Gamma efferent system of muscle contraction. Stabilization of body position

12.05.202027.05.2017

Maintenance function muscle tone provided according to the principle feedback at various levels of regulation of the body. Peripheral regulation is carried out with the participation of the gamma loop, which includes supraspinal motor pathways, interneurons, the descending reticular system, alpha and gamma neurons.

There are two types of gamma fibers in the anterior horn of the spinal cord. Gamma-1 fibers ensure the maintenance of dynamic muscle tone, i.e. tone necessary for the implementation of the movement process. Gamma-2 fibers regulate the static innervation of muscles, i.e. posture, posture of a person. Central regulation of the functions of the gamma loop is carried out by the reticular formation through the reticulospinal tract. The main role in maintaining and changing muscle tone is played by functional status segmental arc of the stretch reflex (myotatic or proprioceptive reflex). Let's take a closer look at it.

Its receptor element is the encapsulated muscle spindle. Each muscle contains large number these receptors. The muscle spindle consists of intrafusal muscle fibers (thin) and a nuclear bursa, braided by a spiral-shaped network of thin nerve fibers, which are the primary sensory endings (anulospinal filament). Some intrafusal fibers also have secondary, grape-shaped sensory endings. When intrafusal muscle fibers are stretched, the primary sensory endings strengthen the impulses emanating from them, which are carried through fast-conducting gamma-1 fibers to the alpha-large motor neurons of the spinal cord. From there, through also fast-conducting alpha-1 efferent fibers, the impulse goes to the extrafusal white muscle fibers, which provide rapid (phasic) muscle contraction. From secondary sensory endings that respond to muscle tone, afferent impulses are carried out along thin gamma-2 fibers through a system of interneurons to alpha-small motor neurons that innervate tonic extrafusal muscle fibers(red), ensuring maintenance of tone and posture.

Intrafusal fibers are innervated by gamma neurons of the anterior horns of the spinal cord. Excitation of gamma neurons, transmitted along gamma fibers to the muscle spindle, is accompanied by contraction of the polar sections of the intrafusal fibers and stretching of their equatorial part, while the initial sensitivity of the receptors to stretch changes (the threshold of excitability of stretch receptors decreases, and tonic tension of the muscle increases).

Gamma neurons are influenced by central (suprasegmental) influences transmitted along fibers that come from motor neurons of the oral parts of the brain as part of the pyramidal, reticulospinal, and vestibulospinal tracts.

Moreover, if the role of the pyramidal system is primarily to regulate the phasic (i.e. fast, purposeful) components of voluntary movements, then the extrapyramidal system ensures their smoothness, i.e. predominantly regulates the tonic innervation of the muscular system. Thus, according to J. Noth (1991), spasticity develops after supraspinal or spinal damage to the descending motor systems with the obligatory involvement of the corticospinal tract in the process.

Inhibitory mechanisms also take part in the regulation of muscle tone, without which reciprocal interaction of antagonist muscles is impossible, and therefore, purposeful movements are impossible. They are realized with the help of Golgi receptors located in muscle tendons and Renshaw intercalary cells located in the anterior horns of the spinal cord. Golgi tendon receptors, when the muscle is stretched or significantly tensed, send afferent impulses along fast-conducting type 1b fibers to the spinal cord and have an inhibitory effect on the motor neurons of the anterior horns. Renshaw intercalary cells are activated through collaterals when alpha motor neurons are excited, and act on the principle of negative feedback, contributing to the inhibition of their activity. Thus, the neurogenic mechanisms of regulation of muscle tone are diverse and complex.

When the pyramidal tract is damaged, the gamma loop is disinhibited, and any irritation by stretching the muscle leads to a constant pathological increase in muscle tone. In this case, damage to the central motor neuron leads to a decrease in inhibitory effects on motor neurons as a whole, which increases their excitability, as well as on interneurons of the spinal cord, which helps to increase the number of impulses reaching alpha motor neurons in response to muscle stretching.

Other causes of spasticity include structural changes at the level of the segmental apparatus of the spinal cord that arise as a result of damage to the central motor neuron: shortening of the dendrites of alpha motor neurons and collateral sprouting (proliferation) of afferent fibers that make up the dorsal roots.

Secondary changes also occur in muscles, tendons and joints. Therefore, the mechanical-elastic characteristics of muscle and connective tissue, which determine muscle tone, suffer, which further enhances movement disorders.

Currently, an increase in muscle tone is considered as a combined lesion of the pyramidal and extrapyramidal structures of the central nervous system, in particular the corticoreticular and vestibulospinal tracts. Moreover, among the fibers that control the activity of the gamma neuron-muscle spindle system, inhibitory fibers usually suffer to a greater extent, while activating fibers retain their influence on the muscle spindles.

The consequence of this is muscle spasticity, hyperreflexia, the appearance of pathological reflexes, as well as the primary loss of the most subtle voluntary movements.

The most significant component of muscle spasm is pain. Painful impulses activate alpha and gamma motor neurons of the anterior horns, which increases the spastic contraction of the muscle innervated by this segment of the spinal cord. At the same time, muscle spasm, which occurs during the sensorimotor reflex, enhances the stimulation of muscle nociceptors. Thus, according to the negative feedback mechanism, a vicious circle is formed: spasm - pain - spasm - pain.

In addition, local ischemia develops in spasmodic muscles, since algogenic chemicals(bradykinin, prostaglandins, serotonin, leukotrienes, etc.) have a pronounced effect on blood vessels, causing vasogenic tissue edema. Under these conditions, substance “P” is released from the terminals of type “C” sensory fibers, as well as the release of vasoactive amines and increased microcirculatory disorders.

Data on the central cholinergic mechanisms of muscle tone regulation are also of interest. Renshaw cells have been shown to be activated by acetylcholine through both motor neuron collaterals and the reticulospinal system.

M. Schieppati et al., (1989) found that pharmacological activation of central cholinergic systems significantly reduces the excitability of alpha motor neurons by increasing the activity of Renshaw cells.

In recent years, researchers in the regulation of muscle tone have attached great importance to the role of descending adrenergic supraspinal pathways starting in the locus coeruleus. Anatomically, these formations are closely related to the spinal structures, especially to the anterior horns of the spinal cord. Norepinephrine, released from the bulbospinal fiber terminals, activates adrenergic receptors located in interneurons, primary afferent terminals and motor neurons and simultaneously acts on alpha and beta adrenergic receptors in the spinal cord (D. Jones et al., 1982). Numerous axons of pain sensitivity approach the nuclear formations of the reticular formation of the trunk. Based on information entering the reticular formation of the brain stem, somatic and visceral reflexes are built. From the nuclear formations of the reticular formation, connections are formed with the thalamus, hypothalamus, basal ganglia and limbic system, which ensure the implementation of neuroendocrine and affective manifestations of pain, which is especially important in chronic pain syndromes.

As a result, the resulting vicious circle includes muscle spasm, pain, local ischemia, and degenerative changes, which self-support each other, reinforcing the root cause of pathological changes.

It should be borne in mind that the more components of this vicious circle that are targeted in treatment, the higher the likelihood of its success. Therefore, modern requirements for muscle relaxant therapy are: the power of the muscle relaxant effect, its selectivity, the presence of anticonvulsant and anticlonic effects, the power of the analgesic effect, as well as the safety and availability of a wide therapeutic range of doses of the drug.

According to modern concepts, most muscle relaxants act on transmitters or neuromodulators of the central nervous system. The effects may include suppression of excitatory mediators (aspartate and glutamate) and/or enhancement of inhibitory processes (GABA, glycine).

Exam questions:

1.5. Pyramidal tract (central motor neuron): anatomy, physiology, symptoms of damage.

1.6. Peripheral motor neuron: anatomy, physiology, symptoms of damage.

1.15. Cortical innervation of the motor nuclei of cranial nerves. Symptoms of damage.

Practical skills:

1. Taking anamnesis in patients with diseases of the nervous system.

2. Study of muscle tone and assessment of motor disorders in the patient.

Reflex-motor sphere: general concepts

1. Terminology:

- Reflex- - the body’s reaction to a stimulus, realized with the participation of the nervous system.

- Tone- reflex muscle tension, ensuring the preservation of posture and balance, preparation for movement.

2. Classification of reflexes

- By origin:

1) unconditional (constantly occurring in individuals of a given species and age with adequate stimulation of certain receptors);

2) conditional (acquired during an individual’s life).

- By type of stimulus and receptor:

1) exteroceptive(touch, temperature, light, sound, smell),

2) proprioceptor(deep) are divided into tendon, which arise when muscles are stretched, and tonic, to maintain the position of the body and its parts in space.

3) interoreceptor.

- By arc closure level:spinal; stem; cerebellar; subcortical; cortical.

- By effect caused: motor; vegetative.

3. Types of motor neurons:

- Alpha large motor neurons- performing fast (phasic) movements (from the motor cortex);

- Alpha small motor neurons- maintaining muscle tone (from the extrapyramidal system), are the first link of the gamma loop;

- Gamma motor neurons- maintaining muscle tone (from muscle spindle receptors), are the last link of the gamma loop - participate in the formation of the tonic reflex.

