The neuron is intercalary. Where are the intercalary neurons located, their function in the work of the brain and spinal cord Interneurons are localized
In the gray matter of the anterior horns each segment spinal cord several thousand neurons are located, which are 50-100% larger than most other neurons. They are called anterior motor neurons. The axons of these motor neurons exit the spinal cord through the anterior roots and directly innervate skeletal muscle fibers. There are two types of these neurons: alpha motor neurons and gamma motor neurons.
Alpha motor neurons. Alpha motor neurons give rise to large nerve motor fibers of the A-alpha (Ace) type with an average diameter of 14 microns. After entering the skeletal muscle, these fibers branch many times, innervating large muscle fibers. Stimulation of a single alpha fiber excites from three to several hundred skeletal muscle fibers, which, together with the motor neuron that innervates them, constitute the so-called motor unit.
Gamma motor neurons. Along with alpha motor neurons, the stimulation of which leads to contraction of skeletal muscle fibers, much smaller gamma motor neurons are localized in the anterior horns of the spinal cord, the number of which is approximately 2 times less. Gamma motor neurons transmit impulses along much thinner nerve motor fibers of the A-gamma (Ay) type with an average diameter of about 5 microns.
They innervate small special fibers skeletal muscles called intrafusal muscle fibers. These fibers form the central part of the muscle spindles involved in the regulation of muscle tone.
Interneurons. Interneurons are present in all areas gray matter spinal cord, in the posterior and anterior horns, as well as in the gap between them. These cells are approximately 30 times larger than the anterior motor neurons. Interneurons are small in size and very excitable, often exhibit spontaneous activity and are capable of generating up to 1500 pulses / sec.
They are have multiple connections with each other, and many also synaptically connect directly to the anterior motor neurons. Interconnections between interneurons and anterior motor neurons are responsible for most of the integrative functions of the spinal cord, as discussed later in this chapter.
Essentially the whole set of different types of neural circuits, is found within the pool of intercalary neurons of the spinal cord, including divergent, convergent, rhythmically discharged, and other types of circuits. This chapter outlines the many ways in which these various circuits are involved in the performance of specific reflex acts by the spinal cord.
Only few sensory inputs, entering the spinal cord along the spinal nerves or descending from the brain, reach directly the anterior motor neurons. Instead, almost all signals are first passed through the interneurons, where they are processed accordingly. The corticospinal tract terminates almost entirely on spinal interneurons, where signals from this tract combine with signals from other spinal tracts or spinal nerves before they converge on anterior motor neurons to regulate muscle function.
Interneurons (also interneurons, conductor or intermediate, interneuron) are a type that are usually located in integral parts, whose (output elements) and (processes) are limited to one area of \u200b\u200bthe brain.
This feature distinguishes them from others, which often have axonal projections outside the region of the brain where their cell bodies and dendrites are located.
While the main networks of neurons are entrusted with the functions of processing and storing information, as well as the formation of the main sources of information output from any area of the brain, conduction neurons, by definition, have local axons that control activity.
As a neurotransmitter, sensory and motor neurons use glutamate, and conduction neurons more often use gamma-aminobutyric acid () for inhibition.
Interneurons work by hyperpolarization of large groups of basic cells. Interneurons of the spinal cord can use glycine or GABA and glycine to inhibit basic cells, while interneurons of the cortical regions or basal ganglia can release various peptides (cholecystokinin, somatostatin, vasoactive intestinal polypeptide, enkephalins, neupopeptide Y, galanin, etc.) and GABA .
Their diversity, both in structure and functionality, increases with the complexity of local networks in the conditioned brain area, which probably correlates with the complexity of the functions performed by the brain area. Accordingly, the six-layer (new cerebral cortex), as the center of higher mental functions, such as conscious perception or cognition, has the largest number types of intercalary neurons.
Video about the principle of the structure and work of the interneuron (in English):
The role of intercalary neurons in the functioning of the spinal cord
The integration of sensory feedback signals and central motor commands at several levels of the central nervous system plays a critical role in movement control.
Studies of the cat spinal cord have shown that receptor afferents and descending motor pathways converge at this level in common dorsal interneurons.
