  Baroreflex is critical to maintain the blood pressure homeostasis, and the
quantification of the baroreflex regulation function (BRF) can provide guidance
for disease diagnosis, treatment and healthcare. Current quantification of the
BRF such as baroreflex sensitivity cannot represent the BRF systematically.
From the perspective of complex systems, we regard that the BRF is the
emergence result of the diverse states and interactions in the physiological
mechanisms. Therefore, the three-layer emergence is constructed in this work,
which is from the physiological mechanisms to the physiological indexes and
then to the BRF. On this basis, since the entropy in statistical physics
macroscopically measures the diversity of the system's states, a new index
called the PhysioEnt is proposed to represent the BRF and quantify the physical
relationships between the BRF and four physiological indexes, baroreflex
sensitivity, heart rate, heart rate variability, and systolic blood pressure.
Based on the proposed method, some new findings with medical significance are
obtained, including the mechanisms that aging and obesity affect the
resting-condition BRF are different, and the resting-condition BRFs of men and
older people depend more on the physiological processes among organs/tissues.
Based on the measurable indexes, the proposed method would support the
individualized medicine prospectively.
