Stretching reflex (syn. R. myostatic nrk) - the general name of P., manifested by contraction of skeletal muscle in response to its passive or active stretching.
Comprehensive Medical Dictionary. 2000 .
See what the "stretch reflex" is in other dictionaries:
See Stretch Reflex. A source: Medical Dictionary … Medical terms
A reflex that causes a muscle to contract in response to stretching. Source: Medical Dictionary ... Medical terms
STRETCH REFLEX, MUSCLE STRETCH REFLEX- (myotatic reflex) reflex causing muscle contraction in response to its stretching ... Explanatory dictionary in medicine
A reflex that occurs in response to a short-term stretching of the quadriceps femoris muscle with a light blow to its tendon below the patella, in which there is a sudden contraction of the quadriceps femoris muscle; as a result, the lower leg unbends (reflex ... Medical terms
I Reflex (lat. Reflexus turned back, reflected) is the reaction of the body, providing the emergence, change or termination of the functional activity of organs, tissues or the whole organism, carried out with the participation of the central nervous ... ... Medical encyclopedia
REFLEX KNEE- (patellar reflex) reflex that occurs in response to a short-term stretching of the quadriceps femoris muscle with a light blow to its tendon below the patella, in which there is a sudden contraction of the quadriceps femoris muscle; as a result the shin ... ... Explanatory Dictionary of Medicine
- (nrk) see stretch reflex ... Comprehensive Medical Dictionary
Stretching reflex- - reflex muscle contraction in response to the tension of the tendon of this muscle. Such reflexes are essential in maintaining posture. Synonyms: Myotactic reflex, Postural reflex ... Encyclopedic Dictionary of Psychology and Pedagogy
REFLEX FOLDING KNIFE- The reaction observed in the limbs of animals that have had their brains removed. If you apply pressure to the limb, resistance will increase due to the stretch reflex, which contracts the muscles. If, however, provide enough ... ...
STRETCH, REFLEX- Reflex muscle contraction in response to the tension of the tendon of the responsive muscle. These reflexes are important in maintaining the posture. Also called myotactic reflex ... Explanatory Dictionary of Psychology
Each movement requires the coordinated actions of several muscles: in order to take a pencil in your hand, several muscles will need to be involved, some of which must contract and others must relax. Jointly acting muscles, i.e. contracting or relaxing at the same time are called synergists, as opposed to opposing them muscle antagonists... In any motor reflex of contraction and relaxation, synergists and antagonists are perfectly coordinated with each other.
In response to muscle stretching, an external force is excited by the muscle spindle receptors that respond only to a change in length ( stretch receptors) (Fig. 7.2), which are associated with a special type of small intrafusal muscle fibers.
From these receptors, excitation is transmitted along a sensitive neuron to the spinal cord, where the end of the axon is divided into several branches. Some branches of the axon form synapses with the motor neurons of the extensor muscles and excite them, which leads to muscle contraction: here is a monosynaptic reflex - its arc is formed by only two neurons. At the same time, the other branches of the afferent axon activate the activity of the inhibitory interneurons of the spinal cord, which immediately suppress the activity of motor neurons for the antagonist muscles, i.e. flexors. Thus, muscle stretching causes excitation of the motor neurons of the synergistic muscles and reciprocally inhibits the motor neurons of the antagonist muscles (Fig. 7.3).
The force with which muscles resist changing their length can be defined as muscle tone... It allows you to maintain a certain position of the body (posture). The force of gravity is aimed at stretching the extensor muscles, and their response reflexive contraction counteracts this. If the extension of the extensors increases, such as when lowering onto the shoulders heavy load, then the contraction also increases - the muscles do not allow themselves to be stretched and thanks to this the posture is maintained. When the body deviates forward, backward or to the side, certain muscles are stretched, and a reflex increase in their tone maintains the required body position.
Reflex length regulation in flexor muscles is carried out according to the same principle. Any bending of an arm or leg raises a load, which can be the arm or leg itself, but any load is an external force that tends to stretch the muscles. The reciprocal contraction is reflexively regulated depending on the size of the load.
Tendon reflexes can be caused by lightly striking the tendon of a more or less relaxed muscle with a neurological hammer. From a blow to the tendon, such a muscle is stretched and immediately reflexively contracted.
Reflex sequence: Stretching a muscle causes it to contract.
The arc of the knee reflex (from the tendon of the quadriceps muscle of the thigh):
Intramuscular stretch receptor (in the intrafusal muscle spindle);
Sensory neuron (body - in the spinal ganglion);
Alpha motor neuron (body - in the anterior horns of the spinal cord);
Skeletal muscle (quadriceps femoris).
Thus, in the arc of this reflex (Fig. 7.4), only two neurons are involved and, accordingly, there is one synapse; hence the name "monosynaptic stretch reflex". In addition, a reciprocal inhibition circuit is associated with the reflex arc, due to which muscle contraction is accompanied by relaxation of its antagonist. Monosynaptic tendon reflexes can be obtained on any muscle group, whether they are flexors or extensors. All tendon reflexes occur when the muscle is stretched (which means they are stretching reflexes) and the receptors of the intrafusal muscle spindles are excited. Any movement associated with muscle contraction requires the activation of not only alpha, but also gamma motor neurons.
Since, as a result of this reflex, stretching (i.e. lengthening) of the muscle leads to its contraction (i.e. shortening), it is aimed at maintaining a constant muscle length. Therefore, this reflex
It is an element of any movement that requires the constancy of the length of the muscles, that is, holding the posture;
Makes movements smoother, as it prevents abrupt changes in muscle length.
These two functions are extremely important, which is why myotatic reflexes are the most common reflexes in the spinal cord.
Reflexes of tension
In addition to length, one more parameter is reflexively regulated in working muscles: tension. When a person begins to lift a load, the tension in the muscles increases to such a value that this load can be torn off the floor, but no more: to lift 10 kg, you do not need to strain the muscles, as for lifting 20 kg. In proportion to the increase in voltage, impulses from the tendon proprioceptors, which are called Golgi receptors (stress receptors)... These are unmyelinated endings of an afferent neuron located between collagen bundles of tendon fibers connected to extrafusal muscle fibers. With increasing tension in the muscle, such fibers stretch and squeeze the Golgi receptors. Increasing in frequency impulses are conducted from them along the axon of the afferent neuron to the spinal cord and are transmitted to the inhibitory interneuron, which prevents the motor neuron from being excited more than necessary (Fig. 7.5).
Reflex sequence: muscle tension leads to its relaxation. Reflex arc:
Tension receptor inside the tendon (Golgi tendon organ);
Sensitive neuron;
Inserted inhibitory neuron;
Alpha motor neuron;
Skeletal muscle.
The physiological meaning of the reflex: thanks to this reflex, muscle tension leads to its relaxation (to stretch the tendon and activate the receptor is possible only with muscle tension). Therefore, it is aimed at maintaining the constancy of muscle tension, therefore:
It is an element of any movement that requires constant muscle tension, that is, holding the posture (for example, an upright position that requires a fairly pronounced tension of the extensor muscles);
Prevents abrupt muscle tension that can lead to injury.
Muscle length and tension are interdependent. If, for example, an outstretched arm relaxes the muscle tension, then the irritation of the Golgi receptors will decrease, and the force of gravity will lower the arm. This will lead to stretching of the muscles, an increase in the excitation of intrafusal receptors and the corresponding activation of motor neurons. As a result, muscle contraction will occur and the hand will return to its previous position.
Stretch reflex - a system for regulating muscle length
An isolated muscle preparation is elastic, that is, it stretches when force is applied to it (Figure 15.3). The relationship between the mouse voltage Τ and its length L is described by the well-known curve of the dependence of the length on the voltage in calm state(see chapter 4).
The same experiment can be done with muscle in situ (in a living organism). For this, it is especially convenient to use the extensor muscle of a decerebrated animal. In conditions when the brain stem is cut at the level of the midbrain and there is no connection with the brain (see Chapter 5), this
the muscle resists the applied external force more - it becomes less pliable (more rigid). In this situation, an increase in voltage ΔΤ causes a significantly smaller increase in length, AL r, than in the case isolated muscle(fig.15.3). If the dorsal or ventral roots of the dorsal segment, from where it is innervated this muscle, are cut, then this increased resistance disappears, and the curve of the dependence of the muscle length at rest on the external load becomes similar to the same curve for the isolated muscle.
When the nerve fibers of the spinal cord are intact, the system “ spinal cord-muscle»Clearly acts to counteract muscle lengthening by reflex contraction (reflex tone). It could also be said that the length of the muscle is kept approximately constant, so that the stretch reflex is reduced to a system for regulating muscle length. The elements of this control scheme are as follows (Fig.15.2):
336 PART IV. PROCESSES OF NERVOUS AND HUMORAL REGULATION
Try to make the same list for other control systems (for example, for the regulation of body temperature, arterial blood pressure, respiratory system), i.e. try to find anatomical and physiological equivalents for each of these technical terms. While doing this, do not forget that there are several different effectors in the composition of most biological regulatory systems.