Human and research studies have documented how the integration of motor commands and receptor response signals are used to control muscle activity during movement. During locomotion, a constellation of convergent inputs from a central generator of ordered activity (a neural network delivering rhythmically ordered motor signals without feedback), sensory feedback, downstream commands, and other intrinsic properties elicited by various neurotransmitters result in the activity of conduction neurons.
neurotransmitters
Sensory information transmitted to the spinal cord is modulated by a complex network of excitatory and inhibitory interneurons. Different neurotransmitters are released from different interneurons, but the two most common neurotransmitters are GABA, the primary inhibitory neurotransmitter, and glutamate, the primary excitatory neurotransmitter. - activating interneurons by binding to a receptor on the membrane.
Inhibitory interneuron
The joints are controlled by two opposing sets of muscles, called extensors and flexors, which must work in sync to allow for the correct given movement. When the neuromuscular spindle is stretched and the stretch reflex is activated, the opposing muscles must be blocked to prevent the agonist muscle from working. The dorsal interneuron is responsible for its inhibition. Thus, during intentional movement, inhibitory interneurons are used to coordinate muscle contraction.
Afferent innervation of antagonist muscles is not possible without the work of interneurons.
(n. intercalatum; synonym: N. associative, N. intermediate) N., involved in the transfer of excitation from afferent N. to efferent.
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- - nerve. a cell consisting of a body and processes extending from it - relatively short dendrites and a long axon; main structural and functional. nerve unit. systems...
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- - common name microscopic structures at the point of contact of adjacent muscle cells of the myocardium, ensuring their connection into muscle complexes and the transfer of excitation from cell to cell ...
- - a cell capable of perceiving irritation, becoming excited, generating nerve impulses and transmitting them to other cells: it is a structural and functional unit of the nervous system ...
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- - a cell of pseudostratified epithelium, occupying an intermediate position between the basal and superficial epitheliocytes ...
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"intercalary neuron" in books
author Alexandrov YuriNEURON
authorChapter 8
author Kholodov Yuri Andreevich2. NEURON. ITS STRUCTURE AND FUNCTIONS
From the book Fundamentals of Psychophysiology author Alexandrov Yuri2. NEURON. ITS STRUCTURE AND FUNCTIONS The human brain consists of 10 12 nerve cells. An ordinary nerve cell receives information from hundreds and thousands of other cells and transmits it to hundreds and thousands, and the number of connections in the brain exceeds 10 14 - 10 15 . Discovered over 150 years ago
NEURON
From the book Fundamentals of Neurophysiology author Shulgovsky Valery ViktorovichNEURON The neuron is the main cell of the central nervous system. The forms of neurons are extremely diverse, but the main parts are the same for all types of neurons. The neuron consists of the following parts: soma (body) and numerous branched processes. Each neuron has
Chapter 8
From the book The Brain in Electromagnetic Fields author Kholodov Yuri AndreevichChapter 8 The blood-brain barrier is a complex anatomical, physiological and biochemical system that determines the rate of penetration of individual substances into the brain. On fig. 11 shows a diagram of the vascular-glio-neuron complex, from
Neuron
From the book Big Soviet Encyclopedia(NOT) author TSBNeuron
From the author's bookNeuron Your little friend that you are too lazy to use. Due to the fact that each cell is part of the brain network, an individual neuron does not know and cannot do anything - just like in distributed computing
Neuron in "Vise"
From the author's bookNeuron in the "vice" Neuron-miner is hidden in the depths of the brain tissue. You won't see it in a living brain, you won't find it. How did you manage to find out such details about his activities? It would seem that for research it is necessary to “cut down” a nerve cell from the thickness of the brain, extract it outside,
2. Neuron. Features of the structure, meaning, types
From the book Normal Physiology: Lecture Notes author Firsova Svetlana Sergeevna2. Neuron. Features of the structure, meaning, types The structural and functional unit of the nervous tissue is a nerve cell - a neuron. A neuron is a specialized cell that is able to receive, encode, transmit and store information, establish contacts with
Neuron
From the book Normal Physiology author Agadzhanyan Nikolai AlexandrovichNeuron A nerve cell (neuron) is a functional unit of the nervous system, the structure and functions of which are adapted to the transmission and processing of information. Each neuron has four various areas: body, dendrites, axon and axon endings (terminals). All these
First look at the neuron
From the book Brain for rent. How human thinking works and how to create a soul for a computer author Redozubov AlexeyA first look at the neuron It is impossible to talk about the brain and not talk about neurons. Neurons are the building blocks from which the very building of the brain is built. A lot of works have been written about the structure of a neuron, but many properties of a neuron are still controversial and remain a mystery.
