From: gts (gts_2000@yahoo.com)
Date: Wed Oct 09 2002 - 08:49:51 MDT
Lee Corbin wrote:
> gts writes
>
> > Neurotransmitters work much like endocrine hormones:
> > after being released by the axon of a neuron they then
> > bind to their corresponding receptors on the dendrite
> > or body of the neighboring neuron. Genes influence
> > the numbers and types of receptors at the receiving
> > neuron, as well as the quantity and types of neuro-
> > transmitters released by the sending neuron.
>
> But isn't this influence (by the genes) far in the past,
No! These genetic influences change dynamically in time, according to
the manner in which one's genes are programmed to respond to different
internal and external stimuli.
The genes themselves are of course fixed, but the manner in which they
are expressed changes. This is why I wrote that your blueprint analogy
is weak. Genes are not like blueprints. They are more like algorithms or
machines. They operate in time as well as space. It's for this reason
that a biological "snapshot" of yourself at a given time is insufficient
for preserving your personality, unless that snapshot includes the
genetic instructions for their expressions in response to future
environments not present in the snapshot.
Depression, for example, can be endogenous or exogenous. In the
exogenous form, the person's brain is affected by external events (e.g.,
death of a family member) rather than by some internal biological or
genetic defect. The response to that exogenous event seems to be
determined largely by the genes. Some people are emotionally resilient
to unfortunate circumstances while others are devastated by them.
> > Genes encode the instructions for the synthesis of
> > both the neurotransmitters and their receptors. Genes,
> > (in response to hormones like Brain Derived Growth
> > Factor), also control the synthesis of the proteins
> > necessary for dendritic expansion, which we know
> > occurs even in adult life.
>
> Yes, but suppose that you were at a podium giving a
> speech. Suddenly, semi-Divine technology makes your
> DNA inert, and the messenger RNA can't work on it,
> although protein synthesis continues (for a while).
> How long, would you guess, would it be before a word
> of your speech was not delivered?
I would guess a very short time. But you make the question vague by
allowing protein synthesis to continue for a while. If we could keep the
transcription process alive and accurate without DNA then we would not
need DNA.
> One more question: suppose that protein synthesis
> had been stopped instead. How long before there is
> a noticeable effect on your delivery?
I'd guess maybe a second or two, at most, but that's only a hunch. It
might be only a couple of nanoseconds. I don't know.
-gts
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