Question

Calveoli in smooth muscles are representative of

• A. T tubule of skeletal muscle
• B. Troponin of Skeletal muscle
• C. Tropomyosin of Skeletal muscle
• D. Actin of Skeletal muscle

Hint:

Smooth muscles lack T-tubules and troponin, relying instead on caveolae for calcium entry and calmodulin for intracellular calcium binding.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Unlike skeletal muscle, smooth muscle has a less organized internal membrane system and lacks a well-developed Transverse Tubule (T-tubule) network.

Step 3: Detailed Explanation:
In smooth muscle cells, the sarcolemma exhibits small, pouch-like invaginations called caveolae (erroneously spelled "calveoli" in some texts).
These caveolae contain a high concentration of extracellular calcium ions and are positioned close to the sarcoplasmic reticulum.
When an action potential depolarizes the smooth muscle membrane, caveolae facilitate the entry of calcium ions into the cell.
Thus, caveolae serve as the functional equivalents of the T-tubules found in skeletal and cardiac muscle fibers, helping to coordinate calcium release and contraction.

Step 4: Final Answer
Caveolae in smooth muscle represent the functional counterpart to the T-tubules of skeletal muscle.