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Über dieses Buch

I started working on membrane noise in 1967 with David Firth in the Department of Physiology at McGill University. I began writing this book in the summer of 1975 at Emory University under a grant from the National Library of Medicine. Part of the writing was also done at the Marine Biological Laboratory Library in Woods Hole and in the Library of the Stazione Zoologica in Naples. I wrote this book because in the intervening years membrane noise became a definable subdivision of membrane biophysics and seemed to deserve a uniform treatment in one volume. Not surprisingly, this turned out to be much more difficult than I had imagined and some areas of the subject that ought to be included have been left out, either for reasons of space or because of my own inability to keep up with all aspects of the field. This book is written for biologists interested in noise and for physicists and electrical engineers interested in biology. The first three chapters attempt to bring both groups to a common point of understanding of electronics and electrophysiology necessary to the study of noise and impedance in membranes. These chapters arose out of a course given over a period of six years to electrical engineers from the Georgia Institute of Technology and biologists from Emory University School of Medicine.

Inhaltsverzeichnis

1. Animal Electricity

Abstract
Although we have come, in many instances, to an understanding of natural phenomena or effects, what we actually mean by “understanding” is unclear. I believe we often mean nothing more than familiarity: if a new phenomenon can be compared to something we are already used to, we seem to understand it and we feel free to go on to the next step. The set of ideas and the phenomena or the effects we are used to depend on the age in which we live and the field in which we work, and no doubt vary from person to person. But such differences, it seems to me, are of secondary importance; the science of other periods and fields and individuals really differs from our own only in where this reduction to the familiar happens to stop.
Louis J. DeFelice

2. Basic Electrophysiology

Abstract
As a solid, common salt forms a well-ordered lattice structure. For example, NaCl has the repeating structure shown in Figure 11.1. When this highly ordered crystal goes into aqueous solution, the order is almost completely broken down and the individual ions form a randomly moving, gaslike substance immersed in the water. One expresses this reaction (shown in Figure 11.2) by writing
$${\rm{NaCl}}{\rm{ N}}{{\rm{a}}^ + } + {\rm{C}}{{\rm{l}}^ - }$$
Louis J. DeFelice

3. Basic Circuit Theory

Abstract
An emf is a device that always maintains the same voltage across its terminals regardless of the current passing through it. A steady emf is represented by the symbol shown in Figure 31.1, where the long bar indicates positive voltage (+) and the shorter bar negative voltage (—). The term “dc” is used to indicate a steady or average property; thus the symbol above represents a dc-emf.
Louis J. DeFelice

4. Noise Analysis

Abstract
The measurement of spectral density is closely connected to the concept of filtering. Here we introduce some simple circuits used for this purpose.
Louis J. DeFelice

5. Noise Sources

Abstract
Previous chapters have presented methods available for the analysis of noise. Examples included white, I/f, and Lorentzian noise, whose properties in three modes of analysis are given in Table 58.1.
Louis J. DeFelice

6. Membrane Impedance

Abstract
The kinetic equation that describes the average number of open channels in a population of N two-state channels is (Section 72)
$$\theta {{d{N_0}} \over {dt}} + {N_0} = pN$$
The solution, NO(t), describes how the number of open channels changes in response to a change in α and β In Section 72 it was shown that a step change in α and β at t = O gives
$${N_0}\left( t \right) = {N_0}\left( 0 \right){e^{ - t/\theta }} + {N_0}\left( \infty \right)\left( {1 - {e^{ - t/\theta }}} \right)$$
where θ= l/(α + β) is the new value of θ immediately after the step. α and β are assumed to change instantaneously.
Louis J. DeFelice

7. Experimental Results

Abstract
Although it is impossible to single out one paper as being the first to study membrane noise, subsequent events in the field have isolated the 1950 note of Fatt and Katz on “biological noise” at the neuromuscular junction as a starting point. In their full paper in 1952 they write the following:
In the course of some earlier work, while recording from the surface of isolated muscle fibers, we occasionally noticed a spontaneous discharge of small monophasic action potentials. The potentials varied somewhat in size, but had a very consistent time course, rising rapidly in 1–2 msec, and declining more slowly, to one-half in about 3–4 msec. They were localized at one region of the fibre, and in their shape and spatial spread resembled the end-plate potential... Not much attention was paid to the phenomenon at the time, and it was suspected to be due to local injury...
Louis J. DeFelice

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