Chemical Signals in Animals

Chemical Signals in Animals
Chapter 45
The Endocrine System

Hormone is a chemical signal that is secreted into body fluids (blood) and communicates regulatory messages within the body
Target cells respond to hormones

Two systems of internal communication and regulation: nervous system and endocrine system
Nervous: high speed signals along neurons movement in response to env changes
Endocrine: all of an animal's hormone secreting cells endocrine glands: hormone secreting organs (ductless glands directly into body fluids)

Endo and nerv are structurally, chemically, and functionally related
-endo organs contain nerve cells called NEUROSECRETORY CELLS secrete hormones, many chemicals = signals in nervous system, hormones in endocrine sys
-each system affects the output of the other ... release of milk: suckling = sensory cells -> nervous signals -> hypothalamus -> oxytocin from pituitary -> secrete milk

Invertebrates: hormones = reproduction and development "nerve and...