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They pass as part of the spinal nerves. Lecture forty-six

1. Characteristics of the nervous system and its functions.

2. Structure of the spinal cord.

3. Functions of the spinal cord.

4. Overview of the spinal nerves. Nerves of the cervical, brachial, lumbar and sacral plexuses.

OBJECTIVE: To know the general structure of the nervous system, topography, structure and functions of the spinal cord, spinal roots and branches of the spinal nerves.

Introduce the reflex principle of the nervous system and the innervation zone of the cervical, brachial, lumbar and sacral plexuses.

Be able to show spinal cord neurons, pathways, spinal roots, nodes and nerves on posters and tablets.

1. The nervous system is one of the systems that ensures the coordination of processes occurring in the body and the establishment of relationships between the body and the external environment. The study of the nervous system - neurology. The main functions of the nervous system: 1) perception of stimuli acting on the body; 2) conducting and processing of perceived information; 3) formation of responses and adaptive reactions, including GNI and the psyche.

According to topographical principles, the nervous system is divided into central and peripheral. The central nervous system (CNS) includes the spinal cord and brain, the peripheral nervous system includes everything that is located outside the spinal cord and brain: spinal and cranial nerves with their roots, their branches, nerve endings and ganglia (nerve nodes) formed by the bodies neurons. The nervous system is conventionally divided into somatic (regulation of relationships between the body and the external environment), and vegetative (autonomous) (regulation of relationships and processes within the body). The structural and functional unit of the nervous system is the nerve cell - neuron (neurocyte). A neuron has a cell body - a trophic center and processes: dendrites, along which impulses travel to the cell body, and an axon, along which impulses travel from the cell body. Depending on the number of processes, there are 3 types of neurons: pseudounipolar, bipolar and multipolar. All neurons are connected to each other through synapses. One axon can form up to 10,000 synapses on many nerve cells. There are 20 billion neurons and 20 billion synapses in the human body.

Based on their morphofunctional characteristics, there are 3 main types of neurons.

1) Afferent (sensitive, receptor) neurons conduct impulses to the central nervous system, i.e. centripetal. The bodies of these neurons always lie outside the brain or spinal cord in the nodes (ganglia) of the peripheral nervous system. 2) Intercalated (intermediate, associative) neurons transmit excitation from the afferent (sensitive) neuron to the efferent (motor or secretory). 3) Efferent ( motor, secretory, effector) neurons conduct impulses along their axons to the working organs (muscles, glands). The bodies of these neurons are located in the central nervous system or on the periphery - in the sympathetic and parasympathetic nodes.

The main form of nervous activity is the reflex. Reflex (Latin reflexus - reflection) is a causally determined reaction of the body to irritation, carried out with the obligatory participation of the central nervous system. The structural basis of reflex activity is made up of neural chains of receptor, intercalary and effector neurons. They form the path along which nerve impulses pass from the receptors to the executive organ, called the reflex arc. It includes: receptor -> afferent nerve path -> reflex center -> efferent path -> effector.

2. The spinal cord (medulla spinalis) is the initial part of the central nervous system. It is located in the spinal canal and is a cylindrical cord, flattened from front to back, 40-45 cm long, 1 to 1.5 cm wide, weighing 34-38 g (2% of the brain mass). At the top it passes into the medulla oblongata, and at the bottom it ends with a point - the medullary cone at the level of the I - II lumbar vertebrae, where a thin terminal (terminal) filament departs from it (a rudiment of the caudal (caudal) end of the spinal cord). The diameter of the spinal cord varies in different areas. In the cervical and lumbar regions it forms thickenings (innervation of the upper and lower extremities). On the anterior surface of the spinal cord there is an anterior median fissure, on the posterior surface there is a posterior median sulcus; they divide the spinal cord into interconnected right and left symmetrical halves. On each half, weakly defined anterior lateral and posterior lateral grooves are distinguished. The first is the place where the anterior motor roots exit the spinal cord, the second is the place where the posterior sensory roots of the spinal nerves enter the brain. These lateral grooves also serve as the boundary between the anterior, lateral and posterior cords of the spinal cord. Inside the spinal cord there is a narrow cavity - the central canal, filled with cerebrospinal fluid (in an adult, it is overgrown in various parts, and sometimes throughout its entire length).

The spinal cord is divided into parts: cervical, thoracic, lumbar, sacral and coccygeal, and the parts are divided into segments. A segment (structural and functional unit of the spinal cord) is an area corresponding to two pairs of roots (two anterior and two posterior). Throughout the entire length of the spinal cord, 31 pairs of roots emerge from each side. Accordingly, 31 pairs of spinal nerves in the spinal cord are divided into 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1-3 coccygeal.

The spinal cord consists of gray and white matter. Gray matter - neurons (13 million), forming 3 gray columns in each half of the spinal cord: anterior, posterior and lateral. In a cross section of the spinal cord, the columns of gray matter on each side have the appearance of horns. The wider anterior horn and narrow posterior one correspond to the anterior and posterior gray columns. The lateral horn corresponds to the intermediate column (vegetative) of gray matter. The gray matter of the anterior horns contains motor neurons (motoneurons), the posterior horns contain intercalary sensory neurons, and the lateral horns contain intercalary autonomic neurons. The white matter of the spinal cord is localized outward from the gray matter and forms the anterior, lateral and posterior cords. It consists predominantly of longitudinally running nerve fibers, united in bundles - pathways. The white matter of the anterior cords contains descending pathways, the lateral cords contain ascending and descending tracts, and the posterior cords contain ascending pathways.

