Gamma efferent system of muscle contraction. Stabilization of body position

12.05.202027.05.2017

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

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

Its receptor element is an encapsulated muscle spindle. Each muscle contains a large number of these receptors. The muscle spindle consists of intrafusal muscle fibers (thin) and a nuclear bag, braided with a spiral network of thin nerve fibers, which are the primary sensory endings (anulospinal thread). On some intrafusal fibers there are also secondary, grape-like sensory endings. When the intrafusal muscle fibers are stretched, the primary sensory endings increase the impulse outgoing from them, which is carried through the fast-conducting gamma-1 fibers to the large alpha motor neurons of the spinal cord. From there, through the also fast-conducting alpha-1 efferent fibers, the impulse goes to the extrafusal white muscle fibers, which provide a fast (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 intercalary neurons to alpha-small motor neurons that innervate tonic extrafusal muscle fibers(red) to maintain tone and posture.

The intrafusal fibers are innervated by the gamma neurons of the anterior horns of the spinal cord. Excitation of gamma neurons, transmitted through gamma fibers to the muscle spindle, is accompanied by contraction of the polar sections of intrafusal fibers and stretching of their equatorial part, while changing the initial sensitivity of receptors to stretch (there is a decrease in the excitability threshold of stretch receptors, and tonic muscle tension increases).

Gamma neurons are under the influence of central (suprasegmental) influences transmitted along the fibers that come from the 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 lies mainly in the regulation of 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 apparatus. So, according to J. Noth (1991), spasticity develops after a supraspinal or spinal lesion of the descending motor systems with the obligatory involvement of the corticospinal tract in the process.

In the regulation of muscle tone, inhibitory mechanisms also take part, without which the reciprocal interaction of antagonist muscles is impossible, which means that it is also impossible to perform purposeful movements. They are realized with the help of Golgi receptors located in the tendons of the muscles, and intercalary Renshaw cells located in the anterior horns of the spinal cord. Golgi tendon receptors during stretching or significant muscle tension 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. Intercalated Renshaw 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. At the same time, 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 the intercalary neurons of the spinal cord, which contributes to an increase in 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 resulting from damage to the central motor neuron: shortening of the dendrites of alpha motor neurons and collateral sprouting (growth) of afferent fibers that make up the posterior roots.

There are also secondary changes 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.

At present, 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. At the same time, among the fibers that control the activity of the "gamma-neuron - muscle spindle" system, inhibitory fibers usually suffer to a greater extent, while activating ones retain their influence on 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. Pain impulses activate alpha and gamma motor neurons of the anterior horns, which enhances the spastic contraction of the muscle innervated by this segment of the spinal cord. In the same time, muscle spasm, which occurs during the sensorimotor reflex, enhances the stimulation of muscle nociceptors. So, according to the mechanism of negative feedback, a vicious circle is formed: spasm - pain - spasm - pain.

In addition, local ischemia develops in spasmodic muscles, since algogenic chemical substances(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 sensitive fibers of the "C" type, as well as the release of vasoactive amines and an increase in microcirculatory disorders.

Of interest are also data on the central cholinergic mechanisms of regulation of muscle tone. It has been shown that Renshaw cells are activated by acetylcholine both through motor neuron collaterals and through the reticulospinal system.

M. Schieppati et al. (1989) found that pharmacological activation of the 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 originating in the locus coeruleus. Anatomically, these formations are closely related to the spinal structures, especially the anterior horns of the spinal cord. Norepinephrine, released from the terminals of the bulbospinal fibers, activates adrenoreceptors located in the intercalary neurons, primary afferent terminals and motor neurons and acts simultaneously on alpha and beta adrenoreceptors 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 the 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 the 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 vicious circle that is formed includes muscle spasm, pain, local ischemia, degenerative changes that self-sustain each other, reinforcing the root cause of pathological changes.

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

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

Exam questions:

1.5. Pyramidal pathway (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 the cranial nerves. Symptoms of damage.

Practical skills:

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

2. Examination of muscle tone and assessment of motor disorders in a patient.

Reflex-motor sphere: general concepts

1. Terminology:

- Reflex- - the reaction of the body to the stimulus, implemented with the participation of the nervous system.

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

2. Classification of reflexes

- Origin:

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

2) conditional (acquired during individual life).

- By type of stimulus and receptor:

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

2) proprioceptive(deep) are divided into tendon, arising from muscle stretching, and tonic, to maintain the position of the body and its parts in space.

3) interoreceptor.

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

- By effect: motor; vegetative.

