PHYSIOLOGICAL BASES OF EMOTIONS, MENTAL AND PHYSICAL WORK
Emotions have both mental and physical components. They involve cognition, an awareness of the sensation and usually its cause; affect, the feeling itself; conation, the urge to take action; and physical changes such as hypertension, tachycardia, and sweating. The hypothalamus and limbic systems are intimately concerned with emotional expression and with the genesis of emotions.
This chapter reviews the physiologic basis of emotion, sexual behavior, fear, rage, and motivation. It also considers the relation of major neurotransmitter systems in the brain to these processes.
The term limbic lobe or limbic system is applied to the part of the brain that consists of a rim of cortical tissue around the hilum of the cerebral hemisphere and a group of associated deep structures—the amygdala, the hippocampus, and the septal nuclei. The region was formerly called the rhinencephalon because of its relation to olfaction, but only a small part of it is actually concerned with smell.
The limbic cortex is phylogenetically the oldest part of the cerebral cortex. Histologically, it is made up of a primitive type of cortical tissue called allocortex, which in most regions has only three layers and surrounds the hilum of the hemisphere. There is a second ring of transitional cortex called juxtallocortex between the allocortex and the neocortex. It has three to six layers and is found in regions such as the cingulate gyrus and the insula. The cortical tissue of the remaining nonlimbic portions of the hemisphere is called neocortex. It generally has six layers and is the most highly developed type. The actual extent of the allocortical and juxtallocortical areas has changed little as mammals have evolved, but these regions have been overshadowed by the immense growth of the neocortex, which reaches its greatest development in humans.
Afferent & Efferent Connections
The fornix connects the hippocampus to the mamillary bodies, which are in turn connected to the anterior nuclei of the thalamus by the mamillothalamic tract. The anterior nuclei of the thalamus project to the cingulate cortex, and from the cingulate cortex there are connections to the hippocampus, completing a complex closed circuit. This circuit was originally described by Papez and has been called the Papez circuit.
Correlations Between Structure & Function
One characteristic of the limbic system is the paucity of the connections between it and the neocortex. However, from a functional point of view, neocortical activity does modify emotional behavior and vice versa. On the other hand, one of the characteristics of emotion is that it cannot be turned on and off at will.
Another characteristic of limbic circuits is their prolonged after-discharge following stimulation. This may explain in part the fact that emotional responses are generally prolonged rather than evanescent and outlast the stimuli that initiate them.
LIMBIC FUNCTIONS
Stimulation and ablation experiments indicate that in addition to its role in olfaction, the limbic system is concerned with autonomic responses. Along with the hypothalamus, it is also concerned with sexual behavior, the emotions of rage and fear, and motivation.
Limbic stimulation produces autonomic effects, particularly changes in blood pressure and respiration. These responses are elicited from many limbic structures, and there is little evidence of localization of autonomic responses. This suggests that the autonomic effects are part of more complex phenomena, particularly emotional and behavioral responses.
Aminergic Systems in the Brain
There are four large aminergic systems in the brain that have in common the presence of their cell bodies in relatively few locations with multiple branched axons projecting to almost all parts of the nervous system. These are the serotonergic, noradrenergic, adrenergic, and histaminergic systems. Dopaminergic neurons have their cell bodies in more locations, but their axons also project to many different areas.
Serotonin
Serotonin-containing neurons have their cell bodies in the midline raphe nuclei of the brain stem and project to portions of the hypothalamus, the limbic system, the neocortex, the cerebellum, and the spinal cord.
The hallucinogenic agent lysergic acid diethyl-amide (LSD) is a serotonin agonist that produces its effects by activating 5-HT2 receptors in the brain. The transient hallucinations and other mental aberrations produced by this drug were discovered when the chemist who synthesized it inhaled some by accident. Its discovery called attention to the correlation between behavior and variations in brain serotonin content. Psilocin, a substance found in certain mushrooms, and N,N-dimethyltryptamine (DMT) are also hallucinogenic and, like serotonin, are derivatives of tryptamine.
