Question

Involuntary muscle fibers are unique of
A. Diaphragm; eye muscles; intercostal muscles
B. Urinary bladder; blood vessels
C. Both A and B
D. None of the above

Answer 1

Hint: Muscles can function normally either under volitional control or without conscious control. Muscles that can be controlled at will are called voluntary muscles. Those who are not under the control of the will are called involuntary muscles.

Complete answer:
Involuntary muscles are of two types’ Smooth muscle and cardiac muscle.
Smooth muscle-These fibers or muscle cells are elongated and spindle-shaped. Each fiber contains an oval nucleus surrounded by cytoplasm (sarcoplasm). In the cytoplasm, myofibrils are located elongated. There is no sarcolemma, but the fibers are covered by a plasma membrane.
 These muscles aid in peristaltic movements that occur in the tubular intestine. The actions of these muscles are controlled by the autonomic nervous system and therefore not under the control of animal desires.
Smooth muscles are located in the back of the oesophagus, stomach, intestines, lungs, urogenital tract, bladder, blood vessels, iris, skin dermis, and hair retaining muscles. Smooth muscle never connects to the skeleton.
Cardiac muscles: The heart muscles are located on the wall of the heart and in the walls of the large veins (for example, pulmonary vein and superior vena cava) through which these veins enter the heart. Each fiber is a long, cylindrical structure with a specific sarcolemma. The fibers are mononuclear and the nucleus is close to the center. The fibers have several lateral branches, called oblique bridges, to form a shortening network. Myofibrils have alternating faint dark and light bands across them.
Now let’s come to the question
Diaphragm, eye muscles, Urinary bladder and blood vessels all the examples of smooth muscles. So they all are made up of involuntary muscles fibers.

Hence, the correct answer is option (C).

Note: The part of the peripheral nervous system that deals with the involuntary work of smooth muscles and the heart is the autonomic nervous system. The autonomic nervous system stimulates these involuntary muscles.