4. Types of proprioceptors:

- Muscle spindles- consist of intrafusal muscle fiber(similar to embryonic fibers) and receptor apparatus, are excited by muscle relaxation (passive lengthening) and inhibited by contraction(parallel activation with muscle) :

1) phasic (1 type of receptors - annulo-spiral, “core-chain”), activated in response to sudden lengthening of the muscle - the basis of tendon reflexes,

2) tonic (type 2 receptors - grape-shaped, “bursa-nuclei”), activated in response to slow lengthening of the muscle - the basis for maintaining muscle tone.

- Golgi receptors- afferent fiber located among the connective tissue fibers of the tendon - Excited when the muscle is tense and inhibited when it relaxes(sequential activation with the muscle) - inhibits overstretching of the muscle.

Reflex-motor sphere: morphophysiology

1. General features of two-neuron pathways for movement implementation

- First neuron (central) is located in the cerebral cortex (precentral gyrus).

- Axons of the first neurons cross over to the opposite side.

- Second neuron (peripheral) is located in the anterior horns of the spinal cord or in the motor nuclei of the brainstem (alpha major)

2. Corticospinal (pyramidal) tract

Pair and precentral lobules, posterior sections of the superior and middle frontal gyrus (body I - Betz cells of layer V of the cerebral cortex) - corona radiata - anterior two-thirds of the posterior limb of the internal capsule - base of the brain (cerebral peduncles) - incomplete decussation at the border of the medulla oblongata and spinal cord: crossed fibers (80%) - in the lateral cords of the spinal cord(to alpha major motor neurons of limb muscles) , uncrossed fibers (Turk's bundle, 20%) - in the anterior cords of the spinal cord (to the alpha large motor neurons of the axial muscles).

- Nuclei of the anterior horn of the spinal cord(body II, alpha large motor neurons) of the opposite side - anterior roots - spinal nerves - nerve plexuses - peripheral nerves - skeletal (striated) muscles.

3. Spinalmuscle innervation (Forster):

- Cervical level (C): 1-3 - small muscles neck; 4 - rhomboid and diaphragmatic muscles; 5 - mm.supraspinatus, infraspinatus, teres minor, deltoideus, biceps, brachialis, supinator brevis et longis; 6 - mm.serratus anterior, subscapullaris, pectoris major et minor, latissimus dorsi, teres major, pronator teres; 7 - mm.extensor carpi radialis, ext.digitalis communis, triceps, flexor carpi radialis et ulnaris; 8 - mm.extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus, palmaris longus, flexor digitalis superficialis et profundus, flexor pollicis brevis;

- Thoracic level (Th): 1 - mm.extensor pollicis brevis, adductor pollicis, flexor pollicis brevis intraosseii; 6-7 - pars superior m.rectus abdominis; 8-10 - pars inferior m.rectus abdominis; 8-12 - oblique and transverse muscles belly;

- Lumbar level (L): 1 - m.Illiopsoas; 2 - m.sartorius; 2-3 - m.gracillis; 3-4 - hip adductors; 2-4 - m.quadroiceps; 4 - m.fasciae latae, tibialis anterior, tibialis posterior, gluteus medius; 5 - mm.extensor digitorum, ext.hallucis, peroneus brevis et longus, quadratus femorris, obturatorius internus, piriformis, biceps femoris, extensor digitorum et hallucis;

- Sacral level (S): 1-2 - calf muscles, finger flexors and thumb; 3 - muscles of the sole, 4-5 - muscles of the perineum.

4. Corticonuclear pathway

- Anterior central gyrus(lower part) (body I - Betz cells of layer V of the cerebral cortex) - corona radiata - knee of the internal capsule - base of the brain (cerebral peduncles) - cross directly above the corresponding nuclei ( incomplete- bilateral innervation for III, IV, V, VI, upper ½ VII, IX, X, XI cranial nerves; full- unilateral innervation for the lower ½ VII and XII cranial nerves - rule 1.5 cores).

- Cranial nerve nuclei(body II, alpha large motor neurons) of the same and/or opposite side - cranial nerves - skeletal (striated) muscles.

5. Reflexarcs of basic reflexes:

- Tendon and periosteal(place and method of evocation, afferent part, level of closure, efferent part, effect) :

1) Superciliary- percussion of the brow ridge - - [ trunk] - - closing the eyelids;

2) Mandibular(Bekhterev) - chin percussion - - [ trunk] - - closing of the jaws;

3) Carporadial- from the styloid process of the radius - - [ C5-C8] - - bending in elbow joint and pronation of the forearm;

4) Bicipital- from the biceps tendon - - [ C5-C6] - - flexion at the elbow joint;

5) Tricipital- from the triceps tendon - - [ C7-C8] - - extension at the elbow joint;

6) Knee- with ligamentum patellae - - - [ n.femoralis] - extension in the knee joint;

7) Achilles- from tendon calf muscle - - [S1-S2] - - plantar flexion of the foot.

- Tonic postural reflexes(regulate muscle tone depending on the position of the head):

1) Cervical,

2) Labyrinth;

- From the skin and mucous membranes(Same) :

1) Corneal (corneal)- from the cornea of the eye - - [ trunk

2) Conjunctival- from the conjunctiva of the eye - - [ trunk] - - closing the eyelids;

3) Pharyngeal (palatal)- from the back wall of the pharynx (soft palate) - - [ trunk] - - act of swallowing;

4) Abdominal upper- line irritation of the skin parallel to the costal arch in the direction from outside to inside - - [ Th7-Th8

5) Abdominal middle - line irritation of the skin perpendicular to the midline in the direction from outside to inside - - [ Th9-Th10] - - contraction of the abdominal muscle;

6) Abdominal lower- line irritation of the skin parallel to the inguinal fold in the direction from the outside to the inside - - [ Th11-Th12] - - contraction of the abdominal muscle;

7) Cremasteric- streak skin irritation inner surface hips from bottom to top - - [ L1-L2] - - raising the testicle;

8) Plantar- streak irritation of the skin of the outer plantar surface of the foot - - [ L5-S1] - - flexion of the toes;

9) Anal (superficial and deep)- streak irritation of the skin of the perianal zone - - [ S4-S5] - - contraction of the anal sphincter

- Vegetative:

1) Pupillary reflex- eye lighting - [ retina (I and II body) - n.opticus - chiasm - tractus opticus ] - [ lateral geniculate body (III body) - superior colliculus of the quadrigeminal (IV body) - Yakubovich-Edinger-Westphal nucleus (V body) ] - [ n.oculomotorius (preganglionic) - gang.ciliare (VI body) - n.oculomotorius (postganglionic) - sphincter of the pupil ]

2) Reflex for accommodation and convergence- tension of the internal rectus muscles - [ same way ] - miosis (direct and friendly reaction);

3) Cervical-heart(Chermak) - see Autonomic nervous system;

4) Ocular-heart(Danyini-Aschner) - see Autonomic nervous system.

6. Peripheral mechanisms for maintaining muscle tone (gamma loop)

- Tonogenic formations of the brain(red nuclei, vestibular nuclei, reticular formation) - rubrospinal, vestibulospinal, reticulospinal tract [inhibitory or excitatory effect]

- gamma neuron(anterior horns of the spinal cord) [intrinsic rhythmic activity] - gamma fiber as part of the anterior roots and nerves

Muscular part of intrafusal fiber - nuclear chains (static, tonic) or nuclear bags (dynamic)

Annulospiral endings - sensory neuron(dorsal ganglion)

- alpha small motor neuron

Extrafusal fibers (contraction).

7. Regulationpelvic organs

- Bladder:

1) parasympathetic center(S2-S4) - contraction of the detrusor, relaxation of the internal sphincter (n.splanchnicus inferior - inferior mesenteric ganglion),

2) sympathetic center(Th12-L2) - contraction of the internal sphincter (n.splanchnicus pelvinus),

3) arbitrary center(sensitive - gyrus of the fornix, motor - paracentral lobule) at the level of S2-S4 (n.pudendus) - contraction of the external sphincter,

4) arc of automatic urination- proprioceptors tensile- spinal ganglia - dorsal roots S2-S4 - parasympathetic center is activated(detrusor contraction) and sympathetic tomositis (relaxation of the internal sphincter) - proprioceptors from the walls of the urethra in the area of the external sphincter- deep sensitivity to the gyrus of the fornix - paracentral lobule - pyramid path(relaxation of the external sphincter) ,

5) defeat - central paralysis(acute urinary retention - periodic incontinence (automatism of MP), or imperative urges), paradoxical ischuria(MP is full, drop by drop due to overstretching of the sphincter), peripheral paralysis(denervation of the sphincters - true urinary incontinence).

- Rectum:

1) parasympathetic center(S2-S4) - increased peristalsis, relaxation of the internal sphincter (n.splanchnicus inferior - inferior mesenteric ganglion),

2) sympathetic center(Th12-L2) - inhibition of peristalsis, contraction of the internal sphincter (n.splanchnicus pelvinus),

3) arbitrary center(sensitive - gyrus of the fornix, motor - paracentral lobule) at the level of S2-S4 (n.pudendus) - contraction of the external sphincter + abdominal muscles,

4) arc of automatic defecation- see MP ,

5) defeat- see MP.