3. Types of motor neurons:

- Alpha large motor neurons- performance of fast (phasic) movements (from the motor cortex of the brain);

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

- Gamma motor neurons- maintenance of 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 proprioreceptors:

- muscle spindles- consist of intrafusal muscle fiber(similar to embryonic fibers) and receptor apparatus, excited by relaxation (passive elongation) of the muscle and inhibited by contraction(parallel connection with muscle) :

1) phase (type 1 receptors - annulo-spiral, "nuclei-chains"), are activated in response to a sudden lengthening of the muscle - the basis of tendon reflexes,

2) tonic (type 2 receptors - grape-like, "nuclei-bags"), are activated in response to slow muscle lengthening - the basis for maintaining muscle tone.

- Golgi receptors- afferent fiber located among the connective tissue fibers of the tendon - energized by muscle tension and inhibited by relaxation(consecutive inclusion with the muscle) - inhibits overstretching of the muscle.

Reflex-motor sphere: morphophysiology

1. General features of two-neuron paths for the implementation of movement

- 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 large)

2. Cortico-spinal (pyramidal) path

A pair and precentral lobules, posterior sections of the superior and middle frontal gyrus (body I - Betz cells of the V layer of the cerebral cortex) - corona radiata - the anterior two-thirds of the posterior leg of the internal capsule - the base of the brain (brain legs) - 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 large motor neurons of limb muscles) , uncrossed fibers (Türk's bundle, 20%) - in the anterior funiculi of the spinal cord (to the alpha large motor neurons of the axial muscles).

- Nuclei of the anterior horns 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):

- Neck level (C): 1-3 - small muscles neck; 4 - rhomboid muscle and diaphragmatic; 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 carpis 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 abdominal muscles;

- 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, flexors of fingers 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 the V layer of the cerebral cortex) - corona radiata - the knee of the internal capsule - the base of the brain (brain legs) - 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).

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

5. Reflexarcs of the main reflexes:

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

1) Superciliary- percussion of the brow ridge - - [ trunk] - - closing of 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 in the elbow joint;

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

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

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

- Tonic position reflexes(carry out the regulation of muscle tone depending on the position of the head):

1) Neck,

2) Labyrinth;

- From 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 of the eyelids;

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

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

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

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

7) Cremaster- dashed irritation of the skin of the inner surface of the thigh in the direction from the bottom up - - [ L1-L2] - - raising the testicle;

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

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

- Vegetative:

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

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

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

4) Eye-heart(Dagnini-Ashner) - 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) [own rhythmic activity] - gamma fiber in the composition of the anterior roots and nerves

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

Annulospiral endings - sensory neuron(spinal ganglion)

- alpha small motor neuron

Extrafusal fibers (reduction).

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 arch, motor - paracentral lobule) at the level of S2-S4 (n.pudendus) - contraction of the external sphincter,

4) arc of automatic urination- proprioreceptors tensile- spinal ganglia - posterior 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 region of the external sphincter- deep sensitivity to the gyrus of the arch - paracentral lobule - pyramidal path(relaxation of the external sphincter) ,

5) defeat - central paralysis(acute urinary retention - periodic incontinence (MT automatism), or imperative urges), paradoxical ischuria(MP is full, drop by drop due to overstretching of the sphincter), peripheral paralysis(denervation of 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 arch, motor - paracentral lobule) at the level of S2-S4 (n.pudendus) - contraction of the external sphincter + abdominal muscles,

4) arc of automatism of defecation- see MP ,

5) defeat- see MP.

- Sex organs:

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

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

3) arc of automatism;)

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

Reflex-motor sphere: research methods

1. Rules for the study of the reflex-motor sphere:

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

At objective study is assessed absolute[muscle strength, magnitude of reflexes, severity of muscle tone] and relative performance[symmetrical strength, tone, reflexes (anisoreflexia)].

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

3. Study of muscle strength

- Voluntary, active muscle resistance(according to the volume of active movements, the dynamometer and the level of resistance to external force on a six-point scale): 5 - full preservation of motor function, 4 - a 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 a pronounced compliance, 2 - active movements in full with the elimination of gravity, 1 - safety of movement, 0 - complete lack of movement. Paralysis- lack of movement (0 points), paresis- decrease in muscle strength (4 - light, 3 - moderate, 1-2 - deep).

