Human Anatomy (Gharbiya STEM High School)
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,ENDOCRINE SYSTEM
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, Endoкrine system
- An animal hormone is a chemical signal that is secreted into the extracellular
fluid, circulates in the blood or hemolymph, and communicates regulatory
messages within the body.
○ A hormone may reach all parts of the body, but only specific target cells have
the receptors that enable a response.
○ A given hormone traveling in the bloodstream elicits specific responses—
such as a change in metabolism—only from its target cells while other cells are
unaffected.
- Chemical signaling by hormones is the function of the endocrine system, one
of two basic systems for communication and regulation throughout the body.
- The other major communication and control system is the nervous system, a
network of specialized cells called neurons that transmit signals along dedicated
pathways.
- Hormones secreted by endocrine cells regulate reproduction, development,
energy metabolism, growth, and behavior.
- Because signaling by neurons can regulate the release of hormones,
the nervous and endocrine systems often overlap in function.
- Hormones convey information via the bloodstream to target cells throughout
the body.
- Other chemical signals—local regulators—transmit information to target
cells near the secreting cells.
- Pheromones carry messages to different individuals of a species.
Intercellular Communication
Communication between animal cells via secreted signals is often classified by
two criteria:
1. The type of secreting cell
2. The route taken by the signal in reaching its target.
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