Question

Identify true (T) and (F) among the following statements and choose the correct option:
(i) Smooth muscle fibers are uninucleate and involuntary.
(ii) Due to presence of very few gap junctions, the cardiac muscles contract together as a unit.
(iii) Skeletal muscles fibers are syncytial and appear striated.
(iv) Smooth muscle fibers have striations and appear fusiform.

• A. (i – T), (ii – T), (iii – F), (iv – F)
• B. (i – T), (ii – F), (iii – T), (iv – F)
• C. (i – F), (ii – T), (iii – F), (iv – T)
• D. (i – T), (ii – T), (iii – T), (iv – F)

Answer 1

Answer: (B)

Skeletal muscles cylindrical and unbranched and are present in association with bones. They have more than one nucleus. Cross striations are present in them. Because of striations, dark and light bands appear in them. They are supplied by somatic nerves only, hence, they are voluntary and can be controlled by the will. They are unable to divide. Skeletal muscles are found in wall of internal organs, blood vessels, stomach, etc. Cardiac Muscles are branched, involuntary muscles present only in the heart. They are uninucleate. They are striated muscles because of the presence of intercalated discs that connects cardiac cells and helps them to perform as a single unit.

Cardiac muscles are both neurogenic and myogenic, hence, they show Auto-rhythmicity. Refractory period is the interval between two contraction. In cardiac tissue, there is a large diastolic phase or the resting, hence they never undergo fatigue. Smooth muscles, also known as visceral muscles are spindle shaped, unbranched muscles. They are involuntary in function. They have tapering ends and are uninucleate. They are supplied by Autonomic Nervous system, hence are involuntary in nature. Smooth muscles have cell junctions like gap junctions which help in the synchronized contractions. They are also known as Single Unit muscle. They are found in iris, oesophagus, urinary bladder, etc.