Neuron
From the book Gestalt: The Art of Contact [A New Optimistic Approach to Human Relations] author Ginger SergeNeuron The neuron is the main nerve cell. It consists of three large parts: the cell body, which includes the nucleus (the carrier of our hereditary basis) and the cytoplasm, surrounded by a membrane, the main "border-contact" between the cell and its environment, the axon (which
6 Faith Neuron
From the book Secrets of the Brain. Why do we believe in everything author Shermer Michael6 Faithful neuron In any experience, the mediator is the brain, the mind is the result of the actions of the brain. "Mind" as such does not exist outside the activity of the brain. Mind is just a word we use to describe the neural activity of the brain. No brain, no mind. We
1.7. Neuron
From the book Phenomenon of Science. Cybernetic approach to evolution author Turchin Valentin Fedorovich1.7. Neuron The appearance of a nerve cell (neuron) is shown schematically in fig. 1.6. The neuron consists of a rather large (up to 0.1 mm) body, from which several processes extend - dendrites, giving rise to thinner and thinner processes, like the branches of a tree. In addition to dendrites,
They make up 90% of all neurons. The processes do not leave the CNS, but provide numerous horizontal and vertical connections.
Feature: can generate an action potential with a frequency of 1000 per second. The reason is the short phase of trace hyperpolarization.
Intercalary neurons process information; communicate between efferent and afferent neurons. They are divided into excitatory and inhibitory.
Efferent neurons.
These are neurons that transmit information from the nerve center to the executive organs.
Pyramidal cells of the motor cortex of the cerebral cortex, sending impulses to the motor neurons of the anterior horns of the spinal cord.
Motor neurons - axons extend beyond the CNS and end in a synapse on effector structures.
The terminal part of the axon branches, but there are branches and at the beginning of the axon - axon collaterals. The place of transition of the body of the motor neuron into the axon - the axon hillock - is the most excitable area. Here, AP is generated, then propagated along the axon.
The body of a neuron has a huge number of synapses. If the synapse is formed by the axon of the excitatory interneuron, then the action of the mediator on the postsynaptic membrane causes depolarization or EPSP (excitatory postsynaptic potential). If the synapse is formed by an axon of an inhibitory cell, then under the action of a mediator on the postsynaptic membrane, hyperpolarization or IPSP occurs. Algebraic sum of EPSP and TPSP on the body nerve cell manifested in the occurrence of PD in the axon hillock.
The rhythmic activity of motor neurons under normal conditions is 10 impulses per second, but can increase several times.
Carrying out excitation.
AP propagates due to local ion currents that arise between the excited and unexcited sections of the membrane. Since AP is generated without energy expenditure, the nerve has the lowest fatigue.
Merging neurons.
There are different terms for associations of neurons.
Nerve center- a complex of neurons in one or different places of the CNS (for example, the respiratory center).
Neural circuits are serially connected neurons that perform a specific task (from this point of view, the reflex arc is also neural circuits).
Neural networks are a broader concept, because in addition to serial circuits, there are parallel circuits of neurons, as well as connections between them. Neural networks are structures that perform complex tasks (for example, information processing tasks).
NERVOUS REGULATION
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In general, depending on the tasks and responsibilities assigned to neurons, they are divided into three categories:
- Sensory (sensitive) neurons receive and transmit impulses from receptors "to the center", i.e. central nervous system. Moreover, the receptors themselves are specially trained cells of the sense organs, muscles, skin and joints that can detect physical or chemical changes inside and outside our body, convert them into impulses and joyfully transmit them to sensory neurons. Thus, the signals go from the periphery to the center.
