s4. chemical control ventilation

Question 1

describe relationship between pH and H+ conc

Answer 1

as pH inc, [H+] dec, more alkaline

Question 2

compare what peripheral and central chemoreceptors sense?

Answer 2

peripheral:
dec in pO2
high pCO2
low pH
* first chemoreceptor to respond

central:
dec in pH
inc in pCO2

Question 3

where are peripheral chemo receptors found?

Answer 3

carotid bodies- bifurcation common carotid arteries

aortic bodies- aortic arch

Question 4

difference between carotid sinus and carotid bodies

Answer 4

carotid bodies- peripheral chemo receptors

carotid sinus- baroreceptors

Question 5

what are glomus cell function? found where?

Answer 5

Sensing cell >pO2, pCO2, pH> [H+]

found in carotid body

Question 6

what happens if peripheral chemoreceptors sense low pO2/ high pCO2

Answer 6

feed back to medulla to INC minute ventilation

Question 7

describe sensory enervation of carotid body and aortic body

Answer 7

carotid- branch of CN IX (glossopharyngeal)

aortic- branch of CN X (vagus)

Question 8

where are central chemoreceptors found?

Answer 8

located on brain side of BBB>bathed in CSF

Question 9

describe the permeability of BBB for H+, HCO3-,CO2

Answer 9

LOW permeability to H+, HCO3-

HIGH permeability to CO2

> CO2 diffuses into CSF bathing brain cells (incl central chemoreceptor neurone cells)

-CNS has limited buffering capacity so even small dec in pH raises the firing rate of central chemoreceptor therefore inc ventilation

Question 10

describe CNS metabolic compensation to respiratory acidosis

Answer 10

if pCO2 remains high, pH slowly recovers/increases
DUE TO choroid plexus increasing active transport of HCO3- into CSF > induced acidosis gradually becomes smaller

> higher level of CO2 is needed to cause acidosis and thereby inc ventilation

• can occur in diseases that lead to chronic hypercapnia

Question 11

respiratory disease associated with obesity?

Answer 11

syndrome of obesity associated hyperventilation

Question 12

what is the haldane effect?

Answer 12

low O2 conc increases the CO2 carrying capacity of haemoglobin because release of O2 from Hb promotes binding of CO2