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ABSTRACT: The baroreflex loop consists of both a fast neural arc and a slow
mechanical arc. We hypothesized that the neural arc of the baroreflex
compensates the slow mechanical response and thereby substantially
improves the quality of blood pressure regulation. In 12 anesthetized,
vagotomized rabbits, we isolated carotid sinuses and randomly changed
intrasinus pressure while measuring intrasinus pressure (P<sub>s</sub>),
cardiac sympathetic nerve activity (SNA) and systemic arterial pressure
(P<sub>a</sub>) using a white noise technique. We estimated the
open-loop transfer characteristics of the neural arc (Hn) of the
baroreflex, that is, from P<sub>s</sub> to SNA, that of the peripheral
mechanical arc (Hp), from SNA to P<sub>a</sub>, and that of the total
baroreflex loop (Ht). The gain of Hn was constant below
0.12±0.057 Hz and increased with a slope of about 6 dB/octave
above it, suggesting that the response was increasingly faster with
frequency. In contrast, the gain of Hp was constant below
0.071±0.030 Hz and decreased with a slope of about -12dB/octave
above it, suggesting the response progressively slowed with increasing
frequency. Although too much acceleration in the high frequency range
could result in instability of the system, numerical analysis of the
closed loop baroreflex response indicated that the neural arc optimized
arterial pressure regulation in achieving both stability and quickness
Engineering in Medicine and Biology Society, 1995., IEEE 17th Annual Conference; 10/1995
