Intercalary neuron: functions and role in the formation of neural networks. Types of neurons

This cell has a complex structure, is highly specialized and contains a nucleus, a cell body and processes in structure. There are over one hundred billion neurons in the human body.

Review

Complexity and variety of functions nervous system are determined by the interaction between neurons, which, in turn, are a set of various signals transmitted as part of the interaction of neurons with other neurons or muscles and glands. Signals are emitted and propagated by ions that generate electric charge, which moves along the neuron.

Structure

The neuron consists of a body with a diameter of 3 to 130 microns, containing a nucleus (with a large number of nuclear pores) and organelles (including a highly developed rough ER with active ribosomes, the Golgi apparatus), as well as processes. There are two types of processes: dendrites and. The neuron has a developed and complex cytoskeleton that penetrates into its processes. The cytoskeleton maintains the shape of the cell, its threads serve as "rails" for the transport of organelles and substances packed in membrane vesicles (for example, neurotransmitters). The cytoskeleton of a neuron is made up of fibrils. different diameter: Microtubules (D = 20-30 nm) - consist of tubulin protein and stretch from the neuron along the axon, up to the nerve endings. Neurofilaments (D = 10 nm) - together with microtubules provide intracellular transport of substances. Microfilaments (D = 5 nm) - consist of actin and myosin proteins, are especially pronounced in growing nerve processes and in. In the body of the neuron, a developed synthetic apparatus is revealed, the granular ER of the neuron stains basophilically and is known as the "tigroid". The tigroid penetrates into the initial sections of the dendrites, but is located at a noticeable distance from the beginning of the axon, which serves as a histological sign of the axon.

A distinction is made between anterograde (away from the body) and retrograde (towards the body) axon transport.

Dendrites and axon

An axon is usually a long process adapted to conduct from the body of a neuron. Dendrites are, as a rule, short and highly branched processes that serve as the main site for the formation of excitatory and inhibitory synapses that affect the neuron (different neurons have a different ratio of the length of the axon and dendrites). A neuron may have several dendrites and usually only one axon. One neuron can have connections with many (up to 20 thousand) other neurons.

Dendrites divide dichotomously, while axons give rise to collaterals. The branch nodes usually contain mitochondria.

Dendrites do not have a myelin sheath, but axons can. The place of generation of excitation in most neurons is the axon hillock - a formation at the place where the axon leaves the body. In all neurons, this zone is called the trigger zone.

Synapse(Greek σύναψις, from συνάπτειν - hug, embrace, shake hands) - the place of contact between two neurons or between a neuron and the effector cell receiving the signal. Serves for transmission between two cells, and during synaptic transmission, the amplitude and frequency of the signal can be regulated. Some synapses cause neuron depolarization, others hyperpolarization; the former are excitatory, the latter are inhibitory. Usually, to excite a neuron, stimulation from several excitatory synapses is necessary.

The term was introduced in 1897 by the English physiologist Charles Sherrington.

Classification

Structural classification

Based on the number and arrangement of dendrites and axons, neurons are divided into non-axonal, unipolar neurons, pseudo-unipolar neurons, bipolar neurons, and multipolar (many dendritic trunks, usually efferent) neurons.

Axonless neurons- small cells, grouped close in the intervertebral ganglia, having no anatomical signs of division of processes into dendrites and axons. All processes in a cell are very similar. The functional purpose of axonless neurons is poorly understood.

Unipolar neurons- neurons with one process, are present, for example, in the sensory nucleus of the trigeminal nerve in.

bipolar neurons- neurons with one axon and one dendrite, located in specialized sensory organs - the retina, olfactory epithelium and bulb, auditory and vestibular ganglia.

Multipolar neurons- Neurons with one axon and several dendrites. This type nerve cells predominate in .

