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Ch. 10- Sensory Physiology (The Eye and Vision)
what is vision?
the translation of reflected light into a mental image
what do photoreceptors of the eye do?
transduce light energy into an electrical signal that passes to visual cortex for processing
what alters the amount of light entering the eye?
the changing size of the pupil
what happens after light enters the eye?
light waves are focused by the lens, whose shape is adjusted by contracting or relaxing the ciliary muscle
what do photoreceptors of the retina do?
convert light into electrical energy
what do signals pass through?
bipolar neurons to ganglion cells, whose axons form the optic nerve
what has the most acute vision? and why?
fovea; it has the smallest receptive field for colors
what are rods responsible for?
monochromatic nighttime vision
what are cones responsible for?
the high-acuity vision and color vision during the daytime
what do light-sensitive visual pigments in photoreceptors do?
convert light energy into a change in membrane potential
what is rhodopsin?
visual pigment in rods
how many different visual pigments do cones have?
what is rhodopsin composed of?
opsin and retinal
what happens in the absence of light?
retinal binds snugly to opsin
how does light transmission occur?
via: cornea, lens, rods, optic disc, optic chiasm, lateral geniculate body of the thalamus and visceral cortex of the occipital lobe
what does 20/20 vision mean?
that you can see objects at 20 feet that individuals with normal eyesight can see at 20 feet
what do we use in order to have a detailed map of sensory receptors?
two-point discrimination test