Norepinephrine
The cell bodies of the norepinephrine-containing neurons in the brain are located in the locus ceruleus and other nuclei in the pons and medulla. From the locus ceruleus, the axons of the noradrenergic neurons form the locus ceruleus system. They descend into the spinal cord, enter the cerebellum, and ascend to innervate the paraventricular, supraoptic, and periventricular nuclei of the hypothalamus, the thalamus, the basal tel-encephalon, and the entire neocortex. From cell bodies in the dorsal motor nucleus of the vagus, the nucleus of the tractus solitarius, and areas in the dorsal and lateral tegmentum, the axons of the nor-adrenergic neurons form a lateral tegmental system that projects to the spinal cord, the brain stem, all of the hypothalamus, and the basal telencephalon. The ascending fibers from the locus ceruleus form the dorsal noradrenergic bundle, whereas the ascending fibers of the lateral tegmental system form the ventral nor-adrenergic bundle.
There is a system of phenylethanolamine-N-methyltransferase (PNMT)-containing neurons with cell bodies in the medulla that project to the hypothalamus. Those neurons secrete epinephrine, but their function is uncertain. Epinephrine-secreting neurons also project to the thalamus, periaqueductal gray, and spinal cord. There are appreciable quantities of tyramine in the CNS, but no function has been assigned to this agent.
Dopamine
There are many dopaminergic systems in the brain. It is convenient to divide them into ultrashort, intermediate, and long systems on the basis of the length of their axons. The ultrashort dopaminergic neurons include the cells between the inner nuclear and the inner plexiform layers in the retina and the periglomerular cells in the olfactory bulb. Intermediate-length dopamine cells include the tuberoinfundibular system, which secretes the dopamine into the portal hypophysial vessels that inhibits prolactin secretion, the incertohypothalamic system, which links the hypothalamus and the lateral septal nuclei, and the medullary periventricular group of neurons scattered along the walls of the third and fourth ventricles. The long dopamine systems are the nigro-striatal system, which projects from the substantia nigra to the striatum and is involved in motor control, and the mesocortical system, which projects from the midbrain tegmentum to the limbic and frontal cortex and the olfactory tubercle, the nucleus accumbens, and related limbic subcortical areas. Recent studies by PET scanning iormal humans show that there is a steady loss of dopamine receptors in the basal ganglia with age. The loss is greater in men than in women.
Histaminergic neurons have their cell bodies in the tuberomamillary nucleus in the ventral portion of the posterior hypothalamus. The axons of these neurons project to all parts of the brain. The function of this diffuse histaminergic system is unknown, but there is evidence linking brain histamine to arousal, sexual behavior, blood pressure, drinking, pain thresholds, and regulation of the secretion of several anterior pituitary hormones.
Acetylcholine
Acetylcholine is distributed throughout the CNS, with high concentrations in the cerebral cortex, thalamus, and various nuclei in the basal forebrain. The distri- bution of choline acetyltransferase and acetylcholinesterase parallels that of acetylcholine. Most of the acetylcholinesterase is ieurons, but some is found in glia. Pseudocholinesterase is found in many parts of the CNS. There are nicotinic and muscarinic cholinergic receptors of various types in the brain. There are multiple nicotinic cholinergic subunit genes, and the proteins they code make up pentameric heterodimers of varying composition. In the brain, there are both postsynaptic and presynaptic nicotinic cholinergic receptors, and their composition varies from place to place.
There are three types of opioid peptide-secreting neurons in the brain that produce one of the three opioid peptide precursor molecules. There are in addition two endomorphins whose precursors are as yet unknown. Proenkephalin-producing neurons are scattered throughout the brain, whereas pro-opiomel-anocortin-producing neurons have their cell bodies in the arcuate nuclei and project to the thalamus and parts of the brain stem. Prodynorphin-producing neurons are located primarily in the hypothalamus, limbic system, and brain stem. The peptides they secrete are involved in various functions including, presumably, the phenomenon of tolerance and addiction produced by morphine, but the details are uncertain.
