1. A SINGLE MUSCLE TWITCH AND TETANIC CONTRACTION
Li Jingxin
Physiologcal Department

2. 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

3. 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.

5. Prepare a nerve and muscle preparation
Sciatic nerve-gastrocnemius of frog

6. femur biceps femoris Quadriceps femoris semimembranous muscle

7. 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

9. 4.connect the tendon to tension transducer with hook of clip
5. Place the nerve over electrodes

10. Tension transducer Stimulus output
Sciatic nerve-gastrocnemius muscle preparation
or Powerlab
Stimulus output

11. 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.

12. Observation 1. Increase frequency 6 stimuli/second
2.Go on increasing frequency stimuli/second

13. 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?