For the first time the nervous system appeared in which animal?

The nervous system in a living organism is represented by a network of communications that ensure its connection with the surrounding world and its own processes. Its basic element is a neuron - cell with processes (axons and dendrites), transmitting information by electrical and chemical means.

Nervous regulation

For the first time the nervous system appeared in living organisms when it is necessary to more effectively interact with the environment. The development of a simple network for impulse transmission helped not only to perceive signals from outside. Thanks to it, it became possible to organize their own vital processes for a more successful functioning.

During the evolution the structure of the nervous system became more complicated: its task was not only the formation of an adequate response to external influences, but also the organization of one's own behavior. Pavlov called this way of functioning a higher nervous activity.

Interaction with the environment of unicellular

For the first time the nervous system appeared in organisms consisting of more than one cell, as it transmits signals between neurons forming a network. But even in the simplest, one can observe the ability to respond to external stimuli provided by intracellular processes.

The nervous system of multicellular cells differs qualitatively from the analogous formation in protozoa. The entire system of bonds is located within the limits of the metabolism of a single cell. On various processes that occur outside or inside, the infusoria "recognizes" because of the change in the composition of protoplasm and the activity of some other structures. Multicellular living beings have a system built of functional units, each of which is endowed with its own metabolic processes.

Thus, for the first time the nervous system appears, who has not one, but several cells, that is, multicellular organisms. The prototype is the conduct of impulses in protozoa. Their level of vital activity reveals the development of protoplasmic structures that have a conductivity of impulses. Similarly, in more complexly organized living beings, this function is performed by separate nerve cells.

Features of the nervous system of coelenterates

Multicellular animals that inhabit colonies do not share functions, and they do not yet have a neural network. It occurs at the stage when different functions in the multicellular organism differentiate.

For the first time the nervous system appears in hydra and other coelenterates. It is a network that conducts non-purposeful signals. The structure is not yet formed, it diffusely distributed throughout the whole body of the coelenterate. Ganglion cells and their Nislev substance are not fully formed. This is the simplest version of the nervous system.

The type of motility of an animal is determined by the diffuse networked nervous system. Hydra performs peristaltic movements, since it does not have special body parts for movement and other movements. For motor activity, it needs a continuous connection between the contracting elements, and it is required that the majority of the conducting cells be located in the contractile part. Which of the animals for the first time the nervous system appears as a diffuse network? Those who are the founders of the system of human regulation. Proof of this is the fact that there is gastrulation in the development of the embryo of animals.

Features of the nervous system of helminths

The subsequent improvement of nervous regulation was associated with the development of bilateral symmetry in place of radial and the formation of neuronal clusters in various parts of the body.

In the form of strands for the first time the nervous system appears in 1 plane worms. At this stage, it is represented by paired head nerve nodes and the fibers formed from them. In comparison with coelenterates, such a system is much more complicated. In helminths, groups of nerve cells in the form of nodes and ganglia are found. The prototype of the brain is the ganglion in the anterior part of the body that performs regulatory functions. It is called the brain ganglion. From it along the entire body go two nerve trunks, connected by jumpers.

All components of the system are not located outside, but are immersed in the parenchyma and are thus protected from injury. For the first time the nervous system appears in flat worms, along with the simplest senses: touch, vision and a sense of balance.

Features of the nervous system of nematodes

The next stage of development is the formation of a ring formation near the pharynx and several long fibers extending from it. With such characteristics, the nervous system first appears in roundworms. The ocellar ring is a single circular ganglion and serves as the basic organ of perception. With it is connected the ventral cord and dorsal nerve.

Nerve trunks in nematodes are located intraepithelial, that is, in hypodermal ridges. In the role of sensory organs are Sensilla - setae, papillae, supplementary organs, amphids and phasmids. All of them are endowed with mixed sensitivity.

The most complex organs of perception of nematodes are amphids. They are paired, can be different in shape and are in front. Their main task is to recognize chemical agents located far from the body. Part of the roundworms also have receptors that perceive internal and external mechanical effects. They are called metaneomes.

Features of the nervous system of the ring

The formation of the ganglion in the nervous system subsequently develops in ringed worms. In most of them ganglionization of the abdominal trunks occurs in such a way that each segment of the worm has a pair of nerve nodes that are connected by fibers to adjacent segments. Ringworms have an abdominal neural chain, formed by a brain ganglion and a pair of cords coming from it. They stretch across the abdominal plane. Perceptive elements are located at the front and are represented by the simplest eyes, olfactory cells, ciliated pits and locators. With paired nodes, the nervous system first appeared in ringed worms, but later it develops in arthropods. They have an increase in ganglia in the head and a combination of nodes in the body.

Elements of the diffuse network in the human nervous system

The apex of evolutionary development of the nervous system is the appearance of the brain and spinal cord in man. However, even with such complex structures, the original diffuse organization remains. This network entangles every cell of the body: the skin, blood vessels, etc. But with such characteristics, for the first time the nervous system appears, who did not even have the opportunity to differentially perceive the environment.

Thanks to these "residual" structural units, the person has the opportunity to feel different effects even on microscopic sites. The body can react to the appearance of the smallest foreign agent by developing protective reactions. The presence of a diffuse network in the human nervous system is confirmed by laboratory research methods based on the introduction of a coloring substance.

The general line of development of the nervous system in the course of evolution

The evolutionary processes of the nervous system proceeded in three stages:

• Diffuse network;
• Gangilia;
• Spinal cord and brain.

The structure and functioning of the CNS are very different from earlier types. In its sympathetic department, ganglionic and reticular elements are represented. In its phylogenetic development, the nervous system became more and more fragmented and differentiated. The ganglionic stage of development from the reticular was distinguished by the presence of neurons still located above the system of conduction.

Any living organism is essentially a monolith consisting of various organs and their systems that continuously and continuously interact with each other and with the external environment. For the first time the nervous system appeared in the coelenterates, it was a diffuse network, providing an elementary impulse.