Visual System Flashcards
Rods
Sensitive to low intensity light; most numerous
Cones
Sensitive to higher levels of light; found in the fovea; provide for greatest acuity and color vision
Photoreceptor layer
When light strikes, breaks down molecules of photopigment; briefly hyperpolarizes the membrane of photoreceptor (releasing less neurotransmitter)
Bipolar layer
Decrease in neurotransmitter depolarizes the membrane of the bipolar cell (causing it to release more neurotransmitter)
Ganglion layer
Release of neurotransmitter excites ganglion cells that send excitatory messages to the brain, increasing its firing rate
Optic chiasm
A cross-shaped connection between the optic nerves, located below the base of the brain, just anterior to the pituitary gland
Dorsal lateral geniculate nucleus (LGN)
A group of cell bodies within the lateral geniculate body of the thalamus; receives inputs from the retina and projects to the primary visual cortex
Dorsal stream of vision
Extends to the posterior parietal cortex; involved in perception of spatial location (where it is; movement)
Ventral stream of vision
Extends to the inferior temporal cortex; involved in perception of form (what it is; color)
Magnocellular layers (LGN)
Sensitive to movement, depth perception, not to color
Parvocelluar layers (LGN)
Associated with receiving information from red and green cones
Koniocellular sublayers (LGN)
Associated with receiving information from blue cones
Simple cells
Excite at one point in the receptive field but inhibit when the stimulus changes orientation
Complex cells
Excite at one point but continue to respond when the stimulus changes orientation
Cerebral achromatopsia
Vision without color; inability to discriminate hues leading to loss of color vision; caused by damage to V8 area of visual associated cortex
