Question

Why can red muscle fibres work for a longer period continuously.

Answer 1

Red muscles are the muscles that have dense capillaries that are rich in myoglobin and mitochondria. Red muscles are red in colour. During contraction, the oxyhemoglobin releases oxygen which is utilised for muscle contraction.

Complete answer:
Red muscles are the skeletal muscles which perform many functions in the body. They are red in appearance due to the presence of dense capillaries and presence of myoglobin and mitochondria. The function of myoglobin is to bind and store oxygen as oxymyoglobin. This oxymyoglobin releases oxygen which is utilised during muscle contraction.

Characteristic of red muscles:
- These muscles can work for a longer period of time without getting fatigue. This is because they have abundant mitochondria and myoglobin which can bind and store oxygen so that they can perform aerobic respiration.
- These muscles rely on oxygen to produce energy so these muscles are used during strenuous activities. - The glycogen and the enzymes required for glycolysis provides the required energy.
- The diameter of these muscles is smaller as compared to the other muscles.
- These muscles exhibit a slow rate of contraction.
- Examples of red muscle are the extensor muscles.
- These muscles do not accumulate lactic acid. Hence do not get fatigue.

Note: The other type of muscle fibres is called the white muscles which is present in the white of the eye. These muscles have less myoglobin and mitochondria. Hence, they appear white. These muscles perform anaerobic oxidation due to which lactic acid accumulation takes place. They show a higher rate of contraction. Due to the lactic acid accumulation, these muscles get fatigued easily.