1. Circulatory Adaptations to Exercise
Chapter 9
Circulatory Adaptations to Exercise

2. The Cardiovascular System
Components
Circulatory system
Pulmonary system
Purposes
Transport O2 to tissues and removal of other products (“waste”)
Transport of nutrients to tissues
Regulation of body temperature

3. The Circulatory System
Heart
Pumps blood
Arteries and arterioles
Carry blood away from the heart
Capillaries
Exchange of materials with tissues
Veins and venules
Carry blood toward the heart

4. Structure of the Heart

5. Pulmonary and Systemic Circuits
Left side of the heart
Pumps oxygenated blood to the whole body via arteries
Returns “deoxygenated” blood to the right heart via veins
Pulmonary circuit
Right side of the heart
Pumps “deoxygen-ated” blood to the lungs via pulmonary arteries
Returns oxygenated blood to the left heart via pulmonary veins

6. The Myocardium

7. The Cardiac Cycle
Systole
Contraction phase
Diastole
Relaxation phase

8. Pressure Changes During the Cardiac Cycle

9. Arterial Blood Pressure
Expressed as systolic/diastolic
Normal is 120/80 mmHg
High is 140/90 mmHg
Systolic pressure (top number)
Arterial pressure during systole
Diastolic pressure
Arterial Pressure during diastole

10. Arterial Blood Pressure
Pulse pressure
Difference between systolic and diastolic
Pulse Pressure = Systolic - Diastolic
Mean arterial pressure (MAP)
Average pressure in the arteries
MAP = Diastolic + 1/3(Systolic - Diastolic)

11. Measurement of Blood Pressure

12. Factors That Influence Arterial Blood Pressure

13. Electrical Activity of the Heart
Contraction of the heart depends on electrical stimulation of the myocardium
Impulse is initiated by the SA node and spreads throughout entire heart
May be recorded on an electrocardiogram (ECG or EKG)

14. Conduction System of the Heart

15. Electrocardiogram

16. Electrocardiogram Records the electrical activity of the heart P-wave
Atrial depolarization
QRS complex
Ventricular depolarization
T-wave
Ventricular repolarization

17. Diagnostic Use of the ECG
ECG abnormalities may indicate coronary heart disease
ST-segment depression can indicate myocardial ischemia (reduced blood flow)

18. Abnormal ECG Response to Exercise

19. Cardiac Output The amount of blood pumped by the heart each minute
Product of heart rate and stroke volume
Heart rate = number of beats per minute
Stroke volume = amount of blood ejected from the heart in each beat .
Q = HR x SV

20. Regulation of Heart Rate
Decrease in HR
Parasympathetic nervous system
Via vagus nerve
Slows HR by inhibiting SA node
Increase in HR
Sympathetic nervous system
Via cardiac accelerator nerves
Increases HR by stimulating SA node

21. A Summary of Cardiovascular Control During Exercise: Fine Tuning

22. Nervous System Regulation of HR

23. Regulation of Stroke Volume
End-diastolic volume (EDV)
Volume of blood in the ventricles at the end of diastole (“preload”)
Average aortic blood pressure
Pressure the heart must pump against to eject blood (“afterload”)
Contractility
Strength of the ventricular contraction

24. 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
Double product
Increases linearly with exercise intensity
Indicates the work of the heart
Double product = heart rate x systolic BP

25. End-Diastolic Volume Frank-Starling mechanism Affected by:
Greater preload results in stretch of ventricles and in a more forceful contraction
Affected by:
Venoconstriction
Skeletal muscle pump
Respiratory pump

26. The Skeletal Muscle Pump
Rhythmic skeletal muscle contractions force blood in the extremities toward the heart
One-way valves in veins prevent backflow of blood

27. The Skeletal Muscle Pump

28. Average Aortic Pressure
Aortic pressure is inversely related to stroke volume
High after load results in a decreased stroke volume
Requires greater force generation by the myocardium to eject blood into the aorta
Reducing after load results in higher stroke volume

29. Ventricular Contractility
Increased contractility results in higher stroke volume
Causes:
Circulating epinephrine and norepinephrine
Direct sympathetic stimulation of heart

30. Hemodynamics Flow of blood through the circulatory system
Based on interrelationships between:
Pressure
Resistance
Flow

31. Components of Blood

32. Hemodynamics: Resistance
Resistance depends upon:
Length of the vessel
Viscosity of the blood
Radius of the vessel
A small change in vessel diameter can have a dramatic impact on resistance!
Resistance =
Length x viscosity
Radius4

33. Hemodynamics: Blood Flow
Directly proportional to the pressure difference between the two ends of the system
Inversely proportional to resistance
Flow =
 Pressure
Resistance

34. Sources of Vascular Resistance
MAP decreases throughout the systemic circulation
Largest drop occurs across the arterioles
Arterioles are called “resistance vessels”

35. Pressure Changes Across the Systemic Circulation

36. Oxygen Delivery During Exercise
Oxygen demand by muscles during exercise is many times greater than at rest
Increased O2 delivery accomplished by:
Increased cardiac output
Redistribution of blood flow to skeletal muscle

37. Changes in Cardiac Output
Cardiac output increases due to:
Increased HR
Linear increase to max after 120 bpm
Increased SV
Plateau at ~40% VO2max
Max HR = Age (years) .

38. Changes in Cardiovascular Variables During Exercise

39. Redistribution of Blood Flow
Increased blood flow to working skeletal muscle
Reduced blood flow to less active organs
Liver, kidneys, GI tract

40. Changes in Muscle and Splanchnic Blood Flow During Exercise

41. Redistribution of Blood Flow During Exercise

42. Circulatory Responses to Exercise
Heart rate and blood pressure
Depend on:
Type, intensity, and duration of exercise
Environmental conditions
Emotional influence

43. Transition From Rest  Exercise and Exercise  Recovery
Increase in HR, SV, cardiac output
Plateau in sub maximal exercise
Recovery depends on:
Duration and intensity of exercise
Training state of subject

44. Transition From Rest  Exercise  Recovery

45. Incremental Exercise Heart rate and cardiac output Systolic BP
Increases linearly with increasing work rate
Reaches plateau at 100% VO2max
Systolic BP
Increases with increasing work rate
Diastolic BP
Decreases slightly then remains even .

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

47. HR, SV, and CO During Prolonged Exercise

48. Summary of Cardiovascular Adjustments to Exercise

49. Chronic Endurance Training
Stronger/ thicker/ larger left ventricle
Lower resting and working HR
Greater resting and working SV
Lower resting and working blood pressure
Greater capillarization which decreases TPR – total peripheral resistance

50. Questions?

51. END