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 of pure water = 7.0 (neutral)
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 <--> H2CO3 <--> 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 body remember the reaction hemoglobin - important buffer when deoxygenated picks up H+ when CO2 is being dumped into blood proteins - 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 > 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