The spinal cord is the control center. Innervation of internal organs. Anatomical and physiological aspects. Visceral afferents and efferents The principle of innervation of internal organs

1. The cranial nucleus of Yakubovich is located:

1. in the diencephalon

2. in the medulla oblongata

3. in the midbrain

4. in the telencephalon

2. In which part of the brain is the Yakubovich nucleus located?

1. in intermediate

2. oblong

3. average

4. ultimately

3. The dorsal nucleus of the vagus nerve is:

1. motor

2. sympathetic

3. parasympathetic

4. sensitive

4. Parasympathetic conductors include:

1. I pair of head nerves

2. II pairs of head nerves

3. III pair of cephalic nerves

4 V pairs of head nerves

5. Parasympathetic ganglia include:

1. superior mesenteric node

2. dorsal ganglion

3. pterygopalatine ganglion

4. celiac ganglion

6. Parasympathetic innervation of the pelvic organs comes from:

2. lateral intermediate nuclei of the thoracic segments spinal cord

3. lateral intermediate nuclei of the lumbar segments of the spinal cord

4. lateral intermediate nuclei of the sacral segments of the spinal cord

7. Sympathetic centers are localized in the following section of the central nervous system:

1. in the midbrain

2. in the medulla oblongata

3. in the spinal cord

4 in the diencephalon

8. The pterygopalatine ganglion receives preganglionic conductors from

1. Yakubovich and Perlia nuclei

2. dorsal nucleus of the vagus nerve

3.

4. inferior salivary nucleus

9. Intermediate lateral nuclei gray matter spinal cord lie in:

1. anterior horns of the gray matter of the spinal cord

2. dorsal horns of the gray matter of the spinal cord

3. lateral horns of the gray matter of the spinal cord

4. in the central part of the gray matter of the spinal cord

10. From which vegetative nuclei parasympathetic innervation of the pelvic organs is carried out

1. dorsal nucleus of the vagus nerve

2. lateral intermediate nuclei of the thoracic segments

3. lateral intermediate nuclei of the lumbar segments

4. lateral intermediate nuclei of the sacral segments

11. Which vegetative nodes belong to the X pair

1. paraorgan

2. intramural

3. paravertebral

4. prevertebrates

12. White connecting branches have:

1. all spinal nerves

2. thoracic spinal nerves

13. Which nerves contain parasympathetic fibers to the pelvic organs?

1. greater and lesser splanchnic nerves

2. lumbar splanchnic nerves

3. sacral splanchnic nerves

4. pelvic splanchnic nerves

14. From which nucleus do the autonomic conductors of the intermediate nerve originate?

1. dorsal nucleus of the vagus nerve

2. superior salivary nucleus

3. inferior salivary nucleus

4. Yakubovich kernels

15. In which part of the central nervous system are sympathetic centers localized?

1. in the midbrain

2. in the rhombencephalon

3. in the spinal cord

4. in the diencephalon

16. Which nucleus of the gray matter of the spinal cord is sympathetic?

1. own

2. chest

3. intermediate medial

4 intermediate lateral

17. Along the gray connecting branches, sympathetic conductors are directed to:

1. organs of the head and neck

2. breast organs

3. organs abdominal cavity

4. soma

18. White connecting branches contain:

1. parasympathetic preganglionics

2. parasympathetic postganglionics

3. sympathetic preganglionics

4. sympathetic postganglionics

19. Gray connecting branches have:

1. all spinal nerves

2. thoracic spinal nerves

3. sacral spinal nerves

4. coccygeal spinal nerves

20. The celiac (solar) plexus innervates:

1. neck organs

2. organs chest cavity

3. organs top floor abdominal cavity

4. pelvic organs

21. The solar plexus does not contain:

1. sympathetic fibers

2. parasympathetic fibers

3. motor conductors

4. sensitive fibers

22. Gray connecting branches contain

1. parasympathetic preganglionic fibers

2. parasympathetic postganglionic fibers

3. sympathetic preganglionic fibers

4. sympathetic postganglionic fibers

23. Gray connecting branches represent the path of sympathetic conductors to

1. to the organs of the head and neck

2. to the organs chest

3. to the abdominal organs

4. to soma

24. The splanchnic nerves contain:

1. only sympathetic preganglionics

2. only sympathetic postganglionics

3. sympathetic preganglionics and postganglionics

4. sympathetic and parasympathetic preganglionics

25. Spinal nerves having gray connecting branches

1. All

2. none

3. breastfeeding only

4. only sacral

26. The solar plexus innervates organs

1. upper floor of the peritoneal cavity

2. middle floor of the peritoneal cavity

3. lower floor of the peritoneal cavity

4. chest cavity

27. Topography of the solar plexus

1. anterior semicircle of the thoracic aorta

2. anterior semicircle abdominal aorta

3. aortic bifurcation

4. anterior semicircle of the inferior vena cava

28. In what part of the brain does the pupillary reflex arc close?

1. in intermediate

2. on average (at the level of the superior colliculi)