- Genital organs:

1) parasympathetic center(S2-S4) - erection (nn.pudendi),

2) sympathetic center(Th12-L2) - ejaculation (n.splanchnicus pelvinus),

3) automatic arc;)

4) defeat - central neuron - impotence (may be reflex priapism and involuntary ejaculation), peripheral- persistent impotence.

Reflex-motor sphere: research methods

1. Rules for studying the reflex-motor sphere:

Grade subjective the patient’s sensations (weakness, awkwardness in the limbs, etc.),

At objective the study is being assessed absolute[muscle strength, magnitude of reflexes, severity of muscle tone] and relative indicators[symmetry of strength, tone, reflexes (anisoreflexia)].

2. Range of active and passive movements in the main joints

3. Muscle strength study

- Voluntary, active muscle resistance(by volume of active movements, dynamometer and level of resistance to external force on a six-point scale): 5 - complete preservation of motor function, 4 - slight decrease in muscle strength, compliance, 3 - active movements in full in the presence of gravity, the weight of the limb or its segment overcomes, but there is pronounced compliance, 2 - active movements in full while eliminating gravity, 1 - preservation of movement, 0 - complete lack of movement. Paralysis- lack of movement (0 points), paresis- decrease in muscle strength (4 - mild, 3 - moderate, 1-2 - deep).

- Muscle groups(check groups by system ISCSCI with corr.) :

1) proximal group of the hand:

1) raising your arm to the horizontal

2) raising the arm above the horizontal;

2) shoulder muscle group:

1) flexion at the elbow joint

2) extension in the elbow joint ;

3) muscle group of the hand:

1) flexion of the hand

2) extension brushes ,

3) flexion of the distal phalanx III finger ,

4) lead V finger ;

4) proximal leg group:

1) hip flexion ,

2) hip extension,

3) hip abduction;

5) groupmusclesshins:

1) flexion of the lower leg,

2) extension shins ;

6) groupmusclesfeet:

1) rear bending feet ,

2) extension big finger ,

3) plantar bending feet ,

- Correspondence level of spinal cord damage and loss of movements:

1) cervical thickening

1) C5 - flexion at the elbow joint

2) C6 - wrist extension,

3) C7 - extension at the elbow joint;

4) C8 - flexion of the distal phalanx of the third finger

5) Th1 - abduction of the first finger

2) lumbar thickening

1) L2 - hip flexion

2) L3 - leg extension

3) L4 - dorsiflexion of the foot

4) L5 - thumb extension

5) S1 - plantar flexion of the foot

- Tests for hidden paresis:

1) upper Barre sample(straight arms in front of you, slightly above the horizontal - weak hand“sinks”, i.e. falls below horizontal)

2) Mingazzini test(similar, but the hands are in a supinated position - the weak hand “sinks”)

3) Panchenko test(arms above your head, palms facing each other - the weak hand “sinks”),

4) lower Barre sample(on the stomach, legs bent at the knee joints 45 degrees - the weak leg “sinks”),

5) Davidenkov’s symptom(symptom of the ring, keeping the ring from “breaking” between the index and thumb - muscle weakness leads to low resistance to “breaking” the ring),

6) Venderovich's symptom(holding the little finger while trying to move it away from the fourth finger of the hand - muscle weakness leads to easy abduction of the little finger).

4. Study of reflexes

- Tendon reflexes: carporadial, bicipital, tricipital, knee, Achilles.

- Reflexes from the surface of the skin and mucous membranes: corneal, pharyngeal, upper, middle, lower abdominal, plantar.

5. Study of muscle tone - involuntary muscle resistance is assessed during passive movements in the joints with maximum voluntary relaxation:

Flexion-extension in the elbow joint (tone of the squeezers and extensors of the forearm);

Pronation-supination of the forearm (tone of the pronators and supinators of the forearm);

Flexion-extension in the knee joint (tonus of the quadriceps and femoral biceps, gluteal muscles etc.).

6. Change in gait (a set of features of posture and movements when walking).

- Steppage(French “steppage” - trotting, peroneal gait, rooster gait, stork) - high raising of the leg with throwing it forward and sharp lowering - with peripheral paresis of the peroneal muscle group.

- Duck gait- rolling the body from side to side - with paresis deep muscles pelvis and hip flexors.

- Hemiplegic gait(mowing, mowing, circumducing) - excessive abduction of the paretic leg to the side, as a result of which it describes a semicircle with each step; in this case, the paretic arm is bent at the elbow and brought to the body - Wernicke-Mann position - with hemiplegia.

Reflex-motor sphere: symptoms of damage

1. Symptoms of loss

- Peripheral paralysis develops when a peripheral motor neuron is damaged in any area, the symptoms are caused by a weakening of the level of segmental reflex activity:

1) decreased muscle strength,

2) muscle areflexia(hyporeflexia) - a decrease or complete absence of deep and superficial reflexes.

3) muscle atony- decreased muscle tone,

4) muscle atrophy- decrease muscle mass,

+ fibrillary or fascicular twitching(symptom of irritation) - spontaneous contractions of muscle fibers (fibrillar) or groups of muscle fibers (fascicular) - specific sign defeats body peripheral neuron.

- Central paralysis (unilateral lesion of the pyramidal tract) develops when the central motor neuron is damaged in any area, symptoms are caused by an increase in the level of segmental reflex activity:

1) decreased muscle strength,

2) hyperreflexia of tendon reflexes with expansion of reflexogenic zones.

3) reduction or absence of superficial (abdominal, cremasteric and plantar) reflexes

4) clonus feet, hands and kneecaps - rhythmic muscle contractions in response to stretching of the tendons.

5) pathological reflexes:

- Foot flexion reflexes- reflex flexion of the toes:

- Rossolimo- a short jerky blow to the tips of the 2-5 toes,

- Zhukovsky- a short jerky blow with a hammer in the middle of the patient’s foot,

- Goffman- pinching irritation of the nail phalanx of the II or III toes,

- Bekhtereva- a short jerky blow with a hammer on the back of the foot in the area of 4-5 metatarsal bones,

- Bekhterev calcaneal- a short, jerky blow to the heel with a hammer.

- Foot extensor reflexes- appearance of extension of the big toe and fan-shaped divergence of 2-5 toes:

- Babinsky- moving the handle of the hammer along the outer edge of the foot,

- Oppenheim- running along the anterior edge of the tibia,

- Gordon- compression of the calf muscles,

- Schaeffer- compression of the Achilles tendon,

- Chaddock- streak irritation around the outer ankle,

- Carpal analogues of flexion reflexes- reflex flexion of the fingers (thumb):

- Rossolimo- a jerky blow to the tips of the 2-5 fingers of the hand in a pronated position,

- Goffman- pinching irritation of the nail phalanx of the II or III fingers of the hand (1), IV or V fingers of the hand (2),

- Zhukovsky- a short jerky blow with a hammer in the middle of the patient’s palm,

- Bekhtereva- a short jerky blow with a hammer on the back of the hand,

- Galanta- a short jerky blow with a hammer on the tenar,

- Jacobson-Lask- a short jerky blow with a hammer on the styloid process.

6) protective reflexes: Bekhterev-Marie-Foy- with sharp painful flexion of the toes, “triple flexion” of the leg occurs (in the hip, knee and ankle joints).

7) muscle hypertension - increased muscle tone of the spastic type (the “jackknife” symptom is determined - when passively extending a bent limb, resistance is felt only at the beginning of the movement), development of contractures, Wernicke-Mann pose(arm flexion, leg extension)

8) pathological synkinesis- involuntary friendly movements that accompany the performance of active actions ( physiological- swinging arms while walking, pathological- arise in a paralyzed limb due to the loss of the inhibitory influences of the cortex on intraspinal automatisms:

- global- change in the tone of the injured limbs in response to prolonged muscle tension on the healthy side (sneezing, laughing, coughing) - shortening in the arm (flexion of the fingers and forearm, shoulder abduction), lengthening in the leg (hip adduction, shin extension, foot flexion),

- coordinator- involuntary contractions of paretic muscles with voluntary contraction of functionally associated muscles (Strumpel's tibial phenomenon - dorsiflexion is impossible, but appears when bending the knee joint; Raymist's symptom - does not adduct the leg at the hip, but when the healthy leg is adducted, movement occurs in the paretic one; Babinski phenomenon - standing up without the help of hands - a healthy and paretic leg rises),

- imitation- involuntary movements of a paretic limb, imitating volitional movements of a healthy one.

- Central paralysis (bilateral damage to the pyramidal tract):

+ dysfunction of the pelvic organs of the central type- acute urinary retention when the pyramidal tract is damaged, followed by periodic urinary incontinence (reflex emptying of the bladder due to overdistension), accompanied by an imperative urge to urinate.

