Title: Control of Ventilation
1Control of Ventilation
- Respiratory control center
- Receives neural and humoral input
- Feedback from muscles
- CO2 level in the blood
- Regulates respiratory rate
2Location of Respiratory Control Centers
3Neural 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
4Humoral 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
5Ventilation vs. Increasing PCO2
6Ventilation vs. Decreasing PO2
7Ventilatory Control During Exercise
- Submaximal exercise
- Linear increase due to
- Central command
- Humoral chemoreceptors
- Neural feedback
- Heavy exercise
- Exponential rise above Tvent
- Increasing blood H
8Respiration Control during Submaximal Exercise
9Respiratory 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
10Effect 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
11Training Reduces Ventilatory Response to Exercise
12Final 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
13Acid-Base Balance
14Acids 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)
15pH
- 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
16Acidosis and Alkalosis
17Acid 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
19Sources of H
20Buffers
- maintain pH of blood and tissues
- accept H when they accumulate
- release H when pH increases
21Intracellular Buffers
- proteins
- phosphates
- PC
- bicarbonate
22Insert table 11.1
23Extracellular 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.
24Buffering Capacity of Muscles vs. Blood
25Respiration 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
26Changes in Lactate, Bicarb and pH vs. Work Rate
27Lines of Defense against pH Change during Intense
Exercise