- muscle groups(test groups by system ISCSCI with corr.) :

1) proximal arm group:

1) raise your hand 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) bending the brush

2) extension brushes ,

3) flexion of the distal phalanx III fingers ,

4) abduction V finger ;

4) proximal leg group:

1) hip flexion ,

2) hip extension,

3) hip abduction;

5) groupmusclesshins:

1) leg flexion,

2) extension shins ;

6) groupmusclesfeet:

1) back bending feet ,

2) extension big finger ,

3) plantar bending feet ,

- Correspondence level of spinal cord injury and movement loss:

1) cervical thickening

1) C5 - elbow flexion

2) C6 - extension of the hand,

3) C7 - extension in the elbow joint;

4) C8 - flexion of the distal phalanx of the III 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 test(straight arms in front of you, slightly above the horizontal - weak hand"sinks", i.e. falls below the horizontal)

2) Mingazzini test(similar, but hands in the supination position - the weak hand "sinks")

3) Panchenko's test(hands above the head, palms to each other - the weak hand “sinks”),

4) lower barre test(on the stomach, bend the legs at the knee joints by 45 degrees - the weak leg “sinks”),

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

6) Venderovich's symptom(holding the little finger when trying to take 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. Examination of muscle tone - the involuntary resistance of the muscles is assessed during passive movements in the joints with maximum voluntary relaxation:

Flexion-extension in the elbow joint (tonus of the sniffer and extensors of the forearm);

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

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

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

- steppage(French "steppage" - trotting, peroneal gait, cock's gait, stork) - high raising of the leg with throwing it forward and sharp lowering - with peripheral paresis of the peroneal muscle group.

- duck gait- transshipment of the body from side to side - with paresis of the deep muscles of the pelvic pelvis and hip flexors.

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

Reflex-motor sphere: symptoms of a lesion

1. Symptoms of prolapse

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

1) decreased muscle strength,

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

3) muscular atony- decreased muscle tone,

4) Muscular Atrophy- decrease muscle mass,

+ fibrillar or fascicular twitches(symptom of irritation) - spontaneous contractions of muscle fibers (fibrillar) or groups of muscle fibers (fascicular) - specific feature defeat body peripheral neuron.

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

1) decreased muscle strength,

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

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

4) clonuses 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 2-5 toes,

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

- Hoffman- pinch irritation of the nail phalanx II or III of the toes,

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

- Ankylosing heel- a short jerky hammer blow on the heel.

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

- Babinsky- holding the handle of the malleus along the outer edge of the foot,

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

- Gordon- compression of the calf muscles,

- Sheffer- compression of the Achilles tendon,

- Chaddock- streak irritation around the outer malleolus,

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

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

- Hoffman- pinch 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,

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

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

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

6) protective reflexes: Ankylosing spondylitis-Marie-Foy- with a sharp painful flexion of the toes, a "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 - with passive extension of the bent limb, resistance is felt only at the beginning of the movement), the development of contractures, Wernicke-Mann pose(arm flexion, leg extension)

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

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

- coordinating- involuntary contractions of the paretic muscles with an voluntary contraction of the muscles functionally related to them (Strumpel's tibial phenomenon - dorsiflexion is impossible, but appears when the knee joint is flexed; Raymist's symptom - does not lead the leg in the thigh, but when adducting a healthy leg, movement occurs in the paretic one; Babinsky's phenomenon - getting up without the help of hands - a healthy and paretic leg rises),

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

- Central paralysis (bilateral lesion of the pyramidal tract):

+ violation of the function of the pelvic organs according to the central type- acute urinary retention in case of damage to the pyramidal tract, followed by periodic urinary incontinence (reflex emptying of the bladder during overstretching), accompanied by an imperative urge to urinate.

- Central paralysis (unilateral lesion of the corticonuclear pathway): according to the rule of 1.5 nuclei, only the lower ½ of the 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 focus,

2) language deviation in the opposite direction to the focus (deviation is always in the direction of weak muscles).

- Central paralysis (bilateral lesion of 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 = reflexes of oral automatism:

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

- Proboscis- a hammer blow on the upper lip causes the lips to stretch forward or contract circular muscle mouth,

- Nasolabial(Astvatsaturova) - a blow with a hammer on the back of the nose causes the lips to stretch forward or contraction of the circular muscle of the mouth,

- Distant-oral(Karchikyan) - bringing the hammer to the lips causes the lips to stretch forward,

- Palmar-chin(Marinescu-Radovici) - dashed irritation of the tenar skin causes contraction of the chin muscle from the side of the same name.

2. Symptoms of irritation

- Jackson epilepsy - paroxysmal clonic convulsions 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 (epilepsiapartialiscontinuous)- persistent convulsions (myoclonus in combination with torsion dystonia, choreoathetosis) with periodic generalization (chronic tick-borne encephalitis)

Reflex-motor sphere: levels of damage

1. Lesion levels in central paralysis:

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

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

- Internal capsule(contralateral hemiparesis with lesions of the corticonuclear tract, more pronounced in the arm, marked increase in muscle tone),

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

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

- Lateral and anterior funiculus of the spinal cord(ipsilatory paralysis below the level of damage).