- Central palsy (unilateral lesion of the corticonuclear pathway): according to the rule of 1.5 nuclei, only the lower ½ nucleus of the facial nerve and the nucleus of the hypoglossal nerve have unilateral cortical innervation:

1) smoothness of the nasolabial fold and drooping of the corner of the mouth on the side opposite to the lesion,

2) tongue deviation in the direction opposite to the lesion (deviation is always towards the weak muscles).

- Central palsy (bilateral damage to the corticonuclear pathway):

1) decreased muscle strength muscles of the pharynx, larynx, tongue (dysphagia, dysphonia, dysarthria);

2) strengthening of the chin reflex;

3) pathological reflexes = oral automatism reflexes:

- Sucking(Oppenheim) - sucking movements with line irritation of the lips,

- Proboscis- hitting the upper lip with a hammer causes the lips to stretch forward or contract orbicularis muscle mouth,

- Nasolabial(Astvatsaturova) - a blow with a hammer to the back of the nose causes the lips to be pulled forward or the orbicularis oris muscle to contract,

- Distance-oral(Karchikyan) - bringing the hammer to the lips causes the lips to be pulled forward,

- Palmomental(Marinescu-Radovici) - line irritation of the thenar skin causes contraction of the mental muscle on the same side.

2. Symptoms of irritation

- Jacksonian epilepsy - paroxysmal clonic spasms of individual muscle groups, with possible spread and secondary generalization (most often from the thumb (maximum zone of representation in the precentral gyrus) - other fingers - hand - upper limb - face - whole body = Jacksonian march)

- Kozhevnikovskaya epilepsy (epilepsypartialiscontinua)- constant convulsions (myoclonus in combination with torsion dystonia, choreoathetosis) with periodic generalization (chronic tick-borne encephalitis)

Reflex-motor sphere: levels of damage

1. Levels of damage in central paralysis:

- Prefrontal cortex - area 6(monoparesis in the contralateral arm or leg, normal tone with rapid increase),

- Precentral gyrus - area 4(monoparesis in the contralateral arm or leg, low tone with long recovery, Jacksonian march - a symptom of irritation),

- Inner capsule(contralateral hemiparesis with damage to the corticonuclear tract, more pronounced in the arm, marked increase in muscle tone),

- Brain stem(contralateral hemiparesis in combination with lesions of the brain stem nuclei - alternating syndromes)

- Pyramid Crossing(complete lesion - tetraplegia, lesion of the external parts - alternating hemiplegia [contralateral paresis in the leg, ipsilateral paresis in the arm]),

- Lateral and anterior cord of the spinal cord(ipsilateral paralysis below the level of injury).

2. Levels of damage in peripheral paralysis:

- Procorneal(muscle paresis in the segment area + fasciculations).

- Koreshkovy(paresis of muscles in the area of innervation of the root),

- Polyneuritic(muscle paresis in the distal limbs),

- Mononeuritic(paresis of muscles in the area of innervation of the nerve, plexus).

Differential diagnosis of motor syndromes

1. Central or mixed hemiparesis- muscle paralysis that has developed in the arm and leg on one side.

- suddenly developing or rapidly progressing:

1) Acute cerebrovascular accident (stroke)

2) Traumatic brain injury and trauma cervical spine spine

3) Brain tumor (with pseudo-stroke course)

4) Encephalitis

5) Postictal state (after an epileptic seizure, Todd's palsy)

6) Multiple sclerosis

7) Migraine with aura (hemiplegic migraine)

8) Brain abscess;

- slowly progressive

1) Acute cerebrovascular accident (atherothrombotic stroke)

2) Brain tumor

3) Subacute and chronic subdural hematoma

4) Brain abscess;

5) Encephalitis

6) Multiple sclerosis

- required examination methods:

1) clinical minimum (OAC, OAM, ECG)

2) neuroimaging (MRI, CT)

3) electroencephalography

4) hemostasiogram / coagulogram

2. Lower spastic paraparesis- muscle paralysis lower limbs symmetrical or almost symmetrical:

- spinal cord compression (combined with sensory disturbances)

1) Tumors of the spinal cord and cranio-vertebral junction

2) Spinal diseases (spondylitis, disc herniation)

3) Epidural abscess

4) Arnold-Chiari malformation

5) Syringomyelia

- hereditary diseases

1) Strumpel's familial spastic paraplegia

2) Spinocerebellar degenerations

- infectious diseases

1) Spirochetoses (neurosyphilis, neuroborreliosis)

2) Vacuolar myelopathy (AIDS)

3) Acute transverse myelitis (including post-vaccination)

4) Tropical spastic paraparesis

- autoimmune diseases

1) Multiple sclerosis

2) Systemic lupus erythematosus

3) Devic's optomyelitis

- vascular diseases

1) Lacunar conditions (occlusion of the anterior spinal artery)

2) Epidural hematoma

3) Cervical myelopathy

- other diseases

1) Funicular myelosis

2) Motor neuron disease

3) Radiation myelopathy

Reflex-motor sphere: characteristics of young children

1. Volume of active and passive movements:

Volume of active movements - by visual assessment: symmetry and completeness of range of motion

Range of passive movements - flexion and extension of limbs

2. Muscle strength - assessed by observation spontaneous activity and when testing unconditioned reflexes.

3. Study of reflexes:

- Reflexes of “adults”- appear and are saved in the future:

1) from birth - knee, bicipital, anal

2) from 6 months - tricipital and abdominal (from the moment of sitting down)

- Reflexes " childhood» - present at birth and normally disappear by a certain age:

1) oral group of reflexes= reflexes of oral automaticity:

- Sucking- with line irritation of the lips - sucking movements (up to 12 months),

- Proboscis- touching the lips - pulling the lips forward (up to 3 months),

- Search engine(Kussmaul) - when stroking the corner of the mouth - turn the head in this direction and open the mouth slightly (up to 1.5 months)

- Palmo-oral(Babkina) - pressing on both palms - opening the mouth and slightly bringing the head to the chest (up to 2-3 months)

2) spinal group of reflexes:

- on the back:

- grasping(Robinson) - pressing on the palms - grasping the fingers (symmetry is important) (up to 2-3 months)

- grasping(Moro) - raising the arms with a sharp lowering (or hitting the table) - 1st phase: raising the arms - 2nd phase: clasping one’s own torso (up to 3-4 months)

- plantar- pressing on the foot - sharp plantar flexion of the toes (up to 3 months)

- Babinsky- irritation of the outer edge of the foot - fan-shaped extension of the toes (up to 24 months)

- cervical tonic symmetric reflex (CTSR)- flexion of the head - flexion in the arms and extension in the legs (up to 1.5-2.5 months)

- cervical tonic asymmetric reflex (ASTR, Magnus-Klein)- turning the head - straightening the arm and leg on the side of the turn, bending on the opposite side - “fencing pose” (visually disappears by 2 months, but when testing the tone, traces of it can be felt up to 6 months).

- on the stomach:

- protective- when lying on the stomach - turning the head to the side (up to 1.5-2 months), then it is replaced by voluntary holding of the head with the crown of the head up),

- labyrinthine tonic(LTR) - when positioned on the stomach - flexion of the arms and legs, then after 20-30 s swimming movements (up to 1-1.5 months),

- crawling(Bauer) - resting the feet in the palm of the researcher - extension of the leg (“crawling”) (up to 3 months),

- Galanta- line irritation paraventrally - flexion in the direction of irritation, flexion of the arm and leg on the same side (up to 3 months),

- Pereza- line irritation along the spinous processes from the coccyx to the neck - extension of the spine, elevation of the head and pelvis, movements of the limbs (up to 3 months),

- vertically:

- supports- feet on the table - 1st phase: withdrawal with flexion, 2nd phase: support on the table - straightens the legs, torso and slightly throws back the head, the researcher has a feeling of a “straightening spring” (up to 3 months, but only the “spring” phenomenon disappears, and the actual support on the foot does not disappear and subsequently becomes the basis for the formation of independent walking),

- automatic walking- when bending to the sides - phase 3: flexion/extension of the legs (“walking”) (up to 2 months).

3) chain symmetrical reflexes- steps towards verticalization:

- straightening from the body to the head- feet on support - straightening of the head (from 1 month to 1 year),

- cervical erector- turn the head - turn the body in the same direction (allows you to turn from back to side, from 2-3 months - up to 1 year)

- straightening the torso- the same, but with rotation between the shoulders and pelvis (allows you to roll over from back to side, from 5-6 months to 1 year)

- Upper Landau- in the position on the stomach - emphasis on the arms and raising the upper half of the body (from 3-4 months - to 6-7 months)

- Landau lower- the same + extension in the back in the form of strengthening of lumbar lordosis (from 5-6 months - to 8-9 months)

4. Muscle tone:

- Peculiarities: In children of the first year of life, the tone of the flexors (“embryonic position”) is increased; during the study it is important correct technique examination (comfortable ambient temperature, painless contact).

- Variants of pathological changes in tone in children:

1) opisthotonus- on the side, head thrown back, limbs straightened and tense,

2) “frog” pose(muscular hypotonia) - limbs in a state of extension and abduction, "seal feet"- drooping hands, "heel feet"- the toes are brought to the front surface of the shin.