Notion “emotions”
Emotions are aspect of higher nervous activity that characterize subjective attitude of person to various stimuli arousal in surroundings. Emotional status reflects actual needs of man and helps in its realization.
Humans’ subjective experience is often that emotions are clearly recognizable in ourselves and others. This apparent ease of recognition has led to the identification of a number of emotions that are said to be basic, and universal among all people. However, a recent debate among experts in the field has questioned this understanding of what emotions are. There has been recent discussion of the progression on the different views of emotion over the years
On “basic emotion” accounts, activation of an emotion, such as anger, sadness, or fear, is “triggered” by the brain’s appraisal of a stimulus or event with respect to the perceiver’s goals or survival. In particular, the function, expression, and meaning of different emotions are hypothesized to be biologically distinct from one another. A theme common to many basic emotions theories is that there should be functional signatures that distinguish different emotions: we should be able to tell what emotion a person is feeling by looking at his or her brain activity and/or physiology. Furthermore, knowledge of what the person is seeing or the larger context of the eliciting event should not be necessary to deduce what the person is feeling from observing the biological signatures.[2]
On “constructionist” accounts, the emotion a person feels in response to a stimulus or event is “constructed” from more elemental biological and psychological ingredients. Two hypothesized ingredients are “core affect” (characterized by, e.g., hedonic valence and physiological arousal) and conceptual knowledge (such as the semantic meaning of the emotion labels themselves, e.g., the word “anger”). A theme common to many constructionist theories is that different emotions do not have specific locations in the nervous system or distinct physiological signatures, and that context is central to the emotion a person feels because of the accessibility of different concepts afforded by different contexts.[4]
Classification of emotions
According to subjective status there are positive and negative emotions. Negative emotions are sthenic (aggression, affect) that stimulate human activity and asthenia (horror, sadness, depression) that inhibit behaviour. Lower or elementary emotions are caused by organic needs of man or animal as hanger, thirst and survival, so on). In humans even lover emotions undergo to cortical control and are brining up. Social, historical and cultural customs cause also formation of higher emotions that regulates public and private relations in society. Higher emotions appear due to consciousness and may inhibit lower emotions.
Appearance of emotions in ontogenesis.
Iewborns emotions of horror, anger, pleasure, are revealed just after birth. Hunger, pain, getting cool, wet bedclothes cause iewborn child negative emotions with grimace of suffering and crying. Suddeew sound or loss equilibrium causes horror and loss of free movement causes anger. Final formation of human emotions develops gradually with maturation of nervous and endocrine regulatory systems and needs up brining.
Biological importance of emotions
Emotions are important element of human behaviour, creation of conditioned reflexes and mentation. Negative emotions give fusty evaluation of current situation does it useful or not. Mobilizing of efforts helps then to satisfy current needs of person. Positive emotions help to put in memory scheme of behaviour, which was useful and have lead to success.
Animal experiments have shown that a sensory experience causing neither reward nor punishment is remembered hardly at all. Electrical recordings from the brain show that newly experienced types of sensory stimuli almost always excite wide areas in the cerebral cortex. But repetition of the stimulus over and over leads to almost complete excitation of the cortical response, if the sensory experience does not elicit a sense or either reward or punishment. That is, the animal becomes habituated to the sensory stimulus and thereafter ignores it. If the stimulus causes either reward or punishment rather then indifference, the cortical response becomes progressively more and more intense during repeated stimulation, and the response is said to be reinforced. An animal builds up strong memory traces for sensation that are either rewarding or punishing but, conversely, develops complete habituation to indifferent sensory stimuli.
