Question

Which muscles act involuntarily?

• A. i and ii
• B. ii and iii
• C. iii and iv
• D. i and iv

Answer 1

The correct option is B

ii and iii

The correct option is B.

Explanation for the correct option:

Option B:

1. Involuntary muscles are muscles that contract without conscious control.
2. These muscles are present in the internal organs that are involved in slow and involuntary movements.
3. Smooth muscles are involuntary muscles that are devoid of cross stripes. They are narrow spindle-shaped cells with a large centrally located nucleus.
4. These smooth muscles are present in the posterior end of the esophagus, stomach, intestines, blood vessels, iris, and skin dermis.
5. Cardiac muscles are smooth involuntary muscles. They are present in the heart and work without fatigue.

Explanation for the incorrect options:

Option A:

1. Striated muscles are voluntary muscles that are capable of contracting voluntarily and are controlled by the brain.
2. These are highly organized tissues and are involved in key processes such as respiration, locomotion, and posture.

Option C:

Skeletal muscles are muscles that are attached to bones and are involved in the functioning of the body.

Option D:

1. Striated muscles are voluntary muscles that are capable of contracting voluntarily and are controlled by the brain.
2. These are highly organized tissues and are involved in key processes such as respiration, locomotion, and posture.
3. Skeletal muscles are muscles that are attached to bones and are involved in the functioning of the body.

Final answer: Smooth muscles and cardiac muscles are involuntary muscles.