Final answer:
Mydriatics dilate the pupil by acting on the sympathetic system's control over radial iris muscles, while cycloplegics both dilate the pupil and paralyze the ciliary muscle, preventing eye accommodation.
Step-by-step explanation:
Mydriatics and cycloplegics are classes of medications used in ophthalmology. Mydriatics are drugs that dilate the pupil, primarily by acting on the radial fibers of the iris smooth muscle, which are under the control of the sympathetic nervous system. When norepinephrine or agents like phenylephrine bind to adrenergic receptors on these muscles, pupillary dilation, or mydriasis, occurs. Mydriatics such as phenylephrine are often used during eye exams to provide a better view of the interior structures of the eye.
On the other hand, cycloplegics not only dilate the pupil but also paralyze the ciliary muscle. This action prevents the eye from accommodating, or focusing on nearby objects, which is essential for certain types of eye examinations. By paralyzing the muscle, cycloplegics can help in the diagnosis of refractive errors and in the treatment of certain eye conditions.
Therefore, the correct answer to the question, 'What are Mydratics and Cycloplegics?' is A): Mydriatics dilate the pupil, while Cycloplegics paralyze the ciliary muscle.