3) “fencer” pose(central hemiparesis) - on the affected side - the arm is extended, internally rotated in the shoulder, pronated in the forearm, bent in the palm; on the opposite side - the arm and leg are bent.

Neural organization of the spinal cord

Neurons of the spinal cord form gray matter in the form of symmetrically located two anterior and two posterior horns in the cervical, lumbar and sacral regions. In the thoracic region, the spinal cord has, in addition to those mentioned, also lateral horns.

The posterior horns perform mainly sensory functions and contain neurons that transmit signals to overlying centers, to symmetrical structures on the opposite side, or to the anterior horns of the spinal cord.

The anterior horns contain neurons that send their axons to the muscles. All descending pathways of the central nervous system that cause motor responses end on the neurons of the anterior horns.

The human spinal cord contains about 13 million neurons, of which 3% are motor neurons, and 97% are intercalary neurons. Functionally, spinal cord neurons can be divided into 5 main groups:

1) motor neurons, or motor neurons, are cells of the anterior horns, the axons of which form the anterior roots. Among motor neurons, a-motoneurons are distinguished, transmitting signals to muscle fibers, and γ-motoneurons, innervating intraspinal muscle fibers;

2) interneurons of the spinal cord include cells that, depending on the course of their processes, are divided into: stinal, the processes of which branch within several adjacent segments, and interneurons, the axons of which pass through several segments or even from one part of the spinal cord to another, forming own bundles of the spinal cord;

3) the spinal cord also contains projection interneurons that form the ascending tracts of the spinal cord. Interneurons are neurons that receive information from the genital ganglia and are located in the dorsal horns. These neurons respond to pain, temperature, tactile, vibration, proprioceptive stimulation;

4) sympathetic, parasympathetic neurons are located mainly in the lateral horns. The axons of these neurons exit the spinal cord as part of the ventral roots;

5) associative cells - neurons of the spinal cord’s own apparatus, establishing connections within and between segments.

In the middle zone of the gray matter (between the posterior and anterior horns) and at the apex of the posterior horn of the spinal cord, the so-called gelatinous substance (gelatinous substance of Roland) is formed and performs the functions of the reticular formation of the spinal cord.

Functions of the spinal cord. The first function is reflexive. The spinal cord carries out motor reflexes of skeletal muscles relatively independently. Examples of some motor reflexes of the spinal cord are: 1) elbow reflex - tapping on the tendon of the biceps brachii muscle causes flexion in the elbow joint due to nerve impulses that are transmitted through 5-6 cervical segments; 2) knee reflex - tapping the tendon of the quadriceps femoris muscle causes extension in the knee joint due to nerve impulses that are transmitted through the 2-4 lumbar segments. The spinal cord is involved in many complex coordinated movements - walking, running, labor and sports activities, etc. The spinal cord carries out autonomic reflexes to change the functions of internal organs - cardiovascular, digestive, excretory and other systems.
Thanks to reflexes from proprioceptors in the spinal cord, motor and autonomic reflexes are coordinated. Reflexes are also carried out through the spinal cord from internal organs to skeletal muscles, from internal organs to receptors and other organs of the skin, from an internal organ to another internal organ.
The second function is conductive. Centripetal impulses entering the spinal cord along the dorsal roots are transmitted along short pathways to its other segments, and along long pathways to different parts of the brain.
The main long pathways are the following ascending and descending pathways.

9. PARTICIPATION OF THE SPINAL CORD IN THE REGULATION OF MUSCLE TONE. ROLE OF ALPHA AND GAMA MOTONEURONS IN THIS PROCESS.

The function of maintaining muscle tone is provided by the principle of feedback at various levels of regulation of the body. Peripheral regulation is carried out with the participation of the gamma loop, which includes supraspinal motor pathways, interneurons, the descending reticular system, alpha and gamma neurons.

There are two types of gamma fibers in the anterior horn of the spinal cord. Gamma-1 fibers ensure the maintenance of dynamic muscle tone, i.e. tone necessary for the implementation of the movement process. Gamma-2 fibers regulate the static innervation of muscles, i.e. posture, posture of a person. Central regulation of the functions of the gamma loop is carried out by the reticular formation through the reticulospinal tract. The main role in maintaining and changing muscle tone is given to the functional state of the segmental arc of the stretch reflex (myotatic or proprioceptive reflex). Let's take a closer look at it.

Its receptor element is the encapsulated muscle spindle. Each muscle contains a large number of these receptors. The muscle spindle consists of intrafusal muscle fibers (thin) and a nuclear bursa, braided by a spiral-shaped network of thin nerve fibers, which are the primary sensory endings (anulospinal filament). Some intrafusal fibers also have secondary, grape-shaped sensory endings. When intrafusal muscle fibers are stretched, the primary sensory endings strengthen the impulses emanating from them, which are carried through fast-conducting gamma-1 fibers to the alpha-large motor neurons of the spinal cord. From there, through also fast-conducting alpha-1 efferent fibers, the impulse goes to the extrafusal white muscle fibers, which provide rapid (phasic) muscle contraction. From secondary sensory endings that respond to muscle tone, afferent impulses are carried along thin gamma-2 fibers through a system of interneurons to alpha small motor neurons, which innervate the tonic extrafusal muscle fibers (red), which maintain tone and posture.

The consequence of this is muscle spasticity, hyperreflexia, the appearance of pathological reflexes, as well as the primary loss of the most subtle voluntary movements.

The most significant component of muscle spasm is pain. Painful impulses activate alpha and gamma motor neurons of the anterior horns, which increases the spastic contraction of the muscle innervated by this segment of the spinal cord. At the same time, muscle spasm that occurs during the sensorimotor reflex increases the stimulation of the muscle's nociceptors. Thus, according to the negative feedback mechanism, a vicious circle is formed: spasm - pain - spasm - pain.

In addition, local ischemia develops in spasmodic muscles, since algogenic chemicals (bradykinin, prostaglandins, serotonin, leukotrienes, etc.) have a pronounced effect on the vessels, causing vasogenic tissue edema. Under these conditions, substance “P” is released from the terminals of type “C” sensory fibers, as well as the release of vasoactive amines and increased microcirculatory disorders.

10. REFLECTOR ACTIVITY OF THE MEDULENA, ITS ROLE IN THE REGULATION OF MUSCLE TONE. DECEREBRATORY RIGIDITY. The medulla oblongata, like the spinal cord, performs two functions - reflex and conductive. Eight pairs of cranial nerves (V to XII) emerge from the medulla oblongata and the pons and it, like the spinal cord, has a direct sensory and motor connection with the periphery. It receives impulses through sensory fibers - information from the receptors of the scalp, mucous membranes of the eyes, nose, mouth (including taste buds), from the organ of hearing, vestibular apparatus(organ of balance), from receptors of the larynx, trachea, lungs, as well as from interoreceptors cordially- vascular system and digestive systems. Through the medulla oblongata, many simple and complex reflexes are carried out, covering not individual metameres of the body, but organ systems, for example, the digestive, respiratory, and circulatory systems.

Reflex activity. The following reflexes occur through the medulla oblongata:

· Protective reflexes: coughing, sneezing, blinking, tearing, vomiting.

· Food reflexes: sucking, swallowing, juice production (secretion) of the digestive glands.

· Cardiovascular reflexes that regulate the activity of the heart and blood vessels.

· The medulla oblongata contains an automatically functioning respiratory center that provides ventilation to the lungs.

· The vestibular nuclei are located in the medulla oblongata.

From the vestibular nuclei of the medulla oblongata begins the descending vestibulospinal tract, which is involved in the implementation of posture reflexes, namely in the redistribution of muscle tone. A bulbar cat can neither stand nor walk, but the medulla oblongata and cervical segments of the spinal cord provide those complex reflexes that are elements of standing and walking. All reflexes associated with the standing function are called positioning reflexes. Thanks to them, the animal, despite the forces of gravity, maintains the posture of its body, as a rule, with the crown of the head upward. The special importance of this part of the central nervous system is determined by the fact that the medulla oblongata contains vital centers - respiratory, cardiovascular, therefore not only removal, but even damage to the medulla oblongata results in death.
In addition to the reflex function, the medulla oblongata performs a conductive function. Conducting pathways pass through the medulla oblongata, connecting the cortex, diencephalon, midbrain, cerebellum and spinal cord with a bilateral connection.

The medulla oblongata plays important role in the implementation of motor acts and in the regulation of skeletal muscle tone. Influences emanating from the vestibular nuclei of the medulla oblongata increase the tone of the extensor muscles, which is important for the organization of posture.

Nonspecific parts of the medulla oblongata, on the contrary, have a depressing effect on the tone of skeletal muscles, reducing it in the extensor muscles. The medulla oblongata is involved in the implementation of reflexes to maintain and restore body posture, the so-called positioning reflexes.

