respiratory: control of ventilation

Question 1

part of brain responsible for neural control of ventilation

Answer 1

brainstem: medulla, pons, midbrain

Question 2

what respiratory nuclei does the medulla contain

Answer 2

dorsal respiratory group in nucleus tractus solitarius
ventral respiratory group containing nucleus ambiguus and retroambigualis
pre-botzinger and botzinger complex near nucleus retrofacialis

Question 3

what is pre-botzinger complex’s function

Answer 3

respiratory rhythmogenesis

Question 4

what does DRG do

Answer 4

contains only inspiratory neurons that fire just prior to and during inspiration
ramp-like activity (steady increase and abrupt cessation)
controls depth/rate/pattern of breathing
input from chemo and mechanoreceptors in lung via CN X & IX & spinal cord
activity relayed to phrenic nerves
inhibits expiratory neurons in VRG and pontine respiratory group

Question 5

what does the pons contain?

Answer 5

pontine respiratory group, which is made of pneumotaxic centre (inhibits inspiratory phase, allowing expiration) and apneustic centre (prolongs inspiration)
pneumotaxic centre comprises of nucleus parabrachialis and kolliker-fuse nucleus

Question 6

components of Central pattern generator, what influences these components

Answer 6

pons: pneumotaxic centre, apneustic centre
medulla: VRG, DRG
higher centres (temp/emotion) influence pons
chemo receptors/mechanoreceptors influence medulla

Question 7

what happens if smooth muscle of bronchial walls are stimulated

Answer 7

inspiration is shorter/shallower

next inspiratory cycle is delayed

Question 8

whats hering-breuer reflex

Answer 8

inflation inhibits inspiration-> prevents over inflation, only present when adults take huge breaths

Question 9

deflation reflex

Answer 9

deflation augments inspiration

Question 10

juxtapulmonary receptors location/effects/stimulants

Answer 10

in alveolar walls close to capillaries
causes apnoea/rapid shallow breathing/bp and hr fall/skeletal muscles relax/larynx constricts
stimulated by increased alveolar wall fluid/oedema/pulmonary congestion/histamine

Question 11

irritant receptors location/effects/stimulants

Answer 11

throughout airways between epithelial cells
trachea-> cough; lower airways-> hyperpnoea; bronchial and laryngeal constriction
responsible for deep breaths every 5-20 mins at rest-> reverse slow collapse of lungs during quiet breathing
stimulated by irritant gases/smoke/dust /rapid inflations and deflations

Question 12

proprioceptive afferents location/stimulants/importance

Answer 12

respiratory muscles
stimulated by shortening and load of respiratory muscles
important for coping with increased load-> optimal tidal volume and frequency achieved

Question 13

what do pain receptors do

Answer 13

brief apnoea-> increased breathing

Question 14

trigeminal region (nose) and larynx

Answer 14

apnoea, spasm, increased hr, sneezing

Question 15

arterial baroreceptors

Answer 15

stimulation inhibits breathing

Question 16

how ventilation is affected by alveolar pco2

Answer 16

at low levels of co2, ventilation rate plateaus out->
increases linearly with increasing levels of co2-> at 9kpa of pco2 respiratory centre is depressed-> ventilation rate drops

Question 17

how does pH change ventilation graph

Answer 17

acidosis-> leftward shift-> hyperventilation (blow off excess co2)
alkalosis-> righward shift-> hypoventilation

Question 18

how do o2 levels affect ventilation? how does hypercapnia affect the graph? what’s so special about hypoxia + hypercapnia?

Answer 18

ventilation decreases with increasing o2 levels;
below 8kpa, o2 dissociates from haemoglobin-> body compensates for this by increasing ventilation below this level of oxygen
when o2 levels are too low-> respiratory centre is depressed
hypercapnia results in rightward + upward shift
hypoxia +hypercapnia are synergistic -> increase ventilation (gap between normal graph and hypercapnic graph increases as environment becomes more hypoxic)

Question 19

where are chemoreceptors in brainstem ?

Answer 19

ventrolateral surface of medulla, at exit of CNX and cnix

Question 20

how is pH affected in brain

Answer 20

central receptors detect
[h] proportional to pco2 from blood
inversely proportional to hco3- from CSF
CSF has little protein-> no buffering of pH-> small rise in pco2 causes large change in pH

Question 21

how do central chemoreceptors respond to prolonged hypercapnia; example of disease

Answer 21

ventilatory drive falls-> CSF pH returns to normal

eg chronic respiratory disease

Question 22

how do central chemoreceptors respond to altitude

Answer 22

CSF initially alkaline due to hypoxia-> increased ventilation
after days/weeks, CSF returns to normal and drive increases

Question 23

what are 2 peripheral chemoreceptors? what cells are they made of and what are their properties? what are their functions?

Answer 23

carotid/aortic bodies;
type I: glomus (rich in NT; in contact with axons)
type II: sheath cells (enclose glomus cells);
fire when pco2/H+ increases
fire when po2 decreases

Question 24

chyne-stokes respiration

Answer 24

rapid breathing-> long pause -> o2 saturation oscillates

caused by heart failure/stroke/altitude sickness

Question 25

central sleep apnoea causes

Answer 25

can’t breathe: neuromuscular eg muscular dystrophy/phrenic nerve damage/disease
wont breathe: brainstem damage/disease