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Biomedical subjects

P Grindrod

Publications and source records attributed to P Grindrod.

6 recordsLinked to original sources
PubMed1991

One-way blocks in cardiac tissue: a mechanism for propagation failure in Purkinje fibres.

The concept of a one-way block, arising from a region of depressed tissue, has remained central to theories for cardiac arrhythmias. We show that both the geometry of a depressed region and spatial heterogeneities in depression are key factors for inducing such a block. By using an asymptotic approximation, known as the eikonal equation, to model qualitatively the movement of a depolarization wave-front down a Purkinje fibre bundle, we show how a one-way block in conduction may result from asymmetric constriction in the width of a depressed bundle. We demonstrate that this theory is valid for biologically relevant parameters and simulate a one-way block by numerically solving the eikonal approximation. We consider the case of non-uniform depression, where the planar travelling wave speed is spatially dependent. Here, numerical simulations indicate that such a spatial dependency may, in itself, be sufficient to produce a one-way block.

Animals↗
PubMed1989

Steady-state spatial patterns in a cell-chemotaxis model.

We investigate a simple cell-chemotaxis model for the generation of spatial patterns in cell aggregations. For simple boundary-value problems, we analyse the local and global bifurcation of spatially heterogeneous patterns away from the uniform equilibria as the total number of cells is varied. We also discuss the existence of periodic spatially structured solutions for the cells and chemoattractant in the infinite domain.

Animals↗
PubMed1987

The geometry and motion of reaction-diffusion waves on closed two-dimensional manifolds.

Chemical or biological systems modelled by reaction diffusion (R.D.) equations which support simple one-dimensional travelling waves (oscillatory or otherwise) may be expected to produce intricate two- or three-dimensional spatial patterns, either stationary or subject to certain motion. Such structures have been observed experimentally. Asymptotic considerations applied to a general class of such systems lead to fundamental restrictions on the existence and geometrical form of possible structures. As a consequence of the geometrical setting, it is a straightforward matter to consider the propagation of waves on closed two-dimensional manifolds. We derive a fundamental equation for R.D. wave propagation on surfaces and discuss its significance. We consider the existence and propagation of rotationally symmetric and double spiral waves on the sphere and on the torus.

Chemical Phenomena↗
PubMed1985

A model of a myelinated nerve axon: threshold behaviour and propagation.

A model of a myelinated nerve axon is developed on the basis of FitzHugh-Nagumo dynamics under the assumption that the nodes of Ranvier are of small but finite width. It is shown that a periodic excited state may not exist if the width of the nodes is too small and the leakage across the myelin sheath is too great. The propagation of a super threshold pulse is prevented in the absence of nodes. Global stability of the resting equilibrium state is investigated as well as the propagation of "wave front", type solutions.

Animals↗