The central nervous system of a person exercises control over the activity of his body and is divided into several departments. The brain sends and receives signals from the body and after processing it has information about the processes. The nervous system is divided into the autonomic and somatic nervous systems.
The differences between the autonomic and somatic nervous system
The somatic nervous system is regulated by the human mind and can control the activity of skeletal muscles. All components of a person’s reaction to external factors are controlled by the cerebral hemispheres. It provides sensory and motor reactions of a person, controlling their excitation and inhibition.
The autonomic nervous system controls the peripheral activity of the body and is not controlled by consciousness. It is characterized by autonomy and generalized effects on the body with a complete lack of consciousness. The efferent innervation of internal organs allows her to control metabolic processes in the body and to ensure trophic processes of skeletal muscles, receptors, skin and internal organs.
The structure of the vegetative system
The work of the autonomic nervous system is controlled by the hypothalamus, which is located in the central nervous system. The autonomic nervous system has a metasegmental structure. Its centers are located in the brain, spinal cord and cerebral cortex. The peripheral departments are formed by trunks, ganglia, plexuses.
In the autonomic nervous system are distinguished:
- Sympathetic. Its center is located in the thoracolumbar spinal cord. It is characterized by paravertebral and prevertebral ganglia of the ANS.
- Parasympathetic. Its centers are concentrated in the middle and medulla oblongata, the sacral spinal cord. Nerve nodes are mainly intramural.
- Metasympathetic. Innervates the gastrointestinal tract, blood vessels, internal organs of the body.
Its structure includes:
- The nuclei of the nerve centers located in the brain and spinal cord.
- Vegetative ganglia that are located on the periphery.
- Nerve fibers.
Reflex arc of the autonomic nervous system
The reflex arc of the autonomic nervous system consists of three links:
- sensitive or afferent;
- insertive or associative;
- effector.
Their interaction is carried out without the participation of additional intercalary neurons, as in the reflex arc of the central nervous system.
Sensitive link
The sensitive link is located in the spinal ganglion. This ganglion has nerve cells formed by groups, and their control is carried out by the nuclei of the central brain, large hemispheres and their structures.
The sensitive link is represented in part by unipolar cells, which have one axon carrying or carrying away, and they belong to the spinal or cranial nodes. As well as nodes of the vagus nerves, having a structure similar to spinal cells. This link includes Dogel type II cells, which are components of the vegetative ganglia.
Insertion link
The insertion link in the autonomic nervous system serves to transmit through the lower nerve centers, which are the autonomic ganglia, and this is done through synapses. It is located in the lateral horns of the spinal cord. There is no direct connection from the afferent link to the preganglionic neurons for their connection, there is a shortest path from the afferent neuron to the associative and from it to the preganglionic neuron. The transmission of signals and nerve impulses from afferent neurons in various centers is carried out with a different number of insertion neurons.
For example, in the arc of the spinal autonomous reflex between the sensory and effector link, there are three synapses, two of which are located in the spinal cord, and one in the vegetative node, in which the efferent neuron is located.
Efferent link
The efferent unit is represented by effector neurons that are located in the vegetative nodes. Their axons form non-myelin fibers, which, together with mixed nerve fibers, innervate the internal organs.
Vegetative reflex arches are located in the side horns.
The structure of the nerve node
Ganglion is an accumulation of nerve cells that look like nodular extensions about 10 mm thick. In its structure, the vegetative ganglion is covered from above with a connective tissue capsule, which forms a stroma from loose connective tissue inside the organs. Multipolar neurons, which are built from a rounded nucleus and large nucleoli, consist of one efferent neuron and several diverging afferent neurons. These cells are of a type of brain cells and are motor. They are surrounded by a loose shell - mantle glia, which creates a permanent environment for nerve tissue and ensures the full functioning of nerve cells.
The vegetative ganglion has a diffuse arrangement of nerve cells and many processes, dendrites and axons.
The cerebrospinal ganglion has nerve cells, which are arranged in groups, and their location is orderly determined.
Autonomic nerve ganglia are divided into:
- Sensory neurons that are located close to the spinal or central part of the brain. The unipolar neurons that make up this ganglion are a delivery or carrying process. They serve for the afferent transmission of impulses, and their neurons form a bifurcation during branching of the processes. These processes transmit information from the periphery to the central afferent neuron - this is the peripheral process, the central one - from the body of the neuron to the brain center.
- Motor, motor are composed of efferent neurons, and depending on their position they are called paravertebral, prevertebral.
Sympathetic ganglia
The paravertebral chains of the ganglia are located along the spinal column in the sympathetic trunks, which run a long string from the base of the skull to the tailbone.
The prevertebral nerve plexuses are located closer to the internal organs, and their localization is concentrated in front of the aorta. They form the abdominal plexus, which consists of the solar, lower and upper mesenteric plexus. They are represented by motor adrenergic and inhibitory cholinergic neurons. Also, the connection between neurons is carried out by preganglionic and postganglionic neurons, which use the mediators acetylcholine and norepinephrine.
Intramural nerve nodes have three types of neurons. Their description was made by the Russian scientist Dogel A.S., who, studying the histology of neurons of the autonomic nervous system, isolated such neurons as long-axon efferent cells of the first type, equally-spaced afferent cells of the second type and associative cells of the third type.
Ganglia receptors
Afferent neurons perform a highly specialized function, and their role is in the perception of stimuli. Such receptors are mechanoreceptors (reaction to tension or pressure), photoreceptors, thermoreceptors, chemoreceptors (responsible for reactions in the body, chemical bonds), nociceptors (the body's response to pain stimuli is skin damage and others).
In sympathetic trunks, these receptors in a reflex arc transmit information to the central nervous system, which serves as a signal about injuries or disorders in the body, as well as its normal functioning.
Ganglia Functions
Each ganglion has its own location, blood supply, and its functions are determined by these parameters. The cerebrospinal ganglion, having innervation from the nuclei of the brain, provides a direct connection between the processes in the body through a reflex arc. From these structural components of the spinal cord, the glands are innervated, the smooth muscles of the muscles of the internal organs. The signals coming along the reflex arc go slower than in the central nervous system, and they are completely regulated by the autonomic system, it also has a trophic, vasomotor function.