightness
frequency
-numvber of wave cycles passing a point per second
-energy
electromagnetic spectrum - range of human vision
red - longer wavelength, lower frequency, lower energy
violet - shorter wavelength, higher frequency, higher energy
Parts of the eye:
iris
opening in iris
Parts of the eye:
cornea
transparent, dome shaped covering, bends light
Parts of the eye:
msucles
contracts lens
Parts of the eye:
lens
flexible, behind iris, focuses light onto retina
Parts of the eye:
retina
light-sensitive back layer of the eye, contains photoreceptors; site of transduction
Parts of the eye:
optic nerve
carries signal from retina to brian
Anatomy of the eye: Photoreceptors
Five layers of the Retina
- Retinal ganglion cell layer
- Amacrine cell layer
- Bipolar layer
- Horizontal layer
- Photoreceptor layer
- Rods
- Cones
Anatomy of the eye: Photoreceptors
photoreceptors
rods and cones
Anatomy of the eye: Photoreceptors
rods
120 million per retina
respond to faint light
Anatomy of the eye: Photoreceptors
cones
6 million per retina
essential for color vision & more useful in bright light
90% of the brains visual input
Anatomy of the eye: Fovea and Peripheral Vision
Fovea
-central portion of the retina
- packed tight with receptor
- high density of cones
- each cone has a direct line to brain, specificty to allow for exact location of input
- responsible for visual acuity
- nearly free of ganglion axons and blood vessels
- vision is dominated by input from cones in fovea
Anatomy of the eye: Fovea and Peripheral Vision
Periphery
-region of the retina that has a greater number of rods
- rods converge into ganglion and bipolar cells
- detailed vision is less in peripheral vision
- allows for the greater perception of much fainter light in peripheral vision
Anatomy of the eye: Fovea and Peripheral Vision
Fovea
one-to-one convergence
Anatomy of the eye: Fovea and Peripheral Vision
Periphery
rods converge into ganglion and bipolar cells
-signal isn’t as clear because more rods than cells
Phototransduction
photopigments
-light sensitive molecules found in rods and cones of retina
-absorb light waves and act as NTs
VIsual Pathways for the Brain
optic nerve
PNS
VIsual Pathways for the Brain
optic chiasm
cross over for some nerves
VIsual Pathways for the Brain
optic tract
CNS
VIsual Pathways for the Brain
left visual field
-temporal hemiretina of left eye (contralateral)
-nasal hemiretina of right eye (ipsilateral)
-left visual field is delivered to right lateral geniculate nucleaus and right visual cortex
