Respiratory Control

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Respiratory Control
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Oxygen consumption (VO2)
the amount of oxygen taken up and consumed by the
body for metabolic processes
VO2 Q x (a VO2 difference)
VO2 depends on
1. Q (HR x SV) amt. of oxygen delivered
2. a VO2 difference amt. of oxygen consumed
the difference between the amount of oxygen per
volume of blood in the artery and the vein (after
gas exchange at the capillary bed)
a VO2 difference -
The Respiratory System
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a - VO difference
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a VO2 difference and activity.

• ?a VO2 with exercise as more oxygen is used by
  muscles

- At rest hemoglobin releases 25 of bound
O2 - During intense exercise 75 80 of bound
O2 is released

• a VO2 0 in active muscle ? 2 4 mL/100mL
  blood in right atrium as venous return is from
  active/inactive tissues

The Respiratory System
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Maximal Oxygen Consumption (VO max)
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VO2 max maximal rate of oxygen consumption
VO2 max is widely considered to be the
Most valid measure of cardiorespiratory fitness!
VO2max (HRmax x SVmax) x (a VO2 differencemax)
Mathematically, VO2max will occur when HR, SV,
and a VO2 diff. are all max values, however, SV
and a VO2 diff. seem to have the greatest
effect on VO2max.
The Respiratory System
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VO max and Training
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• Initial VO2 max gains at onset of training
  program can be large (subsequent gains much more
  difficult)

• Ability to attain high VO2max (60 80 mL/kg/min)
  seems to have a genetic component (increased CR
  capacity)

• Endurance training at 50 85 of VO2max
  involving large muscle groups is most effective
  at ? VO2max

• Training induced ? VO2max mainly due to

• ?SV (?EDV, ?afterload)

2. ?a-VO2 difference (?capillaries,
mitochondria)
The Respiratory System
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VO max and Training
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?VO2 max
?QMax
The Respiratory System
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Females
Males
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• Decrease in VO2 max occurs almost immediately
  (lt 2 weeks) when training is ceased.

• Initial losses are due to ?SV due to a ? plasma
  volume

• Subsequent losses are due to ? a VO2 diff.

The Respiratory System
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VO2max is divided by body mass in order to allow
a greater comparison between body sizes, and
types to be made.
Factors contributing to lower VO2max in Sedentary
people

• Excess body fat accumulation

2. Decreased skeletal muscle function
3. Decreased pumping capacity of the heart

• General decline in VO2max with age (?HR,
  metabolism, lung capacity)

• VO2max in active 50 60 yr old can be as high as
  an average 20 30 yr old

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Females in general have lower VO2max due to

• Females can have twice as much body fat as males
  for all ages past early teens

2. Females have a smaller heart size (lower SV)
3. Females have a lower hemoglobin concentration
in blood, thus reducing its oxygen carrying
capacity
4. Females have smaller active muscle mass
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Exercise is performed on an appropriate ergometer
(treadmill, cycle, swim bench). The exercise
workloads are selected to gradually progress in
increments from moderate to maximal intensity.
Oxygen uptake is calculated from measures oxygen
and carbon dioxide in the expired air and minute
ventilation, and the maximal level is determined
at or near test completion.
Results are presented as either l/min (liters per
minute) or ml/kg/min (mls of oxygen per kilogram
of body weight per minute). The athlete is
considered to have reached their VO2max if
several of the following occurred a plateau or
'peaking over' in oxygen uptake, maximal heart
rate was reached, attainment of a respiratory
exchange ratio of 1.15 or greater, and volitional
exhaustion.
Adult norm values can be found here
http//www.topendsports.com/testing/vo2norms.htm
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Control of Pulmonary Ventilation
The respiratory control centre lies within the
brain stem. Specifically, the medulla oblongata
(Waterboy) and the pons.
Two specialized centres, inspiratory and
expiratory, in the medulla oblongata send signals
to the various respiratory muscles to control
breathing.
Inspiratory centre

• generates rhythmical signal that stimulates the
  diaphragm and the external intercostals to
  contract (freq. 12 15 breaths/min rest)

Expiratory centre

• ensures inspiratory muscles never completely relax

• stimulate forceful expiration during exercise

The Respiratory System
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Control of Pulmonary Ventilation
Two specialized centres found in the pons are the
pneumotaxic and apneustic centres.
These two centres ensure that transitions between
inhalation and exhalation are smooth.
These are not the only areas of the brain
influencing ventilation.

• Areas that control skeletal muscle also stimulate
  the breathing centres

• Sensory systems provide feedback information on
  chemical and pH levels in the blood

The Respiratory System