Exercise; the CV and Respiratory Responses

Question 1

Explain the relationship between O2 consumption and work.

Answer 1

Linear relationship between o2 consumption and work - once O2 max is reached a small further increase in work can be performed anaerobically.

Question 2

What is VO2max?

Answer 2

The maximum rate at which a human uses O2 during dynamic exercise.

Question 3

VO2 max =

Answer 3

Cardiac output x (arterial - mixed venous O2 content)

ie, Litres of O2 containing blood delivered each minute x amount of O2 removed from each litre.

Question 4

What is max HR dependant on?

Answer 4

Age!

maxHR = 220 - age

Question 5

What is resting and submax HR dependent on?

Answer 5

Fitness.
Increase fitness, decrease HR.
Heart has more time to fill!

Question 6

BP=

And explain changes in BP with severe exercise.

Answer 6

BP = CO x TPR

Systolic increase progressively with increaseing exercise intensities.
Diastolic changes less - increase or decreases a small amount in different subjects.

Question 7

What is the relationship between mitochondrial capacity and VO2 max?

Answer 7

Increase ATP man…increase VO2 max - linearly!

Question 8

Resting and max exercise HR vaules?

Answer 8

70bpm

192bpm

Question 9

Resting and max exercise SV?

Answer 9

72ml

90ml

Question 10

Resting and max exercise CO?

Answer 10

5L

20L

Question 11

Resting and max exercise (a-v)O2 content?

Answer 11

5ml/dl

16.5ml/dl

Question 12

Resting and max exercise O2 consumption?

Answer 12

250 ml/min

2800 ml/min

Question 13

Bed rest vs Sedentary vs Training?

Answer 13

Increase VO2 max due to increased O2 extraction and increase CO.

Question 14

How is regional blood controlled in active muscle?

Answer 14

Vasodilation due to local metabolites acting on vascular smooth muscle (increased pCO2, decrease pO2, increased H+, increased adenosine and increased NO).

= increase BP = increased BF.

Question 15

How is regional blood flow controlled in inactive muscle and splanchnic circulation?

Answer 15

Sympathetic vasoconstriction.

Question 16

How is regional blood flow to the skin controlled?

Answer 16

Initial vasoconstriction followed by vasodilation sue to core temperature rise and then at max exercise it falls again.

Question 17

What is the net effect of controlling regional blood flow during exercise?

Answer 17

Decrease TPR.

Question 18

Is redistribution an appropriate term?

Answer 18

There is a massive increase in CO and all in all only about 600ml is actually ‘redistributed’.

Question 19

What increases to increase CO?

Answer 19

Increase is HR
Modest increase in SV due to…
…enhanced filling of the heart (increased VR)
…enhanced emptying (sympathetically mediated increase in contractility).

Question 20

How is the increase O2 consumption by muscles achieved?

Answer 20

Increased BF to active muscles (vasodilation/increased BP)

Increase removal of O2 from each ml of blod passing through the tissues.

Question 21

How is the increased O2 release from Hb aided?

Answer 21

By low tissue pO2.
By decreased affinity of Hb for O2 (shift of the oxyHb dissociation curve to the right, caused by increase in CO2, H+ and temperature.

Question 22

Endurance training - what adaptations occur because of it?

Answer 22

Increases max CO, increases capiliarity, increases~ of mitochondria, increase # of enzymes of oxidative metabolism, increased reliance on fat and glycogen sparing.

Question 23

BP and dynamic exercise?

Answer 23

BP = CO x TPR.

Increase CO, decrease TPR….little change in diastolic, increase systolic meaning mean BP increases moderately.

Question 24

BP and isometric exercise (sustained muscle contractions)?

Answer 24

Increase BP (systolic and diastolic) and increase HR.
For any given O2 consumotion - the BP rise is greater than in dynamic exercise and falls to a plateau.

Question 25

Ventilation =

Answer 25

Tidal volume x respiratory frequency.

Question 26

Alveolar ventilation =

Answer 26

(Tidal volume - dead space volume) x frequency

Question 27

Alveolar and arterial PCO2 depend on what?

Answer 27

The balance between CO2 production and alveolar ventilation.

arteriolar PCO2 is proportional to VCO2/VA.

Question 28

Why does ventilation increase linearly but the rise more steeply?

Answer 28

Extra stimulus to breathing in heavy exercsise is thought to be caused by stimulation of peripheral chemoreceptors by H+ from glycolysis.

Question 29

McArdles syndrome?

Answer 29

Can’t produce lactate but still have an anaerobic threshold.

Question 30

Glycogen depletion?

Answer 30

Decouples ventilatory and lactate thresholds - ventilation earlier, lactate later.

Question 31

How are CO and ventilation matched?

Answer 31

By central command (feedforward), and peripheral mechanisms (metabolic, mechano, chemo and baro receptors).

Question 32

Is PaO2 well maintained?

Answer 32

Normally - but in athletes - faster blood flow therefore PaO2 decreases as it is not as saturated.