Visual acuity is greatest at the fovea because it contains
Correct answer: C. densely packed cones, each with its own connection to the optic nerve
- A. only rods, packed very closely
- B. no photoreceptors at all
- C. densely packed cones, each with its own connection to the optic nerve
- D. the point where the optic nerve leaves the eye
Explanation
At the fovea the cones are crowded together and each has a private line to the brain, so two nearby points of light stimulate two separate pathways and are seen as separate. Rods share connections, which improves sensitivity but destroys detail. The place with no photoreceptors is the blind spot, where the optic nerve leaves, and nothing falling there is seen at all.
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About Receptors
Receptors are specialized cells or proteins that detect stimuli such as light, sound, pressure, temperature and chemicals, then initiate responses through sensory or hormonal pathways. Questions distinguish sensory receptors from effectors, compare receptor types, and examine stimulus conversion into nerve impulses, including the roles of rods, cones, chemoreceptors and mechanoreceptors.
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