HUMORAL INTERRELATIONS IN ORGANISM

Plan

1. Concept of humoral regulatory mechanisms.

2. Concept of hormone. Classification of hormones. Mechanism of action of hormones on target cells.

3. Endocrine glands. Classification.

4. Regulation of activity of endocrine glands.

Formation of multicell organisms in the evolutionary development brought about the need for some mechanisms that could establish relationships between both individual cells in tissues and individual organs in the body.

In result of the evolutionary selection two mechanisms of integration of elements into one whole have been formed – mechanisms of neural and humoral regulation. We have already discussed neural regulatory mechanisms earlier. In this lecture we will speak about humoral regulatory mechanisms.

Humoral regulation is a complex of physiological, biochemical and biophysical mechanisms that change conditions of individual cells, tissues, organs and systems by acting through chemical compounds in the internal environment of the body.

The concept of the internal environment was brought into science by the famous French physiologist Claude Bernard. He understood the internal environment as a complex of biological fluids – blood, lymph and tissue fluid.

Chemical substances that can participate in humoral regulatory mechanisms fall into 3 classes:

1) water-soluble salts, or electrolytes;

2) products of metabolism, or metabolites;

3) biologically active substances including hormones.

The 1^st 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 the condition of cells, tissues, organs and systems.

The 2^nd group of chemical compounds includes CO₂, carbonic acid (H₂CO₃), lactic acid, pyruvic acid, products of ATP cleavage (ADP, non-organic phosphorus, etc.).

The 3^d group includes hormones and parahormones (tissue hormones). The term “hormone” was proposed by English physiologists W.Bayliss and E.Starling in 1905. It originates from the Greek word hormao meaning stimulate, induce, bring to action.

Hormones are highly active chemical substances produced in small amounts by specialized cells, tissues and organs, and released into the internal environment of the body.

Hormones differ from other substances of humoral action in the following way:

1) hormones are produced by specialized cells;

2) hormones act distantly and address their action to all cells but interact only with target cells;

3) hormones are characterized by extremely high biological activity. For example, adrenaline increases the rate and strength of heart contractions. According to calculations, 1 g of adrenaline is capable of activating 100 000 000 of isolated frogs’ hearts. You know insulin hormone, which participates in glucose metabolism: 1 g of insulin can decrease the blood glucose level in 125 000 rabbits.

Date: 2015-01-02; view: 856