Single and tonic contractions of muscles
Single and tonic contractions of muscles
Single and tonic contractions of a muscle can be used to observe the phenomenon of contractile response of a muscle to a stimulus.
Operation method
Single and tonic contractions of muscles
Principle
The outward sign of muscle excitation is contraction. Given a brief effective stimulus to a well-excited muscle, the muscle will undergo a single contraction, called a monocontraction. The whole process of single contraction is divided into latency, systole and diastole. The specific time can be due to different animals, different muscles and muscle function at the time of different states and different: toad gastrocnemius single contraction lasted about 0.12 seconds. If the muscle is given two successive effective stimulus. And so that the interval between the two stimuli is less than the total duration of the single contraction of the muscle, the contraction of the muscle can be summed up, the emergence of continuous contraction, known as compound contraction. When the muscle is given a series of effective stimulation, the muscle may show different forms of contraction depending on the frequency of stimulation. If the stimulus frequency is very low, the interval is greater than the total duration of a single contraction, the muscle will appear a series of single contractions. If the frequency of stimulation is increased. If the stimulus frequency is increased so that the stimulus interval is less than the total duration of a single contraction and greater than the contraction period, the muscle will show a jagged contraction waveform, known as incomplete tonic contraction. Then increase the frequency of stimulation, so that the interval between two successive stimuli is less than the contraction period of a single contraction, the muscle will be in a state of complete sustained contraction, which is called a complete tonic contraction. The amplitude of the tonic contraction is larger than that of the single contraction. And in a certain range, when the stimulus intensity and time of action is unchanged, the contraction amplitude of the muscle increases with the increase of the stimulus frequency. The contraction of skeletal muscle in the body are all tonic contraction.
Materials and Instruments
Toad Move I. Preparation of sciatic nerve gastrocnemius muscle specimen Methods refer to experiment III. The specimen was immersed in Ren's solution for 10-15 minutes. Caveat 1. Allow the specimen to rest for the same amount of time after each stimulus. (0.5 to 1 minute). The specimen was given a drop of Ren's solution. 2. Do not change the stimulus intensity during the experiment. Do not change the intensity of the stimulus. Common Problems Muscles are made up of cylindrical muscle fibers, which in turn contain a number of longitudinally oriented myofibrils, which are the devices for muscle contraction. The myogenic fibers are composed of myoblasts. In each myonule, thick myofilaments composed of myosin and thin myofilaments composed of actin-F-actin are interspersed with each other and are brought into close contact by a cross-bridge at the head end of the thick myofilaments. Muscle contraction results from the relative movement of the thick and thin myofilaments, a process regulated by Ca and requiring hydrolysis of ATP for energy. For more product details, please visit Aladdin Scientific website.
Ren's solution
Motorized tattoo drums Electronic stimulators Electromagnetic markers Universal support tables Myotomes Frog surgical equipment Petri dishes
Placement of the specimen The specimen was fixed in the actuator. The sciatic nerve is attached to the stimulating electrode. The output of the electronic stimulator is connected to the stimulating electrode of the actuator.
Adjust the experimental recording device Adjust the primary screw so that the tracing lever to the horizontal position. Make the tip of the tracing pen tangent to the surface of the striated drum.
First, find the optimal stimulation intensity. That is, choose a single stimulation method or adjust the frequency knob to the lowest electronic stimulator. Fixed transition width of 0.3 ~ 0.5ms. Start with the minimum stimulus intensity. And use the hand to turn the tattoo drum for recording. Gradually increase the stimulation intensity. The contraction amplitude of the muscle is increasing, and the stimulus intensity corresponding to the maximum contraction amplitude of the muscle is the optimal stimulus intensity. Then carry out the experiment according to the following steps.
1. Choose a single stimulus method and record it with an electrically operated tattoo drum (the fastest speed), and trace the single contraction curve. (Figure 3-3①)
2. Select double-pulse stimulation. Shorten the interval between the two stimulations (about 0.06～0.08s). Record the diastolic compound systolic curve. (Figure 3-3 ②)
3. Stimulate in the same way as 2. Further shorten the interval between two stimulations (about 0.03 to 0.04s). Record the compound contraction curve. (Figure 3-3③)
4. Select continuous stimulation at a frequency of 8 to 16 Hz and record an incomplete tonic contraction curve. (Figure 3-3④)
5. Increase the stimulation frequency to 32Hz and record a full tonic contraction curve (Figure 3-3④).
