Bio Bases Exam II Flashcards
What percentage of the cerebral cortex plays a direct role in processing visual information
20%
Perceived color of light is determined by three dimensions. What are they
Hue: determined by wavelength, the visible spectrum displays a range of hues that our eyes detect
Saturation: Relative purity of light that is being perceived
Brightness: the intensity of the electromagnetic radiation
- an image must be focused on the ________ for us to see
retina
What is at the back of the retina
- Photoreceptors (rods and cones),
What are the three layers of the retina?
- Outermost: Ganglion cell layer
Transparent & light passes through - Middle: Bipolar layer
Transparent & light passes through - Innermost: photoreceptor layer
Transduce light
What layer of the retina transduces light?
protoreceptor
What are the 2 types of photoreceptors and describe their differences
- cones –
a. 6 million
b. provide us with most of the visual information we see
c. daytime vision
d. color sensitive (color vision)
e. greatest acuity,
f. concentrated in fovea – central area of retina that contains only cones and has greatest visual acuity - rods –
a. 120 million (20 times the amount of cones)
b. light sensitive (not color)
c. mediate vision in dim illumination
d. low activation threshold
e. peripheral vision
What is the fovea
central region of retina, mediates our most acute vision, contains only cones.
Describe the process that happens after light falls on rods and cones
They form synapses with and activate
Bipolar cells that form synapses with and activate
Ganglion cells in the optic nerve
Optic disk is where ganglion cell axon exit eye in optic nerve. Contains no photoreceptors and creates a blind spot.
What is the optic disk?
where ganglion cell axon exit eye in optic nerve. Contains no photoreceptors and creates a blind spot.
What is a receptive field?
the area in the visual field a neuron (photoreceptor) . A neuron’s (ganglion cell) receptive field is determined by the location in the retina of the photoreceptor it is connected with.
what is the optic chaism?
A. Information from each visual field crosses over at the optic chaism and projects to the opposite side of the primary visual cortex
B. neurons carrying information from medial (inner halves or nasal side) cross to contralateral hemisphere
C. (processed contralaterally)- this results in L field information going to R hemisphere and R field information going to L hemisphere throughout rest of visual system
Discuss the 6 layers of the LGN
A. 6 layers plus sublayer
B. 1 and 2 magnocellular layers (large cells)
receive input from rods and are therefore sensitive to light but not color
C. layers 3-6 are parvocellular layers (small cells)
receives input from cones, thus more sensitive to color and less to light
D. koniocellular – between each magno and parvo layer – also receives input from cones
E. each of these layers projects to a specific area in the visual (striate) cortex and the segregation of information they transmit is preserved in the cortex
F. Optic radiations project from LGN to primary visual cortex
Describe the layers of the striate cortex
layer 4 receives input from magno and parvocellular areas of lateral geniculate
layer 2 and 3 receive input from koniocellular
Blobs
color