Interrelations between nervous and humoral mechanisms in physiological functions regulation.

Regulation nervous and humoral principles described above are united morphologically and functionally in one neuro-humoral regulation. Such regulatory mechanism initial link, as a rule, is afferent sygnal on entrance and informational connection effector channels are either nervous, or humoral. Organism reflectory reactions are initial in complicated integrated reaction, but only in complex with endocrine apparatus organism alive activity regulation system functionning is provided to its optimal adaptation to environmental conditions. One of such alive activity organization mechanisms is general adaptational syndrom or stress. Stress is neuro-humoral regulation, metabolism systems and physiological functions non-specific and specific reactions integrity. Neuro-humoral regulation system level is expressed in course of stress as a whole organism susceptibity increasing to environmental factors action particularly harmful for organism. You will discuss stress mechanisms in details in course of pathological physiology. But now, please, put your attention to the fact that under stress conditions interrelations between nervous and humoral regulatory mechanisms are very brightly expressed. In organism these regulatory mechanisms add one another while forming functionally united mechanism. For instance, hormones influence on processes taking place in brain (behaviour, memory, study). Brain, in turn, controls endocrine apparatus activity.

Organism interrelation with external environment which influences on its functions so much is realized by analizators – special nervous system apparatus.

Endocrine glands significantly influence on maxillo-facial region morpho-functional state, especially one can see such influence under endocrinopathology. Endocrinopathies (hypo- or hyperfunction) leads to special diseases with accompanying changes in oral cavity. These signs in the most cases are far secondary expressions observed in disease height and that’s why they are easily to be diagnostically found out. Most often changes in oral cavity occur at pancreas, sexual glands disorders, more seldom – in course of hypophysis, thyroid, parathyroid and suprarenal glands dysfunctions.

Pancreas disturbances are widely-spread. At insuline insufficiency diabetes mellitus is developed. Distinguishing features: tissular reactions change to local stimuli, organism resiliency decreasing to infections, predisposition to inflammatory processes, retarded wounds repair. Many of this is delt with oral cavity. Though such changes are non-specific they are observed not only in course of diabetes. Main patients’ complaints are the following: dryedness in mouth of different degree, increased appetite and thirst. Oral mucosa is dry or weakly-washed. Dryedness is the dehydratation (liquid loss by tissues) result. One can see also small vessels changes, oral mucosa hyperaemia, tongue increasing, dental stone big coverings, teeth increasing motility and light bleedings from gums.

Sexual hormones physiological secretory fluctuation due to sexual development, pregnancy and other states causes definite changes in oral mucosa too. More seldom such symptoms are observed in connection with endocrine glands diseases. Oral mucosa is changed under estrogen and progesterone influence. Under estrogen action water is delayed in tissues, keratinization is decreased, mitotic activity is enforced. Progesterone causes increased vascularization as a result of which predisposition to bleeding is increased in oral cavity. Gonadothropic hormones cause oral cavity and gums mucosa swelling.

At hypophysis hyperfunction due to jaws increasing and soft tissues (lips, gums, tongue) growing up acromegaly is developed. Hypophysis thyreothropic hormone enforces connective tissue ability to keep water that leads to mucosa oedema. Somatothropic hormone secretion increasing can lead not only to acromegaly, acrocheylia (lips dimensions increasing), macroglossia (tongue size increasing) but also to gums hyperplasia (tissular structural elements excessive forming). Dilated interdental spaces in increased dental arch provides food putting between teeth and parodont injury.

Thyroid hyperfunction results in gums swelling, other oral cavity tissues are not changed. Tongue tremor is often observed, multiple caries is possible. Thyroid hypofunction or its removal leads to mandibule atrophy, multiple caries near cervix and intracervically (with circulatory situation in the latest case) because of phosphorus-calcium exchange disorder.

Suprarenal glands cortex anomalies are accompanied by first disease signs (Addison’s disease) as skin and mucosae pigmentation. That’s why dentist can see such pigmentation before other symptoms appearence. Most often one can observe pigmentation on cheeks mucosa, on lips, on tongue limb. Pigmented locuses size is from 1 to several square millimeters. They are uncorrect-shaped, plate, are not protruded above mucosa level. Their appearence reason is melanine accumulation in connective tissue and in bazal epitheliocytes due to hypophysal hormone melanophore stimulating action.

