GLOSSARY

Tetanus (muscle) in physiology refers to a sustained, fused contraction of muscle in response to high-frequency stimulation, in which twitches have no time to relax and force reaches its maximum.

Types

• Unfused (incomplete) tetanus: at moderate frequencies, force rises but oscillations and partial relaxation between stimuli are seen.
• Fused (complete) tetanus: at high frequencies, twitches fully merge and the force curve becomes smooth.

Mechanism

With repeated stimuli, calcium stays high, cross-bridges are continuously active, and the series elastic components have time to be fully stretched; tetanic force may therefore be 3–5 times the force of a single twitch.