A smooth, sustained contraction resulting from high-frequency stimulation is known as:

A smooth, sustained contraction resulting from high-frequency stimulation is known as:

• A. Tetanus
• B. Twitch
• C. Rigor mortis
• D. Spasm

Answer: (A)

High-frequency stimulation causes multiple muscle fibers to fire so quickly that individual twitches fuse into one continuous contraction. This smooth, sustained contraction is tetanus. The mechanism is that calcium stays elevated in the muscle fiber due to rapid, repeated action potentials, so cross-bridges keep cycling without a return to baseline, making the contraction appear as a single, steady force. If the stimulus is even higher, you get complete (fused) tetanus, where no relaxation is seen between impulses; at slightly lower frequencies you get incomplete tetanus, where contractions begin to fuse but are not completely smooth yet. A twitch is just a single brief contraction from one stimulus. Rigor mortis is the stiffening that occurs after death when ATP is gone and cross-bridges can’t detach. Spasm is a sudden, involuntary contraction that isn’t necessarily sustained or fused like tetanus. So the sustained, smooth contraction described points to tetanus.

High-frequency stimulation causes multiple muscle fibers to fire so quickly that individual twitches fuse into one continuous contraction. This smooth, sustained contraction is tetanus. The mechanism is that calcium stays elevated in the muscle fiber due to rapid, repeated action potentials, so cross-bridges keep cycling without a return to baseline, making the contraction appear as a single, steady force. If the stimulus is even higher, you get complete (fused) tetanus, where no relaxation is seen between impulses; at slightly lower frequencies you get incomplete tetanus, where contractions begin to fuse but are not completely smooth yet.

A twitch is just a single brief contraction from one stimulus. Rigor mortis is the stiffening that occurs after death when ATP is gone and cross-bridges can’t detach. Spasm is a sudden, involuntary contraction that isn’t necessarily sustained or fused like tetanus. So the sustained, smooth contraction described points to tetanus.