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Tonus (Latinized form from ancient Greek τόνος tonos , German 'tension' to the verb τείνειν teinein , German 'tension' , ' an- ' , 'relax') is the "state of tension of the muscles ", which is due to the viscoelastic properties of the tissue and stimuli of the Nervous system is caused. A distinction is also made between “passive muscle tone” and “active muscle tone”.

In the skeletal muscles (striated muscles) it arises primarily through alternating contractions of individual muscle fibers , whereas in the smooth muscles of the inside of the body it is caused by the continuous contraction of muscle cells. The tone depends on the innervation by the nervous system, which can be arbitrary or involuntary, as well as the metabolic state of the muscle.

A prolonged, painful muscle tone is called tension . This condition occurs mainly due to one-sided posture and most often affects the neck and shoulder muscles .

Resting tone

All muscles have a certain resting tone . This tone generally characterizes a force, here the force that the muscle opposes to an external force. In muscle physiology we find this e.g. B. in the so-called elongation curves with the dependence of the muscle length (isolated muscle) on the force (the stretching weight), which is equal to the muscle tension (counterforce). Even an inactive, i.e. resting, muscle opposes a stretching force with tension. After stretching, the resting stretch curve can be briefly shifted to the right ( hysteresis ).

This tension, which can also be measured on the isolated muscle, must be distinguished from the so-called reflex tone as an involuntary tension tone of tonic asynchronous active motor units, which is neurogenic in nature and can have different causes. Contractions take place to a certain extent even in the case of seemingly absolute inactivity. These are sufficient to pull the flexor muscles of this joint into the flexion position , for example in the case of flaccid paralysis of the extensor muscles of a joint . This reflexive resting tone is based on a monosynaptic reflex and only disappears when the nerve supplying the muscle or its nerve root is severed .

There is a technical device with which the depth of a stamp's impression in the muscle surface is measured under defined forces ( myotonometer , Tissiu tensiometer ).

The muscle tension can also be assessed by touching, such as: B. in manual therapy .

Loss and increase

Destruction of the nerves supplying the muscle (a) or toxins that block the nerve-muscle interface ( motor end plate ) (e.g. curare ) can lead to an extensive or complete loss of muscle tone (flaccid paralysis). (b) This usually occurs in the context of central or peripheral paralysis . (a) The condition of decreased muscle tone is called hypotonia , the condition of complete loss of tone is called atony . The complete loss of tone is characterized as paralysis if it is caused by paralysis. (b) Atony basically exists during REM sleep , which inhibits the muscular acting out of dream contents. Loss of tone can also be seen in cataplexy (so-called affective tone loss). (c)

An increased tone is called muscle hypertension . It occurs with cramps - lat. Spasm - or as spasticity with central paralysis - hence also called spastic paralysis. (d)

See also

Individual evidence

  1. ^ DG Simons, S. Mense: Understanding and measurement of muscle tone as related to clinical muscle pain . In: Pain . tape 75 , 1998, pp. 1-17 (English).
  2. ^ A b Hermann Rein and Max Schneider : Introduction to Human Physiology . 15th edition, Springer, Berlin, 1964:
    (a) p. 618 on Stw. "Pyramidenbahn, Extrapyramidales System (= inhibition path)";
    (b) pp. 205, 393, 466, 467 on St. "Curare".
  3. ^ A b c d Klaus Poeck : Neurology . 8th edition, Springer, Berlin 1992, ISBN 3-540-53810-0 :
    (a) p. 86 on Stw. “Central Paralysis”; P. 84 on head. "Peripheral paralysis";
    (b) p. 86 to district “paralysis”;
    (c) p. 286 on “Cataplexy”;
    (d) P. 91 to district “Spasticity”.
  4. T. Sakuma-Sasai, Y. Inoue: Rapid eye movement (REM) sleep behavior disorder in older adults . In: Nihon rinsho. Japanese journal of clinical medicine . tape 71 , no. 10 , October 2013, p. 1853-1857 , PMID 24261219 (English).