Q91. In adult athletes, muscles grow larger when exercised and are capable of
regeneration after injury. This is due to proliferation and differentiation of
(A) satellite cells
(B) myelin sheath
(C) oxyntic cells
(D) choanocytes

Answer: (A) satellite cells

Option Analysis

Satellite cells are muscle stem cells located between the basal lamina and sarcolemma of muscle fibers. They proliferate and differentiate in response to exercise-induced damage or mechanical loading, fusing with existing fibers to add myonuclei, which supports hypertrophy in adult athletes and enables regeneration after injury.​

Myelin sheath insulates neuronal axons to speed nerve impulse conduction but plays no role in skeletal muscle growth or repair.​

Oxyntic cells, or parietal cells, in gastric glands secrete hydrochloric acid and intrinsic factor for digestion and B12 absorption, unrelated to muscle tissue.​

Choanocytes, or collar cells, in sponges generate water currents for feeding and circulation, with no function in vertebrate muscle.​

In adult athletes, muscles grow larger during intense exercise and regenerate effectively after injury due to the proliferation and differentiation of satellite cells. These stem cells are essential for skeletal muscle hypertrophy and repair, making them a key topic in molecular biology and CSIR NET Life Sciences examinations.​

What Are Satellite Cells?

Satellite cells reside in a quiescent state under the basal lamina of adult skeletal muscle fibers. Exercise triggers their activation, leading to proliferation into myoblasts that differentiate and fuse with myofibers, adding myonuclei to support protein synthesis for hypertrophy.​

• Resistance training increases satellite cell numbers, especially in type II fibers, correlating with muscle size gains.​

• They self-renew to maintain the stem cell pool for repeated regeneration cycles.​

Muscle Growth in Athletes

Hypertrophy occurs when mechanical overload from training activates satellite cells, enabling myonuclear accretion beyond what existing nuclei can sustain. Studies show satellite cell depletion prevents overload-induced growth, confirming their necessity in humans and rodents.​

Training volume influences this: high-volume resistance exercise boosts satellite cell expansion more than low-volume, aiding athlete performance.​

Regeneration After Injury

Post-injury, satellite cells proliferate rapidly, differentiate into new myofibers, or fuse to repair damaged ones, restoring function. This process mirrors developmental myogenesis but relies on these adult stem cells.​

Without satellite cells, regeneration fails, as shown in ablation models.​

Why Not Other Options?

Myelin sheath relates to neural insulation, not muscle. Oxyntic cells handle gastric acid secretion. Choanocytes function in sponge filtration. Only satellite cells fit muscle contexts.​