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The Bainbridge reflex is involved in Respiratory (Sinus) Arrhythmia

Simply it means that a stretch of the atria (increased volume) will lead to reflex increase in the heart rate.

During inspiration there will be:

  • Increased heart rate (tachycardia) -- Bainbridge Reflex
  • Decreased blood pressure (hypotension) -- Pulsus paradoxus
As we inhale we will decrease the intrapleural pressure and this will lead to decreased pressure around the atria allowing them to stretch more. This is specially true for the right atrium.

But the decreased pleural pressure also means greater stretch of the pulmonary veins. Since these are very compliant veins then the pressure drops and there will be less blood coming back to the left atrium which leads to decreased arterial systolic pressure (hypotension).

Do not confuse the bainbridge reflex with the baroreceptor reflex which is located in the carotid sinus and aortic arch and sneses changes in the blood pressure in these vascular areas then project impulses to the medulla.
 
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