Cardiovascular Adjustments
Prof. K. Sivapalan
2013 Regional Circulation 2
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 3
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 4
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 5
Changes due to muscle action.
• Muscle pump increases venous return and the cardiac output.
• Metabolites cause local vasodilatation.Other effects:• Increased heat stimulates thermo-
regulatory center and causes coetaneous vasodilatation.
• Respiratory pump.• Increased oxygen extraction.
2013 Regional Circulation 6
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 7
Isometric exercise.
• Sustained muscle contraction.• Increase in peripheral resistance.• Systolic and diastolic pressure increase.• ? Yoga.
2013 Regional Circulation 8
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 9
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 10
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 11
Severe hemorrhage.
• Moderate loss- as in blood donation:– Effective compensation by mobilizing venous
reservoir.
• If unable to compensate:– Circulation mainly to vital organs.– Severe peripheral vaso constriction.– Tachycardia.– Reduced pulse pressure – thready pulse.– Reduced tissue fluid.– Prolong reduced perfusion – acidosis.
2013 Regional Circulation 12
Shock.
• Peripheral circulatory failure.• Emergency- if not recovered goes in
irreversible shock and death.• Causes:
– Hypovolemic– Cardiogenic.– Distributive. [anaphylactic or septic]– Neurogenic [pain, fear]