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Circulatory Adaptations to Exercise

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Presentation on theme: "Circulatory Adaptations to Exercise"— Presentation transcript:

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

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