First an ancient form of interaction between the cells of multicellular organisms – a chemical reaction by means of metabolic products originating in the body fluid. These metabolic products or metabolites are breakdown products of proteins, carbon dioxide and others. It is the transfer of humoral influences humoral mechanism of the correlation or relationship between the bodies.
Humoral communication is characterized by the following features. Firstly, the absence of the exact address, for the guidance of chemical released into the blood or other body fluids. The chemical substance may therefore affect all organs and tissues. Its action is not localized, not limited to a specific place. Secondly, the chemical spreads relatively slowly. And finally, thirdly, it operates in trace amounts and usually rapidly degraded or excreted. Humoral communication are common to the animal world and the plant world.
At a certain stage of development of the animal world with the emergence of new forms of the nervous system, the nervous form of bonds and regulations. The higher the development of their animal body, the greater the role played by the interaction of the nervous system, which is designated as a reflex. In higher organisms, animals nervous system regulates humoral communication. Unlike humoral communication neural connection, firstly, it has the exact direction to a specific organ or even a group of cells and, secondly, through the nervous system can communicate with far greater speed, a hundred times greater than the speed of propagation of chemicals. The transition from the connection to the nervous humoral in highly organized beings are not accompanied by the destruction of humoral communication between the cells of the body and its replacement by neural connections, and the subordination of humoral links nervous appearance of neuro-humoral interaction. It is found that in the terminals of the nerve fibers that contact with the cells or the body or with other nerve cells, are allocated connection specific mediators, special chemicals or neurotransmitters which act in the body fluid and act directly on the nervous system and specialized nerve endings (see. the article “Chemical Communications”).
In the next stage of development of living beings there are special bodies – the prostate, which produced humoral active substances – hormones produced from entering the body of nutrients. Thus, for example, a hormone produced in the adrenal epinephrine from the amino acid – tyrosine. This hormonal regulation.
The main function of the nervous system is the regulation of the interaction of the organism as a whole from the surrounding environment and regulation of the individual bodies and connection between the organs.
Nervous system enhances or inhibits the activity of all the organs, not only waves of excitement or nerve impulses, but also through additions to the blood, lymph, cerebrospinal fluid and tissue mediators, hormones and metabolites, or metabolic products. These chemicals act on organs and nervous system. So naturally there is only regulation of the activities of the nervous and neuro-humoral.
The excitation of the nervous system has a biochemical nature. As it propagates shear waves metabolism, wherein ions selectively pass through the membrane, resulting in a potential difference between the portions in a state of relative rest and excitement, and generate electric currents. These currents are called biocurrents or biopotentials spread through the nervous system and cause excitement in her subsequent sections.