Plan
► Concept of humoral regulatory mechanisms.
► Concept of hormone. Classification of hormones. Mechanisms of action of hormones on target cells.
► Concept of endocrine glands. Classification of endocrine glands.
► Regulation of activity of endocrine glands.
Concept of Humoral Regulatory Mechanisms
In the evolution of multicellular organisms there arose a need in some mechanisms that could provide interrelations both between individual cells of tissues and between individual organs of the whole organism.
Evolutionary selection resulted in formation of two mechanisms of integration of elements into one whole - mechanisms of nervous and humoral regulation. Mechanisms of nervous regulation have already been discussed earlier.
Humoral regulation is a complex of physiological, biochemical and biophysical mechanisms that produce their effect through chemical compounds in the internal environment and induce changes in the state of cells, tissues, organs and systems of an organism.
The concept of the internal environment was introduced by outstanding French physiologist Claude Bernard. He understood the internal environment as a complex of biological fluids - blood, lymph and tissue fluid.
There exist three classes of chemical substances that participate in humoral regulatory mechanisms.
► Water-soluble salts, or electrolytes;
► Products of metabolism, or metabolites;
► Biologically active substances including hormones.
The 1st group includes compounds of potassium, sodium, calcium and magnesium. However, in a human organism there may be found almost all
currently known chemical elements. Therefore, a decrease or increase in the amount of any of these compounds in the internal environment of the body may affect condition of cells, tissues, organs and systems.