Endocrine System
• Chemical Control:
similar to nervous
control, coordinate
body processes by
transmitting messages
from one part of the
body to another
• Achieved through
hormonal action
Endocrine System
Function: to maintain homeostasis
Endocrine glands: synthesize and secrete
hormones (ductless)
Hormones ≡ chemicals secreted in one area of
body which affect responses in other areas.
 The circulatory system aids in the distribution
of these hormones
 Delivered to target tissue which recognize
specific hormones by receptor cells
 Hormones have specific shape that fit the
receptors
Regulation
How we maintain homeostasis
 nervous system
 nerve signals control body functions (faster
& short-lasting)
 endocrine system
 hormones
 chemical signals control body functions
(slower & longer-lasting)
Hormones
Why are hormones needed?
 chemical messages from one body part to cells
in other areas of body
 communication needed
to coordinate whole body
 maintaining homeostasis
growth hormones
Endocrine System
Endocrine system releases hormones
 glands which secrete (release)
chemical signals into blood
 chemicals cause changes
in other areas of body
 growth hormones
 sex hormones
 response hormones
 metabolism hormones
 and more….
Responding to hormones
Lock and key system
 hormone fits receptor on “target” cell
target
cell
secreting
cell
can’t
read
signal
nontarget
cells
can’t
read
signal
Control of the Endocrine system
The hypothalamus
integrates endocrine
and nervous function
Nervous tissue; part of
the mid-brain
Maintaining homeostasis
hormone 1
Feedback
lowers
body condition
gland
high
specific body condition
low
raises
body condition
gland
hormone 2
Negative Feedback
Response to changed body condition
 if body is high or low from normal level a signal
tells body to make changes that will bring body
back to normal level
 once body is back
hormone 1
to normal level,
signal is turned off
gland
lowers
body condition
high
specific body condition
Regulation of Blood Sugar
Feedback
insulin
liver stores reduces
body
sugar
appetite
cells take
up sugar
from blood
pancreas
high
liver
blood sugar level
(90mg/100ml)
liver
triggers releases
hunger sugar
liver
low
pancreas
glucagon
Diabetes: insulin deficiencyresults in an elevated blood
sugar level (glucose)
Regulation by chemical messengers
Neurotransmitters are released by neurons
Hormones are released by endocrine glands
endocrine gland
neurotransmitter
axon
hormone
carried by
blood
receptor proteins
receptor proteins
target cell
Body Regulation
Nervous system &
Endocrine system work
together
 hypothalamus
 “master nerve control
center”
 receives information
from nerves around body
about internal conditions
hormones
hormones
Body Regulation
Nervous system &
Endocrine system work
together
 hypothalamus ‘talks’ with
pituitary gland
 “master gland”
 releases many hormones
 sexual development,
growth, milk
production, pain relief
hormones
hormones
Nervous vs. Endocrine Systems
Nervous system
Endocrine System