The connection between the spinal cord and the periphery is carried out through nerve fibers passing in the spinal roots. The anterior roots contain centrifugal motor fibers, and the posterior roots contain centripetal sensory fibers (therefore, with bilateral transection of the dorsal roots of the spinal cord in a dog, sensitivity disappears, the anterior roots are preserved, but the muscle tone of the limbs disappears).

The spinal cord is covered with three meninges: the inner - soft (vascular), the middle - arachnoid and the outer - hard. Between the hard shell and the periosteum of the spinal canal there is an epidural space, between the hard shell and the arachnoid there is a subdural space. The arachnoid membrane is separated from the soft (vascular) shell by the subarachnoid (subarachnoid) space containing cerebrospinal fluid (100-200 ml, performs trophic and protective functions)

3. The spinal cord performs two functions: reflex and conductive.

The reflex function is carried out by the nerve centers of the spinal cord, which are the segmental working centers of unconditioned reflexes. Their neurons are directly connected to receptors and working organs. Each segment of the spinal cord, through its roots, innervates three metameres (transverse segments) of the body and receives sensitive information also from three metameres. Due to this overlap, each metamer of the body is innervated by three segments and transmits signals (impulses) to three segments of the spinal cord (safety factor). The spinal cord receives afferentation from receptors in the skin, motor system, blood vessels, digestive tract, excretory and genital organs. Efferent impulses from the spinal cord go to the skeletal muscles, including the respiratory muscles - intercostal muscles and the diaphragm, to the internal organs, blood vessels, and sweat glands.

The conductive function of the spinal cord is carried out through ascending and descending pathways. Ascending pathways transmit information from tactile, pain, temperature receptors of the skin and proprioceptors of skeletal muscles through neurons of the spinal cord and other parts of the central nervous system to the cerebellum and cerebral cortex. Descending pathways connect the cerebral cortex, subcortical nuclei and brainstem formations with motor neurons of the spinal cord. They provide the influence of the higher parts of the central nervous system on the activity of skeletal muscles.

4. A person has 31 pairs of spinal nerves, corresponding to 31 segments of the spinal cord: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and a pair of coccygeal nerves. Each spinal nerve is formed by connecting the anterior (motor) and posterior (sensory) roots. Upon exiting the intervertebral foramen, the nerve is divided into two main branches: anterior and posterior, both of which are mixed in function.

Through the spinal nerves, the spinal cord carries out the following innervation: sensitive - to the trunk, limbs and part of the neck, motor - to all muscles of the trunk, limbs and part of the neck muscles; sympathetic - of all organs that have it, and parasympathetic - of the pelvic organs.

The posterior branches of all spinal nerves have a segmental arrangement. They go to the back surface of the body, where they are divided into cutaneous and muscular branches that innervate the skin and muscles of the back of the head, neck, back, lumbar region and pelvis.

The anterior branches are thicker than the posterior ones, of which only 12 pairs of thoracic spinal nerves have a segmental (metameric) location. These nerves are called intercostal nerves because they run in the intercostal spaces on the inner surface along the lower edge of the corresponding rib. They innervate the skin and muscles of the anterior and lateral walls of the chest and abdomen. The anterior branches of the remaining spinal nerves form plexuses before going to the corresponding area of ​​the body. There are cervical, brachial, lumbar and sacral plexuses, nerves arise from them, each has its own name and innervates a specific area.

The cervical plexus is formed by the anterior branches of the four superior cervical nerves. It is located in the area of ​​the four upper cervical vertebrae on the deep muscles of the neck. Sensitive (cutaneous), motor (muscular) and mixed nerves (branches) depart from this plexus. 1) Sensory nerves: lesser occipital nerve, greater auricular nerve, transverse cervical nerve, supraclavicular nerves. 2) Muscular branches innervate the deep muscles of the neck, as well as the trapezius, sternocleidomastoid muscles. 3) The phrenic nerve is a mixed and largest nerve of the cervical plexus, its motor fibers innervate the diaphragm, and its sensory fibers innervate the pericardium and pleura.

The brachial plexus is formed by the anterior branches of the four lower cervical, part of the anterior branch of the IV cervical and I thoracic spinal nerves. In the plexus there are supraclavicular (short) branches (innervate the muscles and skin of the chest, all muscles of the shoulder girdle and back muscles) and subclavian (long) branches (innervate the skin and muscles of the arm).

The lumbar plexus is formed by the anterior branches of the upper three lumbar nerves and partly by the anterior branches of the XII thoracic and IV lumbar nerves. Short branches of the lumbar plexus innervate the quadratus lumborum muscle, the iliopsoas muscle, the abdominal muscles, as well as the skin of the lower abdominal wall and external genitalia. The long branches of this plexus innervate the free lower limb

The sacral plexus is formed by the anterior branches of the IV (partial) and V lumbar nerves and the upper four sacral nerves. The short branches include the superior and inferior gluteal nerves, the pudendal nerve, the obturator internus, the piriformis nerve, and the quadratus femoris nerve. The long branches of the sacral plexus are represented by the posterior cutaneous nerve of the thigh and the sciatic nerve.

Peripheral nervous system (human anatomy)

Depending on which part of the central nervous system the peripheral nerves depart from, spinal nerves (31 pairs) and cranial nerves (12 pairs) are distinguished.

Spinal nerves (human anatomy)

Spinal nerves (nn. spinales) extend from the spinal cord in the form of two roots: the anterior (ventral), consisting of motor fibers, and the posterior (dorsal), which forms sensory fibers. In the area of ​​the intervertebral foramen they unite into one trunk - the mixed spinal nerve. At the junction, the dorsal root forms a nerve spinal ganglion (ganglion spinale), consisting of false unipolar (pseudo-unipolar) cells with a T-shaped branching process. Each spinal nerve upon exiting the intervertebral foramen is divided into four branches: 1) anterior (ventral) - for the anterior wall of the trunk and limbs; 2) posterior (dorsal) - for the muscles and skin of the back and neck; 3) connective - to the node of the sympathetic trunk; 4) meningeal (meningeal), heading back into the spinal canal to innervate the membranes of the spinal cord (Fig. 125).


