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At least 199 records · Page 11Linked to original sources
PubMed1965

Digital computer simulation of respiratory response to cerebrospinal fluid PCO2 in the cat.

The respiratory control system is treated as linear with a transmission delay between ventilation and sensing points (chemoreceptors). To the accepted variables involving body gas stores, ventilatory effects, transmission effects, and steady state pH, P(CO2), P(O2) chemoreceptor response, certain detailed analysis of the central receptors have been added. By construction of a model for medullary CO(2) receptor utilizing expected values of CNS (central nervous system) circulation, CO(2) production, and tissue-buffering effects, results of experimental observation of the effects of alteration of CSF were simulated. The inclusion of CSF effects also allowed simulation of the response to alteration in inspired CO(2), hyperventilation, and the periodic breathing with prolongation of circulation time.

Animals↗
PubMed1966

Digital computer solutions for excitation and propagation of the nerve impulse.

The Hodgkin-Huxley model of the nerve axon describes excitation and propagation of the nerve impulse by means of a nonlinear partial differential equation. This equation relates the conservation of the electric current along the cablelike structure of the axon to the active processes represented by a system of three rate equations for the transport of ions through the nerve membrane. These equations have been integrated numerically with respect to both distance and time for boundary conditions corresponding to a finite length of squid axon stimulated intracellularly at its midpoint. Computations were made for the threshold strength-duration curve and for the repetitive firing of propagated impulses in response to a maintained stimulus. These results are compared with previous solutions for the space-clamped axon. The effect of temperature on the threshold intensity for a short stimulus and for rheobase was determined for a series of values of temperature. Other computations show that a highly unstable subthreshold propagating wave is initiated in principle by a just threshold stimulus; that the stability of the subthreshold wave can be enhanced by reducing the excitability of the axon as with an anesthetic agent, perhaps to the point where it might be observed experimentally; but that with a somewhat greater degree of narcotization, the axon gives only decrementally propagated impulses.

Axons↗
PubMed1982

Estimation of myocardial infarct size by digital computer analysis of the VCG.

This study described the linear relationship of the myocardial infarct size, measured postmortem, to the integral of the sequential vector spatial magnitudes analyzed at 400 samples per second during the initial period of abnormal depolarization (IAD) in 25 patients with myocardial infarction (MI) and ten controls. The equation for the fitted regression line was: %MI = -0.35 + 3.33 IAD; r = .90; p less than .001. The duration of abnormal depolarization was determined by two computer algorithms: first, using the classical method of pathological Q wave duration, whenever possible; and a new method of measurement of an abnormally slow rate of rise of vector spatial magnitude with time (dm/dt), when there were no Q waves in the Frank orthogonal lead input signals. There was not a significant difference in the mean values of IAD of the MI group or the control group calculated by the two algorithms.

Aged↗