Functional analysis of the control system. In order to measure the transfer characteristics of individual components of the circuit, you should open it at some point to eliminate feedback. The stretch reflex can be studied in the absence of feedback by cutting the dorsal or ventral roots or temporarily blocking the conduction of nerve fibers by cooling them.
The transfer characteristics of the sensor, controller and effector are measured with open circuit. The dynamic properties of the control circuit and its elements, i.e., their behavior during a change in the controlled variable under a disturbing action and immediately after it, can be determined by the response to a step action. The corresponding procedure is discussed in the next section. The stationary characteristics of a given circuit and its components are described using characteristic curves, or functions, each of which reflects the relationship between an input variable and an output variable. In the case of the stretch reflex, the characteristic curve for the transducer function relates the muscle length L to the discharge frequency in the afferent fibers 1a that extend from the muscle spindle, F ia. The characteristic curve for the effector shows a gradual increase in the force of contraction of the extrafusal muscles with an increase in the frequency of discharges F a in the Aa axon of the motor neuron. The sequential combination of characteristic curves for individual circuit elements makes it possible to obtain general characteristics control, i.e. the relationship between muscle length and strength muscle contraction(see, for example, the red curve in Figure 15.3). The smaller the slope of the control characteristic, the closer to
the constant value is the length of the muscle and, therefore, the more precise the regulation.
Before proceeding to further presentation, it is necessary to determine at a qualitative level the polarity of the control circuit: when transmitted through a sensor (muscle spindle), changes are carried out in the same direction, i.e., an increase in the length L causes an increase in the frequency of discharges F Ia. The same is true for transmission through the controller (α-motoneuron) when converting the frequency F la into the frequency F a of the discharges of α-motoneurons. However, when transmitted through the effector (extrafusal muscles), changes occur in opposite directions: an increase in F „causes a decrease in L. It is here that a sign change occurs, which is necessary for the formation of negative feedback in the control system.
III. Examples of motor reflexes.
1. Muscle reflexes of stretching and braking.
Consider the muscle stretch reflex. It is designed to regulate the position of the limbs, to ensure a stationary position of the body, to support the body while it is standing, lying or sitting. This reflex maintains a constant muscle length. Muscle stretching causes the activation of the muscle spindles and contraction, i.e., the shortening of the muscle that opposes its stretching. For example, when a person is sitting, a muscle strain occurs. abdominal and an increase in their tone, which counteracts the flexion of the back. Conversely, too much muscle contraction weakens the stimulation of its stretch receptors, muscle tone weakens
Consider the passage of a nerve impulse along a reflex arc. It should be noted right away that the muscle stretching reflex belongs to the simplest reflexes. It runs directly from a sensory neuron to a motor neuron (Fig. 1). The signal (irritation) goes from the muscle to the receptor. The impulse travels along the dendrites of the sensory neuron to the spinal cord and there it takes the shortest route to the motor neuron of the somatic nervous system, and then along the axon of the motor neuron, the impulse enters the effector (muscle). Thus, the muscle stretching reflex is carried out.
Fig. 1. 1 - muscle; 2 - muscle receptors; 3 - sensory neuron; 4 - motor neuron; 5 - effector.
Another example of a motor reflex is the inhibition reflex. It arises as a response to the action of the stretch reflex. The inhibitory reflex arc includes two central synapses: excitatory and inhibitory. We can say that in this case we observe the work of antagonist muscles in a pair, for example, the flexor and extensor in the joint. The motor neurons of one muscle are inhibited during the activation of the other component of the pair. Consider knee flexion. In this case, we observe stretching of the extensor muscle spindles, which increases the excitation of motor neurons and inhibition of flexor motor neurons. In addition, reducing the stretching of the flexor muscle spindles weakens the excitation of homonymous motoneurons and reciprocal inhibition of the extensor motoneurons (disinhibition). By homonymous motor neurons we mean all those neurons that send axons to the same muscle or excite the muscle from which the corresponding path from the periphery to the nerve center originates. And reciprocal inhibition is a process in the nervous system, based on the fact that one and the same afferent pathway excites some groups of cells and inhibition of other groups of cells through the input neurons. Ultimately, the extensor motor neurons are excited and the flexor motor neurons contract. Thus, the regulation of the muscle length takes place.