Knowledge of endocrine glands developmental peculiarities can help to dentist connected to children. In children’s dentistry study the questions delt with endocrine glands and oral cavity tissues embryogenesis, differentiation and hystogenesis in embryo, fetus and child in his first years of life is of special interest and of great importance. Such correlations are important for determining the role of one or other gland in dental-maxillary system development. It is known for example that hormones influence on hysto- and organogenesis. Suprarenal gland cortex and thyroid during their embryogenesis begin their functionning before others (correspondingly on 8-th and 12-th weeks) and are dominant endocrine glands during this onthogenetical period. They stimulate growth and influence greatly upon tissues and organs of all embryo organism and on dental-maxillar system organs too. Beginning from 6-7 th weeks of embryogenesis, soft and hard palate are formed, the division of primary oral and nasal cavities, oral cavity and tongue vestibule development take place. Dental plate begins its formation in course of this period, milky (primary) teeth layings and germs formation occur. Thyroid function maturation in humans coincides with milky teeth germs differentiation period.

One more endocrine system problem is of great importance in dentistry. It is different mother’s (maternal) endocrinopathies influence onto embryo. It was established that preliminary beginning of thyroid functionning in mother and parathyroids in embryo can be at resection of these glands in mother. System hypoplasia (tissular elements insufficient formation) of teeth and their dentition terms disorders take place as the result of such phenomenon.

In children at endocrinopathies one can see differencies in teeth formation and dentition: milky teeth malacia (resorption) retardation, retinated teeth, dentine structure change, hypercementosis, non-caries solid dental tissues injuries (hypoplasia, necrosis, erosion, pathologic desquamation). In course of hyperthyreosis changes in oral cavity will be non-specific and will be expressed mainly in accelerated dentition. On the contrary, changes in oral cavity will be very specific: dentition disorders, enamelogenesis anomalies, lips and tongue size increasing, leading to speech and swallowing retardation. Mucosa is swelled, gums are pale, swelled.

Parathyroids functionning anomalies also have their consequences because it influences on calcium and phosphorus exchange in organism. At parathyroid hyposecretion in childhood one can see enamel hypoplasia and dentinogensis disorders. In 20-50 per cents of cases at these glands hypersecretion one can determine parodont change.

Endocrine glands hypofunction or hyperfunction, hormones overdosage or gland death during puberty is expressed earlier in comparison with developing organism, after growth period ending because developing dental germ and parodont are very sensitive to all organism hormonal status anomalies. Primary (milky) and definite (constant) teeth dentition time is a very important diagnostic symptom at some endocrine diseases determining, for example, congenital hypothyreosis, toxic ingluvies or crop, hypophysal hyperfunction.

Thus, in organism neurochemical and endocrine system add one another, form functionally united mechanism. Hormones influence on processes taking place in brain and brain in turn controls endocrine glands activity. For instance, sympathetic nervous system excitement is accompanied by adrenaline hyperproduction. Hypothalamus causes change in hormones production. Emotional excitement through limbic system and hypothalamus influences greatly on hormonal production. All these reactions influence on dental-maxillary apparatus too.

 

Lection 3

Analizators. Oral cavity role in purposeful behaviour.

 

Human being constantly receives information about multiple changes taking place in external and internal environment. It is realized by means of analizators or sensor systems. Each analizator consists of 3 parts:

1) perypheral or receptor part – performes stimulus energy perception and its transformation in specific excitement process;

2) conductive part - is represented by afferent nerves, spinal and stem centers. It performs specific excitement primary processing and its transmission to brain cortex;

3) central, brain or cortical part – corresponding cortical zones, where ending excitement processing – the highest analysis and corresponding sensation forming – is performed.

Thus, analizators – is structures integrity providing:

· irritator energy perception;

· its transformation into specific excitement process;

· this excitement transmission through CNS structures;

· its analysis, assessment by specific cortex zones with subsequent forming of corresponding sensation.

Peripheral (receptor) analizator part features.

In activity of each analizator and its parts independently from characteristics of stimuli percepted by it one can differentiate several common features. These features are common for perypheral part of any analizator.

1) Specificity – ability to percept only definite, i.e. adequate for given receptor, stimulus. This receptor ability has been formed in course of evolution.

2) High sensitivity – ability to answer to very small by intensivity parameters of adequate stimulus.