Rice. 125. Diagram of the formation and branching of the spinal nerve (thoracic). 1 - anterior root; 2 - shell branch; 3 - node of the sympathetic trunk; 4 - branching of the anterior branch to the skin; 5 - anterior branch (intercostal nerve); 6 - connecting branch to the sympathetic trunk; 7 - posterior branch; 8 - spinal node; 9 - posterior spine

Together with each pair of spinal nerves, the embryo develops a certain area of ​​muscle (myotome) and skin (dermatome). Based on this, segmental innervation of muscles and skin is distinguished. In an adult, such correct distribution of the peripheral branching of the spinal nerves is not observed due to the loss of the initial segmentation of the muscles and areas of the skin that they supply. This is especially pronounced in the area around the limbs. In humans, there are 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and a pair of coccygeal spinal nerves.

The posterior branches of the spinal nerves contain sensory and motor fibers and are directed to the skin and muscles of the back and neck. Among them, the posterior branch of the first cervical nerve stands out - the suboccipital nerve, consisting only of motor fibers, innervates the short muscles of the back of the head, and the second cervical nerve - the greater occipital nerve, innervates most of the skin of the back of the head. Sensory fibers of the posterior branches of the lumbar and sacral nerves innervate the skin of the gluteal region and are called the superior and middle nerves of the buttocks. The remaining posterior branches of the spinal nerves do not have special names.

The anterior branches of the spinal nerves contain sensory and motor fibers intended for the muscles and skin of the neck, the anterior and lateral surfaces of the torso, and the upper and lower extremities. The anterior branches of adjacent nerves are connected to each other in the form of loops, exchanging fibers and forming plexuses. The exception is the anterior branches of the thoracic nerves, which run segmentally in the intercostal spaces. The anterior branches of the remaining nerves form four plexuses: cervical, brachial, lumbar and sacral.

The cervical plexus is formed by the anterior rami of the four superior cervical spinal nerves. It lies on the side of the transverse processes of the upper cervical pores between the muscles and is covered by the sternocleidomastoid muscle. The branches of the cervical plexus emerge from under the posterior edge of this muscle approximately in its middle. Among them, cutaneous, muscular and mixed branches are distinguished.

The sensory branches of the cervical plexus are:

1) the lesser occipital nerve, innervating the lateral part of the skin of the back of the head; 2) the great auricular nerve, innervating the auricle and external auditory canal;

3) transverse cervical nerve, innervating the skin of the neck;

4) supraclavicular nerves - a bundle of nerves going down and innervating the skin above the collarbone, pectoralis major and deltoid muscles.

The muscular (motor) branches innervate the deep muscles of the neck and, connecting with the hypoglossal nerve (XII pair of cranial nerves), form a cervical loop, due to which the anterior muscles of the neck are innervated below the hyoid bone.

The mixed branch of the cervical plexus is the phrenic nerve. It descends along the anterior scalene muscle into the chest cavity, passes in the middle mediastinum between the pericardium and the mediastinal pleura and approaches the thoraco-abdominal barrier. Innervates the diaphragm (motor fibers), pleura and pericardium (sensory fibers) and penetrates the abdominal cavity, innervating the peritoneal ligaments of the liver there.

The brachial plexus is formed by the anterior branches of the four lower cervical and part of the first thoracic spinal nerves. It exits through the space between the anterior and middle scalene muscles into the supraclavicular fossa and is located next to the subclavian artery. Then behind the clavicle it descends into the axillary cavity and here forms three main bundles located around the axillary artery (Fig. 126). From these bundles begin the long nerves of the brachial plexus, which innervate the upper limb. Short nerves that innervate the muscles of the shoulder girdle extend from the upper part of the brachial plexus. The largest of these is the axillary nerve, which goes to the deltoid and teres minor muscles, the skin over them and to the shoulder joint bursa. The remaining nerves innervate the pectoralis major and minor, serratus anterior, subclavian, supraspinatus, infraspinatus, subscapularis, latissimus dorsi, teres major, rhomboids, and levator scapulae muscles.



Rice. 126. Branches of the brachial plexus. 1 - axillary artery; 2 - axillary vein; 3 - brachial plexus; 4 - short branches of the brachial plexus to the pectoralis major and minor muscles; 5 - musculocutaneous nerve; 6 - median nerve; 7 - cutaneous medial nerve of the forearm; 8 - ulnar nerve; 9 - radial nerve; 10 - axillary nerve; 11 - cutaneous medial nerve of the shoulder; 12 - serratus anterior muscle; 13 - short branch to the latissimus dorsi muscle; 14 - short branch to the serratus anterior muscle; 15 - short branch to the subscapularis muscle

The long branches of the brachial plexus include the following:

1. Medial cutaneous nerve of the shoulder; innervates the skin of the inner surface of the shoulder.

2. Medial cutaneous nerve of the forearm; innervates the skin of the inner surface of the forearm.

3. Musculocutaneous nerve; supplies three muscles of the shoulder with motor branches: biceps, brachialis and coracobrachialis, and then passes to the forearm, where it innervates the skin of the outer side.