2. Levels of damage in peripheral paralysis:

- anterior horn(muscle paresis in the area of the segment + fasciculations).

- Root(muscle paresis in the zone of innervation of the root),

- polyneuritic(muscle paresis in the distal extremities),

- Mononeuritic(muscle paresis in the zone of nerve innervation, plexus).

Differential diagnosis of motor syndromes

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

- sudden onset or rapidly progressive:

1) Acute cerebrovascular accident (stroke)

2) Traumatic brain injury and trauma cervical spine

3) Brain tumor (with pseudo-stroke course)

4) Encephalitis

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

6) Multiple sclerosis

7) Migraine with aura (hemiplegic migraine)

8) Abscess of the brain;

- slowly progressive

1) Acute cerebrovascular accident (atherothrombotic stroke)

2) brain tumor

3) Subacute and chronic subdural hematoma

4) Abscess of the brain;

5) Encephalitis

6) Multiple sclerosis

- necessary examination methods:

1) clinical minimum (OAK, OAM, ECG)

2) neuroimaging (MRI, CT)

3) electroencephalography

4) hemostasiogram / coagulogram

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

- spinal cord compression (associated with sensory disturbances)

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

2) Diseases of the spine (spondylitis, disc herniation)

3) Epidural abscess

4) Arnold-Chiari malformation (Arnold-Chiari)

5) Syringomyelia

- hereditary diseases

1) Strümpel's familial spastic paraplegia

2) Spino-cerebellar 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) Devik'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: features of young children

1. Volume of active and passive movements:

The volume of active movements - by visual assessment: symmetry and completeness of the amplitude of movements

The range of passive movements - flexion and extension of the limbs

2. muscle strength - assessed by observing spontaneous activity and when checking unconditioned reflexes.

3. Study of reflexes:

- Reflexes of "adults"- appear and persist in the future:

1) from birth - knee, bicipital, anal

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

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

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

- sucking- with stroke 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 - turning the head in this direction and slightly opening the mouth (up to 1.5 months)

- Palmar-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) - pressure on the palms - grasping of the fingers (symmetry is important) (up to 2-3 months)

- wrapping(Moro) - spreading the arms with a sharp drop (or hitting the table) - 1st phase: spreading the arms - 2nd phase: grasping one's own body (up to 3-4 months)

- plantar- pressure on the foot - sharp plantar flexion of the fingers (up to 3 months)

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

- cervical tonic symmetrical reflex (SNTR)- 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)- turn of the head - straightening of the arm and leg on the side of turn, bending - on the opposite side - "swordsman's position" (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 positioned on the stomach - turning the head to the side (up to 1.5-2 months), then it is replaced by an arbitrary holding of the head with the crown of the head up),

- labyrinth 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) - emphasis of the feet in the palm of the researcher - leg extension ("crawling") (up to 3 months),

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

- Perez- dashed irritation along the spinous processes from the coccyx to the neck - extension of the spine, raising 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: leaning on the table - unbends 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 later becomes the basis for the formation of independent walking),

- automatic walking- when tilted to the sides - 3rd phase: flexion/extension of the legs ("walking") (up to 2 months).

3) chain symmetric reflections- steps towards verticalization:

- straightening from the trunk to the head- feet on the support - head straightening (from 1 month - up to 1 year),

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

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

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

- Landau lower- the same + extension in the back in the form of increased 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 is increased (“embryonic posture”), it is important during the study correct technique examination (comfortable ambient temperature, painless contact).

- Options for pathological changes in tone in children:

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

2) “frog” pose(muscular hypotension) - limbs in a state of extension and abduction, "seal paws"- hanging brushes, "heel feet"- the toes are brought to the front surface of the lower leg.

3) the pose of the "swordsman"(central hemiparesis) - on the side of the lesion - the arm is extended, rotated inward in the shoulder, pronated in the forearm, bent in the palm; on the opposite - arm and leg in flexion.

Neuronal 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 departments. 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 the overlying centers, to the symmetrical structures of the opposite side, or to the anterior horns of the spinal cord.

In the anterior horns there are neurons that give their axons to the muscles. All descending pathways of the central nervous system that cause motor responses end at 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. Functionally, spinal cord neurons can be divided into 5 main groups:

1) motoneurons, or motor, - cells of the anterior horns, the axons of which form the anterior roots. Among motor neurons, there are a-motor neurons that transmit signals to muscle fibers, and y-motoneurons that innervate intrafusiform muscle fibers;

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

3) in the spinal cord there are also projection interneurons that form the ascending pathways of the spinal cord. Interneurons are neurons that receive information from the central ganglia and are located in the posterior horns. These neurons respond to pain, temperature, tactile, vibrational, proprioceptive stimuli;

4) sympathetic, parasympathetic neurons are located mainly in the lateral horns. The axons of these neurons exit the spinal cord as part of the anterior 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 top of the posterior horn of the spinal cord, the so-called gelatinous substance (Roland's gelatinous substance) is formed and performs the functions of the reticular formation of the spinal cord.

