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Endocrine
System
Hormones
AP Biology
2007-2008
Hormone
 from the Greek word “hermon” – to excite or


set into motion
chemicals produced in 1 area of the body that
have an effect in another area
Named according to the affect they have on
the body, not based on the location they are
made
AP Biology
Regulation
 Why are hormones needed?
chemical messages from one
body part to another
 communication needed to
coordinate whole body
 daily homeostasis & regulation of
large scale changes

 solute levels in blood
 glucose, Ca++, salts, etc.
 metabolism
 growth
 development
 maturation
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 reproduction
growth hormones
Regulation & Communication
 Animals coordinate activities of specialized
parts by using major systems of internal
communication,
1)
endocrine system
 system of ductless glands
 secrete chemical signals directly into blood
 chemical travels to target tissue
 target cells have receptor proteins
 slow, long-lasting response
2)
nervous system
 system of neurons
 transmits “electrical” signal &
AP Biology
release neurotransmitters to
target tissue
 fast, short-lasting response
Regulation by chemical messengers
 Neurotransmitters released by neurons
 Hormones release by endocrine glands
endocrine gland
neurotransmitter
axon
hormone
carried by blood
receptor proteins
AP Biology
receptor proteins
target cell
Lock & Key
system
Hormones
 Convey information between


organs via circulatory system
Contact many cells but only
affect those with specific
receptors
Longer lasting affect (in
comparison to
neurotransmitters)
growth hormones
AP Biology
Neurotransmitters
 Chemicals that carry information
between cells of the nervous system or
from nerve cells to muscles, glands, or
other target cells
 Most direct form of chemical
communication
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Endocrine System
 Endocrine system releases hormones

glands which secrete (release)
chemical signals into blood
 chemicals cause changes
in other parts of body
 growth hormones
 sex hormones
 response hormones
 metabolism hormones
 and more….
AP Biology
Responding to hormones
 Lock and key system

hormone fits receptor on “target” cell
target
cell
secreting
cell
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can’t
read
signal
nontarget
cells
can’t
read
signal
Signaling with Hormones
 Hormones have specific shapes –
“fit”/recognized by target cells
 Specific binding of signal to hormones
receptor - a protein either inside target cell
or built into plasma membrane
 Effects of a hormone often countered by
opposing signal (often another hormone)
 A hormone can affect different target cells
within an animal differently
AP Biology
Classes of Hormones
 Protein-based hormones

polypeptides
 small proteins: insulin, ADH

insulin
glycoproteins
 large proteins + carbohydrate: FSH, LH

amines
 modified amino acids: epinephrine, melatonin
 Lipid-based hormones

steroids
 modified cholesterol: sex hormones, aldosterone
AP Biology
How do hormones act on target cells
 Lipid-based hormones

hydrophobic & lipid-soluble
 diffuse across cell membrane & enter cells
 bind to receptor proteins in cytoplasm & nucleus
 bind to DNA as transcription factors
 turn on genes
 enter the nucleus of the target cell &

influence the expression of the cell’s gene
and synthesis of new proteins
http://highered.mcgrawhill.com/olc/dl/120109/bio46.swf
AP Biology
Action of lipid (steroid) hormones
steroid hormone
target cell
S
S
cytoplasm
1
blood
S
protein
carrier
cross cell membrane
2
binds to receptor protein
becomes
transcription factor
5
S
3
mRNA read by ribosome
plasma membrane
DNA
4
mRNA
nucleus
6
protein
7
protein secreted
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ex: secreted protein = growth factor (hair, bone, muscle, gametes)
How do hormones act on target cells
 Protein-based hormones

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hydrophilic & not lipid soluble
 can’t diffuse across cell membrane
 bind to receptor proteins in cell
membrane
 trigger secondary messenger
pathway
 activate internal cellular response
enzyme action, uptake or secretion
of molecules…
How do hormones act on target cells
 unable to cross the plasma membrane of
the target cells, bind with proteins
(receptors) embedded in the plasma
membrane, this sparks a 2nd messenger
(eg. cyclic AMP) to the receptor site. Most
hormones in the brain are peptide
hormones
 Eg. epinephrine binds to the plasma
membrane, ATP → cyclic AMP (messenger)
activates glycogen hydrolysis
AP Biology
signal-transduction pathway
Action of protein hormones
1
protein
hormone
P
signal
plasma membrane
binds to receptor protein
activates
G-protein
activates enzyme
cAMP
receptor
protein
activates
cytoplasmic
signal
GTP
cytoplasm
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target
cell
acts as 2° messenger
transduction
ATP
ATP
activates
enzyme
2
secondary
messenger
system
activates
enzyme
produces an action
3
response
How do hormones act on target cells
 transduction: the action or process of
converting something and especially
energy or a message into another form
 http://highered.mcgrawhill.com/sites/0072437316/student_view0/c
hapter47/animations.html# (adrenaline
video)
AP Biology
Ex: Action of epinephrine (adrenaline)
adrenal gland
signal
1
epinephrine
activates
G protein
receptor
protein
in cell
membrane
activates GTP
3
activates
adenylyl cyclase
cAMP
GDP
transduction
4
GTP
2
ATP
activates
protein kinase-A
5
activates
phosphorylase kinase
cytoplasm
liver cell
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released
to blood
activates
glycogen phosphorylase
glycogen
6
glucose
7
response
Animation of hormone action
 http://www.wisconline.com/objects/ViewObject.aspx?ID
=AP13704 tutorial-try on own time!
AP Biology
Glands
 Pituitary

many hormones:
master gland
 Thyroid

thyroxine
 Adrenal

adrenaline
 Pancreas

insulin, glucagon
 Ovary

estrogen
 Testes

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testosterone
Glands
 Can be either
Exocrine glands – produce sweat,
mucus & digestive enzymes – products
conveyed by ducts
 Endocrine glands – produce hormones
which travel through the blood stream
to their target cells

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Endocrine Glands
 Secretory organs
 Secrete hormones into the bloodstream
 Pancreas
1.
2.
AP Biology
An endocrine gland
 Secretes insulin & glucagon
Is also an exocrine gland
 Produces bicarbonate ions & digestive
ions to small intestine
Nervous & Endocrine systems linked
 Hