The Cardiovascular System and Exercise

1. The Cardiovascular System and Exercise Chapter 10

2. Major Cardiovascular Functions • Delivers oxygen to active tissues • Aerates blood returned to the lungs • Transports heat, a byproduct of cellular metabolism, from the body’s core to the skin • Delivers fuel nutrients to active tissues • Transports hormones, the body’s chemical messengers

5. conduction of the heart SA and AV node Valves - MATP

7. The Heart and the Circulatory System Check out the link

8. Peripheral Vasculature • Arteries • Provides the high-pressure tubing that conducts oxygenated blood to the tissues • Capillaries • Site of gas, nutrient, and waste exchange • Veins • Provides a large systemic blood reservoir and conducts deoxygenated blood back to the heart

10. How does blood pool in the legs?

11. A Significant Blood Reservoir • The veins do not merely function as passive conduits • At rest, the venous system normally contains about 65% of total blood volume • Hence, veins serve as capacitance vessels or blood reservoirs

12. Blood Pressure • Systolic blood pressure • Highest arterial pressure measured after left ventricular contraction (systole) • e.g., 120 mm Hg • Diastolic blood pressure • Lowest arterial pressure measured during left ventricular relaxation (diastole) • e.g., 80 mm Hg

15. Hypotensive Recovery Response • After a bout of sustained light- to moderate-intensity exercise, systolic blood pressure temporarily decreases below pre-exercise levels for up to 12 hours in normal and hypertensive subjects

16. Myocardial Oxygen Utilization • At rest, the myocardium extracts 70 to 80% of the oxygen from the blood flowing in the coronary vessels • Because near-maximal oxygen extraction occurs in the myocardium at rest, increases in coronary blood flow provide the only means to meet myocardial oxygen demands in exercise

17. Myocardial Oxygen Utilization (cont’d) • In vigorous exercise, coronary blood flow increases 4 to 6 times above the resting level because of elevated myocardial metabolism and increased aortic pressure

18. Heart’s Energy Supply • The heart relies almost exclusively on aerobic energy metabolism • Myocardial fibers contain the greatest mitochondrial concentration of all tissues • Myocardial fibers readily metabolize long-chain fatty acids, glucose, and lactate formed in skeletal muscle

20. Cardiovascular Regulation and Integration

21. Heart Rate Regulation • Cardiac muscle possesses intrinsic rhythmicity • Without external stimuli, the adult heart would beat steadily between 50 and 80 times each minute

22. Heart Pumping

23. ECG video

24. Here's a Normal EKG to Compare: Bradychardia Tachycardia VF asystole

25. Extrinsic Regulation of HR • Sympathetic influence • Catecholamine (NE/E) • Results in tachycardia • Parasympathetic influence • Acetylcholine • Results in bradycardia • Cortical influence • Anticipatory heart rate

26. Key Point • Endurance training creates an imbalance between sympathetic accelerator and parasympathetic depressor activity to favor greater vagal (parasympathetic) dominance

28. Arrhythmias • Heart rhythm irregularities • Premature atrial contraction or PAC • Premature ventricular contraction or PVC • Atrial fibrillation • Ventricular fibrillation

29. Blood Flow Regulation • Flow = Pressure ÷ Resistance • Three factors determine resistance to blood flow • Viscosity, or blood thickness • Length of conducting tube • Radius of blood vessel

30. Poiseuille’s Law • Q = pr4P/8hL • Q: flow • P: pressure gradient • r: vessel radius • L: vessel length

31. Local Factors • Enhance regional blood flow via local vasodilatation (a.k.a. autoregulation) in response to local factors  PO2  Temperature  CO2  Adenosine  H+  NO  K+  MG++

32. Neural Mechanisms • Central vascular control via sympathetic and, to a minor degree, parasympathetic portions of the autonomic nervous system overrides vasoregulation afforded by local factors

33. Hormonal Factors • The adrenal gland releases large quantities of epinephrine and a small amount of norepinephrine • E/NE cause a systemic constrictor response, except in blood vessels of the heart and skeletal muscle

34. Cardiovascular Dynamics During Exercise

35. Cardiovascular Dynamics • Q = HR × SV (Fick Equation) • Q: cardiac output • HR: heart rate • SV: stroke volume

37. Close Association Between Max Q & VO2max • An almost proportionate increase in max Q accompanies increases in VO2max with training

38. Q Differences: Men & Women • Women have a 10% lower Hb level than men • Result: • A 5–10% increase in Q at any submax level of O2 consumption

39. Factors Affecting A-vo2difference • Redistribution of flow to active tissues during exercise • Increased capillary density due to training increases surface area and O2 extraction • Increased number and size of mitochondria • Increased oxidative enzymes • Vascular and metabolic improvements

40. Starling Law of the Heart • An increase in end-diastolic volume stretches myocardial fibers, causing a powerful ejection stroke as the heart contracts • Improved contractility of a stretched muscle (within a limited range) probably relates to a more optimum arrangement of intracellular myofilaments as the muscle stretches

44. Maximal Oxygen Consumption • O2max = Max Q • Max a-vO2difference

45. A-vo2 Differences A-vo2 Difference at Rest • 20mL O2/dL blood arterial • 15mL O2/dL blood venous • 5mL a-vO2diff A-vo2Difference During Exercise • 20mL O2/dL blood arterial • 5–15mL O2/dL blood venous • Up to a 3-fold increase in O2 extraction

49. Physiologic Response • Submaximal arm exercise produces: > HR > Pulmonary ventilations > RPE > BP response than comparable leg exercise