PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Bioelectricity, the senses and the physics of the body · Bioelectricity, the senses and the physics of the body
Forces, Machines and Signals, Ch Muscle, heart and the fields outside the body
Problem
A slow (type I) postural muscle fibre, stimulated once, produces a single twitch: tension rises and falls back to baseline over about 100ms.
((a)) Estimate the stimulation frequency at which successive twitches first start to fuse (the interval between impulses becomes shorter than the twitch itself).
((b)) Estimate the stimulation frequency needed for a fully fused tetanus, taking full fusion to require the interval between impulses to be no more than about a third of the twitch duration.
((c)) State briefly, in terms of calcium, why a fibre held at the frequency of part (b) develops several times the force of a single twitch rather than a train of separate twitches.