question_answer 43)

  It is known that red muscle fibres in animals can work for longer periods of time continuously. How is this possible?

Answer:

                There are basically two kinds of muscle fibers (i) Red muscles                   (ii) White muscles Red muscles work for a longer time continuously because (i) These muscle fibres are dark red which is due to the presence of red haemoprotein called myoglobin. Myoglobin binds and stores oxygen as oxymyoglobin in the red fibres. Oxymyoglobin releases oxygen for utilisation during muscle contraction. (ii) Mitochondria are more in number, hence they work for long periods of time. (iii) Red muscles have less sarcoplasmic reticulum. (iv) They carry out considerable aerobic oxidation without accumulating much lactic acid. Thus, red muscle fibres can contract for a longer period without fatigue. (v) These muscle fibres have slow rate of contraction for long periods. e.g., extensor muscles of the human back.