3. average (at the level of the lower colliculi)

4. in the bridge

29. Which nerve provides parasympathetic innervation? Bladder

1. wandering

2. large visceral

3. sacral splanchnic

4. pelvic splanchnic

30. Autonomic conductors of the intermediate nerve begin:

1. from the dorsal nucleus of the vagus nerve

2. from the superior salivary nucleus

3. from the inferior salivary nucleus

4. from the Yakubovich kernel

31. The innervation of the stomach involves:

1. celiac plexus

2. superior mesenteric plexus

3. inferior mesenteric plexus

4. hypogastric plexus

32. The branches of which autonomic plexuses take part in the innervation of the liver

1. sunny

2. superior mesenteric

3. inferior mesenteric

4. hypogastric

33. The branches of which autonomic plexuses take part in the innervation of the spleen

1.sunny

2. superior mesenteric

3. inferior mesenteric

4. hypogastric

34. The branches of which autonomic plexuses take part in the innervation of the uterus and its appendages

1. sunny

2. superior mesenteric

3. inferior mesenteric

4. hypogastric

35. In innervation small intestine takes part:

1. celiac and superior mesenteric plexuses

VEGETATIVE INNERVATION OF INTERNAL ORGANS

AFFERENT INNERVATION. INTEROCEPTIVE ANALYZER

Study of sources of sensory innervation internal organs and the pathways of interoreception is not only of theoretical interest, but also of great practical importance. There are two interrelated goals for which the sources of sensory innervation of organs are studied. The first of them is knowledge of the structure of reflex mechanisms that regulate the activity of each organ. The second goal is to understand the pathways of pain stimuli, which is necessary to create scientifically based surgical methods pain relief. On the one hand, pain is a signal of organ disease. On the other hand, it can develop into severe suffering and cause serious changes in the functioning of the body.

Interoceptive pathways carry afferent impulses from receptors (interoceptors) of the viscera, blood vessels, smooth muscles, skin glands, etc. Sensations of pain in the internal organs can occur under the influence of various factors (stretching, compression, lack of oxygen, etc.)

The interoceptive analyzer, like other analyzers, consists of three sections: peripheral, conductive and cortical (Fig. 18).

The peripheral part is represented by a variety of interoceptors (mechano-, baro-, thermo-, osmo-, chemoreceptors) - the nerve endings of the dendrites of the sensory cells of the nodes of the cranial nerves (V, IX, X), spinal and autonomic nodes.

Nerve cells of the sensory ganglia of the cranial nerves are the first source of afferent innervation of internal organs. Peripheral processes (dendrites) of pseudounipolar cells follow, as part of the nerve trunks and branches of the trigeminal, glossopharyngeal and vagus nerves, to the internal organs of the head, neck, thoracic and abdominal cavities (stomach, duodenum, liver).

The second source of afferent innervation of internal organs is the spinal ganglia, which contains the same sensitive pseudounipolar cells as the ganglia of the cranial nerves. It should be noted that the spinal nodes contain neurons both innervating skeletal muscles and skin, and innervating the viscera and blood vessels. It follows that, in this sense, the spinal nodes are somatic-vegetative formations.

The peripheral processes (dendrites) of the neurons of the spinal ganglia from the trunk of the spinal nerve pass as part of the white connecting branches into the sympathetic trunk and pass in transit through the ᴇᴦο nodes. Afferent fibers travel to the organs of the head, neck and chest as part of the branches of the sympathetic trunk - cardiac nerves, pulmonary, esophageal, laryngeal-pharyngeal and other branches. To the internal organs of the abdominal cavity and pelvis, the bulk of the afferent fibers pass as part of the splanchnic nerves and further, passing in “transit” through the ganglia of the autonomic plexuses, and through the secondary plexuses reaches the internal organs.

Afferent vascular fibers - peripheral processes of sensory cells of the spinal ganglia - pass through the spinal nerves to the blood vessels of the limbs and walls of the body.

Thus, afferent fibers for internal organs do not form independent trunks, but pass as part of the autonomic nerves.

The organs of the head and the vessels of the head receive afferent innervation mainly from the trigeminal and glossopharyngeal nerves. It takes part in the innervation of the pharynx and neck vessels with its afferent fibers glossopharyngeal nerve. The internal organs of the neck, chest cavity and upper “floor” of the abdominal cavity have both vagal and spinal afferent innervation. Most of the internal organs of the abdomen and all pelvic organs have only spinal sensory innervation, i.e. their receptors are formed by the dendrites of spinal ganglion cells.

The central processes (axons) of pseudounipolar cells enter the brain and spinal cord as part of the sensory roots.

The third source of afferent innervation of some internal organs are vegetative cells of the second Dogel type, located in the intraorgan and extraorgan plexuses. The dendrites of these cells form receptors in the internal organs, the axons of some of them reach the spinal cord and even the brain (I.A. Bulygin, A.G. Korotkov, N.G. Gorikov), following either as part of the vagus nerve or through the sympathetic trunks in dorsal roots of spinal nerves.

In the brain, the bodies of the second neurons are located in the sensory nuclei of the cranial nerves (nucl. spinalis n. trigemini, nucl. solitarius IX, X nerves).

In the spinal cord, interoceptive information is transmitted through several channels: along the anterior and lateral spinothalamic tracts, along the spinocerebellar tracts and through the posterior funiculi - the small and wedge-shaped fasciculi. The participation of the cerebellum in the adaptive-trophic functions of the nervous system explains the existence of wide interoceptive pathways leading to the cerebellum. Thus, the bodies of the second neurons are also located in the spinal cord - in the nuclei posterior horns and intermediate zone, and similarly in the thin and wedge-shaped nuclei medulla oblongata.

The axons of the second neurons are directed to the opposite side and as part of the medial lemniscus they reach the nuclei of the thalamus, and similarly the nuclei of the reticular formation and the hypothalamus. It follows that in the brain stem, firstly, a concentrated bundle of interoceptive conductors can be traced, following in the medial loop to the nuclei of the thalamus (III neuron), and secondly, there is a divergence of vegetative pathways heading to many nuclei of the reticular formation and to the hypothalamus. These connections ensure coordination of the activities of numerous centers involved in the regulation of various autonomic functions.

The processes of the third neurons go through the posterior leg of the internal capsule and end on the cells of the cerebral cortex, where awareness occurs pain. Usually these sensations are diffuse in nature and do not have precise localization. I.P. Pavlov explained this by the fact that the cortical representation of interoceptors has little life practice. Thus, patients with repeated attacks of pain associated with diseases of the internal organs determine their location and nature much more accurately than at the beginning of the disease.

In the cortex, vegetative functions are represented in the motor and premotor zones. Information about the functioning of the hypothalamus enters the frontal lobe cortex. Afferent signals from the respiratory and circulatory organs - to the insular cortex, from the abdominal organs - to the postcentral gyrus. The cortex of the central part of the medial surface of the cerebral hemispheres (limbic lobe) is similarly part of the visceral analyzer, participating in the regulation of respiratory, digestive, genitourinary systems, metabolic processes.

The afferent innervation of internal organs is not segmental in nature. Internal organs and vessels are distinguished by a multiplicity of sensory innervation pathways, the majority of which are fibers originating from the nearest segments of the spinal cord. These are the main routes of innervation. Fibers of additional (roundabout) pathways of innervation of internal organs pass from distant segments of the spinal cord.

A significant part of the impulses from the internal organs reaches the autonomic centers of the brain and spinal cord through the afferent fibers of the somatic nervous system due to the numerous connections between the structures of the somatic and autonomic parts of the single nervous system. Afferent impulses from internal organs and the movement apparatus can arrive at the same neuron, which, based on the current situation, ensures the performance of vegetative or animal functions. The presence of connections between the nerve elements of somatic and autonomic reflex arcs causes the appearance of referred pain, which must be taken into account when making a diagnosis and treatment. Thus, with cholecystitis, there are toothaches and a phrenicus symptom is noted; with anuria of one kidney, there is a delay in the excretion of urine by the other kidney. In diseases of the internal organs, skin zones of increased sensitivity appear - hyperesthesia (Zakharyin-Ged zones). For example, with angina pectoris, referred pain is localized in the left arm, with a stomach ulcer - between the shoulder blades, with damage to the pancreas - girdle pain on the left at the level of the lower ribs up to the spine, etc. Knowing the structural features of segmental reflex arcs, it is possible to influence internal organs, causing irritation in the area of ​​the corresponding skin segment. This is what acupuncture and the use of local physiotherapy are based on.

EFFERENT INNERVATION

The efferent innervation of various internal organs is ambiguous. Organs that include smooth involuntary muscles, and similarly organs with secretory function, as a rule, receive efferent innervation from both parts of the autonomic nervous system: the sympathetic and parasympathetic, which have the opposite effect on the function of the organ.

Excitation of the sympathetic part of the autonomic nervous system causes increased heart rate and intensification, increased blood pressure and blood glucose levels, increased release of hormones from the adrenal medulla, dilation of the pupils and bronchial lumen, decreased secretion of glands (except sweat glands), inhibition of intestinal motility, causing spasm of the sphincters .

Excitation of the parasympathetic division of the autonomic nervous system reduces arterial pressure and the level of glucose in the blood (increases insulin secretion), reduces and weakens heart contractions, constricts the pupils and bronchial lumen, increases the secretion of glands, increases peristalsis and contracts the muscles of the bladder, relaxes the sphincters.

Depending on the morphofunctional characteristics of a particular organ, the sympathetic or parasympathetic component of the autonomic nervous system may predominate in the efferent innervation. Morphologically, this is manifested in the number of corresponding conductors in the structure and severity of the intraorgan nervous system. In particular, the parasympathetic department plays a decisive role in the innervation of the bladder and vagina, and the sympathetic one in the innervation of the liver.

