After that read the text aloud, trying to imitate the intonation. Reactivityof the organism is the ability to respond adequately to changing conditions of the internal and external environment

Reactivityof the organism is the ability to respond adequately to changing conditions of the internal and external environment. The adequacy of the reaction is by no means absolute. The reaction is not always useful. It is more or less correspondent to the nature and amount of the acting factors. Mechanisms of reactivity are relatively beneficial and potentially pathogenic.

Reactivity is, in fact, a complete repertoire of reactions that the organism is capable of, including all normal hereditary determined reactions, as well as acquired reactions based on ontogenetic experience. reactivity is not just a library of programs but an internal manager, dealing with and selecting from and blending these programs. The reactivity is the ability to be adaptive.

Although the concept of “reactivity” is associated with the organism as a whole, the concrete mechanisms of reactivity are realized at a certain level of the structure in question. There are several levels of reactivity distinguished in the organism: molecular, subcellular, cellular, tissue, organ, whole-body and population ones. The complementary interactions are particularly important at a molecular level. For instance, the adenylate-cyclase receptor subunit recognizes its peptide bio-regulator in accordance with the key–lock principle resulting in the activation of a catalytic subunit. The best example of a tissue level of reactivity is inflammation, i.e., local response of the vascularized tissue to any acute damage. The formation of system responses starts with the onset of the period of organogenesis. An important component of the tissue and organ substratum of reactivity is the structure–functional unit of the organ (a nephron, a liver acinus, a pancreatic acinus, a lung acinus etc.). The reliability of the system is provided by doubling of the function of a great number of structure–function units the organ consists of. The connective tissue elements of the organ stroma form a group around microcirculation vessels carrying out the supporting trophic and protective function for elements of organ parenchyma. The basis of the functioning of every system that integrates the mechanisms of reactivity (nervous, endocrine, immune) is the complementary interaction of the regulator with its receptor– discriminator system.

3Do the following statements agree with the information given in the text?

Write

TRUE if the statement agrees with the information

FALSE if the statement contradicts the information

1. Thereactivity of the organism is the ability to give an adequate response to changing conditions of the internal and external environment.

2. Each response is always useful.

3. All reactivity mechanisms are beneficial.

4. Reactivity displays a total repertory of reactions the organism is capable of.

5. The concrete mechanisms of reactivity are realized at the level of the whole organism.

6. There exist several levels of reactivity: molecular, subcellular, cellular, tissue, organ, whole-body and population ones.

7. Complementary interactions are especially obvious at a molecular level.

8. The functional basis of every system that integrates the mechanisms of reactivity (nervous, endocrine, immune) is the main interaction of the regulator with its receptor– discriminator system.

4 9 Listen to the following questions and repeat them. Mind the intonation in general and special questions. Then answer the questions and practice them with your partner.

1. Whatis reactivity?

2. Is the adequacy of the organism’s reaction absolute?

3. Is reactivity always useful?

4. Does reaction depend on the nature and amount of active factors?

5. Саn it be pathogenic?

6. What are the mechanisms of reactivity?

7. Why is reactivity compared with a manager?

8. What levels of reactivity are distinguished in the organism?

9. Can you illustrate any interactions at different levels of reactivity?

10. At what stage of ontogenesis does the formation of system responses start?

11. What role does a structure–functional unit of the organ play?

12. How is the reliability of the system provided?

5 9 Match the words and expressions in column A with the words and expressions in column B. Then listen, check and repeat.

A	B
the reactivity	of reactivity
internal and external	elements
mechanisms and levels	receptor
hereditary and acquired	environment
ontogenetic	experience
library	vessels
internal	principle
adenylate-cyclase	of the organism
peptide	reactions
key–lock	damage
result	parenchyma
the activation	of a catalytic subunit
acute	manager
tissue and organ substratum of	reactivity
connective tissue	system
the organ	stroma
microcirculation	of programs
elements of organ	in
receptor– discriminator	bio-regulator