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First-order differential-delay equation for the baroreflex predicts the 0.4-Hz blood pressure rhythm in rats
Ist Teil von
American journal of physiology. Regulatory, integrative and comparative physiology, 1997-12, Vol.273 (6), p.1878-R1884
Ort / Verlag
United States
Erscheinungsjahr
1997
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
D. E. Burgess, J. C. Hundley, S. G. Li, D. C. Randall and D. R. Brown
Department of Chemistry and Physics, Asbury College, Wilmore, Kentucky 40390-1198, USA.
We have described a 0.4-Hz rhythm in renal sympathetic nerve activity (SNA)
that is tightly coupled to 0.4-Hz oscillations in blood pressure in the
unanesthetized rat. In previous work, the relationship between SNA and
fluctuations in mean arterial blood pressure (MAP) was described by a set
of two first-order differential equations. We have now modified our earlier
model to test the feasibility that the 0.4-Hz rhythm can be explained by
the baroreflex without requiring a neural oscillator. In this baroreflex
model, a linear feedback term replaces the sympathetic drive to the
cardiovascular system. The time delay in the feedback loop is set equal to
the time delay on the efferent side, approximately 0.5 s (as determined in
the initial model), plus a time delay of 0.2 s on the afferent side for a
total time delay of approximately 0.7 s. A stability analysis of this new
model yields feedback resonant frequencies close to 0.4 Hz. Because of the
time delay in the feedback loop, the proportional gain may not exceed a
value on the order of 10 to maintain stability. The addition of a
derivative feedback term increases the system's stability for a positive
range of derivative gains. We conclude that the known physiological time
delay for the sympathetic portion of the baroreflex can account for the
observed 0.4-Hz rhythm in rat MAP and that the sensitivity of the
baroreceptors to the rate of change in blood pressure, as well as average
blood pressure, would enhance the natural stability of the baroreflex.