The median nerve in the shoulder passes along with the brachial artery and veins in the medial groove; does not give branches. On the forearm it gives branches to all the muscles of the anterior group (flexors), with the exception of the flexor carpi ulnaris and part of the deep flexor digitorum. Together with the flexor tendons of the fingers, it passes through the carpal canal to the palm, where it innervates the muscles of the eminence of the thumb, except for the adductor and part of the short flexor pollicis, and two lateral lumbrical muscles. The cutaneous branches form common and then proper palmar digital nerves, which innervate the skin of the thumb, index, middle and half of the ring finger.

5. The ulnar nerve runs along the inner surface of the shoulder; does not give branches. It goes around the medial epicondyle of the humerus and passes to the forearm, where in the groove of the same name it runs next to the ulnar artery. On the forearm, it innervates the flexor carpi ulnaris and part of the deep flexor digitorum; in the lower third of the forearm it is divided into dorsal and palmar branches. The palmar branch gives rise to cutaneous and muscular branches. The cutaneous branches are represented by the common and proper palmar digital nerves, innervating the skin of the little finger and the medial side of the ring finger. The muscular branch is deep, passes to the muscles of the eminence of the little finger, all interosseous, two medial lumbricals, adductor pollicis and to the deep head of the short flexor pollicis. The dorsal branch gives rise to the dorsal digital nerves, which innervate the skin of 2 1/2 fingers, starting with the little finger.

6. The radial nerve is the thickest nerve of the brachial plexus. On the shoulder it passes in the brachiomuscular canal between the humerus and the heads of the triceps muscle, giving off muscle branches to this muscle and skin branches to the posterior surface of the shoulder and forearm. In the lateral groove, the ulnar fossa is divided into deep and superficial branches. The deep branch innervates all the muscles of the posterior surface of the forearm (extensors), and the superficial branch runs in the groove along with the radial artery, passes to the back of the hand, where it innervates the skin of 2 1/2 fingers, starting from the thumb.

Anterior branches of the thoracic spinal nerves. These branches do not form a plexus and run in the intercostal spaces. They are called intercostal nerves, innervate the intrinsic chest muscles, participate in the innervation of the muscles of the anterior abdominal wall and give off anterior and lateral cutaneous branches that innervate the skin of the chest and abdomen.

Lumbar plexus. Formed by the anterior branches of the three upper lumbar spinal nerves, partly the twelfth thoracic and the fourth lumbar. It lies in the thickness of the psoas major muscle, its branches come out from under it from the outside, piercing the muscle from the front or from the inside. Among the short branches there are: iliohypogastric, ilioinguinal, femoral-genital nerves, innervating the lower parts of the muscles and skin of the anterior abdominal wall, external genitalia and upper thigh. Long branches extend to the lower limb. These include the following.

1. Lateral cutaneous nerve of the thigh; comes out from under the lateral edge of the psoas major muscle and descends to the thigh; innervates the skin of the outer surface of the thigh.

2. Obturator nerve; lies on the lateral wall of the pelvis, passes through the obturator canal, giving branches to the hip joint; innervates the adductor muscles of the thigh and the skin of the inner thigh.

3. The femoral nerve is the largest nerve of the lumbar plexus; passes between the iliacus and psoas major muscles, passes to the thigh under the inguinal ligament; innervates the anterior group of muscles of the thigh and the skin of its anterior surface. Its longest sensitive branch, the saphenous nerve, goes to the medial surface of the leg; innervates the skin of the anteromedial surface of the leg and dorsum of the foot.

Sacral plexus. Formed by the anterior branches of the fourth (part) and fifth lumbar, all sacral and coccygeal nerves. It is located in the small pelvis on the anterior surface of the sacrum and piriformis muscle and exits through the greater sciatic foramen above and below the piriformis muscle into the gluteal region. Short branches of the sacral plexus innervate the muscles of the pelvis (except for the iliopsoas) and gluteal region (superior and inferior gluteal nerves). The long branches are represented by two nerves: 1) the posterior cutaneous nerve of the thigh innervates the skin of the perineum, gluteal region and posterior surface of the thigh; 2) the sciatic nerve (p. ischiadicus) is a direct continuation of the sacral plexus. Coming out of the pelvis, it moves to the back of the thigh and here passes between the muscles to which it gives off motor branches (the posterior group of thigh muscles). In the popliteal fossa it divides into the tibial nerve and the common peroneal nerve. The tibial nerve, having given off the medial cutaneous nerve of the calf, passes in the ankle-popliteal canal between the muscles of the posterior group of the leg, innervating them, passes to the foot behind the medial malleolus and is divided into the medial and lateral plantar nerves, innervating the skin and muscles of the sole of the foot. The common peroneal nerve runs laterally, giving off a branch to innervate the skin of the posterolateral surface of the leg and. divided into superficial and deep. The superficial peroneal nerve innervates the muscles of the lateral group of the leg and passes to the dorsum of the foot, participating in the innervation of the skin of the dorsum of the foot. The deep peroneal nerve passes between the muscles of the anterior group, giving branches to them, passes to the foot, innervates the short muscles of the dorsum of the foot and the skin of the first interdigital space.

..

The spinal nerves arise from the spinal cord in 31 pairs. Each spinal nerve is formed from the fusion of the posterior, or dorsal, sensory root and the anterior, or ventral, motor root. The mixed nerve thus formed exits the spinal canal through the intervertebral foramen. According to the segments of the spinal cord, the spinal nerves are divided into 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and 1 pair of coccygeal. Each of them, emerging from the intervertebral foramen, is divided into four branches: 1) meningal, which goes into the spinal canal and innervates the membranes of the spinal cord; 2) connective, which connects the spinal nerve with the nodes of the sympathetic trunk located along the spinal column; 3) back and 4) front.

