Cardiovascular System

1. Cardiovascular System Lecture 5 (part I-II) September 28, 2005 October 5, 2005 EXS 558 Dr. Moran

2. Major Cardiovascular Functions w Delivery (e.g., oxygen and nutrients) w w Transportation (e.g., hormones) w w Prevention (e.g., infection—immune function)

3. Just Some Facts • For an average person the heart pumps ~5L/min • With exercise programs the heart (cardiac muscle) can adapt as well

4. Heart

5. Myocardium – Cardiac Muscle w Thickness varies directly with stress placed on chamber walls. w w With vigorous exercise, the left ventricle size increases. w

6. Heart Function • At rest, the heart spends most of its time filling (60% - diastole) than expelling (40% - systole) • Following systole, the AV valves rapidly open and fill the ventricles up to 70-80% • The middle 1/3 of diastole has little filling and is known as diastasis

7. . Cardiac Output (Q) w . • Q = HR ´ SV • Varies considerably between people • Trained athletes have lower resting HR and higher SV (Table 4.1) Stroke Volume & Cardiac Output Stroke Volume (SV) w Volume of blood pumped per contraction w w End-systolic volume (ESV)—volume of blood in ventricle after contraction w SV = EDV – ESV

8. Ejection Fraction w Proportion of blood pumped out of the left ventricle each beat w • Averages 60% at rest

9. Calculation of SV, EF, and Q

10. Vascular System w Arteries w Arterioles • Capillaries • Creates a large surface area ideal for gas exchange w Venules w Veins Blood Flow controlled by the autonomic nervous system During REST  During EXERCISE 

12. Muscle Pump wBlood distribution matched to overall metabolic demands wAutoregulation— wExtrinsic neural control—sympathetic nerves within walls of vessels are stimulated causing vessels to constrict w

13. Blood Pressure w Systolic blood pressure (SBP: s=squeeze) is the highest pressure and diastolic blood pressure (DBP) is the lowest pressure w w MAP = DBP + [0.333 ´ (SBP – DBP)] w

14. w Autoregulation controls blood flow by vasodilation in response to local chemical changes in an area. (continued) Review Vascular System w Blood returns to the heart with the help of breathing, the muscle pump, and valves in the veins. w

15. Review (continued) w Extrinsic neural factors control blood flow primarily by vasoconstriction. w w Mean arterial pressure (MAP) is the average pressure on the arterial walls.

16. Blood Functions w Transports gas, nutrients, and wastes w w Buffers and balances acid base

17. Blood Volume Composition

18. Blood Formed Elements & Hematocrit Blood formed elements w White blood cells—protect body from disease organisms w w Red blood cells—carry oxygen to tissues with the help of hemoglobin Hematocrit • Ratio of formed elements to the total blood volume

19. Oxygen Transport • Oxygen transported in blood combined to hemoglobin (98%) or dissolved in plasma (2%) • Oxygen saturation affected by: 1.) 2.) 3.)

20. Bohr Effect

21. Erythropoietin (EPO) • Protein hormone produced by kidney • Medically used to treat anemia (chronic kidney failure) • Increase oxygen carrying capacity of blood • “Sludging” of blood VERY dangerous

22. . • Increases in HR and SV during exercise cause cardiac output (Q) to increase. . Cardiovascular Response to Acute Exercise • Heart rate (HR) increases as exercise intensity increases up to maximal heart rate. w w All result in allowing the body to efficiently meet the increased demands placed on it.

23. Heart Rate During Exercise • Initial increase b/c of withdrawal of parasympathetic input • Feedback from peripheral mechanical and chemical receptors

24. Stroke Volume During Exercise • Stroke volume changes are because of an increase in EDV • Suctioning Mechanism: • Frank-Starling Mechanism: with a greater volume of blood returning to the heart the ventricles become stretched and respond with a more powerful contraction

25. Cardiac Drift • Increase in HR and decrease in SV • Reason: greater % of blood flowing to skin to dissipate heat  lower EDV causes an increased HR

26. Arteriovenous Oxygen Difference • Rest  25% of O2 extracted from blood • Exercise  up to 75% of O2 extracted from blood (used by exercising muscles) • Fick Equation:

27. Cardiovascular Response to Training • Cardiac Output • Heart Rate • Cardiac Morphology • Table 4.2 (p. 52)

28. Cardiac Output • VO2 max increases due to 1.) Improved oxygen extraction 2.) Increased cardiac output 3.) Max HR NOT affected from training

29. Stroke Volume • Endurance-trained athletes have 60% greater SV • Enlarged left ventricular chamber • (eccentric hypertrophy)

30. Stroke Volume & Training

31. Changes in EDV, ESV, EF

32. Heart Rate • Decrease in resting HR • Highly trained endurance athletes may have resting heart rates of 30 to 40 beats/min

33. Heart Rate Recovery w w With training, heart rate returns to resting level more quickly after exercise w w Conditions such as altitude or heat can affect it w

34. Heart Rate Recovery (continued)

35. Blood Pressure • In hypertensive individuals, endurance exercise reduces both systolic and diastolic blood pressure (3-5x week; 30 min) • Conflicting results from the result of resistance training w

36. Blood Flow Increases With Training w Increased capillarization of trained muscles (higher capillary-to-fiber ratio) w w More effective blood redistribution—blood goes where it is needed w

37. wChanges in plasma volume are highly correlated with changes in SV and VO2max. . Blood Volume and Training wEndurance training, especially intense training, increases blood volume. w wRed blood cell volume increases, but increase in plasma volume is higher; thus, hematocrit decreases. w

38. Blood Volume and Training

39. Cardiac Morphology • Law of LaPlace: ventricular wall pressure is proportional to pressure and the radius of curvature (Ford 1976) • Adaptations from Exercise Programs • Endurance Athletes • Greater than normal left ventricular internal diameter • Resistance Athletes • Left ventricular mass 45% greater than age-matched sedentary controls • (Fleck 1988)

40. Differences in Heart Size Intraventricular septal thickness

41. Research Articles • The effect of acute aerobic exercise on stress related blood pressure responses: A systematic review and meta-analysis • Hamer et al. (2005) • Left Ventricular Mass Index and Sports: the influence of different sports activities and arterial blood pressure • Cubero et al. (2000)

42. Echocardiograph (ultrasound)

43. Research Design • Cross Sectional • collected all at the same time (“snapshot”) • Randomized Controlled Trial • Two groups • Treatment group  receives the treatment under investigation, • Control group 

44. VO2 Max Testing • Depends on testing protocol • Triathletes • cycling ergometer protocol will be 3-6% less than that seen in treadmill running, while swimming is 13-18% less (O'Toole and Douglas, 1995)