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Circulatory Adaptations to Exercise Chapter 9. The Cardiovascular System Components –Circulatory system –Pulmonary system Purposes –Transport O 2 to tissues.

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Presentation on theme: "Circulatory Adaptations to Exercise Chapter 9. The Cardiovascular System Components –Circulatory system –Pulmonary system Purposes –Transport O 2 to tissues."— Presentation transcript:

1 Circulatory Adaptations to Exercise Chapter 9

2 The Cardiovascular System Components –Circulatory system –Pulmonary system Purposes –Transport O 2 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 Systemic circuit –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 MAP = Diastolic + 1 / 3 (Systolic - Diastolic) Mean arterial pressure (MAP) –Average pressure in the arteries

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 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% VO 2max 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 –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 Radius 4

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 O 2 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% VO 2max Max HR = 220 - 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 –Increases linearly with increasing work rate –Reaches plateau at 100% VO 2max Systolic BP –Increases with increasing work rate Diastolic BP –Decreases slightly then remains even.

46 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)

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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