This presentation describes the study conceptualization and design. The underlying physiology is conceptualized as a dynamical system, and resilience, as a property thereof. Resilience signatures will be grounded in dynamical data from multiple stress-response assessments; many other markers are being collected. We propose a data analytic strategy to build signatures, and evaluate their success predicting both short-and long-term responses to stressors, with both data- and theory-driven elements.
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The heart is a four-chambered gm semi-oval muscular organ composed of syncytial myocardium, innervated by the vagus nerve with a sino-atrial SA and a atrial ventricular AV node. The blood circulates through it by way of the pulmonary artery and aorta, carrying blood away from the ventricles, to the lungs and the systemic circulation, respectively, and two veins, the vena cava and pulmonary, carrying blood to the atria from the systemic circulation and lungs, respectively.
The coronary arterial supply is the left anterior and left circumflex artery, and posteriorly, the right coronary artery, supplied by the aorta. Much of the pathology has been referred to in the introduction, except for the molecular pathology of atherosclerosis, which has been well covered in this journal. The chambers are divided centrally by the interventricular septum, which is not completely closed in the blue-baby syndrome, which was repaired surgically by Helen Taussig and Richard Bing.
The piece that follows is primarily directed to the sympathetic innervation of the heart, variation in heart rate, and exercise or reaction to external threats. Some things that can cause a disruption of balance in integrated circulation, neural innervation, innate immune and hormonal response are:. The basis for the physiological distress has long been the primary basis for acupuncture, holistic and transcendental medicine, and stress management. A network of 15 maximal exercise testing facilities in four teaching hospitals, 10 private offices and clinics and an industrial medical department was organized in July to study prospectively the antecedents of myocardial infarction and sudden cardiac death.
Historical, physical and laboratory data were recorded on self-teaching printed forms, with normal, borderline and abnormal responses arranged in three columns. Analysis showed computer-averaged S-T segment responses were more consistent and reliable predictors than visual interpretations.
Cardiac manifestations in healthy men varled with age and risk assessment, and in patients with cardiovascular disease varied with diagnosis and natural history of disease. Many significant differences provided insights into mechanisms of impaired cardiac function in relation to type of clinical disease. Testing was responsible for one post-exertional cardiac arrest. Recovery was effected promptly by defibrillation; there was no mortality.
Of the many factors ultimately important in determining the cardiac output, the heart rate is certainly the easiest to measure. By analysis of the heart rate response to exercise in a variety of disease states we felt that the interrelationships of inotropic state, stroke volume, autonomic dysfunction, and myocardial disease could be clarified.
This paper reviews the normal and abnormal heart rate responses to exercise. The normal heart rate is determined by the frequency of depolarization of specialized cells within the sino-atrial node S-A node. The S-A node, the vestigal sinus venosus, lies in the posterior portion of the heart near the demarcation between the right atrium and the superior vena cava.
Unlike other myocardial cells, the specialized cells of the S-A node have a slow sodium channel and a low resting potential which give these cells their special property. The slowly rising diastolic depolarization stage four leads to a rhythmic slow rising action potential. The autonomic nervous system plays a key role in the regulation of heart rate Fig 1. The sympathetic nervous system input to the heart originates in a nucleus in the medulla oblongata.
Stimulation of this area with implanted electrodes results in increased heart rate and systemic vascular resistance due to increased sympathetic output. Axons from these nuclei descend to the sympathetic trunk via the intermediolateral columns of the spinal cord. From their synapses in cervical ganglia, postganglionic fibers directly innervate the atrial and ventricular musculature, the S-A node, and the A-V node.
The effector neurotransmitter is norepinephrine and the receptors are of the beta adrenergic type. There is evidence from competitive binding studies that the postganglionic fibers are predominantly associated with type I beta receptors. The parasympathetic influence to the S-A node and the myocardium originates from nuclei very near the origin of the sympathetic nerves.
From the motor nuclei of the vagus and the nucleus solitarius come fibers that form part of the vagus nerve. These fibers terminate at ganglia in the wall of the heart. The postganglionic cholinergic fibers end mostly near the S-A node and the A-V node; there is little evidence for the distribution of parasympathetic nerves to the ventricular myocardium although cholinergic muscarinic receptors have been characterized.
In normal conditions there exists a well balanced autonomic tone influencing the S-A node. There is a complex interrelation among many systems to determine the autonomic tone at the S-A node Fig 2. New York, Raven Press, There are cortical inputs to the medullary centers; for example, fear results in tachycardia by this pathway.
Visceral afferent inputs increase parasympathetic tone resulting in bradycardia. Several reflexes are present for homeostasis. For example, the baroreflex is important in sensing changes in blood pressure and increasing or decreasing the heart rate via autonomic influences at the S-A node to maintain appropriate cardiac output. Arterial mechanoreceptors of the carotid sinus and aortic arch respond to changes in arterial pressure and result in appropriate adjustment in the sympathetic and vagal outflow to the heart and resistance and capacitance vessels.
Although the importance of autonomic influence is well accepted in the usual cardioacceleration to exercise, the role of the recovery or deceleration of heart rate following exercise may not be influenced by autonomic input. Six men were studied after peak treadmill exercise. To assess the contribution of autonomic factors in heart rate recovery, the men were given atropine, propranolol, or both agents.
It was found that exponential cardio-deceleration occurred under each experimental condition. They concluded that heart rate recovery after exercise is regulated by changes in venous return mediated through atrial stretch receptors of pacemaker tissue. This study implies that deceleration depends primarily on factors intrinsic to the intact circulation that are independent of autonomic control.
The control of heart rate is complex; autonomic tone, central and peripheral reflexes, hormonal influences, and factors intrinsic to the heart are all important. Although easily measured, the heart rate reflects an integrated physiologic response. The physiologic response to exercise depends on the type of exercise performed; the two major types are isometric and isotonic.
Creating muscle tension with no movement against resistance is a pure form of isometric exercise; this results in increased muscle mass and strength.
Isotonic exercise is the repetitive, rhythmic movement of large muscle masses against little resistance, known also as dynamic or aerobic exercise. Although most activities involve degrees of both, running is predominantly dynamic, and weight lifting is predominantly isometric. Bezucha and colleagues investigated the cardiovascular responses to isometric static exercise leg extension and compared these to those observed during static-dynamic exercise one arm cranking and dynamic exercise leg cycling in normal men.
Cardiac outputs were raised in all three activities in a proportional manner: 6. Stroke volume did not significantly change in the static or combined static-dynamic exercises. The increases in cardiac output were primarily the result of increases in heart rate. This study demonstrates the predominant pressor response and modest cardio-acceleration of isometric exercise.
Longhurst and coworkers, examined the response to acute and chronic exercise in two groups of athletes who typify the two major types of exercise: long distance runners dynamic and weight lifters isometric. The runners responded to isometric exercise with lower double products than the weight lifters. The end-diastolic volume index evaluated by echocardiography in the runners was greater than control subjects both at rest and with exercise. Not only is the type of exercise an important determinant of acute physiologic response, but chronic static exercise results in physiologic responses that are no different from the responses of sedentary men.
Dynamic exercise, also called isotonic or aerobic, involves the rapid movement of large muscle masses that results in the need for the body to respond with increased ventilation to increase oxygen consumption.
Such exercise is called aerobic since it must be performed by using oxygen. The heart must increase its output and performs flow work rather than pressure work. The response to dynamic muscular exercise consists of a complex series of cardiovascular adjustments designed to:. This law states that resistance is proportional to pressure divided by flow. Peripheral resistance increases in the tissues that do not function in the performance of the ongoing exercise and decreases in active muscle.