Functions of the spinal cord. The first function is reflex. The spinal cord carries out motor reflexes of the skeletal muscles relatively independently. Examples of some motor reflexes of the spinal cord are: 1) elbow reflex - tapping on the tendon of the biceps muscle of the shoulder causes flexion in the elbow joint due to nerve impulses that are transmitted through 5-6 cervical segments; 2) knee reflex - tapping on the tendon of the quadriceps femoris causes extension in the knee joint due to nerve impulses that are transmitted through the 2nd-4th lumbar segments. The spinal cord is involved in many complex coordinated movement - walking, running, labor and sports activities, etc. The spinal cord carries out vegetative reflexes of changes in the functions of internal organs - the cardiovascular, digestive, excretory and other systems.
Thanks to reflexes from proprioreceptors in the spinal cord, motor and autonomic reflexes are coordinated. Through the spinal cord, reflexes are also carried out 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 conductor. Centripetal impulses entering the spinal cord through the posterior 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. THE ROLE OF ALPHA AND GAMMA MOTOR NEURONS IN THIS PROCESS.

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

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

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. Pain impulses activate alpha and gamma motor neurons of the anterior horns, which enhances the spastic contraction of the muscle innervated by this segment of the spinal cord. At the same time, the muscle spasm that occurs during the sensorimotor reflex enhances the stimulation of muscle nociceptors. So, according to the mechanism of negative feedback, 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 sensitive fibers of the "C" type, as well as the release of vasoactive amines and an increase in microcirculatory disorders.

10. REFLECTOR ACTIVITY OF THE medulla oblongata, ITS ROLE IN THE REGULATION OF MUSCLE TONE. DECEREBRATIVE RIGIDITY. The medulla oblongata, like the spinal cord, performs two functions - reflex and conduction. Eight pairs of cranial nerves emerge from the medulla oblongata and the pons (from V to XII) and, like the spinal cord, it has a direct sensory and motor connection with the periphery. Through sensitive fibers, it receives impulses - 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 the receptors of the larynx, trachea, lungs, as well as from the interoreceptors of the cardiovascular system and the digestive system. Many simple and complex reflexes are carried out through the medulla oblongata, covering not individual metameres of the body, but organ systems, for example, the digestive system, respiration , blood circulation.

reflective activity. The following reflexes are carried out through the medulla oblongata:

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

Food reflexes: sucking, swallowing, sap secretion (secretion) of the digestive glands.

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

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

The vestibular nuclei are located in the medulla oblongata.

From the vestibular nuclei of the medulla, the descending vestibulospinal tract begins, which is involved in the implementation of the installation reflexes of the posture, namely, in the redistribution of muscle tone. The 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 function of standing are called setting reflexes. Thanks to them, the animal, contrary to the forces of gravity, keeps the posture of its body, as a rule, with the crown of the head up. The special significance of this section of the central nervous system is determined by the fact that in the medulla oblongata there are vital centers - respiratory, cardiovascular, therefore, not only removal, but even damage to the medulla oblongata ends in death.
In addition to the reflex, the medulla oblongata performs a conductive function. Conducting pathways pass through the medulla oblongata, connecting the cortex, diencephalon, midbrain, cerebellum and spinal cord in a two-way connection.

The medulla oblongata plays an 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 the posture.

Nonspecific sections of the medulla oblongata, on the contrary, have a depressing effect on the tone of skeletal muscles, reducing it in the extensor muscles as well. The medulla oblongata is involved in the implementation of reflexes to maintain and restore body posture, the so-called installation 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 rotation inside the arms and legs. and also often opisthotonus. This condition is also called apallic syndrome. It is based on damage to the midbrain, especially wedging into the tentorial foramen during supratentorial processes, primarily neoplasia in the temporal lobes, cerebral hemorrhage with a breakthrough of blood into the ventricles, severe brain contusions, hemorrhage into the trunk, encephalitis, anoxia, poisoning. Pathology may initially manifest itself in the form of "cerebral spasms" and be provoked by external stimuli. With the complete cessation of exposure to 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 the parkinsonism syndrome (accompanied by akinesia, the "gear wheel" phenomenon and often tremor, which first appear on one side) and in other degenerative diseases accompanied by parkinsonism, such as olivopontocerebellar atrophy, orthostatic hypotension, Creutzfeldt-Jakob disease, etc. .

