Home Random Page


CATEGORIES:

BiologyChemistryConstructionCultureEcologyEconomyElectronicsFinanceGeographyHistoryInformaticsLawMathematicsMechanicsMedicineOtherPedagogyPhilosophyPhysicsPolicyPsychologySociologySportTourism






Mechanisms of resistance and reactivity

Factors determining the reactivity and resistance of the body are formed on the basis of its heredity, constitution, features of the metabolism of the nervous, endocrine and immune systems, the system of connective tissue. They depend on the age, sex, environmental factors. The component factors of reactivity reactones are (A.S. Hare, LP Churilov, 1994). Reactones are the basic, genetic features, manifested in the phenotype of the individual. Reactivity operates the reactones and can be considered as a set of reactones. It includes functionally stable combination formed by an integrative unit.

Reactivity is formed at all levels of biological organization. For example, at the molecular level, it appears HbS molecule reaction to hypoxia in sickle-cell anemia, at the cellular level - during phagocytosis, at the organ – by change of reduction rhythm in the isolated heart to the action of temperature stimuli, at the system and organism levels – by changes in the cardiovascular system with heart defects, etc. Molecular, subcellular and cellular mechanisms of reactivity are as individual as its supreme integral expression. For example, tissue and blood thromboplastin is different in composition and mechanisms of its formation, fetal hemoglobin and hemoglobin A are different in binding of oxygen. The main component of tissue and organ substrate of reactivity is a structurally-functional element of the body (tissue). At the system and organism levels qualitatively new integration mechanisms of reactivity is creating due to the "task" of a system. At these levels of reactivity and resistance mechanisms the leading role is played by the nervous system, because the reactivity assumes the answer of the organism to different influences as a whole. In higher animals, the nervous system forms reactivity in all areas - in the initial link (at the receptor level), in the nerve conductors, in the spinal cord and medulla oblongata, in the subcortical region of the reticular formation, cerebral cortex, and in man at the level of the second signal system and to a large extent it is determined by social factors. Therefore, changes in the functional state of the nervous system lead to changes in reactivity, which affects the body's reactions to the various influences on its resistance to harmful agents. For example, due to decortication the resistance to hypoxia increases, in case of gray tuber damage the resistance to infections is reduced, after the transection of the spinal cord of pigeons their immunity to anthrax is reduced, the production of antibodies is inhibited, the protective properties of the connective tissue are reduced, turning off the carotid sinus and aortic reflex zones causes the reduce of adaptation to hypoxia, etc.

Excitation of parasympathetic system is accompanied by an increase in antibody capacity, increase of antitoxic and barrier function of the liver, lymph nodes. Sympathetic arousal causes the abjection of adrenaline and noradrenaline into the blood that stimulates phagocytosis and accelerates metabolism. Inhibition of higher nervous activity reduces the protective role of the connective tissue, absorptive function of its elements, to inhibition of wound healing, and stimulation - stimulates these functions.



In the formation of reactivity and resistance the endocrine system is also important, especially the hormones of the anterior pituitary, bark of adrenal glands (Hans Selye), in particular adrenaline that is called "emergency hormone" (W. Cannon). Thus, adrenalectomy leads to a sharp decrease in the resistance to mechanical injury to an electric current, bacterial toxins, and other pathogens; the introduction of optimal doses of glucocorticoids increases the resistance to the action of extreme stimuli, reduces inflammation; mineralocorticoids have pro-inflammatory effects. In hyperthyroidism inflammation proceeds rapidly, in hypothyroidism it proceeds slowly. In diabetes there are frequent pustular skin lesions, poor wound healing. A significant role is played by the immune system, that provides specific and non-specific immune reactions, and connective tissue system (A.A. Bogomolets) - macrophage phagocytosis, antibody production by plasmatic cells, selection of biologically active substances in the degranulation of mast cells and others. The basis that shaped reactivity to a large extent heredity is, because the received from the parent set of genes determines the level of perfection of the body, the possible degree of development of the nervous, endocrine and immune systems. Nonspecific resistance is provided by biological barriers: the external (skin, mucous membranes, respiratory system, digestive system, liver, etc.) and internal – hysto-hematic ones (hemato-encephalic, haemato-oftalmic, hemato-labirynth, hemato-testicular one). These barriers, as well as biologically active substances from the organism liquors (complement, lysozyme, opsonins, properdin) serve a protective and regulatory function, support optimal nutrient composition for organ, contribute to the preservation of homeostasis.


Date: 2015-01-11; view: 1171


<== previous page | next page ==>
Individual reactivity | The influence of environmental conditions on the reactivity
doclecture.net - lectures - 2014-2024 year. Copyright infringement or personal data (0.008 sec.)