The result is a decrease in systemic vascular resistance. While pressure only increases mildly, flow can increase by as much as five times during dynamic exercise. Since flow increases much more than pressure, the result is a decrease in systemic resistance. Another mechanical adaptation occurs when the increasing venous return dilates the left ventricle and cardiac function is enhanced via the Frank-Starling mechanism.
There is a highly predictable relationship between total body oxygen consumption and both the cardiovascular and respiratory responses to exercise Fig 4. The data was collected from 86 adult male and female subjects. B The linear relationship between cardiac output and oxygen uptake.
C The data was collected from 23 adult male and female subjects. C The linear relationship between minute ventilation and oxygen uptake. Reprinted with permission. Both parameters increase linearly with increasing oxygen consumption until maximal oxygen consumption is approached.
In summary, the type of exercise is an important determinant of both acute and chronic cardiovascular responses. Isometric exercise can be viewed as a pressure load and dynamic exercise as a volume load to the left ventricle.
The acute physiological adjustments to dynamic exercise include peripheral vasodilation in exercising muscle, neural mediated increases in sympathetic tone to the heart and the periphery, the release of catecholamines from the adrenal medulla, and changes in venous return due to mechanical and humoral factors.
A linear relationship exists between the consumption of oxygen and cardiac output and minute ventilation such that the work performed is highly correlated with the amount of blood pumped and the oxygen consumed.
An increase in heart rate is a major factor contributing to the exercise-induced increased cardiac output. Bowditch demonstrated that the time interval between beats is a determinant of the force of myocardial contraction. This has been called the frequency-force relationship Fig 5. A slow increase in isometric tension results from the change in rate implying in increased contractile state. Each vertical line represents an isometric contraction.
Reprinted with permission of W. Although the mechanism of this phenomenon is not known, it may have to do with calcium availability to contractile elements. Thus an increase in heart rate results in an increase in the force of contraction. Variations in clinical noninvasive systolic pressure at the point of symptom-limited exercise on a treadmill were examined in six groups of subjects: 5, men and women classified into three categories each.
Among the men, 2, were asymptomatic healthy, were hypertensive and 1, had clinical manifestations of coronary heart disease that is, typical angina pectoris, prior myocardial Infarction or sudden cardiac arrest with resuscitation.
Among the women, , and were in the corresponding clinical categories. None had had cardiac surgery; all had follow-up status ascertained by periodic mail questionnaires. Reported deaths were reviewed and classified by three cardiologists; deaths were attributed to coronary heart disease, of them in the men classified as having coronary heart disease.
The majority of maximal systolic blood pressure readings were reported to the nearest centimeter rather than millimeter of pressure. Retesting of persons from 1 to 32 months later showed that pressure values agreed within 10 percent in two thirds, the overall mean difference was only 8. Hypertensive patients had a significantly greater body weight than normotensive persons.
Cours de Biodiversité SVI S6 pdf
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The heart is a four-chambered gm semi-oval muscular organ composed of syncytial myocardium, innervated by the vagus nerve with a sino-atrial SA and a atrial ventricular AV node. The blood circulates through it by way of the pulmonary artery and aorta, carrying blood away from the ventricles, to the lungs and the systemic circulation, respectively, and two veins, the vena cava and pulmonary, carrying blood to the atria from the systemic circulation and lungs, respectively. The coronary arterial supply is the left anterior and left circumflex artery, and posteriorly, the right coronary artery, supplied by the aorta. Much of the pathology has been referred to in the introduction, except for the molecular pathology of atherosclerosis, which has been well covered in this journal. The chambers are divided centrally by the interventricular septum, which is not completely closed in the blue-baby syndrome, which was repaired surgically by Helen Taussig and Richard Bing. The piece that follows is primarily directed to the sympathetic innervation of the heart, variation in heart rate, and exercise or reaction to external threats. Some things that can cause a disruption of balance in integrated circulation, neural innervation, innate immune and hormonal response are:.
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