3) Rhythmical excitement impulses generation in answer to the stimulus action.

4) Adaptation – ability to adapt to stimulus action which is expressed in receptor activity and excitement impulses generation freaquency reducing.

5) Functional mobility – increasing or decreasing of functionalreceptors amount dependently of environmental conditions and organism functional state.

6) Specialization ofreceptors to adequate stimulus definite parameters. Receptors in perypheral analizator part composition are unequal as for their attitude to stimulus. One of them answer only to the origin of its action, others – on it stoppage, third – on intensivity change.

Oral cavity mucosa is innervated rich, its receptors are represented by free nervous endings and special structures (Krauze colbs, Ruffini bodies, Meissner’s bodies, Merkel’s bodies et al.).

1) According to information character coming to CNS from oral cavity one can differentiate not less than 6 sensitivity types:

· gustatory;

· of coldness;

· of warmth;

· tactile;

· nociceptive;

· proprioreceptive;

2) according to functionning specificity – there are 3 receptors types:

a) chemoreceptors (gustatory);

b) somatosensor:

· tactile;

· of warmth;

· of coldness;

· of pain;

c) proprioreceptors.

Every group is the origin of corresponding analizator.

First signs of many dental diseases can be expresssed by perceptive processes and oral cavity sensor system adaptive mechanisms disorders. Dentist in his daily practice in course of patients examination usually puts his attention only to nociceptive sensitivity disturbances but it doesn’t usually reflect proper time of disease beginning time and recovery, so it doesn’t always correctly orient (direct) the doctor to proper treatment method choosing. That’s why it’s necessary to remember that for receiving more full disease picture it’s necessary to investigate other sensitivity types too.

Gustatory reception. Gustatory sensitivity is oral mucosa sensor function specific peculiarity. Gustatory analizator physiology knowledge is a very important because change of its function may testifies to serious disorders both in oral cavity and in other organism parts. One can differentiate such problems with taste:

· agevzya – gustatory sensitivity loss;

· hypogevzya – gustatory or taste sensitivity reducing;

· hypergevzya - gustatory or taste sensitivity increasing;

· paragevzya - gustatory or taste sensitivity distortion;

· dysgevzya – gustatory substances detailed analysis disorders;

· gustatory gallucinations.

But gustatory analizator role and its importance is difficult to deternmine separately because natural adequate stimulus - food, coming into oral cavity – excites simultaneously other analizators receptors. Thus, gustatory sensation is a complicated sum of excitements coming into cortex from gustatory, olfactory, tactile, temperature and nociceptive receptors. First of all, in oral mucosa tactile receptors are excited, later – temperature and than receptors answering to chemical food content. Impulses from them go into CNS through different fibres with different velocity. Result - dyspersion on excitement spreading through nervous centers. Different shades of gustatory sensations also depend on the complex of occuring excitations. Gustatory receptor cells are united in gustatory bulbs which are primarily located in tongue papillas: fingiformed, foliatae and vallate. Taste analizator sensitivity assessment is performed by method of gustatory sensation threshold determining as well as by functional mobility method. Gustatory thresholds are defined separately for every stimulus from 4 main gustatory stimuli according to taste fields topography because separate tongue locuses possess different sensitivity to substances of various gustatory quality in the majority of people: tongue end is the most sensitive to sweet, lateral surfaces – to salty and sour, root – to bitter. It was established by means of functional mobility method that active lingual papillas amount is constantly changed according to alimentary tract functional state. Receptor mobilization maximal level is observed on an empty stomach, it is reduced after its irritation with food. This phenomenon is known as gastro-lingual reflex. Gustatory receptors play the effector role in this reflex. Some dental diseases for example glossalgia (pain in tongue), glossitis (tongue inflammation) and others may appear at alimentary tract disorders. There can be taste loss and gastro-lingual reflex disorder that can be used as diagnostic criterium. Gastro-lingual refelx study in these cases help diseases aethiology assessment.

