The concept of gamma loop physiology. Lectures: General characteristics of the functions of the spinal cord Neuronal organization of the spinal cord
Complex movements can be carried out only on the condition that the effector impulses are constantly amended, taking into account the changes that occur every moment in the muscle in the process of its contraction. That's why muscular system is the source of numerous afferent impulses. The spinal cord constantly receives information about the degree of tension of muscle fibers and their length.
The receptor part of the motion analyzer is muscle spindles and Golgi tendon organs.
Muscle spindles. In muscles, mainly extensors, performing anti-gravity function, is muscle fibers, thin and short others. They are placed in small bundles (from 2 to 12 fibers) in the connective tissue capsule. Due to their shape, such structures are called muscle spindles (Figure 4.8). Muscle fibers located in a capsule, called intrafusal(lat. Fusus- spindle), while ordinary fibers, which account for the bulk of the muscle, called extrafusal, or working fibres. Probably one end is attached to the perimysium of the extrafusal muscle fiber, the other - to the tendon. The central part of the intrafusal fibers is actually the receptor part.
There are two types of intrafusal muscle fibers that differ in the arrangement of nuclei: the nuclei of fibers with a nuclear chain and the nuclei of fibers with a nuclear bag. Obviously, these two types of fibers are functionally different.
afferent innervation. Each spindle is penetrated by a thick myelinated nerve fiber; it sends a branch to each intrafusal fiber and ends on its middle part, spirally spitting it and creating the so-called annulo-spiral endings. These afferents are fibers 1a (Aa), and their endings are called primary sensory endings. An adequate stimulus for them is the change and the rate of change in the length of the muscle fiber (Fig. 4.9). Part of the spindles is innervated group II afferent fibers (Ab). These sensory fibers "serve" exclusively intrafusal fibers with a nuclear chain and are called secondary sensory endings; they are located with their processes peripherally from the anulospiral endings. their excitability is lower, and their sensitivity to dynamic parameters is less.
Efferent innervation intrafusal muscle fibers carried by nerve fibers groups A-y. The nerve cell from which they originate is γ-motor neuron.
Rice. 4.8. Diagram of the structure of the muscle spindle (according to R. Schmidt, G. Thevs, 1985)
Rice. 4.9. Scheme for the implementation of the myotatic reflex
Golgi tendon organs special receptors, which are tendon filaments, extending from about 10 extrafusal muscle fibers and are fixed in the tendons of the muscle sequentially, in a vilyadi chain. An adequate stimulus for them is a change in muscle tension.
Thick myelin fibers of group and b (Αβ) fit into the Golgi organs. In the tendon organ, they branch into thinner numerous branches and lose myelin. These receptors are common in skeletal muscles.
The nature of the excitation of muscle spindles and tendon organs depends on their placement: muscle spindles are connected in parallel, and tendon organs are connected in series with respect to extrafusal muscle fibers. So, as a consequence, muscle spindles perceive mainly the length of the muscle, and the tendon organs - his tension.
The sensitive endings of muscle spindles can be excited not only under the influence of muscle stretching, but also as a result of contraction of intrafusal muscle fibers upon excitation of γ-motor neurons. This mechanism is called γ loops(Fig. 4.10). When only intrafusal fibers are contracted, the length or tension of the muscle does not change, however, the central part of these fibers is stretched and, therefore, sensory endings are excited.
Thus, there is two excitation mechanisms muscle spindles: 1) muscle stretching and 2) contraction of intrafusal fibers; these two mechanisms can act synergistically.
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 thoracic region the spinal cord has, in addition to those named, 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, causing motor reactions, 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. Functionally, spinal cord neurons can be divided into 5 main groups:
1) motor neurons, 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 elbow joint thanks 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 knee joint thanks to nerve impulses that are transmitted through the 2nd-4th lumbar segments. The spinal cord is involved in many complex coordinated movements - walking, running, labor and sports activities and others. 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.
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 assigned to the functional state of the 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) that 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 propulsion systems with mandatory involvement in the process of the corticospinal tract.