Next type:
- Motor (motor) neurons, which are rumbling, snorting and bibikaya, carry signals coming out of the brain or spinal cord to the executive organs, which are muscles, glands, etc. Yeah, so the signals go from the center to the periphery.
well and intermediate (intercalary) neurons, simply put, they are "extensions", i.e. receive signals from sensory neurons and send these impulses further to other intermediate neurons, well, or immediately to motor neurons.
In general, this is what happens: in sensory neurons, dendrites are connected to receptors, and axons are connected to other neurons (intercalary). In motor neurons, on the contrary, dendrites are connected to other neurons (intercalary), and axons are connected to some kind of effector, i.e. stimulator of contraction of some muscle or secretion of a gland. Well, respectively, in intercalary neurons, both dendrites and axons are connected to other neurons.
It turns out that the simplest path that a nerve impulse can take will consist of three neurons: one sensory, one intercalary and one motor.
Yeah, and now let's remember the uncle - a very "nervous pathologist", with a malicious smile knocking his "magic" hammer on his knee. Familiar? Here, this is the simplest reflex: when it hits the knee tendon, the muscle attached to it stretches and the signal from the sensitive cells (receptors) located in it is transmitted through sensory neurons to the spinal cord. And already in it, sensory neurons contact either through intercalary or directly with motor neurons, which in response send impulses back to the same muscle, causing it to contract and the leg to straighten.
The spinal cord itself nestled comfortably inside our spine. It is soft and vulnerable, and therefore hides in the vertebrae. The spinal cord is only 40-45 centimeters long, with a little finger thickness (about 8 mm) and weighs some 30 grams! But for all its frailty, the spinal cord is the control center for the complex network of nerves that runs through the body. Almost like a mission control center! :) Without it, neither the musculoskeletal system, nor the main vital organs, by any means, can act and work.
The spinal cord originates at the level of the edge of the foramen magnum of the skull, and ends at the level of the first or second lumbar vertebrae. But already below the spinal cord in spinal canal there is such a dense bundle of nerve roots, coolly called a ponytail, apparently for its resemblance to it. So, the ponytail is a continuation of the nerves coming out of the spinal cord. They are responsible for innervation lower extremities and pelvic organs, i.e. transmit signals from the spinal cord to them.
The spinal cord is surrounded by three membranes: soft, arachnoid and hard. And the space between the soft and arachnoid membranes is also filled with a large amount of cerebrospinal fluid. Through the intervertebral foramina, spinal nerves depart from the spinal cord: 8 pairs of cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 or 2 coccygeal. Why steam? Yes, because spinal nerve comes out with two roots: posterior (sensory) and anterior (motor), connected into one trunk. So, each such pair controls a certain part of the body. That is, for example, if you accidentally grabbed a hot pan (God forbid! Pah-pah-pah!), then a pain signal immediately appears at the endings of the sensory nerve, immediately entering the spinal cord, and from there - to paired motor nerve, which transmits the order: “Achtung-akhtung! Remove your hand immediately!" And, believe me, this happens very quickly - even before the brain registers a pain impulse. As a result, you have time to pull your hand away from the pan before you feel pain. Of course, such a reaction saves us from severe burns or other damage.
In general, almost all of our automatic and reflex actions are controlled by the spinal cord, well, with the exception of those that are monitored by the brain itself. Well, here, for example: we perceive what we see with the help of ophthalmic nerve going to the brain, and at the same time we turn our gaze in different directions with the help of the eye muscles, which are already controlled by the spinal cord. Yes, and we cry the same on the orders of the spinal cord, which "manages" the lacrimal glands.
We can say that our conscious actions come from the brain, but as soon as we begin to perform these actions automatically and reflexively, they are transferred to the spinal cord. So, when we are just learning to do something, then, of course, we consciously think over and think over and comprehend each movement, which means we use the brain, but over time we can already do it automatically, and this means that the brain transfers the “reins of power” by this action to the spinal one, it just became boring and uninteresting ... because our brain is very inquisitive, inquisitive and loves to learn!
Well, it's time for us to inquire...
