Electrical communication

Most cells possess an electrical potential across then-plasma membrane, which is positive on the external surface. This is known as the resting potential. The neurone is no exception it has a potential of between 50 and 75 millivolts (mV). The resting potential arises from the following  

An impulse is initiated by a sudden depolarisation (i.e. marked reversal of the resting potential). The depolarisation is achieved by the sudden opening of a number of Na  

The gap across the synapse is so small that the chemical messenger (neurotransmitter) crosses the cleft in less than a millisecond. Within the brain there are more than 50 neurotransmitters, which include amino acids, amines, purines, peptides and some gases. In contrast, in the peripheral nervous system there are only two, acetylcholine and noradrenaline. One of several questions concerning the concept of neurotransmitters is whether they differ, in principle, from local hormones (See below and Chapter 12). 

It is important, therefore, to have criteria to identify a chemical in the brain that acts as a neurotransmitter. These are as follows  

Box 14.1 Biochemical explanations for some of the physiological terms associated with electrical activity 

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Heaviside made a significant contribution to electrical communications when he advocated the introduction of additional inductance in long-distance telephony cables although there was then no practical means to add it. His idea was eventually patented in 1904 by Michael Campbell of AT T after Heaviside and George Pupin of Columbia University had shown it was possible to apply inductance in the form of uniformly spaced loading coils. By 1920 engineers had installed such loading on thousands of miles of cable, particularly in the United States. 

Once the primary considerations of size, height, conceptual layout, structural loads, servicing (mechanical, electrical, communications, public health, statutory services) requirements, access, material and personnel traffic, etc. have been addressed, a facility brief can be produced to allow collation of the basic project planning information ... 

Describe various routes for facilitating the electrical communication between the redox center of glucose oxidase and an electrode surface. 

EC mechanism, 34, 42, 113 E. Coli, 186 Edge effect, 129 Edge orientation, 114 Electrical communication, 178 Electrical double layer, 18, 19 Electrical wiring, 178 Electrocapillary, 22 Electrocatalysis, 121 Electrochemical quartz crystal, microbalance, 52 Electrochemihuiiinescence, 44 Electrodes, 1, 107... 

Gap junctions provide electrical communication between cells, forming a functional syncytium Myogenic... 

Skeletal and cardiac muscles also have important differences. Skeletal muscle cells are elongated and run the length of the entire muscle furthermore, these cells have no electrical communication between them. Cardiac muscle cells, on the other hand, branch and interconnect with each other. Intercellular junctions found where adjoining cells meet end-to-end are referred to as intercalated discs. Two types of cell-to-cell junctions exist within these discs. Desmosomes hold the muscle cells together and provide the structural support needed when the heart beats and exerts a mechanical... 

Skeletal muscle is neurogenic and requires stimulation from the somatic nervous system to initiate contraction. Because no electrical communication takes place between these cells, each muscle fiber is innervated by a branch of an alpha motor neuron. Cardiac muscle, however, is myogenic, or self-excitatory this muscle spontaneously depolarizes to threshold and generates action potentials without external stimulation. The region of the heart with the fastest rate of inherent depolarization initiates the heart beat and determines the heart rhythm. In normal hearts, this "pacemaker region is the sinoatrial node. 

Y. Degani and A. Heller, Direct electrical communication between chemically modified enzymes and metal electrodes. I. Electron transfer from glucose oxidase to metal electrodes via electron relays, bound covalently to the enzyme. J. Phys. Chem. 91, 1285-1289 (1987). 

Provided that the required enzymes can be immobilized at, and electrically communicated with, the surface of an electrode, with retention of their high catalytic properties and there is no electrolysis of fuel at the cathode or oxidant at the anode, or a solution redox reaction between fuel and oxidant, the biocatalytic fuel cell then simply... 

