Re: question on nerve polarity

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From: Irene Yun Salter (irene@archwayschool.org)
Date: Thu Jun 16 2005 - 10:05:54 PDT 

Message-Id: <4c0307abd2e35a68f5fe3d6262a945ca@archwayschool.org>
From: Irene Yun Salter <irene@archwayschool.org>
Subject: Re: question on nerve polarity
Date: Thu, 16 Jun 2005 10:05:54 -0700

Dear Steve,
Good question about adenaline. Adrenaline is known as epinepherine to
the scientific community. It is both a neurotransmitter (released from
nerve terminals directly onto other neurons) and a hormone (released
from the adrenal glands which then circulates through the blood
stream). The major action of adrenaline is on the sympathetic nervous
system - a group of closely linked nerve pathways that control
reactions to stress, triggering the "flight or fight" reaction. While
the major neurotransmitter of the sympathetic nervous system is
acetylcholine (the same fast-acting neurotransmitter that makes muscles
contract), adrenaline is stored in some neurons of the sympathetic
nervous system and is released when something in the environment
triggers a flight or fight reaction - like being chased by a lion.

Once activated, the sympathetic nervous system makes your heart rate
increase, digestive system stop, eyes dilate, hair stand on end,
glucose is released from storage, and adrenaline is released from the
adrenals. Therefore, once the sympathetic nervous system is triggered,
adrenaline is released into the blood stream, increasing the stress
response even more. An opposing parasympathetic nervous system allows
the body to "rest and digest" in times of calm, in general, having the
opposite effect on the heart, digestive system, glucose stores, etc.

Thus, in answer to your original question, there is an instant response
to stress because the sympathetic nervous system triggers a collection
of responses throughout the body to prepare for fight or flight. The
release of adrenaline from the adrenals is slower than the instant
activation of the sympathetic nervous system, but adrenaline
accentuates and prolongs the initial, immediate neural response.
Adrenaline does not alter the baseline resting potential of ALL your
neurons nor does it change how a signal is propagated through ALL your
nerves, instead, it acts specifically on the sympathetic nervous
system.

For more information, go to:
http://en.wikipedia.org/wiki/Adrenaline

Sorry if I was a bit long winded.
Cheers!
Irene Salter
Archway School
irene@archwayschool.org

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