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Guyton mentions two types of receptor- the baroreceptors and the cardiopulmonary receptors- that are involved in the maintenance of the acute changes in blood pressure. I just wanted to know how these two receptors might differ functionally, i.e. which one is triggered when a certain specific event occurs? According to Guyton:

.. low- pressure receptors play an important role, especially in minimizing arterial pressure changes in response to changes in blood volume...

How is it that these (Cardio-pulmonary) receptors are significant when there is a change in volume? Is there some other physiological explanation to justify why these receptors are implicated in this scenario and not the Baroreceptors? If that is not the case, should I view both these systems as a single unit and that they both do the same function, albeit in a different region of the circulation?

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High-pressure baroreceptors are in the part of the circulatory system with blood pressures higher than 60 mm Hg - in the aortic arc and in the carotid sinus at the bifurcation of the carotid artery. Their activation by high blood pressure results in a decreased heart rate and vasodilation and hence in a drop of blood pressure.

Low-pressure baroreceptors are in the part of the circulatory system with pressures below 60 mm Hg - in the pulmonary arteries and right atria, among other. Their activation by increased blood volume (increased tension of the wall of the right atrium and pulmonary arteries) results in a decreased secretion of the antidiuretic hormone, renin and aldosterone and thus in increased water excretion by the kidneys.

So, the two types of baroreceptors are activated by different stimuli and have different effects.

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