Some organs receive only sympathetic innervation, for example, the pupillary dilator, sweat and sebaceous glands skin, hair muscles of the skin, spleen, and the sphincter of the pupil and the ciliary muscle - parasympathetic innervation. The vast majority have only sympathetic innervation blood vessels. Moreover, an increase in the tone of the sympathetic nervous system, as a rule, causes a vasoconstrictor effect. However, there are organs (the heart) in which an increase in the tone of the sympathetic nervous system is accompanied by a vasodilator effect.
Concept and types, 2018.

Internal organs containing striated muscles (tongue, pharynx, esophagus, larynx, rectum, urethra) receive efferent somatic innervation from the motor nuclei of the cranial or spinal nerves.

Important for determining the sources of nerve supply to internal organs is knowledge of the origin, movements in the process of evolution and ontogenesis. Only from these positions will the innervation, for example, of the heart from the cervical sympathetic nodes, and the gonads from the aortic plexus, be understood.

A distinctive feature of the nervous apparatus of internal organs is the multi-segmentation of sources of formation, the multiplicity of pathways connecting the organ with the central nervous system and the presence of local innervation centers. This can explain the impossibility of complete denervation of any internal organ surgically.

Efferent autonomic pathways to internal organs and vessels are two-neuronal. The bodies of the first neurons are located in the nuclei of the brain and spinal cord. The bodies of the latter are in the vegetative nodes, where the impulse switches from preganglionic to postganglionic fibers.

SOURCES OF EFFERENT VEGETATIVE INNERVATION OF INTERNAL ORGANS

VEGETATIVE INNERVATION OF INTERNAL ORGANS - concept and types. Classification and features of the category "VEGETATIVE INNERVATION OF INTERNAL ORGANS" 2017-2018.

The principle of innervation of internal organs

Routes of approach of afferent nerve fibers:

Pathways of approach of efferent somatic motor nerve fibers:

Paths of approach of efferent autonomic (motor and secretory) nerve fibers:

VII, IX, X pairs of cranial nerves.

10.

11.

12. VESSEL INNERVATION

13.

14. VESSEL INNERVATION

15. WHAT DOES THE ANS INNERVATE?

16. Localization of neuron bodies in a three-neuron autonomic reflex arc.

17. Method of approach of autonomic fibers to innervated organs.

18.

19. Morphofunctional differences between the somatic part of the nervous system and the autonomic one (see previous lecture)

20.

21. TYPES OF INNERVATION

22. The essence of afferent innervation is:

23. The essence of efferent innervation is:

24.

25.

26.

27.

28.

29. VESSEL INNERVATION

30.

31.

32. INNERVATION OF INTERNAL ORGANS

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

Afferent innervation of internal organs and blood vessels is carried out by nerve cells of the sensory ganglia of the cranial nerves, spinal ganglia, and also vegetative ganglia (I neuron). Peripheral processes (dendrites) of pseudounipolar cells follow as part of the nerves to the internal organs. The central processes enter the brain and spinal cord as part of the sensory roots. Bodies II neurons located in the spinal cord - in the nuclei of the dorsal horns, in the nuclei of the thin and wedge-shaped fasciculi of the medulla oblongata and the sensory nuclei of the cranial nerves. The axons of the second neurons are directed to the opposite side and, as part of the medial loop, reach the nuclei of the thalamus (III neuron).

The processes of the third neurons end on the cells of the cerebral cortex, where the awareness of pain occurs. The cortical end of the analyzer is located mainly in the pre- and postcentral gyri (IV neuron).

The efferent innervation of various internal organs is ambiguous. Organs that include smooth involuntary muscles, as well as organs with secretory function, as a rule, receive efferent innervation from both parts of the autonomic nervous system: sympathetic and parasympathetic, causing the opposite effect.

Excitation sympathetic division the autonomic nervous system causes increased heart rate and intensification, increased blood pressure and blood glucose levels, increased release of hormones from the adrenal medulla, dilation of the pupils and bronchial lumen, decreased secretion of glands (except sweat glands), spasm of the sphincters and inhibition of intestinal motility.

Excitation parasympathetic division The autonomic nervous system reduces blood pressure and blood glucose levels (increases insulin secretion), reduces and weakens heart contractions, constricts the pupils and bronchial lumen, increases the secretion of glands, increases peristalsis and contracts the muscles of the bladder, relaxes the sphincters.

SENSE ORGANS

Introduction

Sense organs belong to the sensory systems. They contain the peripheral ends of the analyzers, protecting the receptor cells of the analyzers from adverse effects and creating favorable conditions for their optimal functioning.

According to I.P. Pavlov, each analyzer consists of three parts: peripheral part - receptor which perceives irritations and transforms them into a nerve impulse, conductive transmitting impulses to nerve centers, central, located in the cerebral cortex (cortical end of the analyzer), which analyzes and synthesizes information. Thanks to the sense organs, the body’s relationship with the external environment is established.

