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Biomedical subjects

V I Zalkind

Publications and source records attributed to V I Zalkind.

11 recordsLinked to original sources
PubMed1979

[Spontaneous discharges of muscle receptors of different functional types].

Characteristics of discharges as well as presence or absence of spontaneous impulse activity (SIA) were studied in 473 receptors of deafferented muscles in anesthetized cats. The SIA was absent in majority of Golgi's organs, pressor receptors, and in elementary dynamic and static receptors of muscle spindles. The SIA probability is particularly high in spindle receptors of phasic-tonic type. Absence or presence of the SIA is one of criteria for identifying the type of receptors. Among the universal receptors of dynamic and position types, the SIA probability increases along with enhancement of the static response. The soleus muscle possesses a lesser amount of units with SIA than the m. triceps. Absence or presence of the SIA seem to depend on different ways of connection between sensitive terminals and the intrafusal fibers of the spindles which have been initially stretched in a relaxed muscle.

Adaptation, Physiological↗
PubMed1979

[Decrease in the frequency of muscle spindle discharges during muscle stretching].

When studying responses of 500 muscle receptors to stretching of the m. triceps of the cat deafferented hindlimb, 23 cases revealed a transient decrease in the firing rate (DFR) of muscle spindles' receptors. The DFR occurs in the same receptor at different forms and rates of stretching approximately at the same area of stretching ("the DFR area"). When increasing the rate of stretching, the DFR effect is enhanced. The DFR effect seems to be due to a short-lasting unloading of the spindle area which contains the receptor terminals. The unhomogenous structure of the extrafusal muscle as well as various mechanical properties of the intrafusal muscle fibers can provide necessary conditions for the above effect.

Animals↗
PubMed1978

[Spontaneous activity of the passive muscle spindles of the cat triceps surae].

In a slack deeferented m. triceps surae about 45% of 400 stretch receptors under study have a spontaneous discharge. The following facts indicated that some intrafusal fibres in the slack muscles are presumably in the prestretch state: 1) the isotonic contraction of the muscle diminished or abolished the spontaneous discharge; 2) at the beginning of the stretch of the slack muscle the initial slowing in the discharge frequency of the unit sometimes appeared; this slowing did not depend on the type of unit and occured in a unit among many others in the same preparation and under the same conditions of experiment; 3) the dynamic thresholds of spontaneously discharging units were lower than that of units without spontaneous discharge. It is suggested that a static stretch occurs in some muscle spindles, if the distance between two points of big fibres insertion on extrafusal fibres or tendon fascicules is longer than the length of intrafusal fibres. The initial slowing at the beginning of stretch is presumably due to viscous damping forces which must be higher in more viscous extrafusal fibres in comparison to that of intrafusal fibres.

Action Potentials↗
PubMed1978

[Muscle relaxation and muscle spindle adaptation].

In experiments on deefferented m. triceps surae of the cats, the unequal correlation between speed of muscle relaxation during interval from 2.5 to 40 sec after the beginning of static stretch and the rate of adaptation of three functionally different groups of muscle spindles, was revealed. The dependence of the adaptation of muscle spindle endings on relaxation of both extra-and intrafusal muscle fibers, is discussed.

Adaptation, Physiological↗
PubMed1978

[Participation of muscle spindles in the mechanism of peripheral inhibition].

A relaxed deefferented muscle of an anesthetized cat has spindles with long-lasting impulse activity. The receptors with spontaneous activity are more sensitive to an alteration in the muscle condition than inactive ones. Stimulation of the muscle nerve entails inhibition of discharges not only in the spindles of a contracting muscle but in spontaneously active receptors of the synergic muscles which do not actively contract. The conditions for inhibition of spontaneous activity of the synergic muscles' receptors arise during natural locomotion in rats. The mechanism of peripheral inhibition in motor coordination seems to have an unspecific character and maintains the aiming of motor command at a small number of executive units in the course of the control.

Animals↗
PubMed1978

[Receptor adaptation of muscle spindles treated in different ways].

Comparison of the grades of 60 sensitive muscle spindle terminals on two actions: gradual stretch of the muscle and short intensive tetanization of the muscle nerve, showed that, irrespective of the mode of action, the character of adaptation remains the smae in majority of units. The speed of receptors adaptation depends not on the specific of testing precedures, but, apparently, on the means of connection of the sensitive terminals with different types of intrafusal muscle fibers with different elasticviscous properties. The possible reason for speedy adaptation of muscle receptors of elementary dynamic type, is discussed.

Adaptation, Physiological↗
PubMed1977

[Identification of muscle spindles by direct and indirect electric stimulation of intrafusal muscle fibers].

In two series of experiments on 25 anesthetized deefferented cats methods of quick identification of muscle spindles were used. The first method was based on the postcontractory sensory discharge in a muscle spindle after brief strong electrical stimulation of the muscle nerve. In another approach the concentric electrodes inserted into the muscle were used. If the intrafusal muscle fibers were selectively contracted by direct electrical stimulation the sensory discharge appeared without any increase in the total muscle tension. It seems that these methods enable to identify the unit under study more precisely in comparison with conduction velocity measurements, as the group I and II afferents are sometimes present in muscle nerve from joint and deep tissues.

Animals↗
PubMed1977

[Adaptational characteristics of muscle stretch receptors of the dynamic type].

In cats with deefferented m. triceps, some stretch receptors of the dynamic type were shown to adapt rapidly after stretching of the muscle and keeping it at the new length, whereas other receptors revealed rapid and slow components of the adaptation. The units with different kinds of adaptation coexist in the same muscle, their afferents being related mainly to the group I, although overlapping with the group II afferents does exist. The above differences are revealed at high values of the muscle initial stretch. It seems that the adaptation slow component is based on a mechanical factor depending on the viscous-elastic properties of the tissue in the area of sensitive nerve terminals.

Adaptation, Physiological↗
PubMed1977

[Effect of prolonged preliminary static stretching of de-efferented muscle on the dynamic response of muscle receptors].

Speed of adaptation of muscle receptor discharges during static stretching of the muscle was shown to depend on the grade and duration of muscle tension reducing which, in its turn, is the function of muscle length. The increase in the receptor firing rate during the dynamic phase of muscle stretching (the dynamic response) depends both on the grade and speed of stretching and on whether the muscle is "balanced" after previous stretching. The data obtained suggest insignificant increase in the relaxed muscle length on changing of angle in the talocrural joint within the physiological range.

Animals↗
PubMed1976

[Functional specialization of stretch receptors in the triceps surae muscle of cats].

The behavior of 300 receptors in response to stepwise changes in muscle length was studied in passive m. triceps surae of cats anesthetized with nembutal. Distinct differences in receptor behavior were demonstrated, and receptors were divided into three functional groups according to their sensitivity to slow stretch (0.6 mm/sec in the limit range of 10 mm). The 1st group (elementary dynamic receptors) showed obvious sensitivity (over 70/sec) to dynamic components of stimulus and did not respond to static stretch in the physiological range. It was impossible to study the silent period during muscle contraction and stretch. The units of the 2nd group (elementary static receptors) reached maximal discharge frequency of 20--25/sec in the same range of muscle stationary stretch. The dynamic response of these receptors slightly exceeds the static response. The 3rd group, comprising 80% of units, served as universal detector of both dynamic and static phases of a stimulus. Some units showed significant dynamic response (over 70/sec) and moderate static response (about 30--40/sec), others exhibited moderate dynamic and static responses. The behavior of the receptors of universal type is similar to that of the well--known primary and secondary endings of the muscle spindles. Asto the endings of two elementary types they should be further indentified.

Adaptation, Physiological↗