Typical posture for decerebrate rigidity

Lecture: "Physiology of the spinal cord"

Lecture plan:

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 in the spinal cord, primary analysis of information from proprioreceptors and skin receptors of the trunk, limbs and a number of visceroreceptors. Proprioreceptors 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 receptors and pressure receptors.

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

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 principle of the spinal cord.

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

^ 1. Motoneurons - 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 posterior horns. These are sensitive neurons that respond to pain, temperature, tactile, vibrational and proprioceptive stimuli.

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

4. Associative neurons of the own apparatus of the spinal cord 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 axons of gamma motor neurons. The axon of a motor neuron 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 essential for regulating the sensitivity of the receptor. It is controlled by the gamma motor neuron. All muscle fibers that belong to this muscle and are not part of the muscle spindle are called extrafusal.

Alpha motor neurons innervate skeletal muscle fibers (extrafusal fibers), providing muscle contractions. Gamma motor neurons innervate intrafusal fibers, muscle spindles that are stretch receptors. There is a combined activation of alpha and gamma motor neurons. The axon of the alpha motor neuron 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 the fibers of the descending pathways with alpha motor neurons:

^ 1. Direct downward influence on the alpha motor neuron

2 Indirectly through the intercalary neuron

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

Gamma loop:

Gamma 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 principle 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 depart 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 consists in the innervation by the sensory and motor roots of its own metamere, the 1st overlying and 1st underlying metamere. Knowing the boundaries of body metameres makes it possible to carry out topical diagnostics of diseases of the spinal cord.

^ 3. Conductor organization of the spinal cord

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 the so-called pathways, which are functionally divided into proprioceptive, spinocerebral (ascending) and cerebrospinal (descending).

^ propriospinal pathways interconnect neurons of one or different segments of the spinal cord. The function of such connections is associative and consists in the coordination of posture, muscle tone, movements of various body metameres. One metamere includes 1 pair of spinal nerves and the part of the body innervated by it.

^ spinocerebral pathways connect segments of the spinal cord to brain structures. They are represented by proprioceptive, spinothalamic, spinocerebellar and spinoreticular pathways.

a) The proprioceptive pathway (thin Gaulle's bundle and Burdach's wedge-shaped bundle) starts from the deep sensitivity receptors of the periosteum, joint membranes, tendons and muscles. Through the spinal ganglion, it goes to the posterior roots of the spinal cord, to the white matter of the posterior cords and, without switching to a new neuron at the level of the spinal cord, rises to the nuclei of Gaulle and Burdach of the medulla oblongata. Here there is a switch to a new neuron, 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 makes it possible to correct the posture of the entire body.

b) The spinothalamic pathway starts from pain, temperature, skin baroreceptors. 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 (the first switch). Sensory neurons in the posterior horns send axons to the opposite side of the spinal cord and ascend the lateral funiculus to the thalamus. This is where the second switch takes place and ascends into the sensory cortex. Part of the skin receptor fibers goes to the thalamus along the anterior funiculus of the spinal cord.

c) The spinal tracts start from the receptors of muscles, ligaments, internal organs and are represented by a non-crossing Gowers bundle and a double-crossing Flexig bundle. 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 pathway - starts from the interneurons of the spinal cord and reaches the RF of the brain stem. Carries information from visceroreceptors.

Thus, through the pathways of the spinal cord, impulses are carried from the receptors of the trunk and extremities to the neurons of the spinal cord and overlying structures of the central nervous system.

^ Cerebrospinal pathways start from the neurons of the structures of the brain and end on the neurons of the segments of the spinal cord. These include the paths: the corticospinal path, which provides the regulation of voluntary movements, the rubrospinal, vestibulospinal and reticulospinal paths, which regulate muscle tone. The unifying feature for these pathways is that the final destination for them is 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 subdivided into somatic (motor) and vegetative.

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 the movement of the limbs and torso).

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

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

^ Myotatic reflex - stretch reflex, for example, when a person takes a vertical position, then 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 the muscle is stretched, muscle spindles are activated, which are located parallel to the extrafusal fibers of the skeletal muscle. The impulse from muscle receptors goes through the afferent neuron and enters the alpha motor neurons of this muscle. As a result, there is a shortening of the extrafusal aquifers. Thus, the length of the muscle returns to the original. The myotatic reflex is characteristic of all muscles, well expressed and easily evoked in the flexor muscles, directed against gravitational forces, to maintain balance and muscle tone. It should be noted that the impulse from the receptors simultaneously through the intercalary Renshaw inhibitory cells reaches 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 proprioreceptors of the muscles of the neck and fascia covering the cervical spine. The central part of the reflex arc has a polysynaptic character, i.e. includes intercalary neurons. The reflex reaction involves the muscles of the trunk and limbs. In addition to the spinal cord, the motor nuclei of the brain stem, which innervate the muscles, also participate in it. eyeballs. Neck 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 reflex (repulsion)- when standing on the surface, the tone of the extensor muscles increases.

