A SINGLE MUSCLE TWITCH AND
TETANIC CONTRACTION
Li Jingxin
Physiologcal Department
A SINGLE MUSCLE TWITCH
• When a muscle is stimulated, it contracts
after a latent period and this is immediately
followed by relaxation, this is called single
muscle twitch.
Start stimulating
2
3
1
1.latent period
2.contraction period
3.relaxation period
TETANIC CONTRACTION
• When a muscle is stimulated at very high
frequency(100/s), the successive
contractions completely fuse together and
cannot be distinguished one from the other.
This state of sustained contraction is called
Tetanization.
Prepare a nerve and muscle
preparation
Sciatic nerve-gastrocnemius of frog
femur
Quadriceps femoris
biceps femoris
Semimembranous
muscle
biceps femoris
semimembranous
muscle
procedure
1.fix the knee joint with the help of
pins
2.tie the tendon and cut it below the
thread
3. cut all the structures below the
knee joint except gastrocnemius
muscle
• 4.connect the tendon to tension transducer
with hook of clip
• 5. Place the nerve over electrodes
Tension transducer
Sciatic nerve-gastrocnemius muscle preparation
or Powerlab
Stimulus output
Set up stimulator
• Open the computer
double click “chart for
windows”
• Set up select “stimulator” :Mode “pulse” ; select
“set number of pulses 10 or15”
• Select “ stimulator panel”:frequency 1;pulse
duration 1ms;Amplitude 3v
• Select “Even marker” select “channel 2”
• Switch on “stimulator” ,Adjust “ sampling
velocity and sensitivity” and obtain a normal
curve.
Observation
• 1. Increase frequency 6 stimuli/second
• 2.Go on increasing frequency
15stimuli/second
IMPORTANT QUESTIONS
• 1.What is a single
muscle contraction or
twitch? What does it
consist of?
• 2.what is TETANIC
CONTRACTION? What is
its cause?