Branches

Innervation zone

Peculiarities

1. Front (thick and long)

Skin and muscles of the neck, chest, abdomen and limbs

They form plexuses, with the exception of the thoracic region, from which the intercostal muscles are formed

2. Posterior branches

The deep muscles of the back, the skin of the back surface of the head and torso, form the corresponding pectoral, cervical, lumbar, etc. nerve

Branch 1 of the cervical nerve, the so-called. suboccipital nerve (to the muscles of the back of the neck), posterior branch of the 2nd cervical nerve - greater occipital nerve (to the skin of the back of the head and muscles of the head)

3. Meningeal

Spinal cord membranes

Goes into the spinal canal

4. White connecting branch

Goes to the nodes of the sympathetic trunk

11.7.2. Cranial nerves

All cranial nerves arise from the base of the brain, with the exception of one (IV pair), which exits the brain from its dorsal side (below the roof of the midbrain). Each nerve is assigned a pair number and name. The numbering order reflects the sequence in which the nerves exit.

The olfactory and optic nerves are connected to the telencephalon; oculomotor and trochlear - with the midbrain; trigeminal, pharyngeal, vagus, accessory and sublingual - with the medulla oblongata.

Unlike spinal nerves, which are mixed, cranial nerves are divided into sensory (I, II, VIII), motor (III, IV, VI, XI, XII) and mixed (V, VII, IX, X). Some nerves (III, VII, IX, X) contain parasympathetic fibers going to smooth muscles, blood vessels, and glands.

Table 11.5. Plexus of spinal nerves and anterior branches of the thoracic nerves

Location

Nerves and branches

Innervation zone

1. Cervical plexus(formed by the anterior branches C 1 - C 4)

On the deep muscles of the neck about 1-4 cervical vertebrae, behind the sternocleidomastoid muscle

1. motor (muscular)

Trapezius, sternocleidomastoid, deep neck muscles

2. cutaneous (greater auricular, lesser occipital, transverse, supraclavicular nerves)

Skin of the auricle, external auditory canal, lateral part of the back of the head, neck area, etc.)

3. mixed (diaphragmatic)

Diaphragm, pericardium and pleura

2. Brachial plexus(formed by the anterior branches C 5 -C 8 and partially C 4 and Th 1)

The lower part of the neck behind the sternocleidomastoid muscle, in the interscalene space, forms 3 bundles: lateral, medial and posterior, which go into the axillary cavity and surround the axillary artery

The plexus has 2 parts: supraclavicular and subclavian, as well as short (to the bones and soft tissues of the shoulder girdle) and long branches

1. Short branches (long, lateral and medial thoracic, sub- and suprascapular, axillary nerves)

Bones and soft tissues of the shoulder girdle (serratus anterior, pectoralis minor and major, latissimus, deltoid, subscapularis, supra- and infraspinatus muscles, etc.

2. Long branches (musculocutaneous, median, ulnar, radial nerves, as well as medial cutaneous nerves of the shoulder and forearm)

Anterior muscles and skin of the shoulder, forearm, free upper limb

3. Anterior branches of the thoracic nerves

12 pairs go in the intercostal spaces, except for the 12th thoracic pair - under the 12th rib, the so-called. subcostal nerve

1. Muscular branches

Intercostal muscles, muscles of the anterior abdominal wall

2. Cutaneous branches

Skin of the chest and abdomen

4. Lumbar plexus(formed by branches L 1 -L 3 and partially by the anterior branches Th 12 and L 4)

Located in front of the transverse processes of the vertebrae, in the thickness of the psoas major muscle

Femoral nerve

Skin and muscles of the anterior thigh, knee joint, patella, medial surface of the leg and foot

Obturator nerve

Hip joint, all adductor muscles and skin of the inner thigh

Lateral cutaneous nerve of the thigh

Skin of the outer thigh

Half iliohypogastric nerve

Muscles and skin of the anterior abdominal wall, part of the gluteal region and thighs

Ilioinguinal nerve

Skin of the pubis and anterior surface of the scrotum, groin area

5. Sacral plexus(formed by the anterior branches of L 4 and L 5, all sacral nerves)

On the posterior wall of the pelvis, on the anterior surface of the sacrum and piriformis muscle.

1. Short branches (superior gluteal nerve and inferior gluteal nerve)

Innervates the muscles in the pelvic area - piriformis, internal obturator, twin muscles, quadratus lumborum and pelvic floor muscles

2. Long branches (posterior cutaneous nerve of the thigh and sciatic nerve)

Skin and muscles of the back of the thigh, all muscles and skin of the free lower limb

6. Coccygeal plexus(formed by the anterior branches of the 5th sacral and coccygeal nerves)

On the coccygeus muscle

Anal-coccygeal nerves

Skin in the area of ​​the coccyx and anus

Table 11.6. .Cranial nerves and their functions

Pair number

Nerve name

Olfactory

Sensory input from the olfactory epithelium

Visual

Sensory input from retinal ganglion cells

Oculomotor

Motor output to four of the six extrinsic muscles of the eyeball

Block

Motor output to the superior oblique muscle of the eyeball

Trigeminal

Primary sensory input is from the face. Motor output to the muscles of mastication

Abductor

Motor output to the external rectus muscle of the eyeball

The main motor output to the facial muscles. Sensory input from some taste buds

Auditory

Sensory input from the inner ear and vestibular organ

Glossopharyngeal

Sensory input from receptors (including taste) on the tongue and pharynx

Wandering

The main parasympathetic motor output to the muscles of many internal organs: heart, stomach, intestines, etc. Motor output to the muscles of the pharynx. Sensory input from some taste buds

Additional

Motor output to the sternocleidomastial and trapezius muscles

Sublingual

Motor output to the tongue muscles

Sensory nerves are considered together with their pathways, along the path of excitation, in the centripetal abducens, facial and vestibulocochlear - with the hindbrain; linguistic direction (from the periphery - to the center), motor and mixed nerves - on the contrary, in the centrifugal direction (from the nuclei of the brain - to the periphery).

