Activity 4 of the Skeletal Muscle Physiology virtual lab. Raise the stimulus rate from unfused to fused tetanus and maximal tetanic tension. 50 stimuli/s give…
Background
As the stimulus frequency rises, twitches overlap more and more. In unfused (incomplete) tetanus the muscle relaxes partly between stimuli, so the trace is a wavy plateau. In fused (complete) tetanus the stimuli come so fast that the peaks and valleys merge into a smooth line.
Beyond a certain frequency force stops increasing: the maximal tetanic tension, several times the force of a single twitch.
Steps
Set the voltage to 8.5 V and the stimulus rate to 50 stimuli/s. Click Multiple Stimulus, let it run, then Record Data.
Increase the rate to 130 stimuli/s, click Multiple Stimulus and record.
Click Clear Tracings. Increase the rate to 140 stimuli/s, stimulate and record.
Increase the rate by 2 stimuli/s at a time up to 150, stimulating and recording each time.
Click Plot Data to see force against stimulus rate.
What you should find
50 stimuli/s gives unfused tetanus, a wavy plateau. By 130 stimuli/s the trace is smooth: fused tetanus. From 140 to 150 stimuli/s force barely rises, then stops rising: maximal tetanic tension, about 2.5 times the twitch force.
Check your understanding
At 50 stimuli/s the trace rises to a wavy plateau. This is:
Fused (complete) tetanus is:
Compared with a single maximal twitch, maximal tetanic tension is: