Question

Repeated stimulation of a skeletal muscle fiber causes a sustained contraction (tetanus). Accumulation of which solute in intracellular fluid is responsible for the tetanus?

1) Na⁺
2) K⁺
3) Cl⁻
4) Mg₂⁺
5) Ca₂⁺
6) Troponin
7) Calmodulin
8) Adenosine triphosphate (ATP)

Answer 1

Tetanus in skeletal muscle fibers is caused by the accumulation of calcium ions (Ca2+) in the sarcoplasm, which allows continuous contraction until fatigue sets in.

Step-by-step explanation:

The sustained contraction of a skeletal muscle, known as tetanus, is a phenomenon where repeated stimulation leads to the non-stop shortening of muscle fibers. This continuous contraction is made possible due to the accumulation of calcium ions (Ca2+) in the sarcoplasm. When a muscle fiber receives a signal from a motor neuron, an action potential is triggered, leading to the release of calcium ions from the sarcoplasmic reticulum (SR). Calcium ions then bind to troponin, which exposes actin-binding sites allowing myosin to form cross-bridges with actin, resulting in muscle contraction. As long as calcium ions are present in the sarcoplasm, and ATP is available for energy, the muscle fiber remains contracted, producing tetanus until the muscle fatigues.