chapter 5 Sensation & Perception

Cells optic nerve bipolar cells rods and cones the

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Unformatted text preview: too far from the lens; causes eye ball to become shorter Age related hyperopia often corrects for myopia Photoreceptors:TheRodsandCones - The retina is a multilayered screen that contains specialized sensory neurons - There 2 types of light receptors known as rods and cones 120 million rods and 6 million cones - Rods function best in dim light and are primarily black and white; about 500 times more sensitive to light than cones; - Cones are color receptors and functions best in bright illumination - Humans have rods are found throughout the retina except in the fovea, a small area in the center of the retina that contains only cones - Cones decrease in concentration the further from the center it is - Light  ­> axons of the ganglion cells (optic nerve) ­> bipolar cells  ­> rods and cones - The light sensitive parts of the neuron points away from the light source, seeing only a fraction of the light entering - Many rods connect to 1 bipolar cell where they can combine their electricity to fire it It's easier to see dim light if you look slightly to one side so that the image doesn't fall on the fovea - Many cones also share bipolar cells - In the fovea, each cone has their own private line to a single bipolar cell, which results in visual acuity, our ability to see fine detail when images are projected directly onto the fovea Psych 1000 My Notes Page 30 fovea Some birds have 2 fovea to see very fine details on the ground Axons of the ganglion cells exit through the back of the eye not far from the fovea, producing a blindspot where there are no photoreceptors, but is ordinarily undetectable because the mind fills in the missing information VisualTransduction:FromLighttoNerveImpulses - Transduction is when a stimulus is converted into nerve impulses - Photopigments (proteins) in rods and cones translate light into nerve impulses Absorption of light changes the rate of neurotransmitter release at the receptor's synapse with the bipolar cells; then to the ganglion cells where it is transmitted to the thalamus to be routed to the visual cortex of the brain BrightnessVisionandDarkAdaptations...
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