Autonomic (autonomic) nervous system

Autonomic (vegetative) nervous system ( systems nervesum autonomicum) - part of the nervous system that innervates the heart, blood and lymph vessels, viscera and other organs containing smooth muscle cells and glandular epithelium. This system coordinates the work of all internal organs, regulates metabolic and trophic processes in all organs and tissues of the human body, and maintains the constancy of the internal environment of the body. The function of the autonomic (vegetative) nervous system is not autonomous, although it is not controlled by our consciousness; it is subordinate to the spinal cord, cerebellum, hypothalamus, basal nuclei of the telencephalon and the higher parts of the nervous system - the cerebral cortex. However, in the cerebral cortex, specialized sections (nuclei) directly responsible for the functions of the autonomic nervous system have not yet been discovered.

The distinction of the autonomous (vegetative) nervous system is due to certain features of its structure. These features include the following:

1) focal localization of vegetative nuclei in the central nervous system;

2) accumulation of bodies of effector neurons in the form of nodes (ganglia) as part of the autonomic plexuses;

3) two-neuronality of the nerve path from the autonomic nucleus in the central nervous system to the innervated organ.

The autonomic (autonomic) nervous system is divided into central and peripheral sections.

The central department includes:

1) parasympathetic nuclei of the III, VII, IX and X pairs of cranial nerves lying in the brain stem;

2) the vegetative (sympathetic) nucleus, which forms the lateral intermediate column of the VIII cervical, all thoracic and two upper lumbar segments of the spinal cord (C VIII, Th I - L II);

3) sacral parasympathetic nuclei, located in the gray matter of the three sacral segments of the spinal cord (S II - S IV).

The peripheral section includes:

1) autonomic (autonomic) nerves, branches and nerve fibers emerging from the brain and spinal cord;

2) vegetative (autonomous, visceral) plexuses;

3) nodes of the autonomic plexuses;

4) sympathetic trunk (right and left), with its nodes, internodal and connecting branches and sympathetic nerves;

5) terminal nodes of the parasympathetic part of the autonomic nervous system.

Rice. 11.37. Autonomic nervous system. Sympathetic nuclei (centers) are shaded, nodes and nerves (fibers) are shown with dotted lines, parasympathetic nerves are shown with black lines.

Neurons of the nuclei of the central part of the autonomic nervous system are the first efferent neurons on the way from the central nervous system (spinal cord and brain) to the innervated organ. The nerve fibers formed by the processes of these neurons are called prenodal (preganglionic) fibers, since they go to the nodes of the peripheral part of the autonomic nervous system and end with synapses on the cells of these nodes. Autonomic nodes are part of the sympathetic trunks, large autonomic plexuses of the abdominal cavity and pelvis, located in the head and in the thickness or near the organs of the digestive and respiratory systems, as well as the genitourinary apparatus, which are innervated by the autonomic nervous system. Preganglionic fibers have a myelin sheath, which makes them whitish in color. They leave the brain as part of the roots of the corresponding cranial nerves and the anterior roots of the spinal nerves. The nodes of the peripheral part of the autonomic nervous system contain the bodies of second (effector) neurons lying on the way to the innervated organs. The processes of these second neurons of the efferent pathway, carrying nerve impulses from the autonomic ganglia to the working organs (smooth muscles, glands, tissues), are post-nodular (postganglionic) nerve fibers. Due to the absence of the myelin sheath, they are gray in color.

The structure of the reflex autonomic arc differs from the structure of the reflex arc of the somatic part of the nervous system. In the reflex arc of the autonomic part of the nervous system, the efferent link consists not of one neuron, but of two. In general, a simple autonomic reflex arc is represented by three neurons. The first link of the reflex arc is a sensory neuron, the body of which is located in the spinal ganglia and in the sensory ganglia of the cranial nerves. The peripheral process of such a neuron, which has a sensitive ending - a receptor, originates in organs and tissues. The central process, as part of the dorsal roots of the spinal nerves or sensory roots of the cranial nerves, is directed to the corresponding nuclei in the spinal cord or brain. The second link of the reflex arc is efferent, since it carries impulses from the spinal cord or brain to the working organ. This efferent pathway of the autonomic reflex arc is represented by two neurons. The first of these neurons, the second in a simple autonomic reflex arc, is located in the autonomic nuclei of the central nervous system. It can be called intercalary, since it is located between the sensitive (afferent) link of the reflex arc and the second (efferent) neuron of the efferent pathway. The effector neuron is the third neuron of the autonomic reflex arc. The bodies of effector (third) neurons lie in the peripheral nodes of the autonomic nervous system (sympathetic trunk, autonomic ganglia of cranial nerves, nodes of extraorgan and intraorgan autonomic plexuses). The processes of these neurons are directed to organs and tissues as part of organ autonomic or mixed nerves. Postganglionic nerve fibers end on smooth muscles, glands and other tissues with the corresponding terminal nerve apparatus.