The sense organs include: the organ of vision, the organ of hearing and balance, the organ of smell, the organ of taste, the organ of tactile, pain and temperature sensitivity, the motor analyzer, the interoceptive analyzer.

The motor analyzer is described in detail in the chapter “Central Nervous System. Conducting pathways”, and about the interoceptive analyzer – in the chapter “Autonomic Nervous System”.

Organ of vision

Eye, oculus, comprises eyeball and surrounding ancillary organs.

Eyeball, bulbus oculi, is located in the orbit and has the appearance of a ball, more convex in front. Its anterior and posterior poles are distinguished. The straight line passing through the poles is called the visual axis of the eye. The eyeball is composed of three membranes: fibrous, vascular, and retinal, surrounding the inner core of the eye (Fig. 1).

fibrous membrane, tunica fibrosa bulbi, is a derivative of mesoderm, located externally, performs a protective function and serves as a site of muscle attachment. It is divided into: posterior section - sclera or tunica albuginea, which is a dense connective tissue plate white and the anterior section - cornea, this is the more convex transparent part of the fibrous membrane, reminiscent of a watch glass, which belongs to the light-refracting media of the eye. She has a large number of nerve endings and lacks blood vessels, has high permeability, which is used for administration medicinal substances. At the border of the cornea and sclera, in the thickness of the latter, there is a venous sinus of the sclera, into which fluid outflows from the anterior chamber of the eye.

Fig.1. Diagram of the eyeball. 1 – sclera; 2 – cornea; 3 – the choroid itself; 4 – retina; 5 – iris; 6 – iridocorneal angle; 7 – lens; 8 – vitreous body; 9 – anterior chamber; 10 – rear camera; 11 – yellow spot; 12 – optic nerve.

choroid, tunica vasculosa bulbi, like fibrous, develops from the mesoderm, is rich in blood vessels, located inward from the fibrous membrane. It has three sections: the choroid itself, the ciliary body and the iris.

The choroid itself, choroidea, is 2/3 choroid and is its posterior section. Between the adjacent surfaces of the choroid proper and the sclera there is a slit-like perivascular space, which allows the choroid proper to move during accommodation.

ciliary body,corpus ciliare- thickened part of the choroid. The location of the ciliary body coincides with the junction of the sclera and the cornea. The anterior part of the ciliary body contains about 70 ciliary processes, the basis of which are blood capillaries that produce aqueous humor. From the ciliary body, the fibers of the ciliary girdle (ligament of Zinn) begin, which is attached to the lens capsule. The thickness of the ciliary body is the ciliary muscle, m. ciliaris, involved in accommodation. When tense, this muscle relaxes the ligament, and through it the lens capsule, which becomes more convex. When the muscle relaxes, the ligament of Zinn tightens and the lens becomes flatter. Muscle fiber atrophy and replacement that occurs with age connective tissue leads to a weakening of accommodation.

Iris or iris,iris, makes up the anterior part of the choroid and looks like a disk with a hole in the center - pupil. The base (stroma) of the iris is represented by connective tissue with vessels located in it. In the thickness of the stroma there are smooth muscles: circularly located muscle fibers that constrict the pupil, m. sphincter pupillae, and radial fibers that dilate the pupil, m. dilatator pupillae. Thanks to the muscles, the iris acts as a diaphragm, regulating the amount of light entering the eye. The anterior surface of the iris contains the pigment melanin, the varying amount and nature of which determines the color of the eyes.

Retina, retina- inner lining of the eyeball. Develops from an outgrowth of the anterior brain bladder, which turns into an eye vesicle on a stem, and then into a double-walled glass. The retina is formed from the latter, and the optic nerve is formed from the stalk. The retina consists of two layers: the outer pigment layer and the inner light-sensitive layer (nerve part). Based on function and structure, the inner layer of the retina is divided into two parts: posterior visual, pars optica retinae, containing photosensitive elements (rods, cones) and anterior blind, pars caeca retinae, covering the posterior surface of the iris and the ciliary body, where there are no photosensitive elements. The optic nerve forms at the back of the retina. The place where it exits is called the disk optic nerve where rods and cones are absent (blind spot). Lateral to the optic disc, it is round in shape yellow spot, macula, containing only cones and is the place of greatest visual acuity.

Inner core eyes

The inner nucleus of the eye consists of transparent light-refracting media: the lens, the vitreous body and aqueous humor.

Lens, lens, develops from the ectoderm and is the most important light-refracting medium. It has the shape of a biconvex lens and is enclosed in a thin transparent capsule. The ligament of Zinn extends from the lens capsule to the ciliary body, which acts as a suspensory apparatus for the lens. Due to the elasticity of the lens, its curvature easily changes when viewing objects at a far or near distance (accommodation). When the ciliary muscle contracts, the fibers of the ligament of cinnamon relax, and the lens becomes more convex (set to near vision). Relaxation of the muscle leads to tension in the ligament and flattening of the lens (distance vision).

