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any kind of message transfer, there needs to be messengers. In the
body, these take the form of ligands. Ligands
are substances in the body made out of amino acids. Their job is to
bind with cells. There are three types:
- Neurotransmitters: the
smallest ones, they carry information from one neuron to the next
within the brain and throughout the nervous system. Their range is
local: they transfer messages between neighbouring neurons.
- Steroids: these have been
transformed from cholesterol into a specific type of hormone.
Hormones are produced by one tissue and carried long distances by
the blood stream to another targeted tissue. Receptors for these
ligands are found in the endocrine system as well as in the brain
and immune systems.
- Peptides: the most
"popular" information substances. They are for mass communication.
They can go around the neighbourhood and throughout all the body's
systems: immune, endocrine, digestive, excretory and brain, i.e.
messages that ligands carry range from "breath in, breath out" to
"don't move, snake ahead." Ligands keep the brain informed with
what's happening in the body and vice versa.