Experiments on the effect of stimulus intensity and frequency on skeletal muscle contraction
Experiments on the effect of stimulus intensity and frequency on skeletal muscle contraction
This experiment is from the official website of Zhejiang University Fine Courses
Operation method
Experiments on the effect of stimulus intensity and frequency on skeletal muscle contraction
Principle
Muscle, nerve and glandular tissues are called excitable tissues and they have greater excitability. The excitability of different tissues and cells varies; the excitability of nerve tissues is manifested as action potentials, and the excitability of muscle tissues is mainly manifested as contractile activity. Therefore, observing whether a muscle contracts can determine whether it produces excitation. Whether a stimulus can make the organization excited, not only with the form of stimulation, but also with the stimulation time, stimulation intensity, intensity - time rate of change of the three elements related to the stimulation, with a square electric pulse stimulation of the tissue, the tissue excitation is only related to the stimulation intensity, stimulation time. Square electric pulse stimulation of tissue, in a certain stimulation time (wave width), just can cause tissue excitation stimulation is called threshold stimulation, the stimulation intensity reached is called the threshold intensity, can cause the organization to occur the maximum excitement of the smallest stimulation, called the maximum stimulation, the corresponding stimulation intensity is called the maximum stimulation intensity; boundaries in the threshold stimulation and the maximum stimulation stimulation between the stimulation is called the suprathreshold stimulation, the corresponding stimulation intensity is called the suprathreshold stimulation intensity. Intensity. Stimulation of the nerve nerve cells to produce excitation, excitation along the nerve fiber conduction, through the chemical transmission of the nerve-muscle junction, so that the muscle endplate membrane endplate potential, endplate potential can cause muscle excitation (i.e., action potential), spread throughout the entire muscle fiber, and then through the excitation-contraction coupling to make the muscle fibers in the thick and thin filaments of the muscle to produce the relative slide, the macroscopic manifestation of the contraction of the muscle. The form of muscle contraction is not only related to the stimulus itself, but also related to the stimulus frequency. When the stimulus frequency is small, so that the stimulus interval is greater than the duration of a muscle contraction diastole, then the muscle contraction is manifested as a series of single contraction; increase the stimulus frequency, so that the stimulus interval is greater than the contraction time of a muscle contraction, less than the duration of a muscle contraction diastole, then the muscle produces an incomplete tonic contraction; continue to increase the frequency of the stimulus, so that the stimulus interval is less than the contraction time of a muscle contraction, then the The muscle produces a complete tonic contraction.
Materials and Instruments
Toad or frog, Ren's fluid, Tension transducer, Microcomputerized biological signal acquisition and processing system. Move 1. Simulation experiment window (Figure 1) The upper end of the gastrocnemius muscle was connected to the tension transducer with a cotton thread, and the frequency and amplitude of the gastrocnemius muscle contraction were displayed with a simulated two-channel recorder. For more product details, please visit Aladdin Scientific website.
Figure 1
2. Simulation of two-channel recorder Upper line recording gastrocnemius muscle contraction curve, lower line recording stimulus markers. Simulation recorder panel set sensitivity, displacement, paper speed adjustment buttons, the panel is equipped with a digital display box, respectively, showing the recorder on the line sensitivity, gastrocnemius muscle contraction force, experimental items, experimental time.
3. Stimulator After turning on the power switch, the buttons and switches on the stimulator panel are adjustable. "Continuous, single" switch is set to "single" state, the stimulator issued a single pulse, the switch is set to "continuous" state, the stimulation wave When the switch is set to "Continuous", the stimulation wave will be issued continuously; "Frequency" button, adjustable stimulation frequency; "Intensity" button, adjustable stimulation voltage. Pressing the "start" button, the stimulator generates stimulation pulses to stimulate the sciatic nerve according to the set parameters, and the simulation recorder displays the contraction curve of the gastrocnemius muscle and labels the experimental content.
4. Measurement button Press the measurement button, the simulation recorder displays the experimental curve of the experimental project, the simulation recorder panel buttons become icon buttons, there are zoom in, zoom out, compression, expansion, positioning of the five icon buttons, respectively, can make the experimental curve within the simulation recorder to vertically zoom in or zoom out, horizontally compressed or expanded, positioning icon buttons can be made to the position of the selected recording curve to move to the left side frame position of the simulation recorder. Positioning icon button can move the selected recording curve to the left frame position of the simulator.
5. Measurement state In the measurement state, the mouse moves inside the simulator to measure the experimental curve and read out the contraction force and time of gastrocnemius muscle from the digital display box "Contraction Force" and "Time" on the panel of the simulator. Dragging the scroll bar on the panel of the simulator can make the experimental curve scroll left and right, and display the before and after experimental data curve.
6. Set the "Return" button on the right side of the window prompt bar, click the "Return" button, the program returns to the simulation window.