PRINCIPLES OF CHEMICAL
COMMUNICATION
Chemical messengers – allow cells to
communicate with each other
Secretion – controlled release of chemicals
from a cell
Classes of Chemical Messengers
1. Autocrine – stimulates the cell that
originally secreted it; WBCs during an
infection
2. Paracrine – act locally on nearby
cells; WBCs during allergic reactions
3. Neurotransmitter – activate an
adjacent cell
4. Endocrine – secreted into the
bloodstream by certain glands and
cells
Functions of the Endocrine System (MC3I2
WHUT)
1. Metabolism.
2. Control of blood glucose and other
nutrients.
3. Control of reproductive functions.
4. Control of food intake and digestion.
5. Ion regulation.
6. Immune system regulation.
7. Water balance.
8. Heart rate and blood pressure
regulation.
9. Uterine contraction and milk release.
10. Tissue development.
Characteristics of the Endocrine System
Endocrine System – composed of endocrine
glands + endocrine specialized cells
Hormones – chemical messenger that is
secreted into the blood
Target tissues – effectors; specific site
Endocrine – Greek word; endo (within) +
krino (secrete); ductless glands that directly
secretes their products into the blood stream.
Exocrine glands – have ducts that carry their
secretions to the outside of the body; drains
their secretions through a duct to the outside of
the body or into a holloworgan
Endocrinology – study of the endocrine
system
HORMONES
• Hormones are chemical messengers
that are secreted directly to the blood
stream by endocrine glands or
specialized endocrine cells.
• From the blood stream, they travel to
the effectors or target cells to produce
a response.
Components of Hormones
Receptor site - location on a cell where
hormone binds (lock)
Target tissues - group of cells that respond to
specific hormones
Specificity - specific hormones bind to
specific receptor sites
• Hormones influence their target cells
by chemically binding to specific
ENDOCRINE SYSTEM
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