Recording of simple muscle twitch/ Cardiogram – demonstration.

 Recording of simple muscle twitch/ Cardiogram – demonstration. 

(Virtual frog/ computer-generated) (Analysis of given graph of Frog- muscle twitch or cardiogram In the examination

Equipment and reagents required: 

1.     Frogs ( For gastrocnemius muscle)
2.     Pithing needle
3.      Frog board or tray, pins
4.     Kymogram apparatus to record muscle contraction:
5.     Thread
6.     Pointer
7.     Stimulator
8.     Timer
9.     Ruler

10.    Weights

 Ringer's solution  (for 2l of distilled water)

3g of NaCl, 

0.28g of KCl, 

0.3g of CaCl22h2o,

 0.4g of NaHCO3 

 Collection of Gastrocnemius muscle of Frog  

    1.    Pith the frog with a pithing needle.  

2.  The frog's entire central nervous system brain and spinal cord) has been destroyed by pithing. As a result, they cannot feel pain.

3.   Remove the skin from one leg and thigh  by cutting the skin around the thigh.

4.   Locate the gastrocnemius muscle.

5.  Keep the frog's tissues moist with Ringer's solution during the remainder of the exercise.

6.   Cut the sciatic nerve as proximally to the body.

7.  Cut the thigh muscles first near their origin on the pelvic girdle and then, just above the knee (Figure 1d; be careful not to cut the gastrocnemius muscle or the sciatic nerve!).

8.      Separate and free the gastrocnemius muscle from the other muscle of the frog's leg.

9.       Locate the Achilles tendon (Figure). Tie a piece of thread about 15 cm long (6 inches) around its lowest end and then cut the tendon at the point between the thread and the animal's heel bone.

11.    Cut the femur bone to about 2.5cm

12.     Put the muscle in muscle chamber containing  Ringer's solution.

13.     Run the thread, which is tied to the tendon through the pulley and attach its end to the lever.

14.     Adjust the thread tension by moving the transducer up or down, until the lever is horizontal. Make sure that the thread is aligned at a 90-degree angle to the rotating drum with fixed paper  

 Fig Kymogram with gastrocnemius muscle

 

A SINGLE / SIMPLE 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.

Result 

The given graph of simple muscle twitch  shows three phages: 

The phages of muscle contraction 

1. Latent period              - A-B   : Time taken to spread of current in the muscle and                                                              release    of  calcium⁺⁺ at neuro-muscular junction 

-2.Contraction period    - B-C     :Muscle undergoes Contraction 

3.Relaxation period        - C-D    : Muscle relax and under and undergoes it's original  

                                                         position