Pseudo-unipolar neurons- are unique in their kind. One process departs from the body, which immediately divides in a T-shape. This entire single tract is covered with a myelin sheath and structurally represents an axon, although along one of the branches, excitation goes not from, but to the body of the neuron. Structurally, dendrites are ramifications at the end of this (peripheral) process. The trigger zone is the beginning of this branching (that is, it is located outside the cell body). Such neurons are found in the spinal ganglia.

Functional classification

By position in the reflex arc, afferent neurons (sensitive neurons), efferent neurons (some of them are called motor neurons, sometimes this is not a very accurate name applies to the entire group of efferents) and interneurons (intercalary neurons) are distinguished.

Afferent neurons(sensitive, sensory or receptor). To neurons of this type include primary cells and pseudo-unipolar cells, in which dendrites have free endings.

Efferent neurons(effector, motor or motor). Neurons of this type include final neurons - ultimatum and penultimate - not ultimatum.

Associative neurons(intercalary or interneurons) - a group of neurons communicates between efferent and afferent, they are divided into intrusion, commissural and projection.

secretory neurons- neurons that secrete highly active substances (neurohormones). They have a well-developed Golgi complex, the axon ends in axovasal synapses.

Morphological classification

The morphological structure of neurons is diverse. In this regard, when classifying neurons, several principles are used:

take into account the size and shape of the body of the neuron;
the number and nature of branching processes;
the length of the neuron and the presence of specialized membranes.

According to the shape of the cell, neurons can be spherical, granular, stellate, pyramidal, pear-shaped, fusiform, irregular, etc. The size of the neuron body varies from 5 microns in small granular cells to 120-150 microns in giant pyramidal neurons. The length of a human neuron ranges from 150 microns to 120 cm.

According to the number of processes, the following morphological types of neurons are distinguished:

unipolar (with one process) neurocytes present, for example, in the sensory nucleus of the trigeminal nerve in;
pseudo-unipolar cells grouped nearby in the intervertebral ganglia;
bipolar neurons (have one axon and one dendrite) located in specialized sensory organs - the retina, olfactory epithelium and bulb, auditory and vestibular ganglia;
multipolar neurons (have one axon and several dendrites), predominant in the CNS.

Development and growth of a neuron

The neuron develops from a small progenitor cell that stops dividing even before it releases its processes. (However, the issue of neuronal division is currently debatable) As a rule, the axon begins to grow first, and dendrites form later. A thickening appears at the end of the developing process of the nerve cell irregular shape, which, apparently, paves the way through the surrounding tissue. This thickening is called the growth cone of the nerve cell. It consists of a flattened part of the process of the nerve cell with many thin spines. The microspinules are 0.1 to 0.2 µm thick and can be up to 50 µm in length; the wide and flat area of the growth cone is about 5 µm wide and long, although its shape may vary. The spaces between the microspines of the growth cone are covered with a folded membrane. The microspines are in constant motion - some are retracted into the growth cone, others elongate, deviate into different sides, touch the substrate and can stick to it.

The growth cone is filled with small, sometimes interconnected, irregularly shaped membranous vesicles. Directly under the folded areas of the membrane and in the spines is a dense mass of entangled actin filaments. The growth cone also contains mitochondria, microtubules, and neurofilaments found in the body of the neuron.

Probably, microtubules and neurofilaments are elongated mainly due to the addition of newly synthesized subunits at the base of the neuron process. They move at a speed of about a millimeter per day, which corresponds to the speed of slow axon transport in a mature neuron. Since the average rate of advance of the growth cone is approximately the same, it is possible that neither assembly nor destruction of microtubules and neurofilaments occurs at the far end of the neuron process during the growth of the neuron process. New membrane material is added, apparently, at the end. The growth cone is an area of rapid exocytosis and endocytosis, as evidenced by the many vesicles present here. Small membrane vesicles are transported along the process of the neuron from the cell body to the growth cone with a stream of fast axon transport. The membrane material is apparently synthesized in the body of the neuron, transferred to the growth cone in the form of vesicles, and is included here in plasma membrane by exocytosis, thus lengthening the process of the nerve cell.

