A PATTERNED PLAN OF

Each disease manifests itself in the destructive and defensive mechanisms. The de­structive reactions arise in result of the direct action of the causative factor and defensive ones - in the result of mobilization of regulatory systems and development of adaptation reac­tions. The defensive functions of the organism manifest themselves variously: in production of immunity (in infectious diseases), in elimination of the pathogenic agent (for example, in the vomit, urine, sweat), in bleading of the tissue defect (in traumas, wounds), etc.

The defence reactions during different stages of the development of a disease are not equally strong and sometimes reach an intensity which may even prove harmful to the organ­ism. For example, proliferation which is usually one of the defence mechanisms may be as intensive as to prevent the repair of the damaged part of the tissue; fever which is conductive to elaboration of immunity becomes dangerous to the nervous and cardiovascular systems when the temperature rises two high; vomiting occuring in many forms of intoxication helps to rid the organism of toxic products, but intractable vomiting in toxemia of pregnancy may imperil life.

An important role in the defense physiologic reactions of the organism of higher ani­mals and man is played by the higher divisions of the CNS, especially the cerebral hemi­spheres, the apparatus which adjusts and regulates all functions of the organism.

The role of the CNS in the processes of restoration of functions impaired by disease is particularly easy to observe in cases of deep anesthesia or cerebral trauma, which results in

diminished efficiency of the organism and reduces of compensatory reactions in cases of in­flammation; proliferation and regeneration of damaged tissue notically decrease; after the loss of blood restoration of blood pressure is retarded; in disorders of cardiac activity hypertrophy of the heart muscle develops fully and the blood circulation is impaired.

Main mechanisms ofpathogenesis

The main known mehcanisms of pathogenesis are follows: nervous, hormonal, hu­moral, immune, genetic.

Importance of nervous mechanisms in pathogenesis. The organism is adjusted to its en­vironment by means of its nervous system which controls the functions, blood supply and metabolim of all its organs and tissues. By acting on the organism of higher animals and men the pathogenic agent first stimulates the nerve endings (extero- or introceptors) whose sensi­tivity is many times as high as the sensitivity threshold of the other tissue elements. The re­ceptors are the initial link of reflex arcs by means of which the organism reacts to the patho­logic influences exerted on it by its external or internal environment

The direct and limited disturbances, owing to the simultaneous stimulation of the re­ceptors which send signals to the CNS, lead to a general reaction of the organism, based on the reflex mechanism, which can be observed, for example, in the experiment with the pro­duction of a burn. The action of a thermal agent applied to the surface of the body causes in­jury of the tissue and a simultaneous reflex elevation of arterial pressure, change in hemopoi-esis and metabolism, disturbance in respiration, etc. The reflex mechanism is very important in the pathogenesis of trophic disorders of the skin and (oral) mucosa.

In addition to reflex action, pathogenic stimuli may affect the CNS directly; these stimuli may be carbon dioxide accumulated in the blood or microbal toxins or toxic metabo­lites.

Depending on the etiological factor, the site of its action and properties of the organ­ism, the pathogenesis of a disease may be connected with changes in the functions of various parts of the nervous system - from peripheral endings of afferent nerves to the cerebral cortex. Thus, respiratory disorders may arise in one case as a result of stimulation of the peripheral endings of the pulmonary branches of the vagi, in another - as a result of injury to the medulla oblongata or certain parts of the diencephalon, and in still another - as a result of a disturbed function of the cerebral cortex (for example, dyspnea during excitement or disturbance in higher nervous activity).

In other words, the pathologic process may be engendered in different parts of the or­ganism. The sequence and degree of the functional disorder of the particular part of the nerv­ous system are of certain importance in the character and rate of development of the given pathologic process. However, owing to reflex activity, the pathologic process in the end in­evitably involves other divisions of the nervous system, parts of which are most intimately interconnected.

To elucidate the participation of the higher parts of the nervous system in the patho­genesis of a disease it is also important to study its basic regularities: typological properties, correlation of the processes of excitation and inhibition, phenomena of parabiosis (after We-densky), dominant (Ukhtomsky), trace reactions, etc.

An important part in pathogenesis is played by disturbances in the interrelations be­tween the CNS and the internal environment of the organism. The dependence of the functons of the internal organs on the activity of the higher parts of the CNS was repeatedly observed by clinicians. On the one hand, we know about the effects of various emotional experiences on the heart action, respiration and digestion; for example, we know of cases of cardiac pa­ralysis caused by distressing experiences, changes in the respiratory rhythm due to sudden fright, digestive disorders connected with mental depression and chronick lack of appetite. On the other hand, there are very well known examples of bodily afflictions overcome by positive emotions.

By his many years of studies of the cerebral cortex activity Pavlov demonstrated that the functions of the internal orgnas, regulated by subcortical structures, also had their "cortical representation". For example, be observed a prolonged disturbance in the motor and secretory functions of the stomach of dogs as a result of disturbances in the functional state of the higher parts of the brain caused by a clash of the processes of excitation arid inhibition. Disorders of higher nervous activity were also shown to play an important part in altering the functions of other internal organs - gastric secretion, bile secretion, blood pressure, excretion of urine, hematopoiesis.

