TENDON JERKS

From Big Medical Encyclopedia

TENDON JERKS — own (proprioceptive) instinctive reflexes arising in response to irritation of proprioceptors in passively stretched muscle.

As the main receptors for Neuter serve sensitive trailer devices in muscles — the so-called neuromuscular spindles reacting to the stretching of muscle fibers caused by blow in a sinew (see. Proprioceptors ). Receptors of the sinew do not play an essential role in a reflex since the reflex can be received, e.g., after local anesthesia of a reflexogenic zone or replacement of a sinew with allotransplant. As an afferent link of a reflex arc serve sensitive thick A-fibers of peripheral nerves and back roots of a spinal cord. Reflex arcs of Neuter become isolated in a spinal cord (more often) or in a brain trunk. The beginning and the end of a reflex arc are connected with a muscle.

Fiziol. value of Neuter consists that they, regulating extent of reduction of a muscle according to the irritations falling on it participate in preservation of a statics and position of a body. Normal are not exhausted by Neuter, change from a summation of stimuli a little, their refractory phase is short. Stage of latency of tendon jerks — 6 — 20 ms. Speed of Neuter is connected with simplicity of structure of their reflex arc (in a cut there is usually one switching) and high speed of carrying out excitement on nerve fibrils.

Reflex arcs of Neuter are under the influence of overlying departments of c. N of page, in particular cerebral cortex. It is known, e.g., that during the calling of a knee jerk electric activity of a cerebral cortex changes. Character of a reflex is influenced by a pose of a body, position of the studied extremity, a functional condition of other spinal centers which are directly not connected with this reflex act.

Theoretically Neuter can be so much how many is available muscles, but practically not all reflexes are equally available to a research. Easier razgibatel of the lower extremities, those muscles react to adequate irritation, to-rye resist to gravity (anti-gravitational). Adequate irritation for tendon jerks is stretching, a push or blow in a sinew. During the calling of Neuter the active muscle tension needs to be excluded completely. Always it is necessary to compare reflexes on one and on other party. In a wedge, practice the following of Neuter has the greatest value.

Reflex from a sinew of a biceps of a shoulder (cm. Biceps reflex ). Blow nevrol. a hammer, put on a sinew of a biceps over an elbow bend, causes bending of a hand in an elbow joint. The reflex is connected with a musculocutaneous nerve; its arch becomes isolated in SU — Cvi segments of a spinal cord. At children the reflex is caused from the first days of life.

Reflex from a sinew of a tricipital muscle of a shoulder (triceps-refleks). For calling of a reflex take away passively a shoulder of the relaxed hand of the patient of a knaruzha to horizontal level and support a hand at an elbow joint so that the forearm hanged down at right angle. Strike with a hammer near an elbow shoot since the tricipital muscle has very short sinew. The blow a po.sukhozhiliya of a tricipital muscle causes reduction of this muscle and extension of a hand in an elbow joint. The reflex is connected with a beam nerve; its arch becomes isolated in C4 segments — C7. At children the triceps reflex is caused from the first days of life.

Knee (or patellyarny) reflex (see. Knee jerk ): the blow in a sinew by the four-head of a muscle of a hip below a patella causes extension of a leg in a knee joint.

The reflex is connected with a femoral nerve; its arch becomes isolated in L2 segments — L4. The knee jerk is caused at most of newborns from the first hours of life. At small children knee jerks are expressed stronger, than at adults.

Akhillov reflex is caused at blow in an Achilles tendon, to-rogo bottom bending of foot is caused (see Akhillov a reflex). The reflex is connected with a sciatic nerve; its arch becomes isolated in L5 segments — S1-2. Akhillov a reflex is called approximately at 40% of newborns.

Mandibular (or mandibular) reflex is a reflex from a masseter. The blow by a hammer on a chin of the patient (it is better on a phalanx of the finger attached by the doctor to a chin of the patient) at slightly slightly opened mouth causes the reduction of masseters and the movement of a mandible up causing a smykaniye of jaws. The reflex is connected with a mandibular branch of the V nerve; the reflex arc of a reflex becomes isolated in the bridge; it is found almost in all healthy people.

Listed to Neuter normal easily are caused at nek-rum skill and knowledge of the receptions eliminating any delay of reflexes. Neuter on hands and legs are, as a rule, uniform on both sides.

Change normal Neuter can be shown in their decrease or disappearance that is usually connected with disturbance of integrity of a reflex arc in any its department. Besides, Neuter disappear at a sharp atrophy of muscles owing to absence in them sokratitelny force; temporarily disappear Neuter (see. Areflexia ) at acute increase in intracranial pressure, and also after an epileptic seizure, at a brain stroke and other states, at to-rykh there occurs decrease in excitability of the reflex device of a spinal cord, a temporary functional asinapsiya (see. Diaschisis , Reflex ).

Increase in Neuter comes owing to «release» of a reflex arc from the descending influences of suprasegmentarny educations. At the same time a zone, about a cut it is possible to cause Neuter, extends, there are clonuses of brushes, feet, patellae (see. Clonus ), and also pathological, protective and other reflexes (see. Protective reflexes , Reflexes pathological ). Increase in all Neuter (hyperreflexia) can be observed also at the general increase in excitability of a nervous system (neurosises, a thyrotoxicosis, etc.).

In addition to Neuter, treat the proprioceptive reflexes caused by irritation of the deep receptors which are stuffed up in a periosteum periosteal reflexes (see). During the calling of nek-ry periosteal reflexes there is a muscle strain that gives the grounds to pull together them with Neuter

See also Instinctive reflex , Reflex .



Bibliography: Bogorodinsky D. K., Skoromets A. A. and Shvareva. I. The guide to a practical training by nervous diseases, page 5, M., 1977; M. B. and Fedorov E. A. Crawl. Main neuropathological syndromes, M., 1966; The Multivolume guide to neurology, under the editorship of S. N. Davidenkov, t. 2, page 163, M., 1962; Hodos X. G. Nervous diseases, page 135, M., 1974; Brain W. R. Brain’s diseases of the nervous system, Oxford — N. Y., 1977; about N of e, Brain’s clinical neurology, Oxford a. o., 1978; Monrad-Krohn G. H. The clinical examination of the nervous system, L., 1964.


E. I. Gusev.

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