Question

The strength of contraction of an entire skeletal muscle is dependent on the:
A. Number of muscle fibres that contract simultaneously
B. Frequency of contraction of each muscle fibre
C. Number of active cross-bridges in each muscle fibre
D. All of the above

Answer 1

Hint:
Skeletal muscles are those muscles that are associated with skeletal organs such as bones, ligaments, tendons and cartilage. In appearance they have striations and hence they are called striated muscles. The movement of skeletal muscles is under our control as their activities are under the voluntary control of the nervous system. Thus, they are known as voluntary muscles. They are involved in locomotion and changing body posture.

Complete answer:
The muscle contraction is initiated by the motor neuron that brings the signals from the central nervous system. These motor neurons along with the muscle fibres form the motor unit. Now, the strength of muscle contraction depends upon the stimulation of these motor units. This formation of the motor unit depends upon how many motor neurons and muscle fibres that muscle are activated in a muscle. The higher the stimulation of these motor units, the stronger will be the muscle contraction. The strength of muscle contraction depends upon the summation of muscle fibres and their frequencies. Thus, the more the number of muscle fibres, the more will be their frequency and the stronger will be the muscle contraction. Muscle contraction also depends upon the active cross bridge in a muscle fibre.
Thus, the correct answer is All of the above.

Option ‘D’ is correct

Note:
The strength of muscle contraction directly depends upon the size of the cross-sectional area of muscle fibre. This means that if by excessive training the area of muscle fibres is increased by 40%, then the strength of muscle contraction will also increase by 40%.