Biomedical Engineering Reference
In-Depth Information
Figure 5.1
Relaxation after a jump in conditions: a mixture of two or three exponentials.
Figure 5.2
An example of current through a single ion channel
current stops; an example is given in Figure 5.2. Methods of extracting the idealised
open and closed intervals from the noise are discussed in [35]; see also Section 5.6.
There are channels in which there are identifiable sublevels of conductance but in this
chapter we will deal almost exclusively with the common case of just two observable
current levels, corresponding to channel open and channel closed.
The information in a single channel record is contained in the amplitudes of the
openings, the durations of the open and shut periods, and correlations between them.
We use this information to try to identify the nature of the kinetic mechanism of the
channel and to estimate rate parameters governing transitions between the various
states of such a mechanism. In order to do this we need to develop a mathematical
model to describe the operation of any postulated mechanism and then use mathemat-
ical techniques to predict observable behaviour that the mechanism would exhibit. In
this way we can confront theoretical mechanisms with observed data.
In this chapter we give a brief introduction to such models and what can be pre-
dicted from them. Inevitably, we shall need to introduce some mathematics but we
will try to keep this as simple as possible and not go into too much detail.
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