Tactile reception. Oral mucosa tactile reception is an important part of somato-sensor analizator. It is represented by touching and pressure receptors. These receptors are in strong functional interconnection with parodont mechanoreceptors and masticatory muscles proprioreceptors. Their interrelations define muscle participation in course of mastication act. Besides, on tongue back one can see filiaformed papillas that play touch organs role and perform mechanic function. They look like cone-shaped eminences closely attached one to another. That’s why tongue surface is velvety. Epithelium covering filiaformed papillas is keratinized (cornificated). Filiaformed papillas epithelium superficial layer desquamation is the physiological regeneration process expression. Filiaformed papillas epithelium superficial layer desquamation is retarded at alimentary organs diseases, common inflammatory and infectious diseases. Tongue becomes coated in a result of such unpleasant states.

Tactile sensitivity study demonstrated receptors distribution unequality in facial-maxillar region different regions. Maximal sensitivity has tongue end and red lip limb because these structures are the first instation for the analysis of substances coming into oral cavity. Superior lip (mucosa and red limb) possesses more expressed sensitivity comparatively to inferior one. Tactile sensitivity high level has hard palate mucosa. It is of great importance in course of swallowing act (orienting mastication phase) and in course of food piece forming, swallowing. Vestibular gum surface mucosa possesses minimal tactile sensitivity. One can see decreasing sensitivity gradient to the left and to the right from alveolar arch center in the gingival (gum) papillas region. Sensitivity is more from the right side than from the left. Asymmetry is explained by innervation peculiarities: maximal neurons quantity is located on the right face side.

Tactile sensation study in regions covered by dentures that are denturing bed helps to develop individual peculiarities of adaptation to dentures in dental patients.

Temperature reception. Temperature analizator belongs to somato-sensor analizator too. Some sensor regions possess high sensitivity to temperature fluctuations. Temperature receptors are divided into receptors of warmth and of coldness. Their maximal quantity is located in facies and neck skin.

One can determine increasing gradient from oral cavity anterior to posterior part for thermal sensitivity, for the cold one - on the contrary. Cold receptors predominance in oral cavity anterior part and thermal – in posterior ones is connected with specificity of their functions and their importance in organism thermoregulation processes. Receptor system of coldness being predominant in thermoregulation, answers faster and more adequate to external environment temperature change and thermal one is a characteristics of homeostasis of an organism himself.

Cheek’s mucosa has a little sensitivity to coldess and less one – to warmth. Warmth perception is completely absent in hard palate center and central part of tongue posterior part percepts neither cold nor thermal stimuli. Tongue end and red lip limb possess high sensitivity to temperature irritations. It is determined by functional properity because in course of food taking these regions are irritated first. Information about substances temperature from these regions will switch on corresponding protective reactions if it’s necessary.

Teeth possess both thermal and cold sensitivity. Cold sensitivity threshold for incisive teeth is 20°C, for the rest of teeth – 11-13°C; thermal sensitivity threshold for incisive teeth – 52°C, for rest teeth – 60-70°C. For dental temperature sensitivity study they are washed by water of high or low temperature or use cotton-wool tampon washed in water or either which while fast vaporization leads to the tooth coldness. If temperature stimuli cause adequate sensations it is testifies to absence of any pulp pathological change. Thermal irritation of caries regions is accompanied by pain in course of caries. Depulpated tooth doesn’t answer to such stimuli. Nociceptive sensation can occur either at injured stimulus action to special “noceoceptive” receptor – nociceptor, or at superstrong irritations of other receptors. Nociceptors are 25-40 per cent of all receptors. Nociceptors both of skin and of mucosa are represented by free non-incapsulated nervous endings of different shape (hairiness, spirals, plates et al.). The most investigated in oral cavity is nociceptive sensitivity of alveolar processes and hard palate mucosa that are denturing bed regions. Expressed noceosensitivity possesses mucosal part on mandibule vestibular surface at lateral incisive teeth region. Gums mucosa oral cavity possesses minimal noceoceptive sensitivity.

On cheek internal surface there is narrow locus without noceosensitivity. Maximal quantity of noceoreceptors is in dental tissues. On 1 cm² of dentine 15000-30000 noceoceptive receptors are located, on enamel-dentine boundary – their amount reaches 75000, on skin – not less than 200 noceoreceptors. Pulpal receptors irritation causes extremely strong painful sensation. Even light touching is accompanied by acute pain. Dental pain which belongs to the strongest pains occurs in course of tooth injury with pathological process. Tooth treatment stops it and liquidates pain. But treatment itself may be very painful manipulation. Besides, in course of denturing one should preparate often healthy tooth too that causes painful sensations.

