Question

Describe the different types of muscle fibres.

Answer 1

There are two types of muscle fibres - red muscle fibres and white muscle fibres.

1. Red muscle fibres have small diameter. These muscle fibres are dark red in colour due to the presence of red haemoprotein called myoglobin. Myoglobin binds and stores oxygen as oxymyoglobin in the red fibres. Oxymyoglobin releases oxygen for utilization during muscle contraction. They have more blood capillaries, mitochondria and less sarcoplasmic reticulum. They carry out aerobic oxidation without accumulating much lactic acid. Thus, red muscles fibres can contract for a longer period without fatigue. These muscle fibres have slow rate of contraction for longer periods. Examples are extensor muscles of the human back, flight muscles of kites.

2. White muscle fibres have larger diameter. These muscles fibres are lighter in colour they do not have myoglobin. They have less blood capillaries, mitochondria and more sarcoplasmic reticulum. They carry out anaerobic oxidation for energy production and accumulate lactic acid in considerable amounts during strenuous work and soon get fatigued. These fibres have a fast rate of contraction for short periods. Examples are eye ball muscles, flight muscles of sparrow.