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Blood Flow and Gas Transport --Fill in the blanks style lecture notes with occasional extras about what was especailly important to remember and some further explanations.

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Biomedical Physio & Kines
BPK 142
Paul Lee

1 BLOOD FLOW AND GAS TRANSPORT I. CARDIAC OUTPUT DURING EXERCISE A. Cardiac Output and Oxygen Transport Cardiac output ("Q") - the amount of __blood___ pumped by either the left or right ventricle of the heart per _minute___. Both the left and right ventricles must have the __same___ cardiac output so that blood flow through the pulmonary and systemic circuits is maintained equally. [Rate per minute] Stroke volume - the amount of __blood__ pumped by either the left or right ventricle per __beat__. [Amount pumped per beat] Cardiac output = ___heart rate____ X __stroke volume____ Since the blood transports __oxygen___, when cardiac output increases in exercise more ___oxygen___ will be transported to the working muscles. This relationship can be expressed by the Fick equation: VO = HR X SV X (a-vO ) diff 2 2 where: VO 2 _oxygen__ uptake or utilization by the tissues in the body (a-vO diff = arterial-mixed venous __oxygen__ difference 2) Therefore, in order to increase oxygen uptake, you must increase ___cardiac output___ and/or extract more __oxygen___ from the arterial blood. In general, the higher the maximal _stroke__ volume --> higher maximal cardiac output --> higher maximum oxygen uptake (VO 2ax.) B. Exercise Heart Rate For any given subject, heart usually increases linearly with increasing __workload___ until the subject's maximum heart rate is reached. The heart rate at a given oxygen uptake is higher when the exercise is performed with the _arms__ than with the legs. 2 Since: (1) the cardiac output required for a given workload is reasonably __similar__ for trained and untrained subjects, and (2) trained subjects have a higher __stroke__ volume than untrained subjects --> then, for any given workload, trained subjects will have a lower exercise _heart rate_. Cardiac output = HR[Heart rate] x SV [Stroke volume] C. Stroke Volume During Exercise Stroke volume = __end-disastoolic___ volume minus __end-systolic___ volume Systole - the __contraction___ phase of the cardiac cycle, when the ventricles pump out their stroke volumes. Diastole - the __resting___ phase of the cardiac cycle, between heart beats End-diastolic volume (EDV) – the volume of blood in each ventricle at the end of __diastole___ – 120 ml in an untrained person at rest End-systolic volume (ESV) – the volume of blood that remains in each ventricle after the ventricles have finished _contracting___ – 50 ml in an untrained person at rest Ejection fraction – the __percentage___ of EDV ejected with each contraction Ejection fraction = stroke volume/end-diastolic volume Stroke volume increases to its __highest____ values during submaximal exercise (40% of VO 2max, HR = 110 - 120) and then remains __constant____ during the progress ion from moderate to maximal work. Mechanism of increase in stroke volume during exercise: - greater __systolic_____ emptying = greater ejection fraction. The heart has a functional residual volume - at rest in the upright position, only ___50-60%____ of the blood in the ventricle is pumped out of the ventricle during the contraction - 50 to 80 ml of blood remains in the ventricle. 3 During graded exercise, the heart progressively increases stroke volume by means of a more complete ___emptying_ during systole - due to effect of ___sympathetic____ hormones. II. DISTRIBUTION OF BLOOD FLOW DURING EXERCISE At rest __15-20%____ of the systemic blood flow goes to the skeletal muscles. During maximal exercise __85%__ of the cardiac output can be diverted to the working skeletal muscles. This increased blood flow to the working muscles is caused by: 1. Increased blood __pressure__ 2. ___Dilation__ of arterioles in working muscles due to ___relaxation____ of the smooth muscle in the walls of the arterioles. 3.___Constriction____ of arterioles in the gut area (liver, intestines, stomach, kidneys) and non-working muscles. Poiseuille’s Law: Resistance to flow = Fluid viscosity X Tube length Radius of tube 4 [Don’t need to memorize this equation] [[This is here to explain how a small change in diameter can impact the blood flow]] Thus decreasing tube radius by a factor of 2 will increase resistance to flow by a factor of 16, decreasing flow by a factor of 16. It has been calculated that a 33 % decrease in the radius of the arterioles will produce a 400 % increase in resistance to flow. Conclusion – only a small change in blood vessel _radius__ dramatically alters blood _flow__. MAXIMAL AEROBIC POWER I. DIRECT MEASUREMENT OF MAXIMAL AEROBICPOWER 4 A. Physiological Determinants of VO max. 2 Definition – VO2 max provides an integrated measurement of your physiological systems that contribute to O2 transport and O2 utilization including the cardiovascular, respiratory, neural and muscular systems while maintaining body homeostasis The maximum oxygen uptake provides important information on the capacity of the __oxygen____ transport system. The most important factors that determine VO m2x. in a given person are: 1. The ability to ventilate the __lungs__ and oxygenate the __blood_ passing through the lungs 2. The ability of the heart to __pump__ blood - __cardiac__ output 3. The __oxygen___ carrying capacity of the blood 4. The ability of the working muscles to accept a large __blood__ supply 5. The ability of muscle fibers to extract _oxygen__ from the capillary blood and use it to produce __energy___ - oxidative enzyme levels, etc. As the duration of events requiring heavy continuous energy expenditure becomes progressively greater than one minute, aerobic capacity becomes increasingly important as a determining factor for success. -1 -1 B. Typical Values for VO ma2 (ml∙kg ∙min ) 1. Untrained Canadian male (20-29 years) _40-50_ 2. Untrained Canadian female (20-29 years) _30-50_ 3. World class endurance athlete (M) 80-90 4. World class endurance athlete (F) 65-75 5. Soccer, ice hockey, basketball (M) 54-60 6. Baseball, football, thrower, sprinter 40-50 C. VO max. Test Protocols 2 1. The test protocol should ex
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