Hormones are substances released into the bloodstream by glands or organs, which affect activity in
cells at another site. Most are composed of chains of various lenghts. Others are
Hormones (similar to the and other ) act at low
concentrations with very large responses in the body and bind with high
to specific . These receptors are on the surface or inside the cell and the result
of such binding causes an alteration in the cell's functioning.
Hormones control growth and development, reproduction and sexual characteristics as well as exercising a large influence over the body's use of
Examples include the
(such as Epinephrine and Norepinephrine) and the released by the .