The growth of axons and dendrites is usually preceded by a phase of neuronal migration, when immature neurons settle and find a permanent place for themselves.

Our spinal cord is the most ancient formation of the nervous system in evolutionary terms. Appearing for the first time in the lancelet, in the process of evolution, the spinal cord with its efferent (motor) and afferent (sensory) neurons improved. But at the same time, it retained its main functions - conductive and regulatory. It is thanks to sensory neurons that we pull our hand away from a hot pot even before pain occurs. About the structure of this organ of the central nervous system and the principles of its work in question in this article.

So vulnerable, but very important

This soft organ is hidden inside the spinal column. The human spinal cord weighs only 40 grams, has a length of up to 45 centimeters, and its thickness is comparable to the little finger - only 8 millimeters in diameter. And yet, it is the control center of a complex network that spreads throughout our body. Without it, it will not be able to perform its apparatus and all the vital organs of our body. In addition to the vertebrae, the spinal cord is protected by its membranes. The outer shell is hard, formed by dense connective tissue. This sheath contains blood vessels and nerves. And, besides, it is in it that the highest concentration of pain receptors in the human body is observed. But there are no such receptors in the brain itself. The second shell is arachnoid, filled with cerebrospinal fluid (cerebrospinal fluid). The last shell - soft - fits snugly to the brain, penetrated by blood and lymphatic vessels.

A few words about neurons

The structural unit of nervous tissue are neurons. Very special cells, the main function of which is the formation and transmission of a nerve impulse. Each neuron has many short processes - dendrites that perceive irritation, and one long one - an axon that conducts a nerve impulse in only one direction. Depending on the task, there are both sensitive and motor. Intermediate or intercalary neurons are a kind of "extension" that transmit impulses between other neurons.

The structure of the spinal cord

The spinal cord begins at the foramen magnum of the skull and ends at the lumbar vertebrae. It consists of 31-33 segments that are not separated from each other: C1-C8 - cervical, Th1-Th12 - thoracic, L1-L5 - lumbar, S1-S5 - sacral, Co1-Co3 - coccygeal. Below in the spinal canal are the continuations of the nerves, collected in a bundle and called the cauda equina (apparently for their external resemblance), which innervate lower limbs and pelvic organs. Each segment has two pairs of roots that connect to form 31 pairs of spinal nerves. The two posterior (dorsal) roots are formed by axons of sensory neurons and have a thickening - where the bodies of these neurons are located. The two anterior (ventral) roots are formed by axons of motor neurons.

So different and important

There are about 13 million nerve cells in the human spinal cord. Functionally, they are divided into 4 groups:

Motor - form the anterior horns and anterior roots.
Interneurons - form the posterior horns. Here are sensitive neurons in which it occurs to various stimuli (pain, tactile, vibrational, temperature).
Sympathetic and parasympathetic neurons - are located in the lateral horns and form the anterior roots.
Associative - these are the cells of the brain that establish a connection between segments of the spinal cord.

Gray butterfly surrounded by white

In the center of the spinal cord is a gray matter that forms the anterior, posterior and lateral horns. These are the bodies of neurons. Sensory neurons are located in the spinal ganglia, the long process of which is located on the periphery and ends with a receptor, and the short process is in the neurons of the posterior horns. The anterior horns are formed by axons which go to the skeletal muscles. Neurons are located in the lateral horns vegetative system. The gray matter is surrounded by white - these are nerve fibers formed by the axons of the ascending and descending wire pathways. The first sensory neurons are located in the following segments: cervical C7, thoracic Th1-Th12, lumbar L1-L3, sacral S2-S4. In this case, the spinal nerve connects the posterior (sensory) and anterior (motor) roots into one trunk. In addition, each pair of spinal nerves controls certain parts of the body.