Decerebrate rigidity is a plastic, pronounced increase in the tone of all muscles that function with resistance to gravity (extensor spasticity), and is accompanied by fixation in the position of extension and inward rotation of the arms and legs. and also often opisthotonus. This condition is also called apallic syndrome. It is based on damage to the midbrain, especially herniation into the tentorial foramen due to supratentorial processes, primarily neoplasia in the temporal lobes, cerebral hemorrhage with breakthrough of blood into the ventricles, severe brain contusions, hemorrhage into the brainstem, encephalitis, anoxia, and poisoning. The pathology may initially manifest itself in the form of “cerebral spasms” and be provoked by external stimuli. With the complete cessation of the influence of descending impulses in the spinal cord, spasticity develops in the flexors. Rigidity is a sign of damage to the extrapyramidal system. It is observed in various etiological variants of parkinsonism syndrome (accompanied by akinesia, the “cogwheel” phenomenon and often tremor, which first appear on one side) and in other degenerative diseases accompanied by parkinsonism, for example, olivopontocerebellar atrophy, orthostatic hypotension, Creutzfeldt-Jakob disease, etc. .

Characteristic posture for decerebrate rigidity

Lecture: “Physiology of the spinal cord”

Lecture outline:

4. Spinal reflexes

5. Spinal shock. Characteristics of the spinal animal. Consequences of complete and partial transection of the spinal cord

The spinal cord is the most ancient formation of the central nervous system; it first appears in the lancelet. The spinal cord has a segmental structure.

^ 1. General characteristics spinal cord functions

The main functions of the spinal cord include: sensory, conductive and reflex functions.

At the level of neurons of the spinal cord occurs primary information analysis from proprioceptors and skin receptors of the trunk, limbs and a number of visceroreceptors. Proprioceptors include muscle receptors, tendon receptors, periosteum, and joint membranes. Skin receptors are receptors located on the surface and in the thickness of the skin: pain, temperature, tactile and pressure receptors.

Ascending and descending fibers (white matter) form the spinal cord pathways, through which information coming from receptors is transmitted and impulses come from the overlying parts of the central nervous system.

Due to the functional diversity of spinal cord neurons, the presence of numerous segmental, intersegmental connections and connections with brain structures, conditions are created for reflex activity spinal cord.

^ 2. Neural organization of the spinal cord. Segmental and intersegmental principles of operation of the spinal cord.

The human spinal cord contains about 13 million neurons, of which 3% are motor neurons, 97% are intercalary neurons. Functionally, spinal cord neurons can be divided into 4 groups:

^ 1. Motor neurons are cells of the anterior horns of the spinal cord, the axons of which form the anterior horns.

2. Interneurons receive information from the spinal ganglia and are located in the dorsal horns. These are sensitive neurons that respond to pain, temperature, tactile, vibration and proprioceptive stimulation.

^ 3. Sympathetic (lateral horns of the spinal cord) and parasympathetic (sacral department).

4. Associative neurons of the spinal cord’s own apparatus establish connections within and between segments.

^ Motor neurons of the spinal cord.

Motor neurons are divided into α- and gamma motor neurons. The size of alpha motor neurons ranges from 40-70 microns, gamma motor neurons - 30-40 microns. 1/3 of the diameter of the anterior root is occupied by the axons of gamma motor neurons. The motor neuron axon innervates muscle fibers. Skeletal muscles have 2 types of fibers: intrafusal and extrafusal. The intrafusal fiber is located inside the so-called muscle spindle - this is a specialized muscle receptor located in the thickness skeletal muscle. This fiber is necessary to regulate receptor sensitivity. It is controlled by the gamma motor neuron. All muscle fibers belonging to a given muscle and not part of the muscle spindle are called extrafusal.

Alpha motor neurons innervate skeletal muscle fibers (extrafusal fibers) to produce muscle contractions. Gamma motor neurons innervate intrafusal fibers, muscle spindles, which are stretch receptors. There is a combined activation of alpha and gamma motor neurons. The alpha motor neuron axon is the only channel connecting nervous system with skeletal muscle. Only the excitation of the alpha motor neuron leads to the activation of the corresponding muscle fibers.

There are 3 ways of connecting fibers of the descending pathways with alpha motor neurons:

^ 1. Direct descending influence on alpha motor neuron

2 Indirectly through an interneuron

3. Activation of gamma motor neuron and through intrafusal fiber to alpha motor neuron

Gamma loop:

Gama motor neurons activate infrafusal muscle fibers, as a result of which afferent nerve fibers are activated and the flow of impulses goes to alpha motor neurons or intercalary motor neurons, and from them to alpha motor neurons - this is called the gamma loop.

Segmental and intersegmental principles of operation of the spinal cord:

The spinal cord is characterized by a segmental structure, reflecting the segmental structure of the body of vertebrates. Two pairs of ventral and dorsal roots arise from each spinal segment. 1 sensory and 1 motor root innervates its transverse layer of the body, i.e. metamer. This is the segmental principle of the spinal cord. The intersegmental principle of operation is the innervation by the sensory and motor roots of its metamere, the 1st overlying and 1st underlying metamer. Knowledge of the boundaries of body metameres makes it possible to carry out topical diagnosis of spinal cord diseases.

^ 3. Conductive organization of the spinal cord

Axons of the spinal ganglia and gray matter of the spinal cord go into its white matter, and then into other structures of the central nervous system, thereby creating the so-called pathways, functionally divided into proprioceptive, spinocerebral (ascending) and cerebrospinal (descending).

^ Propriospinal tract connect neurons of the same or different segments of the spinal cord. The function of such connections is associative and consists in coordinating posture, muscle tone, and movements of various metameres of the body. One metamer includes 1 pair of spinal nerves and the area of the body innervated by them.

^ Spinocerebral tracts connect segments of the spinal cord with brain structures. They are represented by proprioceptive, spinothalamic, spinocerebellar and spinoreticular pathways/

a) The proprioceptive pathway (thin fascicle of Gaulle and wedge-shaped fascicle of Burdach) starts from the deep sensitivity receptors of the periosteum, joint membranes, tendons and muscles. Through the spinal ganglion it goes to the dorsal roots of the spinal cord, into the white matter of the posterior cords and, without switching to a new neuron at the level of the spinal cord, rises to the Gaulle and Burdach nuclei of the medulla oblongata. Here a switch to a new neuron occurs, then the path goes to the lateral nuclei of the thalamus of the opposite hemisphere of the brain, here it switches to a new neuron (second switch). From the thalamus, the pathway ascends to the neurons of the somatosensory cortex. Along the way, the fibers of these tracts give off collaterals in each segment of the spinal cord, which creates the possibility of correcting the posture of the entire body.

b) The spinothalamic pathway begins from pain, temperature, and baroreceptors of the skin. The signal from the skin receptors goes to the spinal ganglion, then through the dorsal root to the dorsal horn of the spinal cord, here it switches to a new neuron (first switch). Sensory neurons in the dorsal horn send axons to the opposite side of the spinal cord and ascend along the lateral funiculus to the thalamus. Here the second switch occurs and rises to the sensory cortex. Some of the fibers of the skin receptors go to the thalamus along the anterior cord of the spinal cord.

c) The spinocerebellar tracts begin from the receptors of muscles, ligaments, and internal organs and are represented by the non-crossing Gowers fascicle and the double-crossing Flexig fascicle. Therefore, the right and left cerebellum receive information only from their side of the body. This information comes from Golgi tendon receptors, proprioceptors, pressure and touch receptors.

d) Spinoreticular tract – starts from the interneurons of the spinal cord and reaches the RF of the brain stem. Carries information from visceroreceptors.

Thus, through the conductive tracts of the spinal cord, impulses are carried out from the receptors of the trunk and limbs to the neurons of the spinal cord and overlying structures of the central nervous system.

^ Cerebrospinal tracts start from the neurons of the brain structures and end on the neurons of the spinal cord segments. These include the following pathways: the corticospinal tract, which provides regulation of voluntary movements, the rubrospinal, vestibulospinal and reticulospinal tracts, which regulate muscle tone. What these pathways have in common is that they end at the motor neurons of the anterior horns of the spinal cord.

^ 4. Spinal reflexes

The reflex activity of the spinal cord is based on a reflex, the structural and functional basis of which is the reflex arc. There are monosynaptic and polysynaptic reflex arcs.

^ Spinal reflexes are divided into into somatic (motor) and autonomic.

Motor reflexes, in turn, are divided into tonic(aimed at maintaining muscle tone, maintaining the limbs and the entire body in a certain static position) And phasic(provide movement of the limbs and torso).

Tonic ones include: myotatic reflex, cervical tonic reflexes of position, support reflex (they were first described by the Dutch physiologist Rudolf Magnus, 1924), flexion tonic reflex.

Phasic reflexes include: tendon reflexes, shortening reflexes from Golgi bodies, plantar, abdominal, flexion protective, extensor crossed, rhythmic.

