Muscles response to changes in stimulus frequency

Describe the phenomenon known as temporal, or wave summation

Two identical stimuli are delivered to a muscle in rapid succession. The second twitch will be stronger than thr first. The second twitch appears to ride the shoulders of the first

why does temporal summation occur?

The second contraction begins before the muscle has completely relaxed.

In temporal summation, why is the second contraction stronger

Even more calcium is sent to the cytosol and because the muscle is already partially contracted. The contractions are added together

Will temporal summation occur is the second stimulus arrives before the repolarization is complete

No. it will honor the refractory period

What happens if a muscle is stimulated at an increasingly faster rate

1) the relaxation time between contractions becomes shorter and shorter

2) Calcium ion concentration in the cytosol rises

3) the degree of wave summation becomes greater and greater progressing to a sustained but quivering contraction referred to as unfused or incomplete tetanus

4) muscle tension increases to its maximum, reaching a sustained plateau known as fused, or complete, tetanus

What is unfused (incomplete) tetanus

some relaxation occurs between contractions

What is fused (complete) tetanus?

A state where muscle tension reaches maximum and contractions fuse into one smooth, sustained contraction plateau.