How it works

The branched dendrites of sensitive neurons of the spinal centers of the autonomic nervous system end in receptors, which are biological structures in which a nerve impulse is formed upon contact with a specific stimulus. Receptors provide vegetovisceral sensitivity - they perceive irritation from such parts of our body as blood vessels and heart, gastrointestinal tract, liver and pancreas, kidneys and others. The impulse is transmitted along the dendrite to the body of the neuron. Further, along the axons of afferent (sensitive) neurons, it enters the spinal cord, where they form synoptic connections with the dendrites of efferent (motor) neurons. It is thanks to this direct contact that we pull our hand away from a hot pot or iron even before our main commander - the brain - analyzes the pain sensations that have arisen.

Summing up

All our automatic and reflex actions take place under the supervision of the spinal cord. The only exceptions are those that are controlled by the brain itself. For example, when we perceive what we see using the optic nerve, which goes directly to the brain, we change the angle of vision with the help of the muscles of the eyeball, which are already controlled by the spinal cord. We cry, by the way, also by order of the spinal cord - it is he who “commands” the lacrimal glands. Our conscious actions begin in the brain, but as soon as they become automatic, their control passes to the spinal cord. We can say that our inquisitive brain likes to learn. And when he has already learned, he becomes bored and he gives the “reins of power” to his older brother in evolutionary terms.

1) central- dorsal and
2) peripheral- nerves and ganglions.

Nerves are bundles of nerve fibers surrounded by a connective tissue sheath.
Nerve nodes are clusters of neuron bodies outside the CNS, such as the solar plexus.

The nervous system is divided into two parts

1) somatic- manages skeletal muscles, subject to consciousness.
2) vegetative (autonomous)- manages internal organs, does not obey consciousness. Consists of two parts:

sympathetic: governs organs during times of stress and physical activity

increases heart rate, blood pressure and blood glucose levels
activates the nervous system and sensory organs
dilates the bronchi and pupil
slows down the digestive system.

parasympathetic the system works at rest, brings the work of the organs back to normal (opposite functions).

reflex arc

This is the path along which the nerve impulse passes during implementation. Consists of 5 parts
1) Receptor- a sensitive formation capable of responding to a certain type of stimulus; converts irritation into a nerve impulse.
2) By sensitive neuron the nerve impulse goes from the receptor to the central nervous system (spinal cord or brain).
3) Interneuron located in the brain, transmits a signal from a sensitive neuron to an executive one.
4) By executive (motor) neuron nerve impulse goes from the brain to the working organ.
5) Working (executive) body- muscle (contracts), gland (secrets), etc.

Analyzer

This is a system of neurons that perceive irritation, conduct nerve impulses and provide information processing. Consists of 3 departments:
1) peripheral- these are receptors, for example, cones and rods in the retina of the eye
2) conductive are the nerves and pathways of the brain
3) central located in the cortex - here the final analysis of information takes place.

Choose the one most correct option. The department of the auditory analyzer, which transmits nerve impulses to the human brain, is formed
1) auditory nerves
2) receptors located in the cochlea
3) eardrum
4) auditory ossicles

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. What examples illustrate the excitation of the sympathetic nervous system?
1) increased heart rate
2) increased intestinal motility
3) lowering blood pressure
4) dilation of the pupils of the eyes
5) increase in blood sugar
6) narrowing of the bronchi and bronchioles

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. What effect does the parasympathetic nervous system have on the human body?
1) increases the heart rate
2) activates salivation
3) stimulates the production of adrenaline
4) enhances the formation of bile
5) increases intestinal peristalsis
6) mobilizes the functions of organs under stress

Answer

Choose one, the most correct option. Nerve impulses from receptors to the central nervous system conduct
1) sensitive neurons
2) motor neurons
3) sensory and motor neurons
4) intercalary and motor neurons

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. Receptors are nerve endings in the human body that
1) perceive information from the external environment
2) perceive impulses from the internal environment
3) perceive excitation transmitted to them through motor neurons
4) are located in the executive body
5) convert perceived stimuli into nerve impulses
6) realize the body's response to irritation from the external and internal environment

