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However, demyelination, which exposes internodal membrane with a higher membrane time constant than that of the original node, can also increase strength-duration time constant. [13] The strength-duration time constant of both cutaneous and motor afferents decreases with age, and this corresponds to an increase in rheobase. [7] Two possible ...
First order LTI systems are characterized by the differential equation + = where τ represents the exponential decay constant and V is a function of time t = (). The right-hand side is the forcing function f(t) describing an external driving function of time, which can be regarded as the system input, to which V(t) is the response, or system output.
The growth constant k is the frequency (number of times per unit time) of growing by a factor e; in finance it is also called the logarithmic return, continuously compounded return, or force of interest. The e-folding time τ is the time it takes to grow by a factor e. The doubling time T is the time it takes to double.
A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. B. Actual recordings of action potentials are often distorted compared to the schematic view because of variations in electrophysiological techniques used to make the recording.
Already in 1907 Lapicque was using a linear first-order approximation of the cell membrane, modeled using a single-RC equivalent circuit. Thus: = / (/) where = is the membrane time constant - in the 1st-order linear membrane model:
If the time constant of the cell membrane is sufficiently long, as is the case for the cell body, then the amount of summation is increased. [6] The amplitude of one postsynaptic potential at the time point when the next one begins will algebraically summate with it, generating a larger potential than the individual potentials.
In order to quantify the behavior of electrotonic potentials there are two constants that are commonly used: the membrane time constant τ, and the membrane length constant λ. The membrane time constant measures the amount of time for an electrotonic potential to passively fall to 1/e or 37% of its maximum. A typical value for neurons can be ...
If growth is not limited, doubling will continue at a constant rate so both the number of cells and the rate of population increase doubles with each consecutive time period. For this type of exponential growth, plotting the natural logarithm of cell number against time produces a straight line.