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Cardiovascular Adjustments Prof. K. Sivapalan Cardiovascular adjustment in exercise [isotonic]. • Skeletal muscles require more nutrients and produce more wastes and heat. • CVS, RS, and other systems has to adjust to meet the needs. • The muscles respond to impulses in motor nerves in any exercise: fight of flight. • The needs of muscles are met by various mechanisms. 2013 Regional Circulation 2 Nervous adjustments. • As the brain perceives the idea of exertion and starts planning appropriate movements, hypothalamus also becomes activated. • It activates the sympathetic system and inhibits parasympathetic system. • This brings anticipatory changes in heart and circulation. • These changes are reinforced when exertion begins through impulses from proprioceptors. 2013 Regional Circulation 3 Anticipatory changes. • • • • Heart rate and force increase. Blood pressure increases- systolic. Splanchnic, renal, coetaneous flow reduce. ? Vasodilatation in skeletal muscles. [vaso dilator nerves]. • Dilatation in coronary vessels but no change in cerebral flow. • Adrenal medulla and cortex increase secretions. [detail after study of endocrines] 2013 Regional Circulation 4 Changes due to muscle action. • Muscle pump increases venous return and the cardiac output. • Metabolites cause local vasodilatation. Other effects: • Increased heat stimulates thermoregulatory center and causes coetaneous vasodilatation. • Respiratory pump. • Increased oxygen extraction. 2013 Regional Circulation 5 Net circulatory changes. • • • • • • • • • Increased heart rate and force of contraction. Increased end-diastolic volume. Decreased end-systolic volume. Increased cardiac output. Muscular, skin and coronary vasodilatation. No significant change in cerebral flow. All other places- vasoconstriction. Slightly decreased peripheral resistance. Increased systolic and decreased diastolic pressure 2013 Regional Circulation 6 Isometric exercise. • • • • Sustained muscle contraction. Increase in peripheral resistance. Systolic and diastolic pressure increase. ? Yoga. 2013 Regional Circulation 7 Effects of training. • • • • • • • Inrease in stroke volume. Decrease pulse rate. Quick return to basal valuse after exercise. Reduced coagulability. Healthy vessels. Muscle and bone development. [Feeling better.] 2013 Regional Circulation 8 Hemorrhage. • • • • • Loss of blood- reduced blood volume Reduced venous return. Reduced cardiac output. Reduced blood pressure. Heart rate increases before pressure drops. 2013 Regional Circulation 9 Compensation to hypovolemia. • Anxiety and excitement stimulate sympathetics and adrenals. • Reduced stretch of baro receptors: – Less inhibition to VMC. – Less stimulation to CIC. • Renal compensation- renin – angeotensin – aldesteron. • Tissue fluid dynamics. 2013 Regional Circulation 10 Severe hemorrhage. • Moderate loss- as in blood donation: – Effective compensation by mobilizing venous reservoir. • If unable to compensate: – – – – – – 2013 Circulation mainly to vital organs. Severe peripheral vaso constriction. Tachycardia. Reduced pulse pressure – thready pulse. Reduced tissue fluid. Prolong reduced perfusion – acidosis. Regional Circulation 11 Shock. • Peripheral circulatory failure. • Emergency- if not recovered goes in irreversible shock and death. • Causes: – Hypovolemic – Cardiogenic. – Distributive. [anaphylactic or septic] – Neurogenic [pain, fear] 2013 Regional Circulation 12