Answer

Choose one, the most correct option. Peripheral part of the visual analyzer
1) optic nerve
2) visual receptors
3) pupil and lens
4) visual cortex

Answer

Choose one, the most correct option. Reflexes that cannot be enhanced or inhibited by the will of a person are carried out through the nervous system
1) central
2) vegetative
3) somatic
4) peripheral

Answer

1. Establish a correspondence between the feature of regulation and the department of the nervous system that implements it: 1) somatic, 2) vegetative
A) regulates the work of skeletal muscles
B) regulates metabolic processes
B) provides voluntary movements
D) is carried out autonomously, regardless of the desire of a person
D) controls the activity of smooth muscles

Answer

2. Establish a correspondence between the function of the human peripheral nervous system and the department that performs this function: 1) somatic, 2) vegetative
A) directs commands to skeletal muscles
B) innervates smooth muscles internal organs
B) provides movement of the body in space
D) regulates the work of the heart
D) enhances the work of the digestive glands

Answer

3. Establish a correspondence between the characteristics and the department of the human nervous system: 1) somatic, 2) vegetative. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) directs commands to skeletal muscles
B) changes the activity of various glands
C) forms only a three-neuron reflex arc
D) changes the heart rate
D) causes voluntary body movements
E) regulates smooth muscle contraction

Answer

4. Establish a correspondence between the properties of the nervous system and its types: 1) somatic, 2) vegetative. Write down the numbers 1 and 2 in right order.
A) innervates the skin and skeletal muscles
B) innervates all internal organs
C) actions are not subject to consciousness (autonomous)
D) actions are controlled by consciousness (arbitrary)
D) helps to maintain the connection of the body with the external environment
E) regulates metabolic processes, body growth

Answer

5. Establish a correspondence between the types of the nervous system and their characteristics: 1) vegetative, 2) somatic. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) regulates the work of internal organs
B) regulates the work of skeletal muscles
C) reflexes are carried out quickly and obey the human mind
D) reflexes are slow and do not obey human consciousness
D) supreme body this hypothalamus system
E) the highest center of this system is the cerebral cortex

Answer

6n. Establish a correspondence between the characteristic and the department of the human nervous system to which it belongs: 1) somatic, 2) vegetative. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) regulates the diameter of blood vessels
B) has a reflex arc motor pathway, consisting of two neurons
B) provides a variety of body movements
D) works arbitrarily
D) supports the activity of internal organs

Answer

Establish a correspondence between the organs and types of the nervous system that control their activity: 1) somatic, 2) vegetative. Write the numbers 1 and 2 in the correct order.
A) bladder
B) liver
B) biceps
D) intercostal muscles
D) intestines
E) oculomotor muscles

Answer

Choose three options. Hearing analyzer includes
1) auditory ossicles
2) receptor cells
3) auditory tube
4) sensory nerve
5) semicircular canals
6) cortex of the temporal lobe

Answer

Choose one, the most correct option. Nerve impulses are transmitted to the brain through neurons
1) motor
2) insert
3) sensitive
4) executive

Answer

Choose three consequences of irritation of the sympathetic department of the central nervous system:
1) increased and increased heart contractions
2) slowing down and weakening of heart contractions
3) slowing down the formation of gastric juice
4) increased intensity of activity of the stomach glands
5) weakening of the wave-like contractions of the intestinal walls
6) strengthening of undulating contractions of the intestinal walls

Answer

1. Establish a correspondence between the function of organs and the department of the autonomic nervous system that performs it: 1) sympathetic, 2) parasympathetic
A) increased secretion of digestive juices
B) slow heart rate
B) increased ventilation of the lungs
D) pupil dilation
D) increased undulating bowel movements

Answer

2. Establish a correspondence between the function of organs and the department of the autonomic nervous system that performs it: 1) sympathetic, 2) parasympathetic
A) raises the heart rate
B) reduces the frequency of breathing
C) stimulates the secretion of digestive juices
D) stimulates the release of adrenaline into the blood
D) increases ventilation of the lungs

