Question

In an unfused tetanus, there are small decreases in force on the force vs. time graph. What do these decreases represent?

1) they are shown alongside the repolarization phase of the action potential that stimulated the muscle
2) they represent potassium efflux from the muscle cell
3) they represent an enhanced release of calcium from the RyR
4) they represent a brief period of time where the calcium reuptake is dominating to relax the muscle

Answer 1

In an unfused tetanus, the small decreases in force represent brief periods where calcium reuptake causes the muscle to partially relax before the next stimulus arrives.

Step-by-step explanation:

The small decreases in force on the force vs. time graph during an unfused tetanus represent a brief period of time where the calcium reuptake is dominating to relax the muscle. This relaxation phase occurs as Ca++ ions are pumped out of the sarcoplasm into the sarcoplasmic reticulum (SR), and cross-bridge cycling stops. In an unfused tetanus, these periods are not long enough for the muscle to completely relax, and the muscle remains in a state of partial contraction.