Reflex control of the heart

TLDR: It is concluded that the neck cuff method gives useful information about heart rate changes but is less reliable when blood pressure is used as the response, because the relatively slow changes in arterial smooth muscle tone are probably the result of the differing information sensed by the carotid and aortic receptors.

Abstract: The control of heart rate by the arterial baroreceptors and the evidence that these reflexes are impaired in people with raised arterial pressure are reviewed. The results with the Oxford phenylephrine test are compared with those using neck cuff methods as the stimulus. It is concluded that the neck cuff method gives useful information about heart rate changes but is less reliable when blood pressure is used as the response, because the relatively slow changes in arterial smooth muscle tone are probably the result of the differing information sensed by the carotid and aortic receptors. Contrary to the diminution in baroreflex gain seen with the phenylephrine methods, Mancia and his colleagues in Milan (using a neck cuff) report increased response of blood pressure in patients with hypertension. This may be a result of the increased arteriolar smooth muscle in hypertension. The evidence for the existence of neurogenic “deafferentation” hypertension is reviewed; it is concluded that denervation hypertension does exist, despite the experiments of Cowley and Guyton. It is possible that some cases of human essential hypertension may be the result of arterial baroreceptor partial denervation caused by stiffening of the baroreceptor areas by arteriosclerosis.