Control of Lung

Question 1

What are the 4 regions of the medulla used in lung control?

Answer 1

1. Dorsal respiratory group —> inspiration
   
   • controls breathing rate via intercostal muscles
   • inhibits ventral respiratory group
2. Ventral respiratory group —> expiration (forceful)
   
   • inactive during quiet breathing
   • inhibits dorsal respiratory group
   • inhibits apneustic centre
3. Apneustic centre —> stimulates DRG
   
   • inhibited by pulmonary afferents
   • stimulates dorsal respiratory group
4. Pneumotaxic centre —> stops inspiration
   
   • regulates depth and frequency
   • inhibits dorsal respiratory group

Question 2

What are the 3 receptors of the pulmonary system?

Answer 2

1. Irritant receptors
   
   • senses —> irritants
   • location —> trachea/bronchi epithelium
   • effect —> coughing
2. Stretch receptors
   
   • senses —> excessive inflation
   • location —> bronchiole epithelium
   • effect —> inhibit inspiration
     - inhibit DRG and apneustic
     —> stimulate expiration
     - stimulate VRG and pneumotaxic
3. J-receptors
   
   • senses —> pulmonary capillary engorgement
     (∵ extra blood to lungs suggest issue)
   • location —> alveolar surface
   • effect —> inc breathing frequency —> inc O2 in

Question 3

How is the rate of quiet breathing controlled?

Answer 3

DRG —> starts inspiration
Apneustic —> inc depth of breath
- inc AP frequency —> inc membrane
depolarisation
Pneumotaxic —> stops in breath —> exhale
- stops action potential —> ‘respiratory
pacemaker’

Question 4

How is the phrenic nerve involved in respiratory control?

Answer 4

C3, C4, C5 nerve fibres —> phrenic nerve —> innervates diaphragm muscles
- damage above C3 —> can’t breath

Question 5

How does the medulla sense blood pH?

Answer 5

CO2 lipid soluble —> crosses capillary endothelium into CSF —> H2O + CO2 —> H+ + HCO3- (carbonic anhydrase) —> H+ sensed by nerve endings in medulla —> nerve projections to dorsal respiratory nucleus

Question 6

What happens to arterial O2 and CO2 pressure when you hold your breath?

Answer 6

PaO2 —> dec
- towards O2 threshold for blackout
PaCO2 —> inc
- towards CO2 threshold for breathing

Question 7

How is pH controlled inside a red blood cell?

Answer 7

Blood acts as buffer…
CO2 + H2O —> H+ + HCO3- via carbonic anhydrase
- HCO3- pumped out via AE1 transporter (anti-port
with CO2)
- CO2 mopped up by Hb
- H+ mopped up by proteins

Question 8

How is blood pH regulated?

Answer 8

Artery —> stay between 7.35 to 7.45
- Urine - bicarbonate/proton reabsorption or
excretion
- pH 4-8
- Red blood cells - HCO3- out via AE1 transporter
- Hb (NH2 end) binds to CO2
- protein chains bind to H+

Question 9

What is alkalaemia vs acidaemia?

Answer 9

Alkalaemia —> blood pH too high
Acidaemia —> blood pH too low

Question 10

How do you calculate pH?

Answer 10

pH = log10[H+]
∴ [H+] = 10^-pH

Question 11

What is alkalosis vs acidosis?

Answer 11

Alkalosis —> increase of blood pH (more alkaline)
Acidosis —> decrease of blood pH (more acidic)

Question 12

How is blood oxygen concentration sensed?

Answer 12

Peripheral chemoreceptors
- carotic bodies - aortic arch branches
—> CN IX
- aortic bodies - aortic arch body
—> CN X

Question 13

How do emotions affect lung control?

Answer 13

eg. fear —> higher respiratory rate —> more O2 in

Question 14

How does the skin affect lung control?

Answer 14

Dec temp —> inc inhalation/hyperventilation

Question 15

How does exercise affect lung control?

Answer 15

Afferent - fibres from muscle spindles and golgi
tendons to brain —> cross medulla
Efferent - primary motor cortex to musculature —>
cross medulla