Browsing by Author "Greco, E.C."
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Item A Mathematical Model of the Vagally Driven SA Nodal Pacemaker(1975-01-20) Greco, E.C.; Clark, Jr., J.W.A model is developed for the vagal control of SA nodal activity in the heart and consists essentially of a modified bonhoeffer-Van der Pol (BVP) model of the "free-running" SA node and a lumped model of the neural terminations in that region. The model is capable of mimicing both the driven transient behavior of the node in terms of pacemaker and inhibition curves, as well as steady-state entrainment phenomena. The model data also agrees very well with experimental data from dog experiments performed in our laboratory. The model is described by a set of nonlinear, third-order, ordinary differential equations and provides a relatively uncomplicated functional model of heart period changes due to vagal stimulation patterns.Item Solution of the Forward and Inverse Problems Associated with the Potential Field of a Single Active Fiber in a Volume Conductor(1975-04-20) Greco, E.C.; Clark, Jr., J.W.; Harman, T.L.A solution of Laplace's equation relating the transmembrane potential distribution of an active fiber in a volume conductor to its extracellular field distribution utilizing a Fourier transform method [4] has been reformulated as a one-dimensional linear filtering problem. Formulation of the solution in this manner allows the application of well-known techniques in linear system theory and optimal linear filtering thereby facilitating the solution for both the forward (from transmembrane to field potential distribution) and inverse (from field to transmembrane potential distribution) problems. The forward problem is shown to be a simple two-stage filtering process composed of a membrane and medium filter. In the inverse case the field potential distribution is considered in the presence of additive measurement noise and the best estimate in the least-mean-square sense will be obtained for the transmembrane potential distribution.