Question

The smooth sustained contraction of a muscle due to the fusion of many twitches is called as
A. Tendon
B. Tetanus
C. Muscular fatigue
D. Rigor mortis

Answer 1

When our any body part is deeply cut by anything, we go to the doctor for an injection which helps our muscles to avoid twitching – this is the hint for this answer.

Complete answer:
Tendon is a connective tissue that binds a bone to a muscle. This is made up of collagen and it is very similar to ligaments.
If a repeated and rapid stimulus is given to a muscle, the result will be an amplified muscle contraction, which is sustained in nature. This is called tetanus. When the stimulus is stronger than before and frequency of giving stimulus is very high, the muscle fibers do not get time for recovery and the refractory period is also low. The response is the summation of applied stimulus; as a result muscle fibre twitches.
Muscular fatigues are a symptom that decreases the ability of a muscle to perform. It can be an effect of vigorous exercise or different stages of muscle contraction. During heavy exercise, muscles need a high amount of oxygen for its contraction. But the time for muscle contraction is reduced and not enough oxygen can be supplied to the muscle by blood. As a result, muscles start anaerobic metabolism of glucose and produce lactic acid as the end product which gets stored in the muscle and causes fatigue.
Rigor mortis is a post-mortem change that is the result of stiffening of the muscles of the body due to physio-chemical changes in the body. It helps to determine the timing of death in the post-mortem analysis.

So, here the correct answer is option B. Tetanus.

Note: Refractory period is a period of time after giving a stimulus, in which muscle or nerve fibres are unable to respond to the next stimulus.