CV question, carotid sinus

[alternatego]

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if a person cuts the glossopharyngeal nerves innervating the carotid sinus (which is able to detect both an increase and a decrease in BP), I understand that the CNS will think that there has been a sudden drop in BP and try to compensate by enhancing the sympathetic discharge, thus increasing HR (heart) and BP (by increasing TPR as a result of vasoconstriction).

But, what is the role of the aortic sinus? It can only detect increases in BP, wouldn't it counteract the CNS compensation reflex and keep both BP and HR within normal limits?

 

[ijn]

The aortic chemoreceptors and baroreceptors don't do much in humans. They're more of an evolutionary curiosity than of physiological importance.

 

[alternatego]

The aortic chemoreceptors and baroreceptors don't do much in humans. They're more of an evolutionary curiosity than of physiological importance.

Thanks a lot dude!!! I'll be sure to anotate that into BRS Phys. 👍

 

[ijn]

They had an NBME question where the carotid bodies were removed but the surgeons left the aortic bodies intact. The graph you had to pick basically showed that you had no more hypoxic drive in the body. So essentially it does jack ****.

 

[Phloston]

The aortic chemoreceptors and baroreceptors don't do much in humans. They're more of an evolutionary curiosity than of physiological importance.

Could you please be more specific here? I've never heard of that before.

I had encountered a practice question where this wrestler was in a chokehold (i.e. enjoying a carotid massage), leading to increased afferent glossopharyngeal firing, decreased sympathetic efferent and therefore decreased HR/BP. However the question also asked for the what the aortic arch baroreceptors were doing, and the answer was reactive decreased vagal firing. That makes sense, but I had also wondered whether this was the mechanism that contributes to the baroreceptor reflex, such that although HR/BP decrease initially, it is the lack of aortic vagal response that ultimately is significant for the reversal (i.e. increase) in HR. The opposite would be true if the carotid sinus had decreased stretching.

That's why I'm not so sure it can be said that the aortic arch's effects are not that significant in human/evolutionary terms.

 

[ijn]

Try to find a single article on the effect of a denervated aortic body in a human. I haven't been able to find anything.

 

[Phloston]

Try to find a single article on the effect of a denervated aortic body in a human. I haven't been able to find anything.

I would think that since both the carotid or aortic bodies would be sensitive to paO2 < 60 mm Hg, removal of either would not result in loss of low-O2-induced respiratory drive.

Their redundant functions shouldn't suggest that either the carotid or aortic chemo-/baroreceptors are evolutionarily vestigial.

 

[ijn]

Do you gloss over anything that says NBME? Their recorded correct answer for denervation of the carotid body is graph that displays a complete lack of hypoxic respiratory drive. Therefore the aortic bodies, per the NBME, do nothing of physiological significance in humans. You can find several papers via a quick google search to back that up in humans. However there isn't a single entry on aortic body denervation in humans.

 

[Phloston]

Do you gloss over anything that says NBME? Their recorded correct answer for denervation of the carotid body is graph that displays a complete lack of hypoxic respiratory drive. Therefore the aortic bodies, per the NBME, do nothing of physiological significance in humans. You can find several papers via a quick google search to back that up in humans. However there isn't a single entry on aortic body denervation in humans.

Even if the aortic bodies do in fact play a lesser role with respect to hypoxic drive, are you sure they do nothing? That's keeping in mind that pH and pCO2 are still sensed by them, not just pO2.