Vitreous body, corpus vitreum- a transparent jelly-like mass lying behind the lens and filling the cavity of the eyeball.

Aqueous moisture produced by the capillaries of the ciliary processes and fills the anterior and posterior chambers of the eye. It is involved in nourishing the cornea and maintaining intraocular pressure.

The anterior chamber of the eye is the space between the anterior surface of the iris and the posterior surface of the cornea. Along the periphery, the anterior and back wall the chambers converge, forming the iridocorneal angle, through the slit-like spaces of which aqueous humor flows into the venous sinus of the sclera, and from there into the veins of the eye.

The posterior chamber of the eye is narrower, located between the iris, lens and ciliary body, and communicates with the anterior chamber of the eye through the pupil.

Thanks to the circulation of aqueous humor, a balance is maintained between its secretion and absorption, which is a factor in stabilizing intraocular pressure.

AFFERENT INNERVATION. INTEROCEPTIVE ANALYZER

The study of the sources of sensitive innervation of internal organs and interoceptive pathways is not only of theoretical interest, but also of great practical importance. There are two interrelated goals for which the sources of sensory innervation of organs are studied. The first of them is knowledge of the structure of reflex mechanisms that regulate the activity of each organ. The second goal is to understand the pathways of pain stimulation, which is necessary to create scientifically based surgical methods of pain relief. On the one hand, pain is a signal of organ disease. On the other hand, it can develop into severe suffering and cause serious changes in the functioning of the body.

Interoceptive pathways carry afferent impulses from receptors (interoceptors) of the viscera, blood vessels, smooth muscles, skin glands, etc. Sensations of pain in the internal organs can occur under the influence of various factors (stretching, compression, lack of oxygen, etc.)

The interoceptive analyzer, like other analyzers, consists of three sections: peripheral, conductive and cortical (Fig. 18).

The peripheral part is represented by a variety of interoceptors (mechano-, baro-, thermo-, osmo-, chemoreceptors) - the nerve endings of the dendrites of the sensory cells of the nodes of the cranial nerves (V, IX, X), spinal and autonomic nodes.

Nerve cells of the sensory ganglia of the cranial nerves are the first source of afferent innervation of internal organs. Peripheral processes (dendrites) of pseudounipolar cells follow, as part of the nerve trunks and branches of the trigeminal, glossopharyngeal and vagus nerves, to the internal organs of the head, neck, chest and abdominal cavity (stomach, duodenum intestine, liver).

The second source of afferent innervation of internal organs is the spinal ganglia, which contains the same sensitive pseudounipolar cells as the ganglia of the cranial nerves. It should be noted that the spinal nodes contain neurons both innervating skeletal muscles and skin, and innervating the viscera and blood vessels. Consequently, in this sense, the spinal nodes are somatic-vegetative formations.

The peripheral processes (dendrites) of the neurons of the spinal ganglia from the spinal nerve trunk pass as part of the white connecting branches into the sympathetic trunk and pass in transit through its nodes. Afferent fibers travel to the organs of the head, neck and chest as part of the branches of the sympathetic trunk - cardiac nerves, pulmonary, esophageal, laryngeal-pharyngeal and other branches. To the internal organs of the abdominal cavity and pelvis, the bulk of the afferent fibers pass as part of the splanchnic nerves and further, passing through the ganglia of the autonomic plexuses, and through the secondary plexuses reaches the internal organs.

Afferent vascular fibers - peripheral processes of sensory cells of the spinal ganglia - pass through the spinal nerves to the blood vessels of the limbs and walls of the body.

Thus, afferent fibers for internal organs do not form independent trunks, but pass as part of the autonomic nerves.

The organs of the head and the vessels of the head receive afferent innervation mainly from the trigeminal and glossopharyngeal nerves. The glossopharyngeal nerve takes part in the innervation of the pharynx and neck vessels with its afferent fibers. The internal organs of the neck, chest cavity and upper “floor” of the abdominal cavity have both vagal and spinal afferent innervation. Most of the internal organs of the abdomen and all pelvic organs have only spinal sensory innervation, i.e. their receptors are formed by the dendrites of spinal ganglion cells.

The central processes (axons) of pseudounipolar cells enter the brain and spinal cord as part of the sensory roots.

The third source of afferent innervation of some internal organs are vegetative cells of the second Dogel type, located in the intraorgan and extraorgan plexuses. The dendrites of these cells form receptors in the internal organs, the axons of some of them reach the spinal cord and even the brain (I.A. Bulygin, A.G. Korotkov, N.G. Gorikov), following either as part of the vagus nerve or through the sympathetic trunks in dorsal roots of spinal nerves.

In the brain, the bodies of the second neurons are located in the sensory nuclei of the cranial nerves (nucl. spinalis n. trigemini, nucl. solitarius IX, X nerves).

