The human central nervous system controls the activities of his body and is divided into several departments. The brain sends and receives signals from the body and, after processing them, has information about the processes. The nervous system is divided into autonomic and somatic nervous systems.
Differences between the autonomic and somatic nervous systems
The somatic nervous system is regulated by human consciousness and can control the activity of skeletal muscles. All components of a person's reaction to external factors are under the control of 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 in the complete absence of consciousness. The efferent innervation of the internal organs allows it to control the metabolic processes in the body and ensure the trophic processes of the skeletal muscles, receptors, skin and internal organs.
Buildingautonomic 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 in the brain, spinal cord and cerebral cortex. Peripheral sections are formed by trunks, ganglia, plexuses.
In the autonomic nervous system, there are:
- Sympathetic. Its center is located in the thoracolumbar region of the spinal cord. It is characterized by paravertebral and prevertebral ganglia of the ANS.
- Parasympathetic. Its centers are concentrated in the middle and medulla oblongata, sacral spinal cord. The ganglions are mostly intramural.
- Metasympathetic. Innervates the gastrointestinal tract, blood vessels, internal organs of the body.
It includes:
- Nucles of nerve centers located in the brain and spinal cord.
- Vegetative ganglia, which 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
Sensitive linklocated in the spinal ganglion. This ganglion has nerve cells formed in groups, and their control is exercised by the nuclei of the central brain, the cerebral hemispheres and their structures.
The sensitive link is partially represented by unipolar cells that have one incoming or outgoing axon, and they belong to the spinal or cranial nodes. As well as nodes of the vagus nerves, which have a structure similar to spinal cells. This link includes type II Dogel cells, which are components of the autonomic ganglia.
Insert link
The intercalary 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 the 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 different centers is carried out with a different number of intercalary neurons.
For example, in the arc of the spinal autonomic 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 link is represented by effector neurons, which are located in the vegetative nodes. Their axons form unmyelinatedfibers that, in combination with mixed nerve fibers, innervate the internal organs.
Autonomic reflex arcs are located in the lateral horns.
The structure of the ganglion
Ganglion is an accumulation of nerve cells that look like nodular extensions about 10 mm thick. In its structure, the vegetative ganglion is covered on top with a connective tissue capsule, which forms a stroma of 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 divergent afferent neurons. These cells are similar in type to brain cells and are motor. They are surrounded by a loose shell - mantle glia, which creates a constant environment for the nervous tissue and ensures the full functioning of nerve cells.
The autonomic ganglion has a diffuse arrangement of nerve cells and many processes, dendrites and axons.
The spinal ganglion has nerve cells that are arranged in groups, and their arrangement has a conditioned order.
Autonomic nerve ganglia are divided into:
- Sensory neurons that are located close to the dorsal or central part of the brain. The unipolar neurons that make up this ganglion are an afferent or afferent process. They serve for afferent transmission of impulses, and their neurons form a bifurcation during the branching of processes. These processes transmit information from the periphery to the centralafferent neuron is a peripheral process, the central one is from the body of the neuron to the brain center.
- Motor, motor consist of efferent neurons, and depending on their position they are called paravertebral, prevertebral.
Sympathetic ganglia
Paravertebral chains of ganglia are located along the spinal column in the sympathetic trunks, which run in a long line from the base of the skull to the coccyx.
The prevertebral nerve plexuses are 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, inferior and superior mesenteric plexuses. 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 ganglions have three types of neurons. Their description was made by the Russian scientist Dogel A. S., who, while studying the histology of neurons of the autonomic nervous system, identified neurons such as long-axon efferent cells of the first type, equal-length afferent cells of the second type and associative cells of the third type.
Ganglion receptors
Afferent neurons perform a highly specialized function, and their role is to perceive stimuli. Such receptors are mechanoreceptors (response to stretch 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 the sympathetic trunks, these receptors transmit information through a reflex arc to the central nervous system, which serves as a signal of damage or disturbances in the body, as well as its normal functioning.
Ganglion functions
Each ganglion has its own location, blood supply, and its functions are determined by these parameters. The spinal ganglion, which has innervation from the nuclei of the brain, provides a direct link between the processes in the body through a reflex arc. From these structural components of the spinal cord, the glands, the smooth muscles of the muscles of the internal organs, are innervated. The signals coming through the reflex arc are slower than in the central nervous system, and they are fully regulated by the autonomic system, it also has a trophic, vasomotor function.
