Blood Flow control - Exercise

Question 1

During large muscle mass exercise (i.e. running or cycling) there are two physiological needs
- bf, where to and match what
- bp, what is needed to ensure

What does each play role in oxygen delivery
- Lungs is…
* Heart is…
* Blood vessels is..
* Skeletal muscle is..
- Arterial BP maintained supply for not only muscles but..

Answer 1

• Skeletal muscle blood flow needs to be matched to the metabolic demands of the contracting muscles
• Blood pressure regulation is needed to ensure there is adequate perfusion pressure to all organs
• Lungs (supplier)
• Heart (pump)
• Blood vessels (delivery system)
• Skeletal muscle (end user)
• Arterial BP not only muscles but adequatley perfuse brain and other vital organs

Question 2

What are each structures it uses and what is its function
- Respiratory (3 structures 2 function)
- Cardiovascular (2 structures 2 function)
- Metabolic (1 structures 1 function)

• Skeletal muscle blood flow and Blood pressure regulation appear to “compete with one another” when the mass and vasodilator capacity of….are considered in the context of the maximum values for cardiac output as seen….
• Possibility that vasodilation required to supply the nutrients for the contracting muscles might outstrip…and threaten…

Answer 2

• Lungs, chest-wall, resp muscles, Get O2 from air into blood and remove CO2
• Heart, blood vessels, Pump blood out to active tissue and bring blood back to heart
  -Working muscles, produce energy
• when the mass and vasodilator capacity of skeletal muscle are considered in the context of the maximum values for cardiac outputas seen during (intense exercise
• might outstrip cardiac output and threaten blood pressure regulation across the entire body

Question 3

Oxygen Consumption Range

• At rest, we typically consume ~3–4 ml/kg/min of oxygen, VO2 values for healthy humans to range from
• Over 80% of oxygen consumed at rest is used by (4)
• the other 80-90% of the bodies tissues at rest are supported on..
• The digestive tract does not consume much oxygen unless

Answer 3

• A low of ~0.15 L/min, a high of ~0.40 L/min
• is used by the brain, heart, kidneys and liver
• the other 80-90% of the bodies tissues at rest are supported on just 20% of our resting blood flow
• unless it is stimulated by eating and digestion

Question 4

• The skeletal muscle also does not consume much oxygen unless…
• Bone and fat use only…..of resting VO2
• During exercise in young untrained subjects, oxygen consumption can increase what fold, max values of….

The variability of VO2max is due to a number of factors such as:
* Body_______
* PA level
* BV and Hb ____
*SV

Answer 4

• The skeletal muscle also does not consume much oxygen unless the muscles are active
• Bone and fat use only a small fraction of resting VO2
• an increase 10- to 15-fold and reach maximal values of 30–50 ml/kg/min
• Body composition
• Physical activity level
• Blood volume and Hb mass
• Stroke volume

Question 5

• With intense aerobic exercise training, many healthy young men can achieve max oxygen uptake of..
• provided the training is of sufficient intensity and duration to elicit….and…
• Elite male endurance athletes, VO2max in what range
• VO2max values in women are typically __% lower than men as a result of having relatively less..(2 thing)

Answer 5

• can achieve a maximal oxygen uptake near 60 ml/kg/min
• to elicit a maximal adaptive response and they become lean
• 70–85 ml/kg/min range is often reported
• VO2max values in women are typically 10–15% lower than men as a result of having relatively
  less muscle mass and lower total Hb levels

Question 6

• At rest stroke volume is ~__ ml/beat and resting heart rate is ~__ bpm
• which is how many L/min
• what is rbc density of blood
• how much oxygen per litre of blood

Answer 6

• At rest stroke volume is ~70 ml/beat and resting heart rate is ~70 bpm
• 70 ml x 70 bpm = 4900 ml/min = ~5 L/min
• ~150g/L
• ~200 ml O2/L

Question 7

• Fick principle describes oxygen consumption is the result of what multiplied by what minus what
• Key concept is that only a small fraction of the available oxygen delivered to the _____ by the arterial blood is in fact consumed at ____

O2 can vary by tissue:
- _____% of available oxygen is extracted in the coronary circulation at rest
* Yet only ___ to ____% (or less) in the brain, kidney, and splanchnic circulations

