Does the muscle contraction make noise

Muscle contraction

Muscle contractionw [from Latin. contractio = contraction], E.muscular contraction, Contraction (shortening) of muscles. Any muscle contraction is the result of numerous asynchronous shortening of the individual muscle cells or fibers of a muscle, ultimately its subcellular contractile elements, the myofibrils, and it occurs in all muscle types with ATP consumption due to the same basic molecular processes that occur in the striated muscles of vertebrates are best investigated (see additional information). Under the light microscope, the muscle contraction appears as a shortening of the individual Sarcomeres, i.e. a moving closer together of the Z-disks, whereby the I-zones of the transverse ligament become narrower and in extreme cases disappear (see fig.). The muscle contraction is accompanied by a cyclical binding and loosening of cross-bridges between myosin and actin filaments (see additional information). The former with their movable and laterally protruding HMM heads shimmy along the surrounding actin filaments, so that the filaments slide increasingly further between one another (sliding filament mechanism).

Muscle contraction

The signal for muscle contraction is a sequence of electrical and chemical events. When an action potential hits the motor endplate, the neurotransmitter acetylcholine is secreted from the motor neuron. This binds to the acetylcholine receptors in the postsynaptic membrane, which allow cations to flow into the muscle fiber. This triggers a potential for muscle action. The depolarization of the muscle fiber membrane leads to the intracellular release of calcium ions (approx2+), which are stored in the relaxed state in the sarcoplasmic reticulum. The T-tubules (muscle fibers, fig.), Which are bordered by the flattened membrane system of the sarcoplasmic reticulum, play an important role here. Large calcium channels protrude from the contact points, the Ryadonin receptors, from the membrane of the sarcoplasmic reticulum. When the voltage-dependent dihydropyridine receptors of the T-tubules are activated by an action potential, they open the ryadonin receptors of the sarcoplasmic reticulum through mechanical coupling. Calcium immediately flows into the cytoplasm, which causes further calcium channels to open. The increased calcium level in the cytoplasm is a prerequisite for the binding of the myosin heads to the actin filaments ("electromechanical coupling") and their tilting, which actually triggers a muscle twitch. Calcium is bound to the so-called troponin complex, which on the other hand is linked to myosin via tropomyosin. ATP finally breaks the bond between myosin and actin, but tensions the myosin head like a spring for the next tilting movement. The energy for tipping is obtained from the splitting of ATP into ADP and phosphate, which an enzyme (ATPase) catalyzes on the myosin head. In the absence of further nerve impulses, the calcium ions are immediately pumped back into the sarcoplasmic reticulum.



Muscle contraction

Change in the sarcomere pattern during muscle contraction due to increasing overlap of the filament types.