A smooth, sustained contraction resulting from very rapid stimulation of the muscle, in which no evidence of relaxation is seen, is called:
a. A twitch
b. Temporal summation
c. Multiple motor unit summation
d. Fused tetanus

Verified step by step guidance

Step 1: Understand the definitions of each term related to muscle contractions. A 'twitch' is a single, brief contraction and relaxation cycle in a muscle fiber following a single stimulus.

Step 2: Recognize that 'temporal summation' refers to the process where multiple stimuli occur in rapid succession, causing the muscle contractions to add together, but some relaxation still occurs between stimuli.

Step 3: Know that 'multiple motor unit summation' involves increasing the number of motor units activated to produce a stronger overall muscle contraction, but it does not describe the sustained contraction of a single fiber.

Step 4: Identify that 'fused tetanus' is a smooth, sustained muscle contraction resulting from very rapid stimulation where no relaxation is observed between stimuli, producing a continuous contraction.

Step 5: Based on these definitions, match the description of a smooth, sustained contraction with no relaxation to the correct term, which is 'fused tetanus'.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Muscle Twitch

A muscle twitch is the brief, single contraction and relaxation cycle of a muscle fiber in response to a single stimulus. It represents the simplest form of muscle contraction and is characterized by a quick rise and fall in tension.

Temporal Summation

Temporal summation occurs when a muscle is stimulated repeatedly at a frequency that allows the contractions to build on each other, increasing tension. However, some relaxation still occurs between stimuli, so the contraction is not completely smooth.

Fused Tetanus

Fused tetanus is a sustained muscle contraction resulting from very rapid stimulation where individual twitches merge, and no relaxation occurs between stimuli. This produces a smooth, continuous contraction with maximal tension.

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