NBME 5 block4 q23 - maryam2009

[ArchivalUser]

but you have to think this is an animal. what about the effect of accumulation of CO2 at the same time? it will stimulate the medulla for respiratory center too.

[ArchivalUser]

Hi there
the Q is just showing the relation between oxygen concentration and minute ventilation ...and all choies are also designed for this purpose and I am agree with lovetest

[ArchivalUser]

minute ventilation=tidal volume x breath/min

so the effect of CNS respiratory in the brain also plays a role and should be considered.

[ArchivalUser]

Answer is E (Graph same as original but with lower minute ventilation)
Explanation:
Peripheral Receptors: Respond to o2, co2, ph of BLOOD.
Central Receptors: Respond to co2 & ph of CSF.
Normal situation- Central receptors dominate in controlling ventilation rate. But if o2 drops below 60 then peripheral dominates.

Experimental situation: Since peripheral is removed, central dominates when o2 is above 60 and central still dominates when o2 falls below 60.

Conclusion: Graph looks like as original except with lower ventilation response since central doesnt response as quickly as peripheral.

[ArchivalUser]

@nnoor

Graph A --- is the same as the one in the stem
Graph E --- shows that at Incr O2 concen(x-axis) , Minute Vent Collapsed(y-axis)

*There are no Central PO2 receptors, only the peripheral (Carotid Bodies) which only response to "LOW Peripheral PO2"----- so if carotid body removed, there will be "NO Response to Low PO2"
and u just see that "Flat line on the Graph", which itself represent the "Spontaneous Breathing"
that is controlled by PCO2 mainly on the Central Chemoreceptors.


"D" is the correct answer

[ArchivalUser]

While the central chemoreceptors in the brainstem are highly sensitive to CO2 the carotid body is a peripheral chemoreceptor that mainly provides afferent input to the respiratory center that is highly O2 dependent. However, the carotid body also senses increases in CO2 partial pressure and decreases in arterial pH, but to a lesser degree than for O2

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