^ Myotatic reflex – stretch reflex, for example, when a person takes a vertical position, due to gravitational forces he can fall (flexion in the joints of the lower extremities), but this does not happen with the participation of myotatic reflexes, because When a muscle is stretched, muscle spindles are activated, which are located parallel to the extrafusal fibers of the skeletal muscle. The impulse from the muscle receptors goes through the afferent neuron and enters the alpha motor neurons of the given muscle. As a result, shortening of the extrafusal water pipes occurs. Thus, the length of the muscle returns to its original length. The myotatic reflex is characteristic of all muscles, is well expressed and easily evoked in the flexor muscles, directed against gravitational forces, to maintain balance and muscle tone. It should be noted that impulses from the receptors simultaneously through the Renshaw intercalary inhibitory cells enter the alpha motor neurons of the antagonist of this muscle, therefore, when the agonist is shortened, the antagonist muscle does not interfere with this process.

Receptive field cervical tonic reflexes positions are the proprioceptors of the neck muscles and fascia covering the cervical spine. The central part of the reflex arc is polysynaptic in nature, i.e. includes interneurons. The reflex reaction involves the muscles of the trunk and limbs. In addition to the spinal cord, it also involves the motor nuclei of the brain stem, which innervate the muscles. eyeballs. Cervical tonic reflexes occur when turning and tilting the head, which causes stretching of the neck muscles and activates the receptive field of the reflex.

Support (push-off) reflex– when standing on the surface, the tone of the extensor muscles increases.

Flexion tonic reflex observed, for example, in a frog or a rabbit, in which a tucked position of the limbs is characteristic. This reflex is aimed at maintaining a certain posture, which is possible if there is a certain muscle tone.

Tendon reflex– shortening reflex from Golgi bodies

Plantar reflex– irritation of the skin of the foot leads to plantar flexion of the fingers and toes of the lower limb.

Abdominal reflexes- voltage abdominal muscles, arising from nociceptive afferent influences. This is a protective reflex.

Flexion defensive reflexes- occur when pain receptors in the skin, muscles and internal organs are irritated and are aimed at avoiding various damaging effects.

^ Extensor cross reflex: reflex flexion of one of the limbs is often accompanied by a contraction of the contralateral limb, onto which additional body weight is transferred under natural conditions (when walking).

^ To rhythmic reflexes in mammals this refers to the scratching reflex. Its analogue in amphibians is the rubbing reflex. Rhythmic reflexes are characterized by the coordinated work of the muscles of the limbs and torso, the correct alternation of flexion and extension of the limbs, along with tonic contraction of the adductor muscles, which establish the limb in a certain position to the skin surface.

^ Step reflex – agreed motor activity upper and lower extremities. To implement this reflex, intersegmental interaction of the muscles of the arms, legs and torso is necessary. The mechanisms of stepping movements are located in the spinal cord, but the spinal mechanism is activated from the midbrain.

^ Autonomic spinal reflexes : vascular, sweating, urination, defecation. Autonomic reflexes ensure the reaction of internal organs and the vascular system to irritation of visceral, muscle, and skin receptors.

^ 5. Spinal shock. Characteristics of the spinal animal. Consequences of complete and partial transection of the spinal cord.

Spinal shock(shock) occurs after complete transection of the spinal cord. It lies in the fact that all centers below the transection cease to organize their inherent reflexes. Spinal shock is characterized by a temporary disappearance of the reflex functions of the spinal cord. Disruption of reflex activity after transection of the spinal cord lasts for different times in different animals. In monkeys, the first signs of recovery of reflexes after transection of the spinal cord appear within a few days; in a frog it takes minutes; in humans, the first spinal reflexes are restored after several weeks, or even months.

^ The cause of shock is a violation of the regulation of reflexes on the part of the overlying structures of the central nervous system.

With a spinal cord injury, a person may develop a group of spinal motor reflexes that are normally present only in the first days and months of postnatal development. Disinhibition of these primitive reflexes is a clinical sign of spinal cord dysfunction.

^ Spinal animal – this is an animal in which the spinal cord is separated from the brain; the spinal cord is transected below the 3rd cervical vertebra. Transection above the 3rd cervical vertebra is incompatible with life, because at the level of 1-2 cervical vertebrae there are nerve centers of the respiratory muscles and, if they are destroyed, the animal will die from paralysis of the respiratory muscles, i.e. asphyxia.

In some cases, when a person is injured, a complete or half transection of the spinal cord occurs. With half-lateral damage to the spinal cord, Brown-Séquard syndrome develops. It manifests itself in the fact that in half of the lesion (below the site of the lesion), paralysis of the motor system develops due to damage to the pyramidal tracts. On the opposite side the movements are preserved.

On the affected side (below the lesion site), proprioceptive sensitivity is impaired (from the deep sensitivity receptors of the periosteum, joint membranes, tendons and muscles). This is due to the fact that the ascending pathways of deep sensitivity go along their side of the spinal cord to the medulla oblongata, where they cross (bundle of Gaulle and Burdach).

On the opposite side of the body (relative to the damage), pain and temperature sensitivity (spinothalamic tract) is impaired, because ascending pathways of deep sensitivity go from the spinal ganglion to the dorsal horn of the spinal cord, where they switch to a new neuron, the axon of which passes to the opposite side. As a result, if the left half of the spinal cord is damaged, then pain and temperature sensitivity of the right half of the body below the damage disappears.

After a spinal cord injury, a person experiences distortion of spinal reflexes: weakening of myotatic and musculocutaneous motor reflexes, increased tendon reflexes, and distortion of the plantar reflex.

Used literature:

Lecture No. 2

Topic: “Physiology of the hindbrain”

Lecture outline

3. Reflex function of the hindbrain. Concept of a bulbar animal

^ 4.1. Structure and afferent connections of the reticular formation

4.2. Characteristics of efferent connections of the reticular formation

1. General characteristics of the hindbrain functions

The hindbrain includes the medulla oblongata and the pons (pons). Together with the midbrain, they form the brain stem, which includes a large number of nuclei, ascending and descending pathways.

^ The functions of the hindbrain include:

1) primary analysis of information from vestibuloreceptors and auditory receptors

2) primary analysis of information from proprioceptors and skin receptors of the head

3) primary analysis of information from the body’s visceroreceptors

4) conduction function: paths connecting the structures of the central nervous system pass through the hindbrain: the vestibulospinal, olivospinal and reticulospinal tracts, which provide tone and coordination of muscle reactions, originate here; the tracts of proprioceptive sensitivity of the spinal cord - thin and wedge-shaped - end here.

5) reflex function: the hindbrain carries out reflexes, the reflex arc of which closes at the level of the medulla oblongata and the pons

^ 2. Basic motor and autonomic nuclei of the hindbrain

The nuclei of the V-XII pairs of h.m.n. are localized in the hindbrain. (in the medulla oblongata these are the nuclei of VIII-XII pairs of h.m.n., in the pons - the nuclei of V-VIII pairs of h.m.n.).

Nuclei of the XII pair h.m.s. (hypoglossal nerve) and XI pair of h.m.n. (accessory nerve) are purely motor. Axons located in these motor neuron nuclei innervate, respectively, the muscles of the tongue and the muscles that move the head.

Nuclei of mixed X (vagus) and IX (glossopharyngeal) pairs h.m.n. less isolated into separate nuclear structures. Axons motor nuclei X-IX pairs h.m.s. innervate the muscles of the pharynx and larynx. Viscerosensory nucleusX- IXsteam h.m.s.(called the nucleus of the solitary fasciculus) receives sensory fibers from afferent neurons whose bodies are located in the jugular, fasciculiform and petrosal ganglia (these nodes correspond to the spinal ganglia). Impulses from the receptors of the tongue, larynx, trachea, esophagus, and internal organs arrive here. The viscerosensory nucleus is connected through interneurons with the visceromotor nuclei of the vagus and glossopharyngeal nerves. The neurons located in these nuclei innervate the parotid gland, glandular and smooth muscle cells of the trachea, bronchi, stomach, intestines, as well as the heart and blood vessels.

^VIIIa couple of h.m.s. is sensitive, it contains 2 branches - vestibular and auditory. Auditory branch formed by afferent fibers coming from the organ of Corti of the cochlea. Auditory afferent fibers enter the medulla oblongata and reach the ventral and dorsal auditory nuclei.

A significant part vestibular fibers, coming from the receptors of the semicircular canals, ends on the neurons of the vestibular nuclei: medial (Schwalbe's nucleus), prevesticular superior (Bechterew's nucleus), prevesticular lateral (Deiters' nucleus) and descending (Roller's nucleus). In addition, some vestibular fibers are sent to the cerebellum. When the vestibular nuclei are excited under the influence of adequate stimuli, impulses along the vestibulospinal tract, originating from the Deiters nucleus, excite the alpha motor neurons of the extensors and, at the same time, through the mechanism of reciprocal innervation, inhibit the alpha motor neurons of the extensors. Thanks to this, when the vestibular apparatus is excited, a change in the muscle tone of the limbs ensures the preservation of balance.

Neurons of the vestibular nuclei also give rise to the vestibulocerebellar and vestibulospinal tracts. At the same time, from the vestibular nuclei of the medulla oblongata there is a path to the so-called medial longitudinal fasciculus, which starts from the Darkshevich nucleus and the intermediate nucleus located in the midbrain. The medial longitudinal fascicle connects all the nuclei of the nerves involved in regulating the activity of the muscles of the eyeball (III, IV and VI pairs of the eyeball) into a single functional ensemble. Thanks to this, the movement of the eyeballs normally occurs synchronously.

