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.

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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.

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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]

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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.

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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

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Isometric exercise.

• Sustained muscle contraction.• Increase in peripheral resistance.• Systolic and diastolic pressure increase.• ? Yoga.

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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.]

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Hemorrhage.

• Loss of blood- reduced blood volume• Reduced venous return.• Reduced cardiac output.• Reduced blood pressure.• Heart rate increases before pressure

drops.

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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.

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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.

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Shock.

• Peripheral circulatory failure.• Emergency- if not recovered goes in

irreversible shock and death.• Causes:

– Hypovolemic– Cardiogenic.– Distributive. [anaphylactic or septic]– Neurogenic [pain, fear]