Tracthe: Control of Ventillation Flashcards
What are the major sensors controlling respiration?
Central controller
Peripheral sensors (chemoreceptors)
Efferent mechanisms (nerves and muscles)
Where is the central controller located?
Brainstem (Pons and medulla)
What is unique about the cells of the central controller?
UNSTABLE resting membrane potentials (pacemaker activity)
How can the cortex increase or decrease breathing?
OVERRIDES the brainstem
What affect do panic attacks have on Pco2
HALVE it
How much does alveolar ventilation need to be increased to half PCO2?
Double
What are the most important sensors in day to day regulation of ventilation?
Central chemoreceptors
What do the central chemoreceptors do?
Respond to pH
What and where are the peripheral chemoreceptors located?
Carotid bodies in the Aortic arch
What do the peripheral chemoreceptors respond to?
PCO2 and PO2
AND
pH
What are the lung receptors?
Stretch receptors
irritant receptors
J receptors
Bronchial C fibers
What stimulates the central pH receptors?
increase in H
What affect does alkalosis have on respiration?
SUPPRESSES it
What surrounds the central pH receptors?
Cerebrospinal fluid
How does H stimulate the central pH receptor?
H can’t cross the BBB>
CO2 diffuses across and is converted to CA by carbonic anhydrase>
plasma CO2 determines CSF pH
What is normal CSF pH?
7.32
How does the CSF compensate for an aberrant CSF acidosis?
HCO3 retention
HCO3 retention by the CSF is observed in pts w/ what condition?
Pts with EMPHYSEMA have LOW PO2 and HIGH PCO2 and low respiration rates b/c of the compensation
What are the two types of peripheral chemoreceptors?
Aortic arch
Carotid bodies
What peripheral chemoreceptors are particularly good at detecting hypoxia?
Carotid bodies
When do the peripheral chemoreceptors respond to hypoxia? What happens to the firing rate?
100 mmHG
Increases as PO2 decreaes
Which peripheral chemoreceptors respond to a decrease in pH?
Carotid bodies
Which peripheral chemoreceptors respond to hypercapnia?
Carotid AND aortic but they’re not as important as the CENTRAL CHEMORECEPTORS
What is the stimulus for increased breathing in exercise?
movement of limbs>
joint/muscle receptors>
increases RR
How does an increase in PCO2 affect ventilation?
Each 1 mmHg increase>
2-3 L increase in ventilation
When do most individuals respond to hypoxia?
If CO2 is held constant>
not until PO2 drops BELOW 50 mmHg
What are exceptions to the normal response to hypoxia?
High altitude
Chronic obstructive lung disease (adapts to changes in pH caused by CO2 retention)
How does low pH affect ventilation?
Stimulates it–often seen in metabolic acidosis (diabetic ketoacidosis)
How does exercise typically affect PCO2 and PO2?
FALL in PCO2
RISE in PO2
How does exercise affect pH?
Stable until intense levels
What is the chief baseline control of respiration?
Brainstem (pacemakers)
What are the chief inputs that control respiration?
pH in CSF
PCO2, PO2 and pH in the periphery
How do medullary pH sensors monitor arterial PCO2?
by its influence on CSF acidity
What do carotid and aortic bodies sense?
PCO2
arterial pH
What do ONLY carotid bodies sense?
O2
What causes an increase in breathing?
HIGH PCO2
LOW PO2
pH
What is most relevent for day to day control of ventilation?
CO2
WHat is most relavent for altitude adaptations and chronic lung disease?
PO2