Answer

3. Establish a correspondence between the function of the autonomic nervous system and its department: 1) sympathetic, 2) parasympathetic
A) raises blood pressure
B) enhances the separation of digestive juices
B) lowers the heart rate
D) reduces intestinal peristalsis
D) increases blood flow in the muscles

Answer

4. Establish a correspondence between the functions and divisions of the autonomic nervous system: 1) sympathetic, 2) parasympathetic. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) dilates the arteries
B) speeds up the heartbeat
C) enhances intestinal peristalsis and stimulates the digestive glands
D) constricts the bronchi and bronchioles, reduces ventilation of the lungs
D) dilated pupils

Answer

Choose one, the most correct option. What are nerves made up of?
1) an accumulation of nerve cells in the brain
2) clusters of nerve cells outside the central nervous system
3) nerve fibers with connective tissue sheath
4) white matter located in the central nervous system

Answer

Choose three anatomical structures that are the initial link of human analyzers
1) eyelids with eyelashes
2) rods and cones of the retina
3) auricle
4) cells of the vestibular apparatus
5) lens of the eye
6) taste buds of the tongue

Answer

Choose one, the most correct option. A system of neurons that perceive stimuli, conduct nerve impulses and provide information processing is called
1) nerve fiber

3) nerve
4) analyzer

Answer

Choose one, the most correct option. What is the name of the system of neurons that perceive stimuli, conduct nerve impulses and provide information processing
1) nerve fiber
2) central nervous system
3) nerve
4) analyzer

Answer

Choose three options. The visual analyzer includes
1) the white of the eye
2) retinal receptors
3) vitreous body
4) sensory nerve
5) cortex of the occipital lobe
6) lens

Answer

Choose one, the most correct option. The peripheral part of the human auditory analyzer is formed by
1) ear canal and eardrum
2) bones of the middle ear
3) auditory nerves
4) sensitive snail cells

Answer

With excitation of the sympathetic nervous system, in contrast to excitation of the parasympathetic nervous system
1) arteries dilate
2) blood pressure rises
3) intestinal motility increases
4) the pupil narrows
5) increases the amount of sugar in the blood
6) heart contractions become more frequent

Answer

1. Set the sequence of parts of the reflex arc when a nerve impulse passes through it. Write down the corresponding sequence of numbers.
1) sensitive neuron
2) working body
3) intercalary neuron
4) department of the cerebral cortex
5) receptor
6) motor neuron

Answer

2. Establish the sequence of links in the reflex arc of the sweating reflex. Write down the corresponding sequence of numbers.
1) occurrence in the receptors of nerve impulses
2) sweating
3) excitation of motor neurons
4) irritation of skin receptors that perceive heat
5) transmission of nerve impulses to the sweat glands
6) transmission of nerve impulses along sensory neurons in the central nervous system

Answer

3. Establish the sequence of nerve impulse conduction in the reflex arc, which provides one of the mechanisms of thermoregulation in the human body. Write down the corresponding sequence of numbers.
1) transmission of a nerve impulse along a sensitive neuron to the central nervous system
2) transmission of a nerve impulse to motor neurons
3) excitation of skin thermoreceptors with a decrease in temperature
4) transmission of a nerve impulse to intercalary neurons
5) decrease in the lumen of the blood vessels of the skin

Answer

Choose three options. Interneurons in the human nervous system transmit nerve impulses
1) from a motor neuron to the brain
2) from the working body to the spinal cord
3) from the spinal cord to the brain
4) from sensitive neurons to working organs
5) from sensory neurons to motor neurons
6) from the brain to motor neurons

Answer

Arrange in the correct order the elements of the human knee reflex reflex arc. Write down the numbers in the answer in the order corresponding to the letters.
1) Motor neuron
2) Sensitive neuron
3) Back brain
4) Tendon receptors
5) Quadriceps femoris