In the spinal cord, interoceptive information is transmitted through several channels: along the anterior and lateral spinothalamic tracts, through the spinocerebellar tracts and through the posterior funiculi - the thin and cuneate fasciculi. The participation of the cerebellum in the adaptive-trophic functions of the nervous system explains the existence of broad interoceptive pathways leading to the cerebellum. Thus, the bodies of the second neurons are also located in the spinal cord - in the nuclei of the dorsal horns and intermediate zone, as well as in the thin and wedge-shaped nuclei of the medulla oblongata.

The axons of the second neurons are directed to the opposite side and, as part of the medial loop, reach the nuclei of the thalamus, as well as the nuclei of the reticular formation and the hypothalamus. Consequently, in the brain stem, firstly, a concentrated bundle of interoceptive conductors can be traced, following in the medial loop to the nuclei of the thalamus (III neuron), and secondly, there is a divergence of autonomic pathways heading to many nuclei of the reticular formation and to the hypothalamus. These connections ensure coordination of the activities of numerous centers involved in the regulation of various autonomic functions.

The processes of the third neurons go through the posterior leg of the internal capsule and end on the cells of the cerebral cortex, where the awareness of pain occurs. Usually these sensations are diffuse in nature and do not have precise localization. I.P. Pavlov explained this by the fact that the cortical representation of interoceptors has little life practice. Thus, patients with repeated attacks of pain associated with diseases of the internal organs determine their location and nature much more accurately than at the beginning of the disease.

In the cortex, autonomic functions are represented in the motor and premotor zones. Information about the functioning of the hypothalamus enters the frontal lobe cortex. Afferent signals from the respiratory and circulatory organs - to the insular cortex, from the abdominal organs - to the postcentral gyrus. The cortex of the central part of the medial surface of the cerebral hemispheres (limbic lobe) is also part of the visceral analyzer, participating in the regulation of the respiratory, digestive, genitourinary systems, and metabolic processes.

The afferent innervation of internal organs is not segmental in nature. Internal organs and vessels are distinguished by a multiplicity of sensory innervation pathways, the majority of which are fibers originating from the nearest segments of the spinal cord. These are the main routes of innervation. Fibers of additional (roundabout) pathways of innervation of internal organs pass from distant segments of the spinal cord.

A significant part of the impulses from the internal organs reaches the autonomic centers of the brain and spinal cord through the afferent fibers of the somatic nervous system due to numerous connections between the structures of the somatic and autonomic parts of the unified nervous system. Afferent impulses from internal organs and the movement apparatus can arrive at the same neuron, which, depending on the current situation, ensures the performance of vegetative or animal functions. The presence of connections between the nerve elements of somatic and autonomic reflex arcs causes the appearance of referred pain, which must be taken into account when making a diagnosis and treatment. So, with cholecystitis, there are toothaches and a phrenicus symptom is noted; with anuria of one kidney, there is a delay in urine output from the other kidney. In diseases of the internal organs, skin zones appear hypersensitivity- hyperesthesia (Zakharyin-Ged zone). For example, with angina pectoris, referred pain is localized in the left arm, with a stomach ulcer - between the shoulder blades, with damage to the pancreas - girdle pain on the left at the level of the lower ribs up to the spine, etc. Knowing the structural features of segmental reflex arcs, it is possible to influence internal organs by causing irritation in the area of ​​the corresponding skin segment. This is the basis of acupuncture and the use of local physiotherapy.

EFFERENT INNERVATION

The efferent innervation of various internal organs is ambiguous. Organs that include smooth involuntary muscles, as well as organs with secretory function, as a rule, receive efferent innervation from both parts of the autonomic nervous system: the sympathetic and parasympathetic, which have the opposite effect on the function of the organ.

Excitation of the sympathetic part of the autonomic nervous system causes an increase in heart rate and contractions, an increase in blood pressure and blood glucose levels, an increase in the release of hormones from the adrenal medulla, dilation of the pupils and bronchial lumen, a decrease in the secretion of glands (except sweat glands), inhibition of intestinal motility, and causes spasm of the sphincters .

Excitation of the parasympathetic part of the autonomic nervous system reduces blood pressure and blood glucose levels (increases insulin secretion), reduces and weakens heart contractions, constricts the pupils and bronchial lumen, increases the secretion of glands, increases peristalsis and contracts the muscles of the bladder, relaxes the sphincters.

Depending on the morphofunctional characteristics of a particular organ, the sympathetic or parasympathetic component of the autonomic nervous system may predominate in its efferent innervation. Morphologically, this is manifested in the number of corresponding conductors in the structure and severity of the intraorgan nervous apparatus. In particular, the parasympathetic department plays a decisive role in the innervation of the bladder and vagina, and the sympathetic one in the innervation of the liver.

Some organs receive only sympathetic innervation, for example, the dilator pupil, sweat and sebaceous glands of the skin, the hair muscles of the skin, the spleen, and the sphincter of the pupil and the ciliary muscle receive parasympathetic innervation. The vast majority of blood vessels have only sympathetic innervation. In this case, an increase in the tone of the sympathetic nervous system, as a rule, causes a vasoconstrictor effect. However, there are organs (the heart) in which an increase in the tone of the sympathetic nervous system is accompanied by a vasodilator effect.