Consider the passage of a nerve impulse along a reflex arc. The nerve impulse originates on the extensor muscle and travels along the axons of the sensory neuron to the spinal cord. Since this reflex arc belongs to the dysynaptic type, the impulse bifurcates, one part goes to the extensor motoneuron to maintain the length of the muscle, and the other - to the flexor motor neuron, the extensor is inhibited. Then each part of the nerve impulse is transferred to the corresponding effector. Or, in the spinal cord, a transition to the knee flexor motoneuron is possible through inhibitory synapses, which make it possible to change the length of the muscle, and then along the motor axons exit to the end plates (effector, skeletal muscle). There are two other options, when excitation is perceived by the flexor receptor, then the reflex follows the same path.
ORis.2 1. Extensor muscle. 2. Muscle flexor. 3. Muscle receptor. 4. Sensory neurons. 5. Inhibitory interneurons. 6. Motor neuron. 7. Effector
Let's get acquainted now with more complex reflexes.
2. Flexion and Cross Extension Reflex.
As a rule, reflex arcs include two or more sequentially connected neurons, that is, they are polysynaptic.
An example is the human defense reflex. When influencing a limb, it is withdrawn by bending, for example, in knee joint... The receptors for this reflex arc are found in the skin. They provide movement aimed at removing the limb from the source of irritation.
When the limb is irritated, a flexion reflex occurs, the limb is withdrawn, and the opposite one is straightened. This happens as a result of the passage of the impulse along the reflex arc. We work on the right leg. From the receptor right leg along the axons of the sensory neuron, the impulse enters the spinal cord, then it is sent to four different interneuron circuits. Two chains go to the flexor and extensor motor neurons of the right leg. The flexor muscle contracts, and the extensor relaxes under the influence of inhibitory interneurons. We pull our leg away. In the left leg, the flexor muscle relaxes and the extensor muscle contracts under the influence of an excitatory interneuron.
RiceBlack - inhibitory interneurons; red exciting. 2. Motor neurons. 3.Effectors of relaxed flexor and extensor muscles. 4. Effectors of the contracted muscles of the flexor and extensor.
3. Tendon reflex.
Tendon reflexes are used to maintain a constant muscle tension. Each muscle has two regulatory systems: regulation of length, with the help of muscle spindles as receptors and regulation of tension, tendon organs act as receptors in this regulation. The difference between the tension regulation system and the length regulation system, in which the muscle and its antagonist are involved, is the use of the muscle tone of the entire limb by the tendon reflex.
The strength developed by a muscle depends on its preliminary stretching, the speed of contraction, and fatigue. Deviation from muscle tension from the desired value is recorded by the tendon organs and corrected by the tendon reflex.
The receptor (tendon) for this reflex is located in the tendon of the limb at the end of the flexor or extensor muscle. From there, the signal travels along the axons of the sensory neuron to the spinal cord. There, the signal can pass through the inhibitory interneuron to the extensor motor neuron, which will send a signal to the extensor muscle to keep the muscle in tension. The signal can also go to an excitatory interneuron, which will send a signal through the motor axon to the flexor effector to change the muscle tension and perform a certain action. In the case when the excitation is perceived by the receptor (tendon) of the flexor, the signal passes through the axon of the sensory neuron to the interneuron, and from there to the motor motoneuron, which sends a signal to the flexor muscle along the axons of the motor neuron. In the flexor reflex arch, the path is possible only through the inhibitory interneuron.
Fig. Tendinous receptor. 2. Sensory neuron. 3. Inhibitory interneuron. 4. Excitatory interneuron. 5. Motor neuron. 6. Receptor.
H necessary condition for normal muscle activity is to obtain information about the position of the body in space and the degree of contraction of each of the muscles. This information goes to the central nervous system from receptors of the vestibular apparatus, eyes, skin, as well as from proprioceptors (muscle-articular receptors). Proprioceptors include:
muscle spindles located among muscle fibers,
Golgi bodies located in the tendons,
pacinia corpuscles, located in the fascia covering the muscles, in the tendons, ligaments and periosteum.
All of these proprioceptors belong to the group of mechanoreceptors. Muscle spindles and Golgi corpuscles are stimulated by stretching, and pachinia corpuscles by pressure.
Tone skeletal muscle... At rest, outside of work, muscles in the body are not
completely relaxed, but retain some tension, called tone. The external expression of the tone is a certain elasticity of the muscles.
