"Smart" baroreception along the aortic arch, with reference to essential hypertension.
Beat-to-beat regulation of heart rate is dependent upon sensing of local stretching or local "disortion" by aortic baroreceptors. Distortions of the aortic wall are due mainly to left ventricular output and to reflected waves arising from the arterial tree. Distortions are generally believed to be useful in cardiac control since stretch receptors or aortic baroreceptors embedded in the adventitia of the aortic wall, transduce the distortions to cardiovascular neural reflex pathways responsible for beat-to-beat regulation of heart rate. Aortic neuroanatomy studies have also found a continuous strip of mechanosensory neurites spread along the aortic inner arch. Although their purpose is now unknown, such a combined sensing capacity would allow measurement of the space and time dependence of inner arch wall distortions due, among other things, to traveling waves associated with pulsatile flow in an elastic tube. We call this sensing capability--"smart baroreception." In this paper we use an arterial tree model to show that the cumulative effects of wave reflections, from many sites far downstream, have a surprisingly pronounced effect on the pressure distribution in the root segment of the tree. By this mechanism global hemodynamics can be focused by wave reflections back to the aortic arch, where they can rapidly impact cardiac control via smart baroreception. Such sensing is likely important to maintain efficient heart function. However, alterations in the arterial tree due to aging and other natural processes can lead in such a system to altered cardiac control and essential hypertension.
Kember
G C
GC
Department of Engineering Mathematics, Dalhousie University, P.O. Box 1000, Halifax, Nova Scotia, Canada B3J 2X4.
Zamir
M
M
Armour
J A
JA
D000818:Animals; D001013:Aorta, Thoracic / Q000294:innervation* / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology*; D003198:Computer Simulation; D005246:Feedback / Q000502:physiology; D006487:Hemostasis / Q000502:physiology; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008955:Models, Cardiovascular; D011311:Pressoreceptors / Q000502:physiology*; D011673:Pulsatile Flow / Q000502:physiology*