Pain analizator (noceoceptive analizator). Nociceptors are divided into 2 types: mechanoreceptors and chemoreceptors. Mechanoreceptors are getting excited as the result of mechanical movement of membrane that allows to sodium ions to penetrate inside and to cause nerve ending depolarization. Mechanoreceptor is located so that it provides the control of skin, epidermis, articulatory sacs, muscular surface and periodont integrity. Excitement from the most mechanoreceptors are transmitted through “A” fibres. Chemoreceptors are located in the deeper tissular layers. They control oxidative processes level in tissues: at oxidation level reducing their self-excitement occurs. Ishemia (tissue blood supply decreasing or stoppage) independently from its reason leads to strong painful sensations development. Specific irritators for chemoreceptors are the substances released at cells injury: acethylcholine, hystamine, serotonine, potassium ions and some others. Some products of plasma, tissualr liquid may be activated while contact with side body, acid metabolic products, inflammation products and act to chemoreceptors. Prostaglandine E (is released at inflammation), blood coagulation contact factor – factor XII (Hageman’s factor), plasmine, bradykinines. Excitement from nociceptors of oral mucosa, periodontal, lingual, pulpal receptors are transmitted through nervous fibres of “A’ and “C” group. The biggest part of these fibres belongs to trygeminal nerve second and third branches. Central processes are directed to medulla oblongata where they are finished on neurons of nuclear complex consisting of main sensor nucleus and spinal tract. Trygeminal nerve spinal tract nuclei after the clearence of oral cavity, dental tissues and facial regions receptors are divided into 3 parts: nucleus oralis, interpolaris and caudalis. On the latest 2 trygeminal nerve ganglion neurons central processes are finished. They transmit information from nociceptors (second analizator neurons). Mainly information from mechanoreceptors comes to anterior and main sensor nucleus of this nerve. Excitement comes from second neurons to posterior and ventral specific thalamic nuclei, from which nociceptive excitement is directed to sensor zone and medial parts of brain hemispheres orbital cortex. The result of excitements coming into central brain parts is pain sensation forming with more or less expressed behavioral, emotional and vegetative reactions directed to oral cavity tissues integrity preserving. The term “pain” has different essence. One can differentiate pain as usual sensor modality similar to hearing, taste, vision, that is a sygnal about reaching the physiological function boundaries out if which injury is located. The example of this pain definition is pain sensation appearence while trying to gnaw too solid nuts. Pain can be the result of pathologic processes, for example, pulpitis and periodontitis. Chronic durable pain can become the origin of new pathologic conditions for instance mania-deppressive states and odontogenic trygeminal nerve neuralgia. Primarily pain is situated in injured tooth region but also it can irradiate to neihbouring jaw locuses, in eyeball, head frontal, temporal and occipital regions. Painful sensations also occur at mucosa inflammatory processes: stomatitis, glossitis, at galvanism phenomena et al.

Some CNS structures perform antinociceptive functions. These are separate nuclei of medulla oblongata, midbrain, hypothalamus and big hemispheres. Besides brain structures mentioned above there exist others, cellular elements, disseminated in CNS participating in noceoceptive sensitivity control. Together with well-known opiate and serotoninergic mechanisms we should mention dophamine-, choline- and adrenergic mechanisms switched on in noceoceptive sensitivity regulation at different CNS levels. Pain threshold size depends on nociceptive analizator interconnection to antinociceptive system and can be modulated due to changes the activity of not only noceoceptive analizator afferent systems but also due to nociceptive system activity. Pain threshold is often changed at emotional states which are in dependence on emotions type either activate antinoceptive system (aggression, fury), increasing pain threshold, or decrease its activity (fear), reducing pain threshold.

Purposeful behaviour and oral cavity role in its realizing.