External manifestations of emotions are revealed in motor acts, effects of autonomic and endocrine regulation. Motor manifestations of emotions are mimic, gesticulation, body posture and walk. Emotional excitation usually is followed by autonomic reactions as blush, dilation of pupils; increase of arterial pressure, rate of heartbeat and breathing. Level of catecholamines in blood and 17-oxycetosteroides in urine rises also. Positive emotion may activate parasympathetic division of autonomic nervous system. Severe emotional excitation may result in visceral disorders because of circulatory disturbances and excess hormones in blood.
Nerve substrate of emotions
Several limbic structures are particularly concerned with the affective nature of sensory sensations – that is whether the sensations are pleasant or unpleasant. The major rew3ard centres have been found to be located along the course of the medial forebrain bundle, especially in the lateral and ventromedial nuclei of the hypothalamus. Less potent reward centres are found in the septum, amygdala, certain areas of the thalamus, basal ganglia, and extending downward into the basal tegmentum of the mesencephalon. The most potent areas for punishment and escape tendencies have been found in the central grey area surrounding the aqueduct of Sylvius in the mesencephalon and extending upward into the periventricular zones of the hypothalamus and thalamus. Less potent punishment areas are found in some locations in the amygdala and the hippocampus. Electrical recording from the brain show that newly experienced types of sensory stimuli almost excite areas in the cerebral cortex.
Theories of emotions
Biological theory of emotions (P.K. Anochkin) considers that life course includes two main stages of behavioural act: 1) formation of needs and motivations that results from negative emotions and 2) satisfaction of needs that leads to positive emotions it case of complete accordance of image and result of action. Incomplete compliance of suspected and real result of action cause negative emotions and continues behavioural act.
Information theory of emotions (P.V. Simonov)considers that emotions reflect strength human of need and possibility of its satisfaction in current moment. In absence of needs emotions can’t arise. There is also not emotional excitation, if getting excess information about mode of satisfaction this need. Lac of information already causes negative emotions that help to recall to mind life experience and to gather information about current situation.
Emotions exert anincredibly powerful force on human behavior. Strong emotions can cause you to take actions you might not normally perform, or avoid situations that you generally enjoy. Why exactly do we have emotions? What causes us to have these feelings? Researchers, philosophers, and psychologists have proposed a number of different theories to explain the how and why behind human emotions.
In psychology, emotion is often defined as a complex state of feeling that results in physical and psychological changes that influence thought and behavior. Emotionality is associated with a range of psychological phenomena including temperament, personality, mood and motivation. According to author David G. Meyers, human emotion involves “…physiological arousal, expressive behaviors, and conscious experience.”
The major theories of motivation can be grouped into three main categories: physiological, neurological, and cognitive. Physiological theories suggest that responses within the body are responsible for emotions. Neurological theories propose that activity within the brain leads to emotional responses. Finally, cognitive theories argue that thoughts and other mental activity play an essential role in the formation of emotions.
The James-Lange Theory of Emotion
The James-Lange theory is one of the best-known examples of a physiological theory of emotion. Independently proposed by psychologist William James and physiologist Carl Lange, the James-Lange theory of emotion suggests that emotions occur as a result of physiological reactions to events.
According to this theory, you see an external stimulus that leads to a physiological reaction. Your emotional reaction is dependent upon how you interpret those physical reactions. For example, suppose you are walking in the woods and you see a grizzly bear. You begin to tremble and your heart begins to race. The James-Lange theory proposes that you will interpret your physical reactions and conclude that you are frightened (“I am trembling, therefore I am afraid”).
The Cannon-Bard Theory of Emotion
Another well-know physiological theory is the Cannon-Bard theory of emotion. This theory states that we feel emotions and experience physiological reactions such as sweating, trembling and muscle tension simultaneously. More specifically, it is suggested that emotions result when the thalamus sends a message to the brain in response to a stimulus, resulting in a physiological reaction.
Schachter-Singer Theory
Also known as the two-factor theory of emotion, the Schachter-Singer Theory is an example of a cognitive theory of emotion. This theory suggests that the physiological arousal occurs first, and then the individual must identify the reason behind this arousal in order to experience and label it as an emotion.
