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Unformatted text preview: the lungs where
the cycle will repeat as gas exchange takes place with the alveolar air. VII. RESPIRATORY ACID-BASE BALANCE
Relationship between CO2 and pH:
H2 O + CO2 ¯ H2 CO3 ¯ H+ + HCO3 G HCO3- binds to plasma proteins, so CO2 acts as an acid in the blood
bicarbonate can't stay there and act as a buffer When H2O and CO2 mix, they form carbonic acid which dissociates into hydrogen ions and
pCO2 is the strongest stimulus affecting breathing rate i Respiration is normally adjusted to keep pace with the metabolic rate . more oxygen used and more CO2 made. CO2 levels really affect rate. Acid-Base imbalances:
A. Respiratory acidosis
pH in blood going down. caused by not enough CO2 leaving, breathing too slow will do this (hypoventilation, could be caused by diseases, concussion) B. Respiratory alkalosis
pH in blood becomes more basic, rises. Hyperventilation
relate to renal pH balance? kidneys have a more long-term adjustment. Kidney's job is more chronic, change secretion and absorption of H+ and bicarbonate. Respiration is more
minute changes such as breathing differently during exercise, too quick for kidney to deal with VIII. REGULATION OF RESPIRATION BY CHEMORECEPTORS
Two sets of chemoreceptors detect changes in ____________ & _____________ in the blood.
pCO2 A. Central receptors:
located in the medulla oblongata
monitor the pH of CSF, very similar to pH in blood stream, essentially
equal. B. Peripheral receptors
in the aortic arch and carotid bodies.
measure pH and PO2 levels in the blood
send feedback to the medulla oblongata (somewhat secondary to central for rate moderation) Question: Why isn’t PO 2 an important contributor to control of respiration?
oxygen is variable in our body, 160mmHg at sea level but decreases wherever we go. Don't want pO2 to affect your respiration rate.
small changes in CO2 will change pH and this is why we monitor them
as blood pO2 drops only increases the chemoreceptors sensitivity to PCO2
arterial pO2 has to fall by 50% before this effect occurs IX. REGULATION OF BREATHING
There are 3 locations that help control breathing:
1. Medulla oblongata:
site of the rhythmicity center (much like SA node) normally breath 12 times a minute
semi-voluntary control of breathing
A. inspiratory neurons (excitatory neurons) contract
B. Expiratory neurons: inhibit inspiratory neurons. relaxes diaphragm, exhale. 2. Pons:
a. pneumotaxic center
regulate breathing (12 times a minute)
simply frequency b. apneustic center
increase depth of breathing, example keep inspiratory neurons on a little bit longer
pressure will drop a little bit, and we will breath in a little bit more.
delays onset of inspiratory
cortical control 3. Cerebral cortex:
breathing is "semi-voluntary"
frontal lobe can send voluntary commands to respiratory muscles.
overrides the rhythmicity center X. LUNG VOLUMES AND CAPACITIES
Spirometry is used to measure lung volumes and capacities and is useful in diagnosing
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This note was uploaded on 09/30/2013 for the course P 215 taught by Professor Mynark during the Fall '12 term at Indiana.
- Fall '12