Purposeful behaviour is the base of the highest nervous activity. These are complicated reflectory reactions providing individual organism adaptation to simultaneously changing environmental conditions, i.e. human behaviour. Alongside with congenital (unconditioned) reflexes there exist aquired (conditioned) reflexes. Common for human being and animals are analysis and synthesis of direct, concrete sygnals of surrounding world subjects and phenomena, which come from different organism receptors and are the first sygnal system. In human being besides in course of working activity and social development second sygnal system appeared. It is delt with word sygnals. This signalization system is in perception and analizing of listened and pronounced (speech) or visible (text) words. Word sygnal importance is defined by not only simply combination of sounds but also by its semantic context. Human being as animal has only unconditioned reflexes at his birth. In course of life conditioned-reflectory connections forming occurs by first sygnal system. Further, second sygnal system is simultaneousely formed on the base of the first one. It is human behaviour the highest regulator. Due to the highest nervous activity (HNA) and psyche peculiarities definite attitude to his state is formed in a patient as well to dental diseases. It influences on dental wards visits, therapeutic measures effectiveness and adaptation terms in course of orthopedic treatment. Any denture of any construction and function is a complex of inadequate stimuli. Applied with preventive or medical aim denture is percepted as side body by patient, his attention is concentrated for long on this sensation, it troubles him in his work and rest. In people with unstable nervous system, hardly coming through the least irritation there occurs very big desire to remove the denture and often do this in clinics. Salivation is enforced in parallel to the sensation of denture as side body. Such sensation occurs almost right after denture application and it testifies to salivatory reflex appearence at oral mucosa receptors irritation. This reflex is unconditioned by nature and it reminds the reaction caused by action of removed substances. It is expressed not only in excessive salivation but also in qualitative saliva content change.

Besides, in first time of denture usage food bite, proper masticatory act and swallowing act take place not-coordinatively, insimultaneously, with speech changing, sometimes vomiting reflex occurs. All this requires large physical forces from patient and emotional tension. Such state is determined by the fact that denture is oral cavity sensor apparatus active irritator, from which afferent impulses powerful stream comes into CNS. This afferentation causes strong excitement not only of specific structures but also irradiates in brain non-specific structures. Adaptation velocity to dentures depends both on HNA individual features and on organism functional state (fatigue, agitation, psychiatrical trauma). It’s necessary to remember that word being the irritator of the second sygnal system can act very strongly to one’s organism. The highest communication form between people is possible due to speech communicative function. Speech can also perform regulatory function in course of communication between people. That’s why dental patients with speech disorders are in special psycho-emotional state. Psychotherapy in dentistry is first of all a fear sense prevention and liquidating. It’s necessary to use digressive (distractive) measures (external inhibition) e.g. interesting topics for the patient for fear inhibiting and emotional tension liquidation.

Main expressions of human purposeful activity with oral cavity organs participation are the following: sucking, mastication, speech-forming. Sucking act is formed in human being in the early developmental period and it is completely expressed after birth. New-born can not neither masticate nor talk in comparison to adult person. Adequate for swallowing alimentary piece forming begins its functioning with first teeth dentition (in 6-8 months) and finishes with root milky (primary) teeth dentition ending (up to 2-3 years). To first teeth dentition moment a child can’t masticate. Mandible masticatory movements become more differentiated with milky teeth amount increasing. But ending adequate for swallowing alimentary piece forming occurs only up to 12-13 years (after primary teeth change to constant ones). In elderness alimentary piece forming time increasing occurs due to involuntary processes taking place in dental-maxillary system because of ageing.

Speech-forming begins its formation from 8-10 months and finishes till 2-3 years. Oral cavity organs and neuroendocrine apparatus state is a very essential for speech-forming. Because of growth of relative weight growth for professions delt with speech activity orthopedic dentistry problems became more directed to the significance of speech-forming adequate repair and speech behavior.

 

Lecture 4

Blood circulation and its regulation. Blood circulation and its regulation peculiarities in maxillar-facial region

 

Blood circulation and its regulation. Blood circulation main significance is organs and tissues blood supply. Blood, as it is well-known, performs its vital functions while its movement through vessels. Main force providing blood movements through vessels are heart periodic contractions.

Cardiac muscle like sceletal muscles possesses physiological features:

· excitability;

· conductance;

· contractility;

· automatism – this feature differs cardiac muscle from sceletal muscles and means the ability to be excited under impulses influences appearing in itself.

Heart muscle excitability is fluctuated in cardiac cycle different phases. If one put stimulus on heart in course of its contraction (systole) than cardiac muscle doesn’t answer to these irritations with contraction even if their force is bigger than threshold size because cardiac muscle is in absolute refracteveness phase. At the end of systole cardiac muscle excitability begins to restore – relative refractiveness phase. In course of this phase only superliminal (strong, higher than threshold one) stimulus can cause cardiac muscle contraction – extrasystole. More durable than usually pause occurs after extrasystole – so-called compensatory pause. It appears because next impulse appears in sinus node in the absolute refracteveness period of preliminary systole. Short phase of increased excitability – exhaltation phase comes after relative refracteveness period. It coincides cardiac muscle relaxation beginning (dyastole). In this period heart muscle answers to subliminal stimuli (lower than threshold). After exhaltation phase excitability restoration to origin size occurs. Heart work is performed with phases changings.