Flexion tonic reflex observed, for example, in a frog or in a rabbit, in which the bent 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 foot of the lower limb.

Abdominal reflexes- tension of the abdominal muscles that occurs with nociceptive afferent influences. This is a protective reflex.

Flexion defense reflexes- occur when the pain receptors of the skin, muscles and internal organs are irritated; they 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, to which, under natural conditions (when walking), additional body weight is transferred.

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

^ Walking reflex – agreed physical activity upper and lower limbs. To implement this reflex, intersegmental interaction of the muscles of the arms, legs and torso is necessary. The mechanisms of stepping movements are incorporated in the spinal cord, but the activation of the spinal mechanism is carried out from the midbrain.

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

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

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

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

With a spinal cord injury, a person may develop a group of motor spinal reflexes, which are normal 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 the nerve centers of the respiratory muscles lie at the level of 1-2 cervical vertebrae and, if they are destroyed, the animal will die from paralysis of the respiratory muscles, i.e. asphyxia.

With injuries in humans, in some cases, there is a complete or half intersection of the spinal cord. With half lateral damage to the spinal cord, Brown-Séquard syndrome develops. It manifests itself in the fact that on the 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 of the movement are preserved.

On the side of the lesion (below the site of the lesion), 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 paths of deep sensitivity go along their side of the spinal cord to the medulla oblongata, where they cross over (the bundle of Gaulle and Burdach).

On the opposite side of the body (relative to the damage), pain and temperature sensitivity (spinothalamic pathway) is disturbed. ascending pathways of deep sensitivity go from the spinal ganglion to the posterior 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 the pain and temperature sensitivity of the right half of the body below the damage disappears.

After a spinal cord injury, a person has a perversion of spinal reflexes: a weakening of myotatic and musculoskeletal motor reflexes, an increase in tendon reflexes, and a perversion of the plantar reflex.

References:

Lecture #2

Topic: "Physiology of the hindbrain"

Lecture plan

3. Reflex function of the hindbrain. The concept of the bulbar animal

^ 4.1. The structure and afferent connections of the reticular formation

4.2. Characteristics of the efferent connections of the reticular formation

1. General characteristics of the functions of the hindbrain

The hindbrain includes the medulla oblongata and the pons of the brain (pons varolii). Together with the midbrain, they form the brainstem, 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 proprioreceptors and skin receptors of the head

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

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

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

^ 2. Main motor and autonomic nuclei of the hindbrain

In the hindbrain, the nuclei of the V-XII pair of c.m.s. are localized. (in the medulla oblongata these are the nuclei of VIII-XII pairs of ch.m.n., in the pons varolius - the nuclei of V-VIII pairs of ch.m.n.).

Nuclei of the XII pair of ch.m.s. (hyoid nerve) and XI pair of ch.m.n. (accessory nerve) are purely motor. The axons located in these nuclei of motor neurons innervate, respectively, the muscles of the tongue and the muscles that move the head.

Nuclei of mixed X (vagus) and IX (glossopharyngeal) pairs of ch.m.n. less separated into separate nuclear structures. axons motor nuclei X-IX pairs of Ph.D. innervate the muscles of the pharynx and larynx. Viscerosensory nucleusX- IXsteam ch.m.s.(called the nucleus of the solitary bundle) receives sensory fibers from afferent neurons, the bodies of which are located in the jugular, bundle-shaped and stony nodes (these nodes correspond to the spinal ganglia). This receives impulses from the receptors of the tongue, larynx, trachea, esophagus, and internal organs. The viscerosensory nucleus is connected through intercalary neurons 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.

^ VIIIcouple of ch.m.s. is sensitive, in its composition there are 2 branches - vestibular and auditory. Auditory branch formed by afferent fibers coming from the organ of Corti cochlea. Auditory afferent fibers enter the medulla oblongata and reach the ventral and dorsal auditory nuclei.

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

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

In the bridge of the brain 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 mimic muscles of the face.

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

Trigeminal nerve is also mixed. Its neurons innervate the muscles of mastication, the muscles of the palatine curtain and the muscle of the straining eardrum. The sensory nucleus of the trigeminal nerve, starting at the lower (caudal) end of the medulla oblongata, extends through the entire bridge, 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) increased myotatic spinal reflexes, which are directed against gravitational forces, play a role in maintaining muscle tone and balance.

