Question

Which of the following is incorrect?
A) Cardiac muscle is striated.
B) Smooth muscle does not contain actin.
C) Skeletal muscle is considered voluntary.
D) Smooth muscle is found in the iris of the eye and the walls of the bladder.

Answer 1

Hint:
Muscle is a specialized tissue of mesodermal origin. Muscles consist of 40-50 percent of body weight. Muscles can contract, and excite. And these exhibit elasticity and extensibility.

Complete step by step answer:
Muscle tissues are the main organ for the performance of mechanical tasks of the human body. Their mechanical action is a response to nerve signals and represents the conversion of electrical and chemical energy to mechanical energy. There are 3 types of muscles: Skeletal muscles are attached to bones by tendons, cardiac muscles in the heart wall, and smooth muscles in the walls of hollow internal structures like an alimentary canal, reproductive tract, etc. So they are also called smooth muscles or nonstriated muscles. Smooth muscles contain large, amounts of actin and myosin. These filaments help in muscle contraction. Skeletal muscles are controlled voluntarily and cardiac and smooth muscles are involuntarily controlled.
Cardiac muscles are the muscles of the heart. Based on the appearance cardiac muscles are striated. The nervous system does not control the activities of cardiac muscles directly so these muscles are involuntary.
Hence the correct answer is Smooth muscle does not contain actin .

Option ‘B’ is correct

Note:
Smooth muscles are activated involuntarily so these are also called involuntary muscle tissue. The sarcoplasm contains thick and thin filaments in the ratio of 1:10. These are not orderly arranged and do not show striated patterns as in skeletal muscles. So these are also called unstriated muscle or smooth muscle