nerve message transmission. Help please.
lthomsen at interlynx.net
Sun Oct 19 02:29:21 EST 1997
Brian Bjørn wrote in message <344598C0.875E1A20 at mdb.ku.dk>...
>> If it is electro/chemical what sort of levels. I assume the greater the
>> level the greater the reaction?
>No, not really. Action potentials are all-or-none responses: If a certain
>treshold level is reached an action potential with a distinct shape
>(amplitude and duration) is fired. The transmitter release from one single
>nerve terminal is therefore also an all-or-none response.
A little correction here...
Gradually changing the frequency of action potential will give a gradual
release of neurotransmitters. So the neurotransmitter realease is not an
all-or-none event. Furthermore, the post-synaptic membrane potential is
strongly modulated (in many systems e.g. by GABA)
>Yes, there are different electrophysiological ways of assessing nerve and
>muscle function. The techniques are quite sofisticated and requires a lot
>more explanation and understanding of the basic principles underlying the
>function of the motor system.
The principle behind measurements are very simple...just as you can read the
voltage of a battery with a voltmeter you can read the voltage across a
neurone (or any other cell). However, to record from a cell you need a small
electrode (at least if you want to record the cell membrane potential). You
make the electrode by heating a thin glass tube and pulling it only the tip
gets very thin...this electrode can then be inserted into a cell (which can
be done by hand...e.g. dropping the electrode into a big collection of
cells...like the brain...brrr...)
>> Are the same nerves used to transmit as well as to receive?
> No, not under physiological conditions.
Not motorneurones...(ok..they dont recieve anything from the same target,
but they do recieve) and many neurones in the peripheral system (e.g. the
enteric nervous system) has a much more branched morphology that would give
them the ability to recieve a signal from a cell in the surroundings and
also act on it...Take for example neurones with P2X receptors innervating
some kind of cell...the cell gets damanaged and releases some ATP which
activates the neurone via the P2X receptors...just one example of a target
that interacts with the post-synaptic cell and the wellknown NO/VIP relation
betwwen smooth muscle cells and neurones is another..
Lars Thomsen, Msc. Phd
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