Neurotransmission of emotional excitation
Emotional excitation is spread in the brain due to variety of neurotransmitters (noradrenalin, acetylcholine, serotonin, dopamine and neuropeptides including opioides. Positive emotions may be explained by revealing catecholamines and negative emotions, aggression result from production acetylcholine in the brain. Serotonin inhibits both kinds of emotions. Decrease of serotonin in blood is followed by groundless anxiety and inhibition of noradrenergic transmission results in sadness.
Structure of behavioural act
According to theory of functional systems (Anochking) there are such stages of behavioural act: 1) afferent synthesis; 2) taking of decision; 3) acceptor of result of action; 4) efferent synthesis (or programming of action); 5) performing of action; 6) evaluation of final result of action. Due to converging and processing of both sensory information and memory traces afferent synthesis in the brain is performed. Taking of decision is based on afferent synthesis by choosing optimal variant of action.
Neuronal mechanisms of behaviour.
In the very lowest animals olfactory cortex plays essential roles in determining whether the animal eats a particular food, whether the smell of a particular object suggest danger, and whether the odour is sexually inviting, thus making decisions that are of life-or-death importance. The hippocampus originated as part of olfactory cortex. Very early in the evolutionary development of the brain, the hippocampus presumably becomes a critical decision-making neuronal mechanism, determining the importance of the incoming sensory signals. Once this critical decision-making capability had been established, presumably the remainder of the brain began to call on it for the same decision making. Therefore, if the hippocampus says that a neuronal signal is important, the information is likely to be committed to memory. Thus, a person rapidly become habituated to indifferent stimuli but learns assiduously any sensory experience that causes either pleasure or pain. It has been suggested that hippocampus provides the drive that causes translation of short-term memory into long-term memory.
Adaptation as a process
Adaptation is process of adjustment of body functions to surrounding conditions or some new level of activity, which is carried out through human’s life. For instance there is adaptation to outer temperature, oxygen supply, physical load, emotional pressure, rate of activity, light conditions, so on. People, who live in different Earth regions differ one to each other to functional peculiarities of their organisms, bat have similar body structure. This is adaptation to climate as complex of various outer conditions. Stress syndrome explains main regularities of adaptation as physiological process. Low intensity of stress factors cause improvement of workability iew conditions. Extreme strength of stress factors causes distress that may result in pathological disorders in body functions.
Stages of adaptive process
Changing in outer conditions may causer adjustment of function of one organ, for instance rising of mass of the heard in chronic increase of blood return to the heart. Adaptation to high altitude or new climate causes functional and morphological changes in entire body. New outer conditions mobilize homeostatic mechanisms.
Energetic resources of cells are activated at first and plastic changing are of second order. So, first stage is urgent adaptation or alarm stage. It’s performed due to mobilizing of functional reserves of organs and their systems like increase of stroke volume in heart, tidal volume in lungs, so on. Usual level of organs activity at rest consist 1/6 – 1/10 part of potential activity. Increase of functional activity of organ or their systems requires rising of metabolic rate and oxygen consumption. Sympatho-adrenal regulatory system controls these ergotropic reactions of the human organism. Such kind of regulatory effects last not long.
Second stage of adaptation is morphological that is named stage of resistance also. In case of repeated action of all new conditions as physical load or high altitude, so on, structural reorganization of functioning cells occur. For example in regular hard physical exercises rises quantity of contractile elements in muscle cell and number of cells in motor units.
Cross-adaptation
When adaptive processes are not considerable, besides adjustment to some special factors, general body adaptation occurs. For instance, adaptation to physical exercises is followed by high resistance to cold, hypoxia and bad weather. Such a condition is named as cross-adaptation. Factually this is side effect of stimulation of sympathetic system and metabolic supply as a result. Cross-adaptation is possible mainly for factors, which require increased activity of similar organ system and regulatory mechanisms.