Heart activity phases. Heart work beginning is atriums systole. Right atrium contracts before left atrium on 0,01 sec because main pacemaker is in right atrium. Excitement spreading through heart begins from it. This phase duration is 0,1 sec. During atrium systole pressures in atriums are increased: in right – to 5-8 mm, in left – till 8-15 mm mercury col. Blood moves to atriums and it is accompanied by atrio-ventricular foramens closage. Ventricles systole takes place simultaneously (atriums are relaxed in that time). Ventricles systole duration is about 0,3 sec. Ventricles systole begins with asynchronic contraction phase. It lasts about 0,05 sec and is the process of excitement spreading and contraction through myocardium. Pressure in ventricles is practically constant. While further contraction when pressure in ventricles increases to the size sufficient to atrio-ventricular valves closage but insufficient to semilunar valves opening, isometric contraction phase occurs. Its duration is up to 0,03 sec. Sometimes these phases are united in one and are called by tension phase (0,05-0,08 sec). In this phase pressure in right ventricle increases up to 30-60 mm merc.col., in left one – up to 150-200 mm merc.col. Tension is increased (valves are closed) and muscular fiber length doesn’t change in course of asynchronic contraction. At the end of tension phase pressure provides semilunar valves opening and ventricle systole next phase is begun – of fast blood expulsion. In course of this phase which lasts from 0,05 to 0,12 sec, pressure reaches its maximal ziphras. Later pressure reduces up to 20-30 and 130-140 mm merc. col. in corresponding ventricles and this moment of their work is called slow blood expulsion. This ventricle systole phase duration is from 0,13 to 0,20 sec. Pressure is sharply reduced with its ending. Pressure is decreased rather slower in magistral arteries that provides later clapping of semilunar valves and prevent blood regurgitation. But it occurs in the moment when ventricle muscle begins its relaxation and their dyastole takes place. Space time from ventricles relaxation beginning to semilunar valves closage is first dyastole phase – protodyastolic. Next dyastole phase – tension reducing or isometric relaxation takes place. It is expressed at closed valves and lasts approximately 0,05-0,08 sec from the moment when pressure in atriums is higher than in ventricles (206 mm.merc.col.) that leads to atrio-ventricular valves opening after which blood comes in ventricle. First, it occurs quickly (for 0,05 sec) – ventricles fast filling with blood phase and then slowly (for 0,25 sec) - ventricles slow filling with blood phase. Uniterrupted blood coming from magistral veins both in atriums and in ventricles takes place at the beginning of this phase. And, finally, last phase of ventricles dyastole is their filling due to atriums systole (0,1 sec). If to sum ventricles systole and dyastole time than we will receive time corresponding to complete cardiac cycle which is 0,8 sec in adults. In course of heart work there is such moment when both atriums and ventricles together (simultaneousely) are in dyastole state. This heart work period is called heart pause the duration of which is 0,4 sec.

In course of systole heart pumps in blood circulation up to 70-100 ml of blood. This blood volume is known as systolic volume (SV). If SV multiply on heart contraction freaquency (HFC) we will receive minute volume (MV) of heart work the size of which is about 4,0-5,0 l.

Heart tones. These are sound phenomena by which heart work is accompanied by. Different heart structures fluctuations (of valves, muscles, vessel wall) are on the basis of their occurence. As any fluctuations, tones are characterized by intensivity (altitude), freaquency and duration. There are 2 clinical methods of their assessment: auscultation (hearing by sthethoscope) and graphical one – phonocardiography.

I-st tone – systolic – is lower and more prolonged, it occurs in atrio-ventricular valves region simultaneousely with ventricle systole beginning. Duration: 0,08-0,25 sec, freaquency – 15-150 Gz. Optimal place for auscultation: heart apex. Its reasons:

· atrio-ventricular valves closage and tension;

· heart cavity walls fluctuation in course of systole;

· ventricles musculature contraction.