Based on the topography of the autonomic nuclei and nodes, differences in the length of the first and second neurons of the efferent pathway, as well as features of function, the autonomic nervous system is divided into three parts: sympathetic (SNS), parasympathetic (PNS) and metasympathetic (MNS). The sympathetic and parasympathetic centers are under the control of the hypothalamic centers that coordinate their function, as well as the cerebral cortex, which, through the autonomic nervous system, carries out a holistic response of the body to various influences, as well as maintaining the level of intensity of basic life processes in accordance with current needs. As a rule, most internal organs have double and sometimes triple innervation (SNS, PNS, MNS). Some organs (vessels, sweat glands, adrenal medulla) are under the control of only the sympathetic nervous system. The SNS and PNS have opposite effects on most organs: respectively, dilation and constriction of the pupil, increased and slowed heart rate, changes in intestinal secretion and motility, etc. (Fig. 11.38, 11.39).

To the sympathetic part(sympathetica) include:

1) lateral intermediate (gray) substance (vegetative nucleus) in the lateral (intermediate) columns from the VIII cervical segment of the spinal cord to the II lumbar;

2) nerve fibers and nerves going from the cells of the lateral intermediate substance (lateral column) to the nodes of the sympathetic trunk and autonomic plexuses;

3) right and left sympathetic trunks;

4) connecting branches;

5) nodes of the autonomic plexuses located anterior to the spine in the abdominal and pelvic cavity and nerves lying near large vessels (perivascular plexuses);

6) nerves running from these plexuses to the organs;

7) sympathetic fibers that travel as part of the somatic nerves to organs and tissues. Sympathetic preganglionic nerve fibers are usually shorter than postganglionic fibers.

Parasympathetic part (parasympathetica) divided into cephalic and sacral sections. The head section includes the autonomic nuclei and parasympathetic fibers of the oculomotor (III pair), facial (VIII pair), glossopharyngeal (IX pair) and vagus (X pair) nerves, as well as the ciliary, pterygopalatine, submandibular, sublingual and auricular nodes and their branches. The sacral region includes the sacral parasympathetic nuclei of the II, III and IV sacral segments of the spinal cord, splanchnic pelvic nerves and parasympathetic pelvic nodes.

Depending on the mediators located at the endings of nerve fibers, the latter are divided into cholinergic (associated with the release of acetylcholine in the PNS), adrenergic (norepinephrine in the SNS) and purinergic (ATP and related nucleotides in the MNS). The fibers of the function of the autonomic nervous system are characterized by a low speed of excitation and low excitability; they have the ability to regenerate.

Rice. 1.38. Organs innervated by the sympathetic system.

Rice. 1.39. Organs innervated by the parasympathetic system.

Security questions

    List the patterns of the structure of the peripheral nervous system.

    Name the sensory, motor and mixed cranial nerves and the serial number of each of them.

    Name the branches into which each spinal nerve is divided.

    Describe the structural features and innervation of the cervical, brachial, and lumbar plexuses.

    Name the centers of the autonomic nervous system and their locations.

    Describe the structural features and main autonomic centers of the sympathetic and parasympathetic systems.

Schematic representation of the plexus of spinal nerves ">

Schematic representation of the spinal nerve plexuses.

Spinal nerves and plexuses. Through the spinal nerves, the spinal cord exercises control over the trunk, limbs, and internal organs of the chest, abdomen, and pelvis. According to the number of trunk segments and corresponding segments of the spinal cord, humans have 31 pairs of spinal nerves. Each of them begins in the area of ​​“its own” intervertebral foramen, where it is formed by the anterior (motor) and posterior (sensitive) roots connecting into one trunk. The spinal nerves are very short, so after about 1.5 cm of travel they already end, branching, all in the same way, into the anterior, posterior and meningeal branches.

Each of the 31 right and left posterior branches passes between the transverse processes of a pair of vertebrae in the dorsal region, where it provides sensitive innervation to the calf and deep muscles (torso extensors).

The anterior branches of the spinal nerves behave in a more complex manner, since the structure of the anterior parts of the body they control is influenced by the developing limbs. This disrupts the external signs of orderliness (segmentation) in the organization of the corresponding parts of the peripheral nervous system.

The anterior branches of the thoracic (12) spinal nerves maintain this ordering; they each go in their own intercostal space (intercostal nerves) and innervate the skin and deep muscles of the anterior and anterolateral walls of the body (chest and abdomen).

The anterior branches of the cervical (8 nerves), lumbar (5), sacral and coccygeal (1) nerves form several plexuses, connecting with each other in a complex way. At the junctions, fibers are exchanged between the nerve trunks; as a result, from such a plexus, nerves with a different set of fibers will go to the limbs, needed for certain muscle groups and skin areas of the limb.

The cervical plexus is formed by the anterior branches of the 1st-4th cervical spinal nerves. The nerves emanating from it innervate the skin of the anterior neck and, partially, the head near the ears, as well as part of the anterior neck muscles.

The brachial plexus is formed by the anterior branches, mainly of the 5th-8th cervical spinal nerves. It lies in the axillary cavity, behind the collarbone. The branches extending from it innervate the skin and muscles of the shoulder girdle and free upper limb.

The lumbar plexus is formed by the anterior branches of the 1st-4th lumbar spinal nerves; it is located in the thickness of the muscles on the anterolateral surface of the lumbar vertebrae. Its branches penetrate the inner, anterior and outer surfaces of the thigh.

The sacral plexus is located in the small pelvis, it is formed by the connecting anterior branches from the 5th lumbar to the 4th sacral spinal nerves. The branches it gives off extend into the gluteal region. The largest of them is the sciatic nerve.

The nerves of the lumbar and sacral plexuses innervate the skin and muscles of the pelvic girdle and free lower limb, as well as the external genitalia.

Content

The spinal cord consists of numerous plexuses that form the spinal nerves, which are paired trunks. Each pair corresponds to a specific part of the body, internal organs, and performs its own unique functions. There are 31 pairs in total, which corresponds to the number of pairs of spinal cord segments. It is important to understand what human nerve plexuses are, why they are needed, and what functions will be performed in the body when they work.