^ B) increased cervical spinal reflexes(posture-tonic). They lead to a change in muscle tone when the position of the head and neck changes (called the Magnus River).

IN) vestibular position reflexes, the main component of which is represented by reflex effects on the muscles of the neck. Due to the redistribution of the tone of the cervical 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 goes to the vestibular nuclei, which are involved in determining the muscle groups and segments of the spinal cord that should take part in changing the posture, and then the command goes to the spinal cord.

e) Vegetative reflexes - most of them 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, tearing, eyelid closure with the participation of nuclei V, VII, IX, X, pairs of medical sciences).

g) organization and implementation of reflexes of eating behavior: sucking, chewing and swallowing, where 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 was made between the medulla oblongata and the midbrain (below the posterior tubercles of the quadrigemina). 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 a pons, is capable of implementing more complex reactions to external influences than a spinal one. All the main vital functions in these animals are united by more perfect control and are more coordinated.

^ 4. Physiology of the reticular formation

4.1 Structure and afferent connections of RF

The reticular or reticular formation (the name was given by Deiters, 1855) is located in the medial part of the brainstem, 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 provides high reliability of RF functioning, resistance to damaging effects, since local damage is always compensated for by the remaining network elements. On the other hand, the high reliability of RF functioning is ensured by the fact that irritation of any of its parts is reflected in the activity of the entire RF of the given structure due to the diffuseness of connections.

At the level of the medulla, the RF nuclei 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 rise to numerous collaterals ending in neurons of different nuclei of the CNS. The respiratory and vasomotor centers are located in the Russian Federation.

^ To the main afferent connections of the RF (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 brain stem (medulla oblongata, midbrain, diencephalon), as well as RF neurons of the medulla oblongata receive numerous collaterals from the fibers of all ascending pathways of the spinal cord .

^ 4.2. Characteristics of RF efferent connections

RF efferent connections (starting from RF) - go in an upward direction to the overlying structures and in a downward direction. Rising Influences of RF are sent to the bp (reticulo-cortical pathway), to the thalamus and to the hypothalamus (reticulothalamic and reticulo-hypothalamic pathways), they carry out the transfer of sensory information from the body. Ascending influences to the cerebral cortex are divided into activating (tonic) and hypnogenic (inhibiting). So, during experimental studies on animals, by the American physiologist Magun and the Italian researcher Moruzzi, it was shown that when stimulated by the hypnogenic influences of the RF brain, animals fall into sleep. Moruzzi and Magun (1948) observed an awakening reaction on the EEG upon excitation of the activating ascending influences of RF.

Downward Influences RF (Megun, 50s of the last century) is divided into 2 groups:

A) influences on motor centers

^ B) influences to vegetative centers

A) Influences to motor centers, in turn, are divided into specific and non-specific. Specific reticulospinal pathways: activate flexor and inhibition of 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 RF, carry out a generalized activating effect on all spinal neurons, and cause relief of spinal reflexes. For example, the temporary absence of spinal reflexes in spinal shock is associated with the absence of facilitating RF effects.

Inhibitory - start from the inhibitory zone of the medulla oblongata in the medial part of the RF, reach the gamma motor neurons of the spinal cord that innervate the muscle spindles, cause inhibition of spinal reflexes.

^ B) Influences to the vegetative centers. The structure of the RF includes the vasomotor center (SDC) 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, from receptors of the somatic system. Efferent paths of reflexes go along the reticulospinal tract to the lateral horns of the spinal cord. The effect of a change in blood pressure depends not only on which neurons fire, but also on the frequency with which they generate impulses. 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, on which the reticulospinal pathways from the vasomotor center end, reduces vascular tone, while high-frequency stimulation increases it. The excitation of the SDC changes the respiratory rhythm, the tone of the bronchi, the muscles of the intestines, the 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.

DC is divided into the center of inhalation and exhalation, respectively, DC neurons are divided into inspiratory and expiratory. The neurons of the respiratory center have the ability to self-excite, i.e. capable of rhythmically delivering volleys of impulses without an influx of irritation from the structures of the respiratory organs. DC neurons respond to changes in the level of oxygen, carbon dioxide, and blood pH.

Thus, the RF has bilateral connections with all structures of the CNS; RF neurons are chemically sensitive. In the RF region, both ascending and descending impulses interact, circulation is also possible through closed circular neural circuits, which determines a constant level of excitation of RF neurons, thereby providing a tone and a certain degree of readiness for the activity of various parts of the CNS. It should be emphasized that the degree of RF excitation is regulated by the c.b.p.

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. RF of the brainstem regulates the level of activity of almost all parts of the CNS.

References:

^ 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, Nizhny 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