Answer

Choose three functions of the sympathetic nervous system. Write down the numbers under which they are indicated.
1) enhances ventilation of the lungs
2) reduces heart rate
3) lowers blood pressure
4) inhibits the secretion of digestive juices
5) enhances intestinal motility
6) dilates pupils

Answer

Choose one, the most correct option. Sensory neurons in the three-neuron reflex arc are connected to
1) processes of intercalary neurons
2) bodies of intercalary neurons
3) motor neurons
4) executive neurons

Answer

Establish a correspondence between the functions and types of neurons: 1) sensitive, 2) intercalary, 3) motor. Write down the numbers 1, 2, 3 in the order corresponding to the letters.
A) transmission of nerve impulses from the sense organs to the brain
B) transmission of nerve impulses from internal organs to the brain
B) transmission of nerve impulses to muscles
D) transmission of nerve impulses to the glands
D) transmission of nerve impulses from one neuron to another

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. What organs are controlled by the autonomic nervous system?
1) organs of the digestive tract
2) gonads
3) limb muscles
4) heart and blood vessels
5) intercostal muscles
6) chewing muscles

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. The central nervous system is
1) sensory nerves
2) spinal cord
3) motor nerves
4) cerebellum
5) bridge
6) nerve nodes

Answer

Analyze the Neurons table. For each cell labeled with a letter, select the appropriate term from the list provided. © D.V. Pozdnyakov, 2009-2019

A neuron is a specific, electrically excitable cell in the human nervous system and has unique features. Its functions are to process, store and transmit information. Neurons are characterized complex structure and narrow specialization. They are also divided into three types. This article details the interneuron and its role in the operation of the central nervous system.

Classification of neurons

The human brain has approximately 65 billion neurons that are constantly interacting with each other. These cells are divided into several types, each of which performs its own special functions.

A sensitive neuron plays the role of a transmitter of information between the sense organs and the central parts of the human nervous system. It perceives a variety of stimuli, which it converts into nerve impulses, and then transmits a signal to the human brain.

Motor - sends impulses to various organs and tissues. Basically, this type is involved in the control of spinal cord reflexes.

The intercalary neuron is responsible for processing and switching impulses. The functions of this type of cells are to receive and process information from sensory and motor neurons, between which they are located. Moreover, intercalary (or intermediate) neurons occupy 90% of the human central nervous system, as well as in large quantities found in all areas of the brain and spinal cord.

The structure of intermediate neurons

An interneuron consists of a body, an axon, and dendrites. Each part has its own specific functions and is responsible for certain action. His body contains all the components from which cellular structures are created. An important role of this part of the neuron is to generate nerve impulses and perform a trophic function. The elongated process that carries the signal from the cell body is called the axon. It is divided into two types: myelinated and unmyelinated. There are various synapses at the end of the axon. The third component of neurons is dendrites. They are short processes that branch out in different directions. Their function is to deliver impulses to the body of the neuron, which provides a connection between various types neurons of the central nervous system.

Sphere of influence

What determines the area of influence of an intercalary neuron? First of all, his own structure. Basically, cells of this type have axons, the synapses of which terminate on the neurons of the same center, which ensures their unification. Some intermediate neurons are activated by others, from other centers, and then deliver information to their neuronal center. Such actions amplify the impact of a signal that is repeated in parallel paths, thereby extending the storage life of information data at the center. As a result, the place where the signal was delivered increases the reliability of the influence on the executive structure. Other intercalary neurons may receive activation from connections of motor "brothers" from their center. Then they become transmitters of information back to their center, which creates feedback. Thus, the intercalary neuron plays an important role in the formation of special closed networks that prolong the storage of information in the nerve center.

