Page 198 - The Miracle of Hormones

THE MIRACLE OF HORMONES

The walls of the blood vessels are covered
by smooth muscles that can contract and
relax. When plaque forms in an artery of the
heart, the blood flow diminishes. A clogged
artery of the heart suddenly goes into
spasm, the amount of blood going to the
heart is reduced and chest pain occurs. In
this situation, the level of nitric oxide rises
causing dilation in the arteries that nourish
the heart muscles.

in size, containing only two atoms. These tiny molecules act as mail
deliverers finding the GC enzyme that is the recipient of the message
they carry. There are thousands of different enzymes performing differ-
ent functions inside cells. Despite this, the message is delivered every
time to the right address, that is, to the correct enzyme. Moreover, mes-
senger molecules have a very limited life span, but they never make a
mistake in timing. The molecules that carry the messages do not have a
compass or similar device to show them the direction, but they never

lose their way.
The speed with which the nitric oxide molecule performs its func-
tion can be compared to modern communication by e-mail. NO acts just

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