Physiology: chemical control of respiration

Question 1

what type of control system is chemical control of respiration an example of

Answer 1

negative feedback control system

Question 2

where are peripheral chemoreceptors found

Answer 2

the aortic bodies and carotid bodies

Question 3

where are the central chemoreceptors found

Answer 3

near the surface of the medulla in the brainstem

Question 4

what do the peripheral chemoreceptors sense

Answer 4

the tension of O2 and CO2 in the blood, and the conc. of H+

Question 5

what do the central chemoreceptors sense

Answer 5

the conc. of H+ in the cerebrospinal fluid(CSF)

Question 6

how does the system respond to changes in the Pco2

Answer 6

it is very responsive

via CO2 generated H+ sensed through the central chemoreceptors

Question 7

give some important properties of the CSF and blood brain barrier

Answer 7

CO2 readily diffuses across

impermeable to H+

Question 8

what effect does hypercapnia have on ventilation

Answer 8

increased Pco2(hypercapnia) increases ventilation

Question 9

what influence does arterial PCO2/[H+] in brain CSF have on the peripheral and central chemoreceptors

Answer 9

peripheral = weak stimulation
central = strong stimualation + dominant control over ventilation

Question 10

what influence does arterial Po2 have on the peripheral and central chemoreceptors

Answer 10

peripheral = only important if Po2 falls < 8kPa
central = severe hypoxia depresses respiratory centre

Question 11

what influence does arterial H+ conc. have on peripheral and central chemoreceptors

Answer 11

peripheral = stimulates it
central = H+ cant cross blood-brain barrier so no stimulation