In the brain bridge the nuclei of the facial (VII pair), abducens (VI pair) and trigeminal (V) nerves are located.

Facial nerve is mixed, the afferent fibers in its composition transmit signals from the taste buds of the anterior part of the tongue. Efferent fibers of the facial nerve innervate the facial muscles.

Abducens nerve is motor, its motor neurons innervate the external rectus muscle of the eye.

Trigeminal nerve is also mixed. Its neurons innervate masticatory muscles, muscles of the velum palatine and the tensor tympani muscle. The sensory nucleus of the trigeminal nerve, starting at the lower (caudal) end of the medulla oblongata, extends across the entire pons, up to the upper (rostral) end of the midbrain. Axons from afferent neurons of the semilunar ganglion approach the sensitive nucleus of the trigeminal nerve, delivering signals from receptors in the skin of the face, parietal, temporal region, conjunctiva, nasal mucosa, periosteum of the skull bones, teeth, dura mater, and tongue.

^ 3. Reflex function of the hindbrain. Characteristics of the bulbar animal

A) strengthening of myotatic spinal reflexes, which are directed against gravitational forces, play a role in maintaining muscle tone and balance.

^ B) strengthening of cervical spinal reflexes(postural-tonic). They lead to changes in muscle tone when the position of the head and neck changes (called Magnus rivers).

IN) vestibular position reflexes, the main component of which is represented by reflex effects on the neck muscles. Thanks to the redistribution of the tone of the neck muscles, when moving, the head constantly maintains its natural position.

^ Cervical and vestibular reflexes provide a relatively stable standing posture when turning and tilting the head.

D) posture maintenance reflexes: information from the vestibuloreceptors is sent to the vestibular nuclei, which take part in determining the muscle groups and segments of the spinal cord that should take part in changing the posture, and then the command is sent to the spinal cord.

e) Autonomic reflexes - most are realized through the nuclei of the vagus nerve, which receive information about the state of activity of the heart, blood vessels, digestive tract, lungs, digestive glands, etc. In response, the nuclei organize the motor and secretory reactions of these organs.

- digestive reflexes:

e) Protective reflexes. The medulla oblongata organizes and implements a number of protective reflexes (vomiting, sneezing, coughing, lacrimation, closing the eyelids with the participation of nuclei V, VII, IX, X, pairs of h.m.n.).

g) organization and implementation of reflexes of eating behavior: sucking, chewing and swallowing, where they are involved various groups neurons that are covered by excitation in a certain order, respectively, the muscles of the pharynx, larynx and tongue contract in a certain sequence.

^ Bulbar animal - this is an animal in which a transection has been made between the medulla oblongata and midbrain (below the posterior tubercles of the quadrigeminal). The bulbar animal has all spinal reflexes and reflexes that close at the level of the hindbrain. The bulbar animal, which has a medulla oblongata and pons, is capable of carrying out more complex reactions to external influences than the spinal animal. All the basic vital functions of these animals are united by more advanced control and are more coordinated.

^ 4. Physiology of the reticular formation

4.1.Structure and afferent connections of the Russian Federation

The reticular or reticular formation (named by Deiters, 1855) is located in the medial part of the brain stem; the RF is a cluster of neurons separated by many fibers passing in different directions. This interweaving of neurons and fibers continues in the pons and midbrain. The network structure ensures high reliability of the functioning of the Russian Federation and resistance to damaging influences, since local damage is always compensated by the surviving network elements. On the other hand, the high reliability of the functioning of the Russian Federation is ensured by the fact that irritation of any of its parts is reflected in the activity of the entire Russian Federation of a given structure due to the diffuseness of connections.

At the level of the medulla oblongata, the nuclei of the Russian Federation are distinguished: reticular giant cell, reticular small cell, reticular lateral. The giant cell nucleus is the beginning of the reticulospinal tract.

RF neurons are highly sensitive to chemical stimuli: hormones and some metabolic products. RF cells are the beginning of both ascending and descending pathways, giving numerous collaterals ending on neurons of different nuclei of the central nervous system. The respiratory and vasomotor centers are located in the Russian Federation.

^ To the main afferent connections of the Russian Federation (i.e., coming from different structures of the central nervous system to the RF) include afferent pathways from the CBP, cerebellum, motor nuclei of the brainstem (medulla oblongata, midbrain, diencephalon), as well as RF neurons of the medulla oblongata receive numerous collaterals from fibers of all ascending tracts of the spinal cord .

^ 4.2. Characteristics of efferent connections of the Russian Federation

Efferent connections of the Russian Federation (starting from the Russian Federation) - go in an ascending direction to the overlying structures and in a descending direction. Rising influences of the Russian Federation are directed to the cbp (reticulo-cortical path), to the thalamus and to the hypothalamus (reticulothalamic and reticulo-hypothalamic paths), through which sensory information is transmitted from the body. Ascending influences to the cerebral cortex are divided into activating (tonic) and hypnogenic (inhibiting). Thus, during experimental studies on animals, the American physiologist Magun and the Italian researcher Moruzzi showed that when the hypnogenic effects of the RF brain are stimulated, animals fall asleep. When excited by activating ascending influences of the Russian Federation, Moruzzi and Magun (1948) observed an awakening reaction on the EEG.

Descending influences The Russian Federation (Megun, 50s of the last century) is divided into 2 groups:

A) influences on motor centers

^ B) influences on the vegetative centers

A) Influences on motor centers, in turn, are divided into specific and nonspecific. Specific reticulospinal pathways: activate flexor and inhibit extensor alpha motor neurons of the trunk muscles.

Nonspecific reticulospinal pathways are divided into activating and inhibitory pathways.

Activating pathways come from the lateral part of the Russian Federation, exert a generalized activating effect on all spinal neurons, and cause facilitation of spinal reflexes. For example, the temporary absence of spinal reflexes during spinal shock is associated with the absence of the facilitating effects of the RF.

Inhibitory - start from the inhibitory zone of the medulla oblongata in the medial part of the Russian Federation, reach the gamma motor neurons of the spinal cord, innervating the muscle spindles, causing inhibition of spinal reflexes.

^ B) Influences on the vegetative centers. The structure of the Russian Federation contains the vasomotor center (VMC) and the respiratory center (RC).

SDC. Afferent impulses in the SDC come from vascular receptors and, through other brain structures, from bronchioles, heart, from abdominal organs, and from receptors of the somatic system. The efferent pathways of reflexes go along the reticulospinal tract to the lateral horns of the spinal cord. The effect of changing blood pressure depends not only on which neurons fire, but also on the frequency at which they fire. High-frequency impulses increase, and low-frequency impulses decrease blood pressure. This is due to the fact that low-frequency stimulation of the sympathetic neurons of the spinal cord, where the reticulospinal tracts from the vasomotor center end, reduces vascular tone, and high-frequency stimulation increases it. Excitation of the SDC changes the respiratory rhythm, tone of the bronchi, intestinal muscles, bladder, etc. This is due to the fact that the RF of the medulla oblongata is closely connected with the hypothalamus and other nerve centers. In addition, SDC neurons are characterized by high chemical sensitivity. As a result, the frequency of their rhythm is determined by changes in the chemical composition of the blood.

The DC is divided into the centers of inhalation and exhalation; accordingly, the DC neurons are divided into inspiratory and expiratory. Neurons of the respiratory center have the ability to self-excite, i.e. are able to rhythmically issue volleys of impulses without the influx of irritation to them from the structures of the respiratory organs. DC neurons respond to changes in the levels of oxygen, carbon dioxide and blood pH.

Thus, the Russian Federation has bilateral connections with all structures of the central nervous system; RF neurons have chemical sensitivity. In the RF region, interaction of both ascending and descending impulses occurs; circulation through closed circular neural circuits is also possible, which determines a constant level of excitation of RF neurons, thereby ensuring tone and a certain degree of readiness for the activity of various parts of the central nervous system. It should be emphasized that the degree of excitation of the Russian Federation regulates the bp.

Thus, in the hindbrain there are centers of both relatively simple and more complex reflexes, in the implementation of which various muscle groups, vessels and many internal organs. Brainstem RF regulates the level of activity of almost all parts of the central nervous system.

Used literature:

^ 1. Human physiology / Ed. V.M. Pokrovsky, G.F. Briefly. T.1. M., 1998

2. Human physiology Agadzhanyan N.A., Tel L.Z., Tsirkin V.I., Chesnokova S.A. – M.: Medical Book, N. Novgorod: Publishing House of NGMA, 2001. – 526 p.

^ 3. Human physiology / Ed. G.I. Kositsky. - M., 1985

4. Fundamentals of human physiology / Ed. B.I. Tkachenko. T.1.- St. Petersburg, 1994

5. Guide to practical exercises in physiology. /Ed. G.I. Kositsky, V.A. Polyantseva. M., 1988

^ 6. General course of human and animal physiology in 2 books/Ed. HELL. Nozdracheva.-M., “Higher School”, 1991