Excitatory type of intermediate neurons

Interneurons are divided into two types: excitatory and inhibitory. When activated, the first facilitates the transfer of data from one neural group to another. This task is performed precisely by “slow” neurons, which have the ability for long-term activation. They transmit signals for quite a long time. In parallel with these actions, intermediate neurons also activate their “fast” “colleagues”. When the activity of “slow” neurons increases, the reaction time of “fast” neurons decreases. At the same time, the latter somewhat slow down the work of the “slow”.

Inhibitory type of intermediate neurons

The intercalary neuron of the inhibitory type comes into an active state due to direct signals that come to their center or come from it. This action takes place through feedback. Direct excitation of this type of intercalary neurons is characteristic of the intermediate centers of the sensory pathways of the spinal cord. And in the motor centers of the cerebral cortex, interneurons are activated due to feedback.

The role of intercalary neurons in the functioning of the spinal cord

In the work of the human spinal cord, an important role is assigned to the conductive pathways, which are located outside of the bundles that perform the conductive function. It is along these paths that the impulses that are sent by the intercalary and sensitive neurons move. Signals travel up and down these pathways, relaying various information to the appropriate parts of the brain. The interneurons of the spinal cord are located in the intermediate-medial nucleus, which, in turn, is located in the posterior horn. Interneurons are an important anterior part of the spinal cerebellar tract. On the reverse side of the horn of the spinal cord are fibers consisting of intercalary neurons. They form a lateral dorsal-thalamic pathway, which performs a special function. It is a conductor, that is, it transmits signals about pain sensations and temperature sensitivity first to the diencephalon, and then to the cerebral cortex itself.

More information about interneurons

In the human nervous system, intercalary neurons perform a special and extremely important function. They connect different groups of nerve cells to each other, transmit a signal from the brain to the spinal cord. Although this type is the smallest in size. The shape of the intercalated neurons resembles a star. Most of these elements are located in gray matter brain, and their processes do not protrude beyond the central nervous system of a person.

A neuron is a specific, electrically excitable cell in the human nervous system and has unique features. Its functions are to process, store and transmit information. Neurons are characterized by a complex structure and narrow specialization. They are also divided into three types. This article details the interneuron and its role in the operation of the central nervous system.

Classification of neurons

The human brain has approximately 65 billion neurons that are constantly interacting with each other. These cells are divided into several types, each of which performs its own special functions.

Motor - sends impulses to various organs and tissues. Basically, this type is involved in the control of spinal cord reflexes.

The intercalary neuron is responsible for processing and switching impulses. The functions of this type of cells are to receive and process information from sensory and motor neurons, between which they are located. Moreover, intercalary (or intermediate) neurons occupy 90% of the human central nervous system, and are also found in large numbers in all areas of the brain and spinal cord.

The structure of intermediate neurons

An interneuron consists of a body, an axon, and dendrites. Each part has its own specific functions and is responsible for a specific action. His body contains all the components from which cellular structures are created. An important role of this part of the neuron is to generate nerve impulses and perform a trophic function. The elongated process that carries the signal from the cell body is called the axon. It is divided into two types: myelinated and unmyelinated. There are various synapses at the end of the axon. The third component of neurons is dendrites. They are short processes that branch out in different directions. Their function is to deliver impulses to the body of the neuron, which provides communication between different types of neurons in the central nervous system.

Sphere of influence

Excitatory type of intermediate neurons

Inhibitory type of intermediate neurons

The intercalary neuron of the inhibitory type comes into an active state due to direct signals that come to their center or come from it. This action occurs through feedback. Direct excitation of this type of intercalary neurons is characteristic of the intermediate centers of the sensory pathways of the spinal cord. And in the motor centers of the cerebral cortex, interneurons are activated due to feedback.

The role of intercalary neurons in the functioning of the spinal cord

More information about interneurons

In the human nervous system, interneurons perform a special and extremely important function. They connect various groups of nerve cells with each other, transmit a signal from the brain to the spinal cord. Although this type is the smallest in size. The shape of the intercalated neurons resembles a star. The main amount of these elements is located in the gray matter of the brain, and their processes do not protrude beyond the human central nervous system.