Electrophysiological studies show that tone is associated with the inflow of rare nerve impulses to the muscle, exciting alternately different muscle fibers... These impulses arise in the motor neurons of the spinal cord, the activity of which, in turn, is supported by impulses emanating from both the higher centers and from the proprioceptors (muscle spindles, etc.) located in the muscles themselves. The reflex nature of skeletal muscle tone is evidenced by the fact that the transection of the dorsal roots, through which sensory impulses from the muscle spindles enter the spinal cord, leads to complete muscle relaxation.
Myotatic reflexes- reflexes to stretch the muscle. Rapid stretching of a muscle, just a few millimeters by a mechanical blow to its tendon, leads to a contraction of the entire muscle and motor response. For example, a light blow to the patella tendon causes the thigh muscles to contract and the lower leg extends. The arc of this reflex is as follows: muscle receptors of the quadriceps femoris muscle à spinal ganglion à posterior roots à posterior horns of the III lumbar segment à motor neurons of the anterior horns of the same segment à extrafusal fibers of the quadriceps femoris muscle. The implementation of this reflex would be impossible if the flexor muscles were not relaxed simultaneously with the contraction of the extensor muscles. The stretch reflex is common to all muscles, but in the extensor muscles, they are well defined and easily invoked.
Spinal cord conduction. Characteristics of afferent impulses coming along the ascending pathways to the structures of the brain. Descending pathways, their main physiological functions. Myelination of the pathways in the process of ontogenesis. Consequences of transverse spinal cord injury at different levels.
The white matter of the spinal cord consists of myelin fibers, which are collected in bundles. These fibers can be short (intersegmental) and long - connecting different parts of the brain with the spinal cord and vice versa. Short fibers (called associative fibers) connect neurons of different segments or symmetrical neurons on opposite sides of the spinal cord.
Long fibers (they are called projection fibers) are divided into ascending, going to the brain, and descending - going from the brain to the spinal cord. These fibers form the pathways of the spinal cord.
The bundles of axons form around the gray matter the so-called cords: the anterior ones are located medially from the anterior horns, the posterior ones are located between the posterior horns of the gray matter, and the lateral ones are located on the lateral side of the spinal cord between the anterior and posterior roots.
The axons of the spinal ganglia and gray matter of the spinal cord go to its white matter, and then to other structures of the central nervous system, thereby creating ascending and descending pathways.
V anterior cords located downward paths:
1) anterior cortical-cerebrospinal, or pyramidal, path (tractus corticospinalis ventralis, s.anterior), which is direct non-crossed;
2) the posterior longitudinal bundle (fasciculus longitudinalis dorsalis, s.posterior);
3) tecto-spinal, or tectospinal, path (tractus tectospinalis);
4) vestibulospinal, or vestibulospinal path (tractus vestibulospinalis).
V posterior cords pass ascending paths:
1) a thin bundle, or Gaul's bundle (fasciculus gracilis);
2) a wedge-shaped bundle, or Burdakh's bundle (fasciculus cuneatus).
V lateral cords there are descending and ascending paths.
TO downward paths include:
1) the lateral cortical-spinal, or pyramidal, path (tractus corticospinalis lateralis) is crossed;
2) red-nuclear-spinal, or rubrospinal, path (tractus rubrospinalis);
3) reticular-spinal, or reticulospinal, path (tractus reticulospinalis).
TO ascending paths include:
1) dorsal thalamic (tractus spinothalamicus) path;
2) lateral and anterior spinal cerebellar, or Flexig and Govers bundles (tractus spinocerebellares lateralis et ventralis).
Associative, or propriospinal, pathways connect neurons of one or different segments of the spinal cord. They start from the gray matter neurons of the intermediate zone, go to the white matter of the lateral or anterior cords of the spinal cord and end in the gray matter of the intermediate zone or on the motor neurons of the anterior horns of other segments. These connections perform an associative function, which consists in coordinating posture, muscle tone, and movements of different metameres of the trunk. The propriospinal pathways also include commissural fibers that connect functionally homogeneous symmetrical and asymmetric areas of the spinal cord.
Cerebrospinal descending pathways start from the neurons of the brain structures and end on the neurons of the spinal cord segments. This includes the following pathways: anterior (straight) and lateral (crossed) cortical-spinal (from pyramidal neurons of the pyramidal and extrapyramidal cortex, which provide regulation of voluntary movements), red-nuclear-spinal (rubrospinal), vestibular-spinal (vestibulospinal) reticulospinal) pathways are involved in the regulation of muscle tone. The common point for all of these pathways is that their final destination is the motor neurons of the anterior horns. In humans, the pyramidal pathway ends directly on motoneurons, while other pathways end mainly on intermediate neurons.