Other researchers have showed the possibility of forming conditioned reflexes involv­ing the functions of the internal organs and the importance of interoception of these proc­esses.

They demonstrated the possibility of conditioned reflex polyuria (passage of an exces­sive quantity of urine) and anuria (arrest of urinary output), conditioned reflex bile secretion, contraction of the spleen, vasoconstriction and vasodilatation, changes in respiration, me­tabolism, etc. These studies formed the basis of the concept of feedback relations between the activity of the cerebral cortex and the function of the internal organs (corticovisceral rela­tions, according the internal environment of the organism, but in its turn is also under con­tinuous influence of impulses coming from the periphery.

As soon aL, impulses from the extero- and interoceptors reach the cerebral cortex, the latter sets off a complex process of analysis and synthesis and creates the correlations be­tween the processes of excitation and inhibition which determine the character of its influ­ence on the functions of the internal organs. Disturbances in the normal relations between the cortex and subcortical region not infrequently underlie a number of diseases.

These data have shaped new conceptions of the role of the CNS in the pathogenesis of a member of diseases, for example, ulcers, hypertensive vascular disease, bronchial asthma and coronary insufficiency.

The influence of the higher part of the CNS is exerted through its lower parts. The pathogenesis of diseases of the internal organs may also be primarily connected with distur­bances in the functions of the subcortical region, particularly the region of the subcortical re­gion, particularly the region of the hypothalamus which contains the centres that regulate, by means of efferent neurons, the processes operating in the internal environment of the organ­ism.

Studies in the physiology of the cerebral hemispheres have established the role of cor­tical inhibition as a defence reaction of exhaustion and great damage to or destruction of nerve cells.

This inhibition is conducive to restoration of cortical activity and is, according to Pav­lov, a safeguard. It often comes into play in the course of various pathologic processes as a defence reaction to noxious agents and the damage caused by them, for example, in cerebral anemia, various forms of poisoning and infectious diseases.

Production of defensive inhibition underlies the use of prolonged natural or artificial (induced by medication) sleep (if the latter closely resembles natural sleep). Prolonged sleep therapy is now indicated in some cases of traumatic shock, hypertensive vascular disease, ul­cers, etc.

Humoral mechanisms, especially neuroendocrine and endocrine regulation, also con­stitute a very important link in the regulation of functions. Through their various functions endocrine glands determine, in close interaction with the nervous system, the reaction of the complex organism to the action of the stimulus. For example, disorders of urinary output may occur through subcortical vegetative centres and their connection with the posterior lobe of the hypophysis which secretes an antidiuretic hormone that influences water reabsorption in the kidneys.

With the evolutionary development of organism the neuroendocrine relations assume increasing importance in pathologic reactions. The cortico-diencephalohypophyseal correlations and the hypophyseal-adrenal function closely connected with them play a particularly important role in higher animals and man. This system actively praticipates in the adaptability of the organism, in its nonspecific reactions to the action of any pathologenic stimulus.

In addition to the hormones produced by endocrine glands, tissue hormones may also take part in the pathogenesis'of disease; these hormones, for example, active polypeptides and proteins, histamine, acetylcholine, serotonin are physiologically active substances. They may also participate in disturbing the regulation of functions, which is often discovered in patho­logic processes.

Recovery (convalescence)

Recovery is the active process consisting of the complex of reactions which (i) arise in the Beginning of disease and (ii) provide normalization of the organism's functions and (iii) compensation of disturbances in its relationships with external environment.

Mechanisms of the recovery include:

1) elimination of the cause of the disease,

2) disruption of the cause-and-effect relations,

5) enchancing of defensive and adaptive reactions,

4) formation of compensatory reactions,

5) adaptive changes of the regulatory system functions.

The main mechanisms of restoration of destroyed functions in the organism are the compensation (i) and regeneration (ii).

Compensation makes up structural and functional disorders.

Mechanisms of the compensation:

1. involving of the reserve possibilities of organ;

2. increasing in the function of the vicarious organ;

3. change of metabolism and increasing in activity of normal part of the organ or replacement

of one part of a single functioning system by another.

The main stages of the development of compensation: (i) formation, (ii) fastering, (iii) exhaustion.

Regeneration is the kind of compensation characterized by structural repair of damaged organ. Regeneration is called true if it develops by means of cell proliferation. Regeneration •s called partial if it develops by means of hyperthophy of preserved cells in the damaged organ.

The main principles of treatment of diseases.

The main tasks of disease treatment are:

to prevent the mortal outcome

to achieve recovery;

to restore capacity for work and social useful -1 activity.

Medical measures providing the elimination or neutralization of the causative factor are called etiotropic therapy.

Medical measures acting on mechanisms of disease, development and also providing elevation of organism's resistance and restoration of its functions are called pathogenetic therapy

These measure correspond to the recovery mechanisms.

A PATTERNED PLAN OF

Date: 2015-01-02; view: 853