Control of Respiration

Question 1

what is main respiratory center in brain

Answer 1

rostral ventrolateral medulla (part of brain stem)

generates breathing rhythm spontaneously without input from lungs

Question 2

what is mechanism of spontaneous breathing rhythm in brain

Answer 2

1) receive input into medulla
2) drives motor neurons that control respiratory muscles (changed by change in tidal volume and breathing rate)
3) drive inspiratory and expiratory muscles

Question 3

after breathing rhythm generated, how can frequency of breathing be modulated

Answer 3

1) central and peripheral chemoreceptors
2) cortex
3) limbic system
4) pons
5) pulm irritant receptors
6) pulm stretch receptors

Question 4

location of peripheral chemoreceptors

Answer 4

carotid on type 1/glomus cells in aortic arch

Question 5

what stimulates PERIPHERAL CHEMOreceptors

how do peripheral chemoreceptors respond

Answer 5

decr arterial O2

incr arterial PCO2

incr arterial [H+] = decr arterial pH

–> INCR VENTILATION

Question 6

describe response of peripheral chemoreceptors to high arterial pCO2

when is it important

Answer 6

VERY RAPID within sec to exhale CO2

–> important in sudden physical exertion when resp system must quickly match ventilation to metab rate

Question 7

describe response of carotid bodies to decr pH

Answer 7

RAPID
vasodilatory

ONLY MEDIATOR OF RESPONSE TO METABOLIC ACID/BASE INSULTS

Question 8

where are central chemoreceptors located

what do they sense

Answer 8

ventral surface of medulla

1) H+ receptors that incr activity with incr H+ binding IN CSF
2) sense arterial pCO2

Question 9

describe mechanism of central chemoreceptors sensing pCO2

Answer 9

1) CO2 cross BBB into CSF (impermeable to charged)
2) CO2 + H2O H+ + HCO3-
3) chemoreceptors in brain bind H+
4) incr ventilation in response to low pCO2 long term (80% OF VENTILATORY RESPONSE)

Question 10

is the central chemoreceptor response to pCO2 fast or slow

Answer 10

slow- minutes

Question 11

why do central chemoreceptors have such a strong response to changes in blood pCO2

therefore, small change in CO2 = ____

Answer 11

because buffering capacity of CSF is low since it lacks large amount of protein

–> small changes in CO2 = large incr in CSF protons

Question 12

what is role of BBB in terms of what can pass through

Answer 12

blocks H+

allows fat soluble molec (CO2) to pass through

Question 13

what is implication of BBB allowing passage of CO2

what do H+ ions formed bind to?

Answer 13

central chemoreceptors sensitive ONLY TO ARTERIAL CO2 NOT ARTERIAL H+ CONCENTRATION

H+ formed by dissociation of H2CO3 bind central chemoreceptor

Question 14

a

Answer 14

a

Question 15

a

Answer 15

a

Question 16

a

Answer 16

a

Question 17

how does high altitude affect PAO2

Answer 17

at high altitude, decr PIO2, decr PAO2 –> hypoxemia

Question 18

how does high altitude affect ventilation

Answer 18

at high altitude low PIO2
cause hypoxia
incr breathing via peripheral chemoreceptors

Question 19

how does high altitude affect PCO2 and H+ in CSF and blood

how does this affect breathing response

Answer 19

at high altitude

1) low PIO2 (low inspired O2)
2) decr PaO2 (low arterial O2)
3) incr activ of peripheral O2 receptors
4) incr ventilation (incr VAdot)
5) incr PaO2

5) incr ventilation also decr PaCO2,
6) decr PCO2 (CSF), decr [H+] CSF
7) decr activity of central H+ receptors
8) decr drive to incr ventilation and stops incr in ventilation as a result of low PaO2

INITIAL RECOVERY OF PaO2 at high altitude is incomplete

Question 20

how does body adjust over days to high altitude

Answer 20

compensation over 2-3 days because time for bicarb levels in blood to decr so normal PaO2 obtained eventually

low blood pCO2,
decr [H+] in blood because less CO2 to undergo hydrolysis – alkalosis

compensation: decr in bicarb reabsorb in kidney
decr bicarb in blood
so gradient for bicarbonate to leave CSF
frees up H+ to activ central H+ receptor
back to near normal activity of H+ receptors so ventilation incr

Question 21

how does body respond to incr CO2 with exercise

Answer 21

CO2 removal must keep up with incr production

peripheral + central chemoreceptors for pCO2 and pH INCR VENTILATION to breathe off incr CO2

INCR TIDAL VOLUME AND INCR BREATHING FREQ

Question 22

WITH MODERATE EXERCISE, what is relationship between O2 consumption/CO2 production and ventilation

Answer 22

linear

incr O2 consumption/CO2 production, incr ventilation to blow it off

Question 23

with intense exercise what happens to O2 consumption/CO2 production vs. ventilation

why?

Answer 23

steep incr in ventilation

b/c incr lactic acid in blood, incr pH ventilator stimulus (anaerobic threshold)

Question 24

what is anaerobic threshold

Answer 24

when intense exercise

incr lactic acid in blood, incr pH ventilator stim

Question 25

if there are regions of low V/Q, regions of high V/Q develop in order to ___

Answer 25

maintain normal CO2 levels and pH

Question 26

how can total ventilation be changed at level of motor neurons

Answer 26

change tidal volume

change breathing rate

Question 27

describe relationship between alveolar ventilation (VA dot) vs. PaO2

Answer 27

non-linear, negative expontential

in Denver, we at shallow part of curve (PaCO2 = 36 Torr)

Question 28

WHAT IS MOST IMPORTANT DAY TO DAY REGULATOR OF VENTILATION

Answer 28

CENTRAL CHEMORECEPTORS

Question 29

CSF has ___ buffering capacity

Answer 29

low

Question 30

which receptor type mediates incr in ventilation?

climbing mt everest

Answer 30

peripheral O2 receptors

Question 31

which receptor type mediates incr in ventilation?

ketoacidosis

Answer 31

peripheral proton receptors

Question 32

which receptor type mediates incr in ventilation?

climbing stairs

Answer 32

peripheral CO2 receptors

short time frame, central chemoreceptors not affected

Question 33

which receptor type mediates incr in ventilation?

bronchitis

Answer 33

central proton receptors/CO2 sensors

long time, CO2 is main element could mediate compensatory incr in ventilation

Question 34

What elements in blood potentially mediate compensatory incr in ventilation for obstructive disease (bronchitis)

why not others?

Answer 34

CO2

not H+ b/c limited by buffering in blood

not O2 b/c low sensitivity of receptors in O2 levels that would occur with low O2 with high CO2 (little change in VAdot vs. PaO2 curve)