Answer 7

• Fick principle describes oxygen consumption is the result of blood flow multiplied by the arterial-venous oxygen difference (VO2 = Q x (CaO2-CvO2))
• A key concept is that only a small fraction of the available oxygen delivered to the periphery by the arterial blood is in fact consumed at rest (not 100% efficient with extraction)
• 70% of available oxygen is extracted in the coronary circulation at rest
• Yet only 20–30% (or less) in the brain, kidney, and splanchnic circulations

Question 8

• These patterns of organ-specific oxygen extraction at rest suggest that blood flow might be safely diverted away from tissues like…..during _______
• During maximal exercise, heart rate increases to values of ~_____ bpm in…..
• Stroke volume also increases during exercise, what does it plateau at in untrained individuals

Answer 8

• These patterns of organ-specific oxygen extraction at rest suggest that blood flow might be safely diverted away from tissues like the liver and kidney during exercise

– During maximal exercise, heart rate increases to values of ~200 bpm in young healthy humans

• Stroke volume also increases during exercise and in untrained individuals, plateaus at ~100 ml/beat

Question 9

• During maximal exercise in an untrained reference male (70 kg), mixed venous oxygen saturation falls from what to what (percent)
• Means that ~___to ___ ml of oxygen is extracted by…. for each liter of cardiac output
• Blood flow redistribution will occur in skeletal muscle vascular beds with active tissues receiving….compared to…
• As a result of sympathetic vasoconstriction blood flow is…

Answer 9

• During maximal exercise in an untrained reference male (70 kg), mixed venous oxygen saturation falls from 75% at rest to 25–30% (body use more oxygen during exercise)
• Means that ~140–150 ml of oxygen is extracted by the peripheral tissues for each liter of cardiac output
• Blood flow redistribution will occur in skeletal muscle vascular beds with active tissues receiving more
  blood compared to the less active skeletal muscles
• As a result of sympathetic vasoconstriction blood flow is reduced across the entire vascular tree

Question 10

• Release of local vasodilators will increase blood flow where in direct proportion to….
• As a result of sympathetic vasoconstriction, renal and splanchnic blood flow can both fall to ~___% of resting values during heavy exercise in humans
• Oxygen consumption in these tissues is preserved by marked increases in ______

Answer 10

• Release of local vasodilators will increase blood flow to the active muscles in direct proportion to the level of activity
• As a result of sympathetic vasoconstriction, renal and splanchnic blood flow can both fall to ~25% of resting values during heavy exercise in humans
• Oxygen consumption in these tissues is preserved by marked increases in extraction

Question 11

• Blood flow to the kidneys at rest is ____ L/min, and the liver receives ____ L/min = ____L/min total
• given 25% of resting value, how much during exercise
• This means ____ L/min of blood flow can be redirected from these vascular beds to….

Answer 11

• Blood flow to the kidneys at rest is 1.2 L/min, and the liver receives 1.6 L/min = 2.8 L/min total
• 2.8 L/min x 0.25 = 0.7 L/min during exercise
• This means 2.1 L/min of blood flow can be redirected from these vascular beds to the skeletal muscles during heavy exercise

Question 12

• Cerebral blood flow on the other hand is ____% of resting cardiac output
• During exercise, this absolute value vary based on…..
• However, the relative blood flow contribution to the brain during maximal exercise is therefore is….(what percent of exercise CO)

Answer 12

• Cerebral blood flow on the other hand is 0.75 L/min or (0.75 / 5 = 15%) of resting cardiac output
• During exercise, this absolute value vary based on intensity of exercise
• However, the relative blood flow contribution to the brain during maximal exercise is therefore
  greatly reduced (0.75 / 20 = ~4%)

Question 13

• As the heart is much, much more active during exercise coronary blood flow increases three- to four- fold from rest to maximal exercise, from what value to what value
• driven by what
• With endurance exercise training there can be an increase in what two things without wall thickening
• adaptation augments stroke volume and thus…

Answer 13

• from 0.15–0.20 L/min at rest to 0.50–0.80 L/min during maximal exercise
• driven primarily by the three- to four-fold increase in heart rate (~60 → ~200 bpm)
• increase in left ventricular mass and chamber volume without wall thickening (sarcomeres add in series so thicker to increase SV)
• adaptation augments stroke volume and thus maximum cardiac output (max HR doesn’t change much)

Question 14

• In addition to changes in stroke volume, peripheral oxygen extraction…
• there can large increases in skeletal muscle _____content with ______ training
• This can help with decreasing….

