eye - begins w/ capture of light energy by photoreceptors
- eyespot - predecessor to the eye
- cluster of photoreceptors
- sensitive to light, but cannot form images
- sclera - white of the eye, made of connective tissue
- light enters eye through transparent cornea
- iris - colored portion of eye
- can decrease size of pupil (opening)
- lens focuses image onto the retina on the back of the eye
- light has to pass layer of bipolar cells and ganglion to reach rods/cones
- rods - photoreceptor for black/white vision
- rhodopsin - photopigment in rods
- cones - photoreceptor for color vision
- found mostly in fovea (central region of retina)
- photopsin - photopigment in cones
- 3 different cones >> 3 color sensitivities (blue, green, red)
- dark >> photoreceptors release neurotransmitter that inhibits bipolar neurons >> less action potential goes to brain
- occipital lobe of brain interprets messages from the eye
- blind spot - where nerves come out of the eye, leading to the brain
- myopic (near-sighted) - image focused in front of fovea
- hyperopic (far-sighted) - image focused behind fovea
- color blindness - sex-linked trait
- due to lack of certain type of cones
- trichromats - people w/ normal color vision
- binocular vision - ability to see 3D images and sense depth
- due to 2 eyes viewing object from different angles
- less binocular vision >> larger overall field of view
other sensory experiences - other parts of electromagnetic spectrum used to sense environment
- heat - wavelengths longer than visible light
- poor environmental stimulus in water
- pit viper - only vertebrate known to sense infrared radiation
- electricity - good environmental stimulus in water
- all aquatic animals general electrical currents from muscle mov’t
- magnetism - eels, sharks, bees, birds navigate according to earth’s magnetic lines
- used in migration
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