What are spinal nerves

The spinal canal contains the spinal cord, which represents the initial structure of the central nervous system organs. This important part of the body, flattened in front, has a cylindrical shape. Structurally, it has anterior branches and dorsal roots, which serve to transmit impulses to the cerebral cortex. The answer to the question of how many spinal nerves arise from the spinal cord is simple - 31 pairs. This amount is the same for women and men, and does not depend on the age of the patients.

Anatomy

The spinal nerve consists of a large number of cells - neurons, which provide reflex, sympathetic and motor functions of the body. Each such process originates from the intervertebral foramen and is formed from sensory and motor roots. Individual nerves are woven into bundles, which have an official name, moving along afferent pathways (ascending) and descending pathways. Formed spinal plexuses are of three types: lumbosacral, brachial, cervical.

The nerves of the spinal cord region are short structures, since their length is 1.5 cm. Then they branch on all sides, forming the posterior and anterior meningeal branches. Structurally, the posterior branches of the spinal nerves extend between the transverse processes of the pair in the back region, promoting flexion and extension of the torso. There is a median fissure on the anterior surface. Such structural elements conditionally divide the brain into right and left halves, closely related to each other in functionality.

In each component, lateral grooves are distinguished: anterior and posterior. The first is the area with the exit of the posterior sensory roots of the spinal nerves, and the second provides a branch of the motor nerves. The lateral grooves are considered conditional boundaries between the posterior, lateral, and anterior cords. The central canal is located in the cavity of the spinal cord - a gap filled with a special substance called cerebrospinal fluid.

Number of spinal nerves

An adult has 31 pairs of spinal nerves, and such elements are characterized by their conditional classification. This division is represented by 8 cervical, 5 lumbar, 12 thoracic, 5 sacral, 1 coccygeal plexuses. The total number of nerves is 62 positions; they are part of most internal organs and systems (body parts). Without their presence, muscle activity is excluded, and normal brain activity is also pathologically reduced.

Departments

When studying the structural parts of the human spine, it is necessary to identify those important structures that are penetrated by nerves and fibers and contain the spinal cord. They are responsible for the motor activity of the musculoskeletal system, sensitivity to provoking factors from the outside. These are the following sections of the spinal column:

  1. If we study the neck area, the cervical plexus is formed by the anterior branches, localized between the deep muscle structures. The supply of nerve cells is observed in the areas of the back of the head, ear canal, collarbone, muscle tissue of the neck, and pectoral abdomen. In this way, nerve impulses are transmitted to ensure mobility of the upper limbs. In case of pathology, the occipital region is the first to suffer.
  2. The spinal structures of the sacral and lumbar region are responsible for the mobility of the lower extremities, the formation and maintenance of muscle tone. At the same time, the pelvic area and all internal organs are monitored. The sciatic, coccygeal and femoral nerves are especially sensitive, pinching of which leads to acute pain. If such unpleasant sensations are present, this means that a pathological process is occurring in the body.
  3. The nerves of the chest are represented in 12 pairs and are located in the intercostal space. The main task is to ensure mobility of the chest and the muscles of the thin walls of the peritoneum. In such an area, the spinal plexuses do not form and extend directly onto the muscles. Pathologies of a characteristic area are accompanied by pain, but with timely treatment, the pain syndrome will subside.

Internal Contents

The spinal roots have a main center - the spinal cord, the membranes of which are filled with cerebrospinal fluid. It contains gray and white matter. Each structure performs its own unique functions. For example, white matter consists of neurons that form three columns - lateral, anterior and posterior. Each element in the section takes the form of horns and carries out its task.

Thus, the anterior horns contain motor nerves, the posterior ones consist of sensory fibers, and the lateral ones directly communicate with the gray matter of the spinal cord. Each nerve structure contains spinal plexuses and numerous nodes. The gray matter is surrounded by white matter, which forms the cords of the spinal cord from longitudinally located nerve fibers.

Functions

The main tasks of the spinal nerves are conduction and reflex. In the first case, we are talking about the passage of nerve impulses to the cerebral cortex in order to further ensure a natural reaction to external and internal irritating factors, for example, pain, temperature, cold, irritation. The reflex function carried out by the nerve centers provides innervation to skeletal muscles and supplies the work of all internal organs and systems. Given this classification, spinal nerves are:

  • sensitive – ensure the body’s (skin) reaction to external and internal stimuli mainly through the skin;
  • motor – accept and control the physical activity of muscles, maintain balance, ensure coordination of movements, tone of smooth muscles;
  • mixed are spinal plexuses formed from motor and sensory fibers. The functions of such nodes are numerous and depend on the location of the nerve endings.

Nerve fibers differ not only in their functionality, but also in their area of ​​action in the human body (innervation). Such solid structures are located and spread throughout the body, and inflammation of the nodes leads to irreversible consequences for the body. Habitual motor activity and sensitivity do not return immediately; conservative treatment is required.

How are nerves formed?

Nerve endings have a standard structure, and their differences are explained by the functional characteristics of the roots. Structurally, the anterior branches and posterior roots are distinguished. In the first case, we are talking about motor neurons formed by axons that are responsible for the mobility of the limbs. As for the dorsal roots, these are formations of the spinal nerve and its branches, which are connected in series with the dorsal horns and sensory nuclei of the spinal cord. Such anatomical structures quickly transmit nerve impulses.

Video: Formation of the spinal plexuses

Attention! The information presented in the article is for informational purposes only. The materials in the article do not encourage self-treatment. Only a qualified doctor can make a diagnosis and give treatment recommendations based on the individual characteristics of a particular patient.

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