Answer 14

• In addition to changes in stroke volume, peripheral oxygen extraction can increase modestly with training
• there can large increases in skeletal muscle mitochondrial content with endurance training
• This can help with decreasing blood lactate levels for a given submaximal workload

Question 15

• elite athletes the aforementioned alterations in SV (to what value) can have a profound impact on ….
• it is not uncommon for Elite male athletes can typically have VO2max values between…
• These effects though are not ______ and when elite endurance athletes retire from training and become inactive their vo2 max…

Answer 15

• elite athletes the aforementioned alterations in stroke volume (increased to ~200 ml) can have a profound impact on cardiac output (200sv x200hr = 40L/min vs 20L/min in moderatley trained)
• it is not uncommon for Elite male athletes can typically have VO2max values between 70 and 85 ml/kg/min
• their VO2max drifts downward towards values similar to untrained controls

Question 16

• if Q was 20 L/min with ____ L/min directed to the heart, ____ L/min directed to the brain, and _____ L/min directed to renal and splanchnic vascular beds, this would permit ~____ L/min of blood flow be directed to skeletal muscle
• However, if the exercise is being performed in warm/hot humid environments, total skin blood flow can increase to allow for thermoregulation
• if we take the range of cardiac outputs in normal humans to be between what L/min for healthy young men, and what /min for healthy young women
• Total muscle blood flow can reach 30-35+ L/min in male and 20-25+ L/min in female…

Answer 16

• if Q was 20 L/min with 0.55 L/min directed to the heart, 0.75 L/min directed to the brain, and 0.70 L/min directed to renal and splanchnic vascular beds, this would permit ~18 L/min of blood flow be directed to skeletal muscle
• total skin blood flow can increase to ~6-8 L/min to allow for thermoregulation (to cool down)
• if we take the range of cardiac outputs in normal humans to be between 20-40+ L/min for healthy young men, and 15-30+ L/min for healthy young women
• Total muscle blood flow can reach 30-35+ L/min in male and 20-25+ L/min in female elite endurance athlete

Question 17

• During maximal exercise almost all of the increase in oxygen consumption caused by exercise is…
• ~___% of the oxygen delivered to the leg muscles during maximum running or cycling is being ______

What is peak or maximum blood flow per kilogram of contracting muscle
- it will depend on what two things

Answer 17

• During maximal exercise almost all of the increase in oxygen consumption caused by exercise is occurring in the contracting skeletal muscles
• ~90% of the oxygen delivered to the leg muscles during maximum running or cycling is being extracted
• It will depend on both the mass of active muscle and perfusion pressure

Question 18

• Skeletal muscle typically comprises ____ to ____% of lean body mass in young humans
• For running and cycling contracting skeletal mass in young men might be….
• Respiratory muscles are ~__ kg and highly active during….

Answer 18

• Skeletal muscle typically comprises 40- 50% of lean body mass in young humans
• For running and cycling contracting skeletal mass in young men might be 10-15 kg (33–50% of skeletal
  muscles mass)
• Respiratory muscles are ~2 kg and highly active during heavy exercise

Question 19

• Mean arterial pressure typically remains ~100 mmHg during…in young healthy humans
• The limited rise is partially due to the….
• The biggest factor though is the vast majority of the blood is now…

Answer 19

• Mean arterial pressure typically remains ~100 mmHg during aerobic whole body exercise
• The limited rise is partially due to the resetting of the baroreceptors
• The biggest factor though is the vast majority of the blood is now going to the active muscles

Question 20

• This means that vasodilation in the contracting muscles far outstrips changes in blood
  pressure as the major determinant of….
• To counter sympathetic vasoconstriction, active tissues release ______ to increase….
• Blood flow is distributed to ~15 kg of active skeletal muscles in an untrained male with a peak cardiac output of ____ L/min during heavy exercise
• Blood flow is distributed to ~15 kg of active skeletal muscles in a highly trained male with a
  peak cardiac output of ___ L/min during heavy exercise

Answer 20

• This means that vasodilation in the contracting muscles far outstrips changes in blood
  pressure as the major determinant of exercise hyperemia in humans
• To counter sympathetic vasoconstriction, active tissues release vasodilators (i.e. nitric
  oxide) to increase local blood flow
• Blood flow is distributed to ~15 kg of active skeletal muscles in an untrained male with a peak cardiac output of 22 L/min during heavy exercise (120ml/min/100g of active muscle)
• Blood flow is distributed to ~15 kg of active skeletal muscles in a highly trained male with a
  peak cardiac output of 38 L/min during heavy exercise (200ml/min/100g of active muscle)