Question

Which of the following types of muscle is found in the eye and are used to regulate the size of the pupil?

a. visceral muscle
b. intrinsic muscle
c. multiunit smooth muscle
d. cardiac muscle
e. skeletal muscle.

Answer 1

The muscles found in the eye that regulate the size of the pupil are known as intrinsic muscles. Thus the correct option is b.

Explanation

The muscles found in the eye that regulate the size of the pupil are known as intrinsic muscles. These muscles specifically control the iris, which adjusts the size of the pupil in response to varying light conditions.

Unlike skeletal muscles (which are under conscious control) or cardiac muscles (found in the heart), intrinsic muscles are a type of smooth muscle. They operate involuntarily, responding reflexively to stimuli, such as changes in light intensity. While visceral muscles are also a type of smooth muscle, they're associated more with internal organs' movement and function.

Multiunit smooth muscles are found in specific locations like blood vessels or the iris dilator muscles, but they don’t play a role in regulating the pupil's size. The intrinsic muscles' precise control over the pupil's diameter enables the eye to adjust rapidly to different light levels, aiding in visual clarity and protecting sensitive retinal cells from excessive light exposure.

Thus the correct option is b.

Answer 2

The muscles in the eye that regulate the size of the pupil are multiunit smooth muscles, which are a type of involuntary muscle not under conscious control (option c).

Step-by-step explanation:

The type of muscle found in the eye that is used to regulate the size of the pupil is multiunit smooth muscle. Smooth muscles, unlike skeletal and cardiac muscles, are part of the involuntary muscle group and are not under voluntary control. In the eye, these muscles adjust the pupil size to control the amount of light entering the eye. The pupil changes size through the contraction and relaxation of the smooth muscle tissue located in the iris of the eye. These muscles operate without conscious thought, making them part of the involuntary muscle group, necessary for regulating vision in response to brightness.

Hence, the answer is option c.