II-nd tone – dyastolic – is higher and shorter. Its duration is 0,04-0,12 sec, freaquency – 500-1250 Gz. Optimal place for auscultation: second intercostal space on the right and on the left from sternum. Reason: semilunar valves fluctuation. Sometimes these fluctuations are so expressed that tone’s division into two is observed.

III-rd tone – ventricular gallop – is delt with ventricles muscular wall fluctuations at their stretches right after the second tone. It is sometimes called as tone of filling. It is most often auscultated or registrated on phonocardiogram (PCG) in children and sportsmen. One can hear it as a weak, muffled sound, the most comfortable place – on heart apex (when patient is lying) and sternum region (when he is standing).

IV-th tone – atrial gallop – is connected with atriums contraction when they fill actively ventricle with blood. It is auscultated seldom, more often it is registrated on phonocardiogram.

Registration and analysis of electrical potentials occuring in course of heart activity has received the widest spreading in clinical practice.

Electrocardiogram – is a curve, periodically repeated and reflecting heart excitation process spreading in course of time. Separate ECG elements have received their special names: denses, segments, intervals and complexes. Every ECG element reflects excitation process spreading through definite heart regions and has time (in seconds) and altitude (in mV) characteristics. ECG analysis independently from abduction (lead) is given on the bas eof denses study (P,Q,R,S,T), intervals (PQ, ST, TP, RR), segments (PQ, ST) and complexes (P – atrial and QRST – ventricular).

As cardiac cycle begins with atriums excitation the first dens on ECG – is dens P. It characterizes atriums excitement. Its ascendant part – of right, descendant - of left one. Its characteristics under norma: duration - from 0,07 to 0,11 sec, altitude - from 0,12 till 0,16 mV. It may be absent in III-rd standard lead (abduction), two-phased or negative. In V₁-V₂ - it is positive, V₃-V₄ - it is gradually increased. In one-poled abductions form extremities: aVR – it is negative, in aVL and aVF – positive.

Segment PQ – is a right line section on isoelectric axis from dens P end to dens Q beginning. It characterizes atrio-ventricular lack time and is about 0,04-0,1 sec.

Interval PQ - ECG locus from dens P beginning till dens Q beginning, it characterizes excitement distribution from atriums to ventricles. Its duration is 0,12-0,21 sec.

Dens Q – characterizes interventricular septum and papillar musculature excitement. Its duration under norma is from 0,02 till 0,03 sec, altitude – up to 0,1 mV. It may be absent in the I.

Dens R – characterizes main ventricles musculature excitement. Its altitude is 0,8-0,16 mV, duration – 0,02-0,07 sec. In thoracic abductions V₁-V₂ it is small, V₃-V₄ - it is increased, in V₅-V₆ it is reduced again.

Dens S – describes excitement in distant ventricles locuses. Its altitude reaches up to 0,01 mV and duration – up to 0,02-0,03 sec. It may be absent in I. In V₁-V₂ it is deep, then it is decreased, in V₅-V₆ it may be absent.

Segment ST - is a right line section on isoelectric axis from dens S end till dens T beginning and describes the moment when both ventricles are simultaneousely excited. Its duration is from 0,1 till 0,15 sec.

Dens T – describes myocardium repolarization process, it altitude is 0,4-0,8 mV, duration – 0,1-0,25 sec. In I it is always positive, in II - often positive and in III – may be positive, two-phased and negative. In V₁-V₂ it is negative sometimes, in aVF – usually negative.

Interval TP – characterizes common heart pause, its duration is 0,4 sec.

Interval R-R – characterizes complete cardiac cycle, its duration is 0,8 sec.

Complex P – atrial.

Complex QRST – ventricular.

As heart excitation begins from its base, than this region is a negative pole, apex region – positive one. Heart electromoving force (EMF) has its size and direction. EMF direction is considered to call heart electrical axis. In the most common cases it is located in parallel to heart anatomical axis (normogram). Direction of one or another dens on ECG reflects an integral vector direction. When vector is directed to heart apex, one can registrate positive (as for electrical axis) denses, if to the heart base - negative. Due to definite heart location in thorax and human body shape, electrical force lines occuring between excited and unexcited heart locus, are distributed unequally on body surface. If heart axis becomes horizontal (lying heart) than such situation is called left-gram, in a case of its vertical localization (hanging heart) – right-gram.