This vm is measured against the baseline of the recording.
So this much is vm. So at point A, vm is equal to 40.
Now on the other hand, capital VM is measured with respect to a voltage of
zero. So at point A, this much would be capital
Vm. So at point A, lower case vm the diff, the
voltage off the base line is plus 40. While capital Vm the voltage reference to
zero is minus 30. Now obviously one is related to the other.
So that we have as a matter of mathematical fact, VM relative to the
baseline is capital VM. The absolute VM minus the voltage of the
signal when the waveform is at rest, VR. Here's a few comments on while there is
both of, both capital VM and lower VM. Vm with the lower case V is much easier to
measure experimentally, because if you have the trace of voltage versus time, you
can take the actual recording, mark the base line, mark another point and just
find the voltage difference. Whereas, on the choice of voltage versus
time recorded from the squid, there's not going to be any line for zero.
The reason there is not any line for zero is that the base line zero, or that is to
say the zero value, is affected by the drift in the equipment.
In measuring DC voltages. In preparations such as the squid is
notoriously difficult, so when you do try to measure capital VM, it is often the
case that it is affected the measurement by what is called DC drift.
Or, in other words, for the value of voltage equal to zero to move up and down
the page a little bit as time goes by. Then I should call your attention to the
fact, that here I am trying as much as possible to be consistent, and call
voltages. That are measured relative to the va-,
baseline with a lower case vm. And the voltages that are absolute, to
call those uppercase VM. I'm trying to maintain that difference
consistently. And I hope I do it without making too many
mistakes. If you take the world around us, the big
wide world. I would say everyone recognizes everyone
in electro-physiology, recognizes that sometimes measurements were given with
respect to the base line and sometimes are given absolute, but the way they are
denoted changes from an author to another. So they may or may not follow this lower
case capital VMI notation, notational difference.
Now, in a minute, we're gonna look at the actual alpha and beta functions.
But let me give you a few preliminaries. As we said, the basic idea of the alpha
and beta functions are to measure how fast, for the alpha function is to measure
how fast the n, m, and h particles are opening.
Or, putting that a little bit differently, to measure the rate at which the
probability is increasing. If you go to Washington D.C., and ride on
the metro train in Washington D.C., one hears the phrase, doors are opening, each
time the doors open. And in a way that's a corollary.
Alpha is telling us, doors are opening, and here's the rate at which that's
happening. In contrast, the Beta function.