Muscle contraction is a phenomenon of muscle contraction response to stimulation.In a narrow sense, it meansvertebrateSkeletal muscles rely on transmission activitiespotentialAnd shrinkage occurs.A single active potential produces a single contraction, and repeated active potentials produce a tonic contraction.Muscle contractions that do not pass through the active potential are mostly due to non disseminationDepolarizationIf depolarization is only limited to local muscles and is temporary, it is called local contraction.If depolarization is complete and continuous in muscles, it is called constriction.The continuous contraction seen in smooth muscle is generally called spasm, but many are still accompanied by repeated active potential or continuous depolarization.But in the bivalveAdductor muscleThere is no potential change in the continuous contraction seen by others. This contraction is due to the gate structure.
Chinese name
Muscle contraction
Interpretation
The phenomenon of muscle contraction response to stimulation
Muscle contraction is the basic characteristic of muscle tissue, which refers to the mechanical response of muscle fibers after being stimulated.The maintenance of body posture, spatial movement, complex movements and breathing movements are all realized through muscle contraction activities[1]。
Contractile mechanism
Announce
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according toMyofilament gliding theoryThe basic process of muscle contraction is: muscle cells produce action potential, which causes
The concentration increases,
When combined with troponin C, the conformation of troponin changes, which weakens the combination of troponin I and actin, and changes the conformation of tropomyosin, which exposes the binding site on actin. The transverse bridge combines with actin, and the transverse bridge twists, dragging the thin filaments toward the center of the thick filaments.Passing cross bridge andActinIn the process of transverse bridge circulation formed by the combination, twisting, dissociation, and re combination and re twisting of, the thin muscle filaments continue to slide and the sarcomere is shortened.Energy source during muscle contractionATP hydrolysisEnergy released[2]。
（1） Isotonic contraction and isometric contraction
1. Isotonic contraction refers to the form of contraction in which the main performance is that the length changes while the tension basically remains unchanged when the muscle contracts.
2. Isometric contraction refers to the contraction form in which the tension changes while the length basically remains unchanged when the muscle contracts[2]。
Type of muscle contraction[4]
（2） Single contraction and tetanic contraction
1. Single contraction refers to a contraction and relaxation of muscle after a short stimulation.The contraction process is divided into three periods: incubation period, systolic period and diastolic period.
2. Ankylosing contraction refers to the continuous stimulation of muscles. When the stimulation frequency reaches a certain degree, the last contraction will fall in the process of the previous contraction, resulting in a strong and continuous contraction.If the stimulation frequency is low, the last contraction occurs in the diastole of the previous contraction process, which is called incomplete tetanic contraction. The zigzag curve is recorded in the experiment.If the stimulation frequency is high, the last contraction occurs in the contraction period of the previous contraction process, which is calledComplete tetanic contraction, what is traced is a smooth curve.
In human muscle activity, both isotonic contraction and isometric contraction exist.Under the regulation of the nervous system, the muscle can quickly adjust the intensity of contraction through the sum of contraction.There are two forms of summation: the summation of the number of motion units and the summation of frequency effects (i.emotor neuronThe frequency of impulses can affect the form and intensity of muscle contraction, such as tetanic contraction)[2]。
