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Transcript
Cardiovascular Physiology PHYE 280: Exercise Physiology Kevin Petti, Ph.D. Departments of Natural Sciences, Health, Exercise Science and Nutrition San Diego Miramar College Objectives ω ω ω ω Identify the four components of fitness Identify basic heart anatomy and blood flow Understand the following cardiodynamic variables: systole, diastole, stroke volume, cardiac output, ejection fraction, the cardiac conducting system, blood pressure, and venous return Describe how these adapt to exercise 1 Components of Fitness ω Cardiorespiratory Endurance ν ω Muscular Strength ν ω Maximum amount of force a muscle can exert during a single contraction Flexibility ν ω Ability of heart, lungs and blood vessels to deliver O2 to exercising muscles Range of Movement (ROM) at a joint Body Composition ν ν High lean mass or fat-free mass (muscle and bone) Low fat mass 2 Basic Cardiac Anatomy 3 4 The Coronary Arteries ω ω Right Left ν ν Anterior Descending Circumflex Valves of the Heart ω Atrioventricular Valves ν Tricuspid Valve λ ν Between RA and RV Bicuspid/Mitral Valve λ ω Between LA and LV Semilunar Valves ν ν ω Pulmonary Valve Aortic Valve ω ω Chordae tendineae and papillary muscles associated w/ AV Valves Valves prevent the regurgitation of blood Valves open and close via changes in chamber BP 5 Cardiac Physiology Concepts ω ω ω Conducting System of the Heart Electrocardiogram (ECG) Cardiodynamics ν ω EDV, ESV, SV, EJ, Q Cardiac Output λ λ ω At rest vs. exercise Trained vs. untrained Blood Pressure 6 Conducting System of the Heart ω ω ω The heart is autorhythmic beats w/o nervous stimulation The cells responsible for initiating and distributing the stimulus for cardiac contraction are the heart’s conducting system Comprised of ν ν ν Sinoartial (SA) Node Atrioventricular (AV) Node Conducting Cells λ λ λ AV Bundle Bundle Branches (Bundle of His) Purkinje Fibers 7 The Electrocardiogram (ECG) ω ω Systole - chamber contraction Diastole - chamber relaxation 8 Cardiodynamics ω End-Diastolic Volume (EDV) ν ω End-Systolic Volume (ESV) ν ω Volume of blood in each ventricle at the end of ventricular systole Stroke Volume (SV) ν ν ω Volume of blood in each ventricle at the end of ventricular diastole Amount of blood ejected from each ventricle per beat Can be expressed as EDV - ESV = SV Ejection Fraction ν Percentage of EDV ejected in ventricular systole Cardiodynamics ω Cardiac Output Amount of blood ejected from each ventricle in one minute ν Perhaps the most important variable of cardiac function ν Can be expressed as below: Q = Hr x SV ν Cardiac Output (ml/min) Heart Rate (beats/min) Stroke Volume (ml/beat) 9 Cardiac Output at Rest Q = Hr Cardiac Output (ml/min) Heart Rate (beats/min) 6000 ml/min = or 6 l/min 75 bpm x SV Stroke Volume (ml/beat) x 80 ml/beat Cardiac Output at rest equals 6 liters/minute Average adult has ≈ 5 liters of blood Cardiac Output During Exercise Q = Hr Cardiac Output (ml/min) Heart Rate (beats/min) 13,440 ml/min = or 13.4 l/min 120 bpm x SV Stroke Volume (ml/beat) x 112 ml/beat Cardiac Output can more than double during moderate exercise for the average adult Elite athletes can have Cardiac Outputs in excess of 25 l/min! 180 bpm x 160 ml/beat = 28.8 l/min 10 Cardiac Output Adaptations in Response to Aerobic Training ω ω ω ω Resting heart rate decreases as a result of increased fitness What would this do to SV if Q remains constant? This answer is a result of Starling’s Law that states ⇑EDV = ⇑ SV SV ⇑ with training, so what happens to exercising HR at a particular intensity (10 min. mile) as one becomes more trained? Factors Affecting Stroke Volume 11 Factors Affecting Cardiac Output Blood Pressure ω Systemic arterial pressure ν ν ω Mean Arterial Pressure (MAP) is most often used in studies reporting a single blood pressure ν ω ω Measured in mm Hg millimeters of mercury Declines further from heart 1/3 of pulse pressure (systolic-diastolic) + diastolic pressure Regulated closely by neural and hormonal mechanisms; is a function of resistance to blood flow Resistance is a function of vessel diameter, vessel length, blood viscosity, blood turbulence 12 Measuring Blood Pressure systolic/diastolic Blood Pressure ω ω ω Resting BP ≈120/80 mmHg MAP = 93.3mm Hg Exercising MAP can exceed 113 mmHg (200/70) 13 Blood Pressure and Venous Return ω ω ω ω BP at start of venous system is 1/10 of that at start of arterial system BP at right atrium is only 2 mm Hg! Venous return is assisted by muscular compression, and the respiratory pump Both of these are extremely important during exercise ν Why is it important to cool down after aerobic exercise? 14