Individual peculiarities of adaptation
Adaptive processes in different people use similar regulatory systems, bat everybody has some peculiarities of physiological functions. It depends on hereditary and acquired fitches. For example people, who have grater activity of parasympathetic regulation, comparing to sympathetic, are more resistible to extreme factors of surroundings. There is correspondence: grater volume of functional reserves in the human body, the easier adaptation to outer conditions. Physical exercises, tempering of the body, using special plant extracts are used to increase adaptability of a person.
Loss of adaptation and readaptation
After development of morphological adaptation to certain kind of outer conditions human organism keeps this ability for a long time. There are various duration of adaptive changing in different organs. In case of repeated action of the same set of conditions adaptive abilities may be renewed and are developed rapidly. This is readaptation. Very often effort for adaptation may course functional and morphologic disorders in the body. This is loss of adaptation.
Age peculiarities of adaptation
In early age adaptive processes are performed more rapid then in aged persons. In children regulatory systems of the body are not maturated yet. So, both high reactivity and low resistance to stress occur. For instance, newborn children are very sensitive to change of outer temperature that may lead to deep functional disorders. In old age functional reserves of most important organ systems like circulatory or respiratory get decreased. Low activity of hormonal regulation in aged persons also occurs. So, both urgent and morphologic adaptation gets worse in old age.
Physiology of work
General characteristic of mental work
Mental work is kind of activity, which provides receiving and processing of information by a person. It needs activation of attention, memory, thinking and emotional control also. Mental work produces great activation of central nervous system, mostly cortical areas and subcortical centers, which provide functioning of second signal system.
Work of operator includes professions, which require machining control of some technologic processes. This work gives great load to attention, thin motions of arms and static contraction of large muscles for keeping the certain body posture. Work of official includes leadership of factories, companies and hospitals so on. This work requires processing of great volume of information, taking complex decision in lack of time and high responsibility for result of work. Modern official have to keep in memory large volume of professional information be good in social relations and muster a lot of professional skills. Creative work is one of most complex forms of human activity, as work of artist, scientist so on. Work of physician includes communication with patients, taking decision of high responsibility in lack of information and performing of complex medical manipulations. So, physician have to master a lot of professional information, practical skills, know people psychology and be high responsible for his action. Work of students includes processing and storage in long-term memory great volume of information. It requires high activity of cortical areas, which provide attention, perception, memory and thinking. Passing exams, without proper learning before, may produce a stress for the student with all following functional disorders.
Workability and tiredness in course of mental work
Main functional mechanism, which explains mental work is producing dominant center in the brain. Different areas in the brain when performing mental work act independently bat are interconnected functionally for performing common task. Analyzer systems provide income of information, and associative areas help in its processing. During mental activity the more complex task is solved, the greater quantities of brain centers get synchronization of their activity. For performing mental work autonomic and emotional reactions, which provide activation of attention and memory, occur. Activity of sympathetic system and adrenalin production helps in proper metabolic supply of central neurons. Long lasting mental work may result in tiredness, inhibition of thinking and memory process, decrease of attention, incomplete coordination of movements and some functional circulatory disorders in viscera.
Age specialties of central regulatory mechanisms cause different workability in young and old persons, comparing to adults. In children tiredness because of slight inhibitory process develops rather quickly. They can’t keep attention in the same subject for along time. It’s caused by not perfect maturation of central neurons and incomplete myelinisation of all conductive pathways in the brain. In old age both metabolic rate of neurons and synthesis of neurotransmitters decreases. Some quantity of neurons dies in life course. So, close nerve cells take their function. In old age mental work may lead to severe autonomic and emotional reactions. For example, stimulation of heart activity in mental work may result in disorders of heart function.
