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Exercise and the Heart

Exercise and the Heart. Q increase is in direct proportion to the O2 demand of the muscles Heart Rate Stroke Volume Blood pressure Systolic Diastolic a-v O2 Difference. O2 Delivery. Redistribution of Blood Flow. Muscle blood flow to working skeletal muscle

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Exercise and the Heart

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  1. Exercise and the Heart

  2. Q increase is in direct proportion to the O2 demand of the muscles Heart Rate Stroke Volume Blood pressure Systolic Diastolic a-v O2 Difference O2 Delivery

  3. Redistribution of Blood Flow • Muscle blood flowto working skeletal muscle • Splanchnic blood flow to less active organs (Liver, kidneys, GI tract, etc.)

  4. Redistribution of Blood Flow During Exercise Fig 9.19 (c) 2004 The McGraw-Hill Companies, Inc. All rights reserved.

  5. Redistribution of Blood Flow

  6. Increased Blood Flow to Skeletal Muscle During Exercise • How? • Withdrawal of sympathetic vasoconstriction • Autoregulation • Blood flow increased to meet metabolic demands of tissue • Vasodilation:  O2 tension,  CO2 tension, pH, potassium, adenosine, nitric oxide

  7. Circulatory Responses to Exercise • Depend on: • Type, intensity, and duration of exercise • Environmental condition • Emotional influence

  8. Transition From Rest  Exercise and Exercise  Recovery • Rapid increase in HR, SV, cardiac output • Plateau in submaximal (below lactate threshold) exercise • O2 supply = O2 demand • Recovery depends on: • Duration and intensity of exercise • Training state of subject

  9. O2 supply = O2 demand Transition From Rest  Exercise  Recovery O2 supply < O2 demand

  10. Recovery • O2 supply > O2 demand • What is the extra oxygen used for? • Restore O2 inside muscles (myoglobin) • Removal of lactic acid • Reduce body temperature

  11. Incremental Exercise • Heart rate and cardiac output • Increases linearly with increasing work rate • Reaches plateau at 100% VO2max • Systolic blood pressure • Increases with increasing work rate

  12. Incremental Exercise • Stroke Volume • Reaches plateau at 40-60% VO2max • Why?

  13. Arm vs. Leg Exercise • At the same oxygen uptake arm work results in higher: • Heart rate • Due to higher sympathetic stimulation • Blood pressure • Due to vasoconstriction of large inactive muscle mass .

  14. Heart Rate and Blood Pressure During Arm and Leg Exercise

  15. Prolonged Exercise • Cardiac output is maintained • Gradual decrease in stroke volume • Gradual increase in heart rate • Cardiovascular drift • Due to dehydration and increased skin blood flow (rising body temperature) Fig 9.22 .

  16. HR, SV, and CO During Prolonged Exercise Fig 9.22

  17. Cardiovascular Adjustments to Exercise Fig 9.23

  18. Summary of Cardiovascular Control During Exercise • Initial signal to “drive” cardiovascular system comes from higher brain centers • Fine-tuned by feedback from: • Chemoreceptors • Mechanoreceptors • Baroreceptors Fig 9.24

  19. A Summary of Cardiovascular Control During Exercise Fig 9.24

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