Wed24November0743AM 4

Which of the following best describes the physiological properties of a fast glycolytic (fast twitch) muscle fibre?

(Please select 1 option)

Generally fatigue resistant

Small diameter to initiate short term intense contractions

Red in colour

Synthesis of ATP is brought about by anaerobic respiration This is the correct answer

High myoglobin Incorrect answer selected

Explanation

Human skeletal muscle is composed of a diverse collection of muscle fibre types. These muscle fibre types can differ histologically, biochemically and physiologically.

The biochemical classification is based on muscle fibre myosin ATPase histochemistry and split into two groups, type 1 and type II.

Type I (slow twitch) muscle fibres usually depend upon aerobic glycolytic metabolism and aerobic oxidative metabolism. They are rich in mitochondria, have a good blood supply, rich in myoglobin and are resistant to fatigue.

Type II (fast twitch) muscle fibres are thicker because they contain more motor units. They are more easily fatigued but produce short bursts of power. These are "white" muscle fibres; the capillary networks and mitochondria are less dense than type I fibres. They also have a low myoglobin content.

Type II (fast twitch) muscle fibres are subdivided into:

Type IIa - these rely on aerobic/oxidative metabolism

Type IIb - these fibres rely on anaerobic/glycolytic metabolism.

The twitch speeds of cardiac and smooth muscle are relatively slow compared with skeletal muscle.

Answer Statistics

1

5%

2

21%

3

22%

4

30%

5

24%

Times answered: 245