Daily, week and year cycle of mental workability
Mental work is most effective in regular regimen of work and rest. The phenomena of dynamic stereotype underlie many behavioral reactions of the person, and also speech, labor, professional, musical, sports and other skills of the person. In conditions of a dynamic stereotype activity of the person occurs much more effectively, saving regulatory systems of an organism. Therefore principle of dynamical stereotype may be used for organization of a mode of day in medical, educational, children’s establishments. The same principle is useful the individual organization of labor activity. It is more usable to build this dynamic stereotype according to biologic rhythms of a person – day, week and year cycles of activity.
Functional peculiarities of central nervous system when performing mental work
Keeping of high mental workability requires autonomic control of metabolic supply in the brain, which is necessary for proper excitability of nerve cells. Intensive blood circulation ierve centers is possible due to redistribution of blood. Activity of sympathetic-adrenal and hypothalamo-hypophisial systems rises considerably. Positive effect causes only not long duration of emotional excitation. Stimulation of adrenal glands provides high level of glucose and free fatty acids in blood. Arterial pressure rises. Long lasting mentation and emotional pressure leads to unwanted result. For instance ECG failure is reveled.
Notion about Physical exercises
Exercise is associated with very extensive alterations in the circulatory and respiratory system. If some of the extremes of exercise were continued for even moderately prolonged periods, it may act as stressor. Main systems, which help to keep high level of physical activity, are phosphocreatine-creatine system, the glycogen-lactic acid system and aerobic system. In addition to large usage of carbohydrates by the muscles during exercise, especially during early stage of exercise, muscles use large amount of fat for energy in the form of fatty acids and acetoacetic acid. They use also to a much less extent proteins in the form of amino acids. Ability to training depends on genetic peculiarities of the organism.
Main kinds of work activity
1) hard physical load – not mechanizing work that is low effective and causes hard efforts, produce severe load to circulatory and respiratory system; 2) mechanizing work – decrease role of large body muscles, but give load to small muscles (arms and fingers), requires exact and rapid movements, complex program of action requires special skills and knowledge; 3) conveyer – requires also synchronizing of work in people group, produce monotone load and so increases pressure to central nervous system; 4) partial mechanizing of work, driving and control of machine requires rapid reaction and taking decision; 5) control of machine using electronic monitoring – produce load mostly to central nervous system, because requires high sensory attention, using special knowledge and taking correct and rapid decision.
Condition before starting exercises
Before starting well known exercises stimulation of appropriate regulatory systems occur. This causes preparing the organism for future physical activity. For instance increase of heart beat rate, breathing and gas transport are revealed. Activation of sympathetic nervous system and adrenal glands provide it. Repeated occurrence of all these conditions helps to produce conditioned reflex to time of the day, kind of work or surrounding situation.
Rising workability
After starting the exercises activity of muscles rises rather quickly – after 4-5 sec. Excitation of central nervous system and neurotransmission take this time. After 20-30 sec due to somato-visceral reflexes stimulation of breathing occurs, but perfect correspondence of lung ventilation to metabolic needs appears only after some minute. Rising of heart beat rate and stroke volume provide proper intensity of blood supply after 3-5 min. Time of development of high workability during exercises depends on previous training and hereditary fitches of the organism.
High workability
There is correspondence: the harder physical load, the shorter time of high workability. It depends on previous training and hereditary fitches of the organism also. Functional processes, which provide high intensity of exercises, are muscle blood flow and metabolic supply, systemic circulatory changes, temperature regulation.
Tiredness after exercises
Tiredness in physical exercises has some reasons – decrease of metabolic reserves in muscle cells, exhaustion of neurotransmitters ierve cells, excess of metabolic products in blood and tissues, defensive inhibition in central nervous system, so on.
Recovery after exercises
There are two effects of tiredness – training that helps to increase workability and severe chronic tiredness that lead to functional disorders and disease. The result depends on correspondence between exhaustion of functional reserves of the organism and activity of recovery processes. For recovery status of central nervous system is important. Active rest means change of kind of activity. This helps to create the new dominant focus in the brain that causes centers, which are tired from previous activity, to inhibit impulsation and get rest. Aging process decreases both physical and mental workability.
