Physiology

Question 0

Affect of high altitude on ventilation. 
• What is the stress? 
• What does it result in?
• Body compensation?
• Most serious side effect?
• Rx?

Answer 0

Stress = ⬇️ total pressure!

1)

Question 1

Neural Regulation of Alveolar ventilation?

What systems & what stimulates each?

Answer 1

1) Chemoreceptors 
• Central receptors on medulla:
Stimulation = ⬆️ ventilation. 
Stimulus => ⬆️ CSF CO2. 
NB: adapt to chronic changes e.g COPD. 
Don't respond to O2. 

• Peripheral receptors on carotid & aortic arch.
Monitor arterial blood!
Stimulated by > PaCO2, very low PaO2 & H (acidosis).
NB: DO NOT ADAPT!
=> Anemia doesn’t stimulate the receptors b/c PaO2 is normal. It could stimulate them if O2 delivery decreases and acidosis forms.

2) Brainstem (Pons & medulla).
Control RR & rhythm.

Question 2

Pathophysiology of nephrogenic DI?

Answer 2

• ❌ ADH receptors => No re absorption at collecting ducts.

- Loss of free water => ⬆️ Na.

Question 3

Rx of nephrogenic DI?

Answer 3

• thiazides to reduce ECF = ⬆️ Oncotic pressure = ⬆️ re absorption.
• Reabsorption of H2O & loss of Na corrects low Na.