Question

multiple choice 2 points

the sympathetic division of the autonomic nervous system has what effect on the muscles of the eye?

decrease in bulging of lens to prepare for close vision
decrease in bulging of lens to prepare for distant vision
no effect at all
stimulates to increase bulging of the lens for close up vision

Explanation:

Analyze autonomic control of the eye

The question asks about the effect of the Sympathetic Nervous System on the muscles of the eye, specifically regarding lens shape. The autonomic nervous system controls the ciliary muscle, which regulates the curvature (bulging) of the lens.

Understand ciliary muscle mechanics

The ciliary muscle is a circular ring of smooth muscle.

• When the ciliary muscle contracts (parasympathetic stimulation), tension on the suspensory ligaments (zonules) decreases, allowing the elastic lens to bulge (become more spherical) for close vision.
• When the ciliary muscle relaxes (sympathetic stimulation), tension on the suspensory ligaments increases, pulling the lens flat (decreasing its bulging) to focus on distant objects.

Evaluate the given options

• decrease in bulging of lens to prepare for close vision: Incorrect, flattening the lens prepares the eye for distant vision.
• decrease in bulging of lens to prepare for distant vision: Correct, sympathetic activation relaxes the ciliary muscle, flattening the lens (decreasing bulging) for distant vision.
• no effect at all: Incorrect, the sympathetic system actively modulates ciliary muscle tone.
• stimulates to increase bulging of the lens for close up vision: Incorrect, this describes parasympathetic stimulation (Accommodation Reflex).

Answer:

• decrease in bulging of lens to prepare for close vision
• decrease in bulging of lens to prepare for distant vision (Correct answer)
• no effect at all
• stimulates to increase bulging of the lens for close up vision