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Control of Ventilation

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Respiratory control center Receives neural and humoral input Feedback from muscles CO2 level in the blood Regulates respiratory rate Location of Respiratory Control ... – PowerPoint PPT presentation

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Title: Control of Ventilation


1
Control of Ventilation
  • Respiratory control center
  • Receives neural and humoral input
  • Feedback from muscles
  • CO2 level in the blood
  • Regulates respiratory rate

2
Location of Respiratory Control Centers
3
Neural Input to the Respiratory Control Center
  • motor cortex - impulses from cortex may spill
    over when passing through medulla on way to
    heart and muscles
  • afferent - from GTO, muscle spindles or joint
    pressure receptors
  • mechanoreceptors in the heart relay changes in Q

4
Humoral Input to the Respiratory Control Center
  • central chemoreceptors - respond to changes in
    CO2 or H in CSF
  • peripheral chemoreceptors - aortic bodies and
    carotid bodies
  • both similar to central receptors, carotids also
    respond to increases in K and decreases in PO2

5
Ventilation vs. Increasing PCO2
6
Ventilation vs. Decreasing PO2
7
Ventilatory Control During Exercise
  • Submaximal exercise
  • Linear increase due to
  • Central command
  • Humoral chemoreceptors
  • Neural feedback
  • Heavy exercise
  • Exponential rise above Tvent
  • Increasing blood H

8
Respiration Control during Submaximal Exercise
9
Respiratory Control during Exercise
  • Central commmand initially responsible for
    increase in VE at onset
  • combination of neural and humoral feedback from
    muscles and circulatory system fine-tune VE
  • Ventilatory threshold may be result of lactate or
    CO2 accumulation (H) as well as K and other
    minor contributors

10
Effect of Training on Ventilation
  • Ventilation is lower at same work rate following
    training
  • May be due to lower blood acidity
  • Results in less feedback to stimulate breathing

11
Training Reduces Ventilatory Response to Exercise
12
Final Note
  • the pulmonary system is not thought to be a
    limiting factor to exercise in healthy
    individuals
  • the exception is elite endurance athletes who can
    succumb to hypoxemia during intense near maximal
    exercise

13
Acid-Base Balance
14
Acids and Bases
  • Acid - compound that can loose an H and lower
    the pH of a solution
  • lactic acid, sulphuric acid
  • Base - compound that can accept free H and raise
    the pH of a solution
  • bicarbonate (HCO3-)
  • Buffer - compound that resists changes in pH
  • bicarbonate (sorry)

15
pH
  • pH -log10 H
  • pH goes up, acidity goes down
  • pH of pure water 7.0 (neutral)
  • pH of blood 7.4 (slightly basic)
  • pH of muscle 7.0

16
Acidosis and Alkalosis
17
Acid Production during Exercise
  • CO2 - volatile because gas can be eliminated by
    lungs
  • CO2 H2O lt--gt H2CO3 lt--gt H HCO3-
  • The next point is erroneous
  • Lactic acid and acetoacetic acid - CHO and fat
    metabolism respectively
  • termed organic acids
  • at rest converted to CO2 and eliminated, but
    during intense exercise major load on acid-base
    balance

18
  • Sulphuric and Phosphoric acids - produced by
    oxidation of proteins and membranes or DNA
  • called fixed because not easily eliminated
  • minor contribution to acid accumulation

19
Sources of H
20
Buffers
  • maintain pH of blood and tissues
  • accept H when they accumulate
  • release H when pH increases

21
Intracellular Buffers
  • proteins
  • phosphates
  • PC
  • bicarbonate

22
Insert table 11.1
23
Extracellular Buffers
  • bicarbonate - most important buffer in
    bodyremember the reactionhemoglobin - important
    buffer when deoxygenatedpicks up H when CO2 is
    being dumped into bloodproteins - not important
    due to low conc.

24
Buffering Capacity of Muscles vs. Blood
25
Respiration and Acid-Base Balance
  • CO2 has a strong influence on blood pH
  • as CO2 increases pH decreases (acidosis) CO2
    H2O gt H HCO3-
  • as CO2 decreases pH increases (alkalosis)
  • so, by blowing off excess CO2 can reduce acidity
    of blood

26
Changes in Lactate, Bicarb and pH vs. Work Rate
27
Lines of Defense against pH Change during Intense
Exercise
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