Presentation on theme: "Cardiovascular System"— Presentation transcript:
1 Cardiovascular System Cardiovascular Dynamics during ExerciseMcArdle, Katch and Katch, 4th ed.
2 Cardiovascular Dynamics During Exercise Cardiac Output (Q): amount of blood pumped per minute.Q = Heart Rate x Stroke Volume.Fick Equation. VO2 = HR x SV x a-v O2 diff
3 Resting Cardiac Output Cardiac Output = 5 L/min trained & untrainedUntrained = 70 bpm x 71 ml = 5000 ml/minTrained = 50 bpm x 100 ml = 5000 ml/minLarger stroke volumes after training due to increased vagal tone & strengthen heart.
4 Exercise Cardiac Output Blood flow from heart increases in direct proportion to exercise intensity.higher intensity mainly due to increases in heart rate.Untrained max 22 L/minTrained max 35 L/min
6 Increased Cardiac Output Venous return must increaseVenoconstriction - reduces capacity to hold large volume of bloodMuscle pump - active muscles squeeze veins forcing blood back towards heartRespiratory pump - inspiration lowers thoracic pressure
7 Stroke VolumeStroke Volume: amount of blood pumped each cardiac cycle.Increased diastolic filling before systole occurs through any factor that increases venous return (preload).Left Ventricular End Diastolic VolumeMinusLeft Ventricular End Systolic Volume
8 Stroke Volume & VO2 maxSV increases progressively with intensity up to about 50% max VO2After reach 50% max VO2, Q increases because of heart rateWell trained endurance athletes’ SV rises to maximal levels
9 Stroke Volume Increases SV increases due toEnhanced filling increases EDV (preload)Greater contractility from neurohormonal influence- greater systolic emptyingExpanded blood volume and decreased afterload
10 Stroke Volume Increases Increased EDVfuller ventricle = greater stroke volumeFrank-Starling’s mechanismDecreased ESVcatecholamines increase contractility via increased Ca2+Afterload - pressure required to open the aortic semilunar valvedecreases during exercise due to vasodilation
12 Exercise Heart RateHeart rate and VO2 are linearly related in trained and untrained throughout major portion of exercise range.Endurance training reduces HR at any given submaximal workload due to ↑ SV.
13 Heart Rate and Oxygen Consumption In healthy individuals, heart rate increases linearly with exercise load or oxygen uptake and plateaus just before maximal oxygen consumption.If exercise load is held constant, below lactate threshold, steady state is reached in about minutes.
14 Distribution of Cardiac Output Blood flow to tissues is proportional to metabolic activityMuscle tissue receives about same amount blood as kidneys at restDuring intense exercise, significant blood is shunted from kidneys & splanchnic regions (areas that temporarily tolerate reduced flow)Splanchnic syn. visceral. Visceral pleural viscus. Viscus an organ of the digestive, respiratory, urogenital, and endocrine systems, as well as the spleen, heart, and great vessels; [L. the soft parts, internal organs].
15 Shunting of blood via constricting arterioles and closing precapillary sphincters.
16 Distribution during Exercise Blood flow to skin increases during light and moderate exerciseDuring intense exercise, nearly 85% blood shunted to muscles. Cutaneous blood flow reduced even when hot.
17 Cardiac Output and Oxygen Transport Maximal cardiac output relates to maximal oxygen uptake in 6:1 ratio.Females have a larger cardiac output compared to males at any level of submaximal VO2 – most likely due to 10% lower [hemoglobin].Children have small SV
18 Oxygen ExtractionVO2(ml/min)SV(L/min)HR(bpm)a-v O2(ml/L)UntrainedRest300 ml.0758248.8Max3100 ml.112200138Trained.1055849.33440 ml.126192140.5Increased arterio-venous oxygen extraction with increased work intensityFick Equation:VO2 max = maximum cardiac output x maximum a-v O2 diffarterial O2 - venous O2 = extractionIncreased arterial capacity to carry oxygen because of hemoconcentration
19 Increasing Oxygen Consumption During Exercise O2 extraction depends upon O2 content of blood & removal rate by tissuesO2 removal depends upon:capillary density; improves with aerobic training.myoglobin content; improves with aerobic training.mitochondria number; improves with aerobic trg.oxidative capacity of mitochondria; improves with aerobic training.muscle fiber typePO2 gradient from capillaries to tissue
20 Upper-Body ExerciseHighest VO2 attained during upper body exercise ranges between 70%-80% of VO2 max in lower body exercise.Max HR and pulmonary ventilation probably less because smaller muscle mass.Produces greater physiological strain (SBP) for any level VO2 than lower-body exercise.
21 Illustration References McArdle, William D., Frank I. Katch, and Victor L. Katch Essentials of Exercise Physiology 3rd ed. Image Collection. Lippincott Williams & Wilkins.Plowman, Sharon A. and Denise L. Smith Digital Image Archive for Exercise Physiology. Allyn & Bacon.