Core Conductor Theory and Cable Properties of Neurons

2011 ◽  
Author(s):  
Wilfrid Rall
Keyword(s):  
Cable Properties ◽  
Core Conductor

Outward current and repolarization in hypoxic rat myocardium

1983 ◽  
Vol 244 (3) ◽  
pp. H341-H350
Author(s):  
C. H. Conrad ◽  
R. G. Mark ◽  
O. H. Bing
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Outward Current ◽  
Iodoacetic Acid ◽  
Mechanical Activity ◽  
Potential Range ◽  
Papillary Muscles ◽  
Rat Myocardium ◽  
Cable Properties ◽  
Sucrose Gap

We studied the effects of brief periods (20-30 min) of hypoxia in the presence of 5 and 50 mM glucose and of glycolytic blockade (10(-4) M iodoacetic acid, IAA) on action potentials, membrane currents, and mechanical activity in rat ventricular papillary muscles using a single sucrose gap voltage-clamp technique. Steady-state outward current (iss) was determined at the end of a 500-ms clamp to the test potential following a 600-ms clamp to a holding potential of -50 mV. In the presence of 5 mM glucose, hypoxia resulted in a decrease in action potential duration (APD) and an increase in iss (on the order of 60% at 0 mV) over the potential range studied. The increase in iss did not appear to be due to an increase in leakage current or to a change in the cable properties of the preparation. Addition of 50 mM glucose prevented the change in both APD and iss with hypoxia. In addition, glycolytic blockade with IAA did not alter iss in the presence of oxygen. We conclude that an increase in iss appears to be a major factor in the abbreviation of rat ventricular action potential seen with hypoxia. Glycolysis appears to be a sufficient (with 50 mM glucose) but not necessary source of energy for the maintenance of normal iss.

Voltage-Dependent Properties of Dendrites That Eliminate Location-Dependent Variability of Synaptic Input

1999 ◽  
Vol 81 (2) ◽  
pp. 535-543 ◽  
Author(s):  
Erik P. Cook ◽  
Daniel Johnston
Keyword(s):  
Synaptic Input ◽  
Outward Current ◽  
Compartment Model ◽  
Inward Current ◽  
Voltage Gated ◽  
Cable Properties ◽  
Dendritic Membrane ◽  
Voltage Dependent ◽  
Dendritic Location ◽  
Voltage Gated Channels

Voltage-dependent properties of dendrites that eliminate location-dependent variability of synaptic input. We examined the hypothesis that voltage-dependent properties of dendrites allow for the accurate transfer of synaptic information to the soma independent of synapse location. This hypothesis is motivated by experimental evidence that dendrites contain a complex array of voltage-gated channels. How these channels affect synaptic integration is unknown. One hypothesized role for dendritic voltage-gated channels is to counteract passive cable properties, rendering all synapses electrotonically equidistant from the soma. With dendrites modeled as passive cables, the effect a synapse exerts at the soma depends on dendritic location (referred to as location-dependent variability of the synaptic input). In this theoretical study we used a simplified three-compartment model of a neuron to determine the dendritic voltage-dependent properties required for accurate transfer of synaptic information to the soma independent of synapse location. A dendrite that eliminates location-dependent variability requires three components: 1) a steady-state, voltage-dependent inward current that together with the passive leak current provides a net outward current and a zero slope conductance at depolarized potentials, 2) a fast, transient, inward current that compensates for dendritic membrane capacitance, and 3) both αamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid– and N-methyl-d-aspartate–like synaptic conductances that together permit synapses to behave as ideal current sources. These components are consistent with the known properties of dendrites. In addition, these results indicate that a dendrite designed to eliminate location-dependent variability also actively back-propagates somatic action potentials.

Cable Properties and Propagation

1995 ◽  
pp. 289-317
Author(s):  
Nicholas Sperelakis
Keyword(s):  
Cable Properties

scholarly journals Confirmation of Hypothesis on Cable Properties for Cable-Driven Robots

2012 ◽  
pp. 85-93 ◽  
Author(s):  
Julien Alexandre dit Sandretto ◽  
Gilles Trombettoni ◽  
David Daney
Keyword(s):  
Cable Properties

Effect of Dry-Zone Formation around Underground Power Cables on Their Ratings

2016 ◽  
pp. 188-210
Keyword(s):  
Thermal Resistivity ◽  
Power Cables ◽  
Zone Formation ◽  
Thermal Failure ◽  
Underground Cables ◽  
Buried Cables ◽  
Cable Properties ◽  
Dry Zone ◽  
Rating Factor ◽  
Underground Power Cables

Current ratings of buried cables are determined by the characteristics of surrounding soils and cable properties as given in IEC 60287-1-3 (1982). In this standard the soil thermal resistivity of the surrounding soil is supposed to be varies from 0.5 oC m/w to 1.2 oC m/w but under loading the heat dissipated from underground power cables increases the soil thermal resistivity and this may leads to cable thermal failure and thermal instability of the soil around the underground cables. For this reason de-rating factors for cable loading taking the dry zone formation into consideration has to be considered during distribution cable network design. Several approaches have been adopted to establish current ratings of buried cables based on constant values of soil thermal conductivities. Mathematical models are suggested by many researches to study the drying out phenomenon around underground power cables. In this chapter de-rating factor for underground power cables taking dry zone formation into account is calculated depending on IEC 60287-1-3 (1982). This chapter also contains an experimental work carried out on different types of soils to investigate the formation of dry zone phenomena under loading by heat source simulates the underground cables.

Linear Cable Theory

1998 ◽  
Author(s):  
Christof Koch
Keyword(s):  
Cell Body ◽  
Electrical Potential ◽  
Giant Axon ◽  
Electrically Conducting ◽  
Cable Theory ◽  
Neuronal Processes ◽  
Spatially Extended ◽  
1960S And 1970S ◽  
The 1960S ◽  
Core Conductor

In the previous chapter, we briefly met some of the key actors of this book. In particular, we introduced the RC model of a patch of neuronal membrane and showed an instance where such a “trivial” model accounts reasonably well for the input-output properties of a neuron, as measured at its cell body. However, almost none of the excitatory synapses are made onto the cell body, contacting instead the very extensive dendritic arbor. As we will discuss in detail in Chap. 3, dendritic trees can be quite large, containing up to 98% of the entire neuronal surface area. We therefore need to understand the behavior of these extended systems having a cablelike structure. The basic equation governing the dynamics of the membrane potential in thin and elongated neuronal processes, such as axons or dendrites, is the cable equation. It originated in the middle of the last century in the context of calculations carried out by Lord Kelvin, who described the spread of potential along the submarine telegraph cable linking Great Britain and America. Around the turn of the century, Herman and others formulated the concept of Kemleitermodel, or core conductor model, to understand the flow of current in nerve axons. Such a core conductor can be visualized as a thin membrane or sheath surrounding a cylindrical and electrically conducting core of constant cross section placed in a solution of electrolytes. The study of the partial differential equations describing the evolution of the electrical potential in these structures gave rise to a body of theoretical knowledge termed cable theory. In the 1930s and 1940s concepts from cable theory were being applied to axonal fibers, in particular to the giant axon of the squid (Hodgkin and Rushton, 1946; Davis and Lorente de No, 1947). The application of cable theory to passive, spatially extended dendrites started in the late 1950s and blossomed in the 1960s and 1970s, primarily due to the work of Rail (1989). In an appropriate gesture acknowledging his role in the genesis of quantitative modeling of single neurons, Segev, Rinzel, and Shepherd (1995) edited an annotated collection of his papers, to which we refer the interested reader. It also contains personal recollections from many of Rail's colleagues as well as historical accounts of the early history of this field.

Correlation between electrical and morphological properties of canine pyloric circular muscle

1991 ◽  
Vol 260 (3) ◽  
pp. G390-G398 ◽  
Author(s):  
F. Vogalis ◽  
S. M. Ward ◽  
K. M. Sanders
Keyword(s):  
Single Cells ◽  
Electrical Coupling ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Morphological Properties ◽  
Morphological Examination ◽  
Isolated Cells ◽  
Time Constants ◽  
Morphological Studies ◽  
Cable Properties

Electrical slow waves decay in amplitude as they conduct from the myenteric to the submucosal regions of the circular muscle layer in the canine pyloric sphincter. We used the partitioned chamber method to study the passive and active properties of pyloric muscles, and we found that length constants of circular muscles of myenteric region were significantly longer than muscles near the submucosal surface. These data suggested differences in either membrane resistance, junctional resistance, or cytoplasmic resistance. The first parameter was evaluated by measuring time constants in intact tissues and single cells isolated from the submucosal and myenteric regions. Membrane time constants were not different in the two regions, nor were differences found in the input resistances of isolated cells. Morphological studies failed to demonstrate differences in cell diameters in the two regions suggesting that cytoplasmic resistances are similar. These findings suggest that the different cable properties in the two regions may be due to differences in electrical coupling. Morphological examination revealed similar numbers of gap junctions between cells in the two regions, but large differences were noted in the size of muscular bundles. Muscles of the myenteric region were arranged into large, tightly packed bundles, whereas muscles of the submucosal region consisted of small bundles with an extensive extracellular space filled with connective tissue. We suggest that the difference in cable properties may be due to differences in electrical coupling between bundles. These data suggest that submucosal muscles function more like a multiunit smooth muscle, whereas myenteric muscles behave as a single unit.

Dynamic Modeling and Adaptive Control of a Single Degree-of-Freedom Flexible Cable-Driven Parallel Robot

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Harsh Atul Godbole ◽  
Ryan James Caverly ◽  
James Richard Forbes
Keyword(s):  
Adaptive Control ◽  
Numerical Simulations ◽  
Dynamic Modeling ◽  
Parallel Robot ◽  
Control Law ◽  
Single Degree Of Freedom ◽  
Flexible Cable ◽  
Single Degree ◽  
Cable Properties ◽  
Adaptive Control Law

This paper investigates the dynamic modeling and adaptive control of a single degree-of-freedom flexible cable-driven parallel robot (CDPR). A Rayleigh–Ritz cable model is developed that takes into account the changes in cable mass and stiffness due to its winding and unwinding around the actuating winch, with the changes distributed throughout the cables. The model uses a set of state-dependent basis functions for discretizing cables of varying length. A novel energy-based model simplification is proposed to further facilitate reduction in the computational load when performing numerical simulations involving the Rayleigh–Ritz model. For control purposes, the massive payload assumption is used to decouple the rigid and elastic dynamics of the system, and a modified input torque and modified output payload rate are used to develop a passive input–output map for the naturally noncollocated system. A passivity-based adaptive control law is derived to dynamically adapt to changes in cable properties and payload inertia, and different forms of the adaptive control law regressor are proposed. It is shown through numerical simulations that the adaptive controller is robust to changes in payload mass and cable properties, and the selection of the regressor form has a significant impact on the performance of the controller.

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