Model inferences on baroreceptor & sinus wall responses

Mechanical associations between sinus wall elements and those between wall and baroreceptor were modeled with differential equations. Viscoelastic relationships were tested using frequency domain analysis (TUTSIM, FANSIM). Two wall models were examined. The first had a single degree of freedom (df) and the second was a cascade system with two df. Component of the cascade model represented adventitia and media layers of the wall. This wall model had little deviation in gain between 0.1 and 10 Hz; regardless of a 100 fold difference in component damping. Properties of a wall-receptor model were in part estimated from myelinated baroreceptor responses (Brown et al., Circ. Res. 42:694-702, 1978). The wall-receptor model was designed with a natural frequency (omega b) of 12.7 Hz and damping ratio (zeta b) of 0.2 for the receptor and omega w of 50 Hz and zeta w of 1.2 for the wall component. Analysis of receptor responses, with respect to input forcing function, resulted in a omega b of 12.6 Hz. Analysis of responses with respect to those of the wall, resulted in a omega b of 16.0 Hz. These results are indicative of the complexity involved with interactive systems. If frequency analysis is used to estimate mechanical associations between sinus wall elements and baroreceptors, modeling can provide comparative data for interpretation of experimental responses.