Pyramid path consists of two bundles: lateral and straight. The lateral bundle starts from the neurons of the cerebral cortex, at the level of the medulla oblongata, passes to the other side, forming a cross, and descends along the opposite side of the spinal cord. The straight bundle descends to its segment and there passes to the motoneurons of the opposite side. Hence, the entire pyramidal path is crossed.
Red-spinal cord, or rubrospinal, path(tractus rubrospinalis) consists of the axons of the neurons of the red nucleus. These axons, immediately after exiting the nucleus, move to the symmetrical side and are divided into three beams. One goes to the spinal cord, the other to the cerebellum, and the third to the reticular formation of the brainstem.
The neurons that give rise to this path are involved in the control muscle tone... Rubromocerebellar and rubroreticular pathways provide coordination of the activity of pyramidal neurons of the cortex and neurons of the cerebellum involved in the organization of voluntary movements.
Predoor-cerebrospinal, or vestibulospinal, path(tractus vestibulospinalis) starts from the neurons of the lateral vestibular nucleus (Deiters' nucleus), which lies in the medulla oblongata. This nucleus regulates the activity of the spinal cord motor neurons, provides muscle tone, coordination of movements, and balance.
Reticular-spinal cord, or reticulospinal, pathway(tractus reticulospinalis) goes from the reticular formation of the brain stem to the motor neurons of the spinal cord, through which the reticular formation regulates muscle tone.
Damage to the conductive apparatus of the spinal cord leads to disorders of the motor or sensory system below the site of damage.
The intersection of the pyramidal pathway causes hypertonicity of the muscles below the transection (motoneurons of the spinal cord are freed from the inhibitory effect of the pyramidal cells of the cortex) and, as a result, to spastic paralysis.
When crossing the sensitive pathways, muscle, articular, pain and other sensitivity below the site of the spinal cord transection is completely lost.
Spinocerebral ascending tracts (see Fig. 4.10) connect segments of the spinal cord to the structures of the brain. These pathways are represented by pathways of proprioceptive sensitivity, thalamic, spinal-cerebellar, spinal-reticular. Their function is to transmit information to the brain about extero-, intero- and proprioceptive stimuli.
Proprioceptive pathway(thin and wedge-shaped bundles) starts from the receptors of deep sensitivity of the muscles of the tendons, periosteum, membranes of the joints. A thin bundle starts from the ganglia, which collect information from the caudal parts of the body, the pelvis, lower limbs... The wedge-shaped bundle starts from the ganglia that collect information from the muscles chest, upper limbs. From the spinal ganglion, the axons go to the posterior roots of the spinal cord, to the white matter of the posterior cords, rise to the thin and wedge-shaped nuclei of the medulla oblongata. Here the first switch to a new neuron takes place, then the path goes to the lateral nuclei of the thalamus of the opposite hemisphere of the brain, switches to a new neuron, that is, the second switch occurs. From the thalamus, the path rises to the neurons of layer IV of the somatosensory cortex. The fibers of these tracts give off collaterals in each segment of the spinal cord, which makes it possible to correct the posture of the entire trunk. The speed of the excitation through the fibers of this path reaches 60-100 m / s.
Dorsal thalamic pathway(tractus spinothalamicus) - the main pathway of skin sensitivity - starts from pain, temperature, tactile receptors and baroreceptors of the skin. Pain, temperature, tactile signals from skin receptors go to the spinal ganglion, then through the dorsal root to the dorsal horn of the spinal cord (first switch). Sensory neurons of the dorsal horns send axons to the opposite side of the spinal cord and rise along the lateral cord to the thalamus; the speed of conduction of excitation through them is 1-30 m / s (second switching), from here to the sensory area of the cerebral cortex. Part of the fibers of the cutaneous receptors goes to the thalamus along the anterior cord of the spinal cord.
Dorsal cerebellar tract(tractus spinocerebellares) lie in the lateral cords of the spinal cord and are represented by non-overlapping anterior, spinal-cerebellar pathways (Govers bundle) and double-overlapping posterior spinal-cerebellar pathways (Fleksig bundle). Consequently, all spinal cord tracts begin on the left side of the body and end in the left lobe of the cerebellum; in the same way, the right lobe of the cerebellum receives information only from its side of the body. This information comes from the Golgi tendon receptors, proprioceptors, pressure receptors, touch. The speed of the excitation along these paths reaches 110-120 m / s.