Question

Though vertebrates are aerobes, their .....(i)..... show anaerobic respiration during ......(ii)..... During this, ......(iii)...... of skeletal muscle fibers is broken down to release lactic acid and energy. Lactic acid, if accumulates causes muscle fatigue.
Fill up the blanks in the above paragraph and select the correct option.

• A. i- Skeletal muscles ; ii-heavy exercise ; iii-glucose
  
• B. i- Skeletal muscles ; ii-mild exercise ; iii-glycogen
  
• C. i- Skeletal muscles; ii-heavy exercise ; iii-glycogen
  
• D. i- Cardiac muscles; ii-heavy exercise ; iii-glycogen
  

Answer 1

The correct option is A i- Skeletal muscles ; ii-heavy exercise ; iii-glucose

Muscle fatigue is the reduction in force of contraction of a muscle after prolonged stimulation. In the absence of oxygen, skeletal muscle of human beings can contract for a short time, but it gets fatigued soon. This is due to the fact that in the absence of oxygen, products of glycolysis mainly lactic acid is not disposed of and accumulates in the muscles. This leads to muscle fatigue and pain in the muscles. A muscle gets fatigued sooner after a strenuous exercise than after a mild exercise. Faster breathing for sometime after a strenuous exercise supplies extra oxygen disposes off excess lactic acid and muscle fatigue disappears.

So the correct option is 'i-Skeletal muscles ; ii-heavy exercise ; iii-glucose'.