Week 1 .5 Flashcards
How is rate of ventilation typically controlled? (2 examples)
Mechanosensory input - stretch reflex, chemical composition of blood
What kinds of chemoreceptors do we have?
central and peripheral
what do central chemoreceptors respond to?
levels of CO2
How do central chemoreceptors detect a change in CO2?
detect changed in [H+] in CSF around brain. CSF isn’t soluble to H+, so CO2 dissolves in and then dissociates into H+ and HCO3-. Chemoreceptors then detect [H+]
How do chemoreceptors respond to low [H+] in CSF?
That means pH is high and there’s less CO2 so ventilation decreases
what is hypercapnea?
too much CO2 in blood. causes H+ to rise. you begin to ventillate to remove excess CO2 and avoid respiratory acidosis
How is ventilation monitored in people with chronic lung disease like COPD?
central mechanoreceptors are less sensitive to change in [H+], so peripheral chemoreceptors detect changes in pO2 in arterial blood instead
Why are peripheral chemoreceptors inferior to central ones?
a small change in pCO2 leads to a large response in ventilation, which is very efficient for maintaining homeostasis.
however a large change in pO2 is required for peripheral chemoreceptors to respond
What effect does anaesthetic have on resp. rate and tidal volume?
increases resp rate but decreases tidal volume so alveoli are less ventilated - hypoventillation
How do barbiturates and opioids effect resp. centres?
Decreases sensitivity to H+ and pCO2, and peripheral chemoreceptors response to pO2 decreases too
How does nitrous oxide effect our resp. centres?
Its safe for most, but blunts peripheral pO2 chemoreceptors. it can be very dangerous for people with chronic lung disease
How do you know what the cause of a change in pH is?
If pH changes due to CO2 changes, it’s a respiratory problem. Is pH changes due to HCO3- changes, it’s a metabolic problem.
What happens to an individual whose pO2 is normal but pCO2 is high?
They’ll have higher pCO2 in alveoli vs circulation, so CO2 wont be able to escape the body. Patient will be very distressed