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 in general, which increases their excitability, as well as on the interneurons of the spinal cord, which increases 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 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.
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.
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, the vestibular apparatus (organ of balance), from the receptors of the larynx, trachea, lungs, and also from the interoreceptors of the heart - the vascular 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, respiratory, and circulatory systems.
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
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 proprioceptors:
- 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 of the 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, finger flexors and thumb; 3 - muscles of the sole, 4-5 - muscles of the perineum.
4. Corticonuclear pathway
- Anterior central gyrus (Bottom 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] - - flexion in the 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- from the tendon of the gastrocnemius 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 - a 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 deep muscles 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) - a specific sign of damage 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 with damage to the pyramidal tract, followed by periodic urinary incontinence (reflex emptying Bladder with overstretching), accompanied by imperative urge to urinate.
- Central paralysis (unilateral lesion of the corticonuclear pathway): according to the rule of 1.5 nuclei, only the lower ½ nucleus has unilateral cortical innervation facial nerve and nucleus of the hypoglossal nerve:
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) - streak irritation of the tenar skin causes contraction mental muscle from the same side.
2. Symptoms of irritation
- Jackson epilepsy - paroxysmal individual clonic convulsions muscle groups, with possible spread and secondary generalization (most often from the thumb (the 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- is assessed by observing spontaneous activity and by 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 - bending in the direction of irritation, bending the arms and legs 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 tilting 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.
The Importance of the Gamma Efferent System highlights the fact that 31% of all motor nerve fibers to muscles are thin type A efferent fibers rather than thick ones motor fibers type A. Whenever signals are transmitted from the motor cortex or any other area of the brain to alpha motor neurons, in most cases, gamma motor neurons are simultaneously stimulated, which is called alpha and gamma motor neuron coactivation.
This leads to simultaneous contraction of extrafusal fibers skeletal muscles and intrafusal fibers of muscle spindles.
Reduction intrafusal muscle fibers simultaneously with the contraction of large muscle fibers of skeletal muscles has a double meaning. First, it keeps the length of the receptor portion of the muscle spindle from changing during contraction of the entire muscle. Therefore, coactivation inhibits the reaction of the muscle spindle reflex to muscle contraction. Second, it maintains the proper damping function of the muscle spindle, regardless of any changes in muscle length.
For example If the muscle spindle did not contract and relax along with large muscle fibers, the receptor part of the spindle would either be too loose or overstretched, which does not correspond to optimal conditions for spindle function.
Gamma efferent system excited directly by signals from the bulboreticular facilitating region of the brainstem and indirectly by impulses transmitted to the bulboreticular region from: (1) the cerebellum; (2) basal ganglia; (3) cerebral cortex. Little is known about the exact mechanisms of control of the gamma efferent system. However, since the bulboreticular facilitating area is primarily associated with contractions of anti-gravity muscles (and these muscles have a very high density of muscle spindles), it is believed that the gamma-efferent mechanism is of particular importance for damping (smoothing) the movements of different parts of the body during walking and running.
Muscle spindle system stabilizes the position of the body during strenuous activity. One of the most important functions of the muscle spindle system is to stabilize the position of the body during strenuous muscular activity. To do this, the bulboreticular facilitating area and associated areas of the brain stem transmit excitatory signals through the gamma nerve fibers to the intrafusal muscle fibers.
This shortens the ends of the spindles and stretches their central receptor areas, enhancing the sensory signal. However, if the spindles are simultaneously activated in the skeletal muscles located on both sides of each joint, the reflex excitation of these muscles also increases, providing a strong tension in the muscles surrounding the joint, opposing each other. As a result, the position of the joint becomes very stable, and any force that tries to break it is counteracted by extremely sensitive stretch reflexes acting on both sides of the joint.
Every time a person should do muscle work, which requires fine and precise adjustment of body position, excitation of the corresponding muscle spindles by signals from the bulboreticular facilitating region of the brainstem stabilizes the position of the main joints. This greatly aids in the additional fine voluntary movements (with fingers or other parts of the body) required for complex motor manipulations.
