The medical term muscle relaxation is used in two senses. In physiology it describes the normal relaxation of the muscle after a contraction as well as the medication-induced, longer-lasting, reversible deactivation of the muscle function, as it is practiced during anesthesia . Finally, there is progressive muscle relaxation as a relaxation technique .
Physiological muscle relaxation
Under muscle refers to the relaxation of the muscle after previous tension ( contraction ). The prerequisite for this is lowering the intracellular calcium ion concentration to the resting value or desensitization of the contractile apparatus. The intracellular calcium concentration can be reduced to the resting value (about 100 nM) by the following principles:
- Inhibition of the Ca 2+ influx (e.g. inhibition of L-type calcium channels)
- Inhibition of Ca 2+ release
- Promotion of Ca 2+ extrusion (absorption into the sarcoplasmic reticulum or export into the extracellular space )
Ca 2+ desensitization can occur through activation of myosin phosphatase (in smooth muscle).
The following molecules are mainly involved:
- the ATP- dependent calcium pump ( SERCA ) in the sarcoplasmic reticulum,
- the ATP -dependent calcium pump in the sarcolemma and
- the sodium-calcium exchanger .
Pharmacological muscle relaxation
By applying muscle relaxants , the function of the skeletal muscle can be reversibly inhibited over a longer period of time (also referred to as muscle relaxation or neuromuscular blockade ). A distinction is made between active substances that reduce muscle tension centrally (in the brain) and are used in neurology , for example, and those that prevent the peripheral transmission of nerve impulses to the muscle fiber. This can be desirable in the case of anesthesia during an operation. The monitoring is carried out by means of relaxometry .