Internal organs containing striated muscles (tongue, pharynx, esophagus, larynx, rectum, urethra) receive efferent somatic innervation from the motor nuclei of the cranial or spinal nerves.

Important for determining the sources of nerve supply to internal organs is knowledge of its origin, its movements in the process of evolution and ontogenesis. Only from these positions will the innervation, for example, of the heart from the cervical sympathetic nodes, and the gonads from the aortic plexus, be understood.

A distinctive feature of the nervous apparatus of internal organs is the multisegmental nature of the sources of its formation, the multiplicity of pathways connecting the organ with the central nervous system and the presence of local innervation centers. This may explain the impossibility of complete denervation of any internal organ surgically.

Efferent autonomic pathways to internal organs and vessels are two-neuronal. The bodies of the first neurons are located in the nuclei of the brain and spinal cord. The bodies of the latter are in the vegetative nodes, where the impulse switches from preganglionic to postganglionic fibers.

SOURCES OF EFFERENT VEGETATIVE INNERVATION OF INTERNAL ORGANS

Organs of the head and neck

Parasympathetic innervation. The first neurons: 1) accessory and median nucleus of the third pair of cranial nerves; 2) the superior salivary nucleus of the VII pair; 3) the lower salivary nucleus of the IX pair; 4) dorsal nucleus of the X pair of cranial nerves.

Second neurons: periorgan nodes of the head (ciliary, pterygopalatine, submandibular, auricular), intraorgan nodes of the X pair of nerves.

Sympathetic innervation. The first neurons are the interlateral nuclei of the spinal cord (C 8, Th 1-4).

The second neurons are the cervical nodes of the sympathetic trunk.

Organs of the chest cavity

Parasympathetic innervation. The first neurons are the dorsal nucleus of the vagus nerve (X pair).

Sympathetic innervation. The first neurons are the interlateral nuclei of the spinal cord (Th 1-6).

The second neurons are the lower cervical and 5-6 upper thoracic nodes of the sympathetic trunk. Second neurons for the heart are located in all cervical and upper thoracic ganglia.

Abdominal organs

Parasympathetic innervation. The first neurons are the dorsal nucleus of the vagus nerve.

The second neurons are periorgan and intraorgan nodes. The exception is the sigmoid colon, which is innervated as pelvic organs.

Sympathetic innervation. The first neurons are the interlateral nuclei of the spinal cord (Th 6-12).

The second neurons are the nodes of the celiac, aortic and inferior mesenteric plexuses (II order). Chromophine cells of the adrenal medulla are innervated by preganglionic fibers.

Organs of the pelvic cavity

Parasympathetic innervation. The first neurons are the interlateral nuclei of the sacral spinal cord (S 2-4).

The second neurons are periorgan and intraorgan nodes.

Sympathetic innervation. The first neurons are the interlateral nuclei of the spinal cord (L 1-3).

The second neurons are the inferior mesenteric node and the nodes of the superior and inferior hypogastric plexuses (II order).

INNERVATION OF BLOOD VESSELS

The nervous apparatus of blood vessels is represented by interoceptors and perivascular plexuses, spreading along the vessel in its adventitia or along the border of its outer and middle membranes.

Afferent (sensitive) innervation is carried out by nerve cells of the spinal ganglia and ganglia of the cranial nerves.

Efferent innervation of blood vessels is carried out due to sympathetic fibers, and arteries and arterioles experience a vasoconstrictor effect continuously.

Sympathetic fibers travel to the vessels of the limbs and torso as part of the spinal nerves.

The bulk of the efferent sympathetic fibers to the vessels of the abdominal cavity and pelvis passes through the splanchnic nerves. Irritation of the splanchnic nerves causes a narrowing of the blood vessels, while transection causes a sharp dilation of the blood vessels.

A number of researchers have discovered vasodilator fibers that are part of some somatic and autonomic nerves. Perhaps only the fibers of some of them (chorda tympani, nn. splanchnici pelvini) are of parasympathetic origin. The nature of most vasodilator fibers remains unclear.

T.A. Grigorieva (1954) substantiated the assumption that the vasodilator effect is achieved as a result of contraction of not circular, but longitudinally or obliquely oriented muscle fibers of the vascular wall. Thus, the same impulses brought by sympathetic nerve fibers cause a different effect - vasoconstrictor or vasodilator, depending on the orientation of the smooth muscle cells themselves in relation to the longitudinal axis of the vessel.

Another mechanism of vasodilation is also possible: relaxation of the smooth muscles of the vascular wall as a result of inhibition in the autonomic neurons innervating the vessels.

Finally, expansion of the lumen of blood vessels as a result of humoral influences cannot be excluded, since humoral factors can organically enter into the reflex arc, in particular as its effector link.