The electron-transfer rate between large redox protein and electrode surface is usually prohibitively slow, which is the major barricade of the electrochemical system. The way to achieve efficient electrical communication between redox protein and electrode has been among the most challenging objects in the field of bioelectrochemistry. In summary, two ways have been proposed. One is based on the so-called electrochemical mediators, both natural enzyme substrates and products, and artificial redox mediators, mostly dye molecules and conducted polymers. The other approach is based on the direct electron transfer of protein. With its inherited simplicity in either theoretical calculations or practical applications, the latter has received far greater interest despite its limited applications at the present stage. 

Holt83] Holt, A. W., H. R. Ramsey, and J. D. Grimes. 1983. Coordination system technology as the basis for a programming environment. Electrical Communication, 57(4). 

TAKESHI OKADA—Ibaraki Electrical Communication Laboratory, Nippon Telegraph and Telephone Public Corporation, Tokai-Mura, Ibaraki, Japan... 

Figure 3.15 [63]. The table in Figure 3.15 also shows enhanced electron transfer rates for ferrocene attatched on aligned SWNTs as compared to ferrocene attatched on randomly dispersed SWNTs [124]. Moreover, such vertically aligned SWNTs act as molecular wires that allow efficient electrical communication between the underlying electrode and the redox enzymes [45, 123, 127[.

Enzyme biocatalyst assemblies on electrode surfaces usually do not achieve significant electron-transfer communication between the redox center and the conductive support, mostly because of the electrical insulation of the biocatalytic site by the surrounding protein matrixes. During the past four decades, several methods have been proposed and investigated in the field of bioelectrochemical technology in an effort to establish efficient electrical communication between biocatalysts and electrodes. " In general, electron transfer is classified by two different mechanisms (see Figure 2) ... 

It is clear that the presence of Cu02 planes is an essential feature required for superconductivity in these oxides. However, superconductivity can be achieved only if the chemical entity inserted between these planes allows them to electrically communicate. This is, for instance, the role played by the chains in the 123 or by the double Bi-O layers in the Bi compounds. 

In electrical communication, changes in membrane potential are used to conduct a stimulus within a nerve cell. Changes in membrane potential can also be used for intercellular commimication. In this case, communication between the cells takes place via electrical synapses at which the potential change can be directly passed on to neighboring cell. Central components of electrical communication are voltage-dependent ion channels with open states regulated by changes in the membrane potential. 

Beny JL, Pacicca C Bidirectional electrical communication between smooth muscle and endothelial cells in the pig coronary artery. Am J Physiol 1994 266 H1465-H1472. 

Willner and coworkers have extended this approach to electron relay systems where core-based materials facilitate the electron transfer from redox enzymes in the bulk solution to the electrode.56 Enzymes usually lack direct electrical communication with electrodes due to the fact that the active centers of enzymes are surrounded by a thick insulating protein shell that blocks electron transfer. Metallic NPs act as electron mediators or wires that enhance electrical communication between enzyme and electrode due to their inherent conductive properties.47 Bridging redox enzymes with electrodes by electron relay systems provides enzyme electrode hybrid systems that have bioelectronic applications, such as biosensors and biofuel cell elements.57... 

The electrical contact of redox proteins is one of the most fundamental concepts of bioelectronics. Redox proteins usually lack direct electrical communication with electrodes. This can be explained by the Marcus theory16 that formulates the electron transfer (ET) rate, ket, between a donor-acceptor pair (Eq. 12.1), where d0 and d are the van der Waals and actual distances separating the donor-acceptor pair, respectively, and AG° and X correspond to the free energy change and the reorganization enery accompanying the electron transfer process, respectively. 

The authors are grateful to S. Imamura, O. Kogure, and K. Murase of Ibaraki Electrical Communication Laboratory for helpful discussions. 

Research Institute of Electrical Communication, Tohoku University... 

T. Dietl, Research Institute of Electrical Communication, Tohoku University, Sendai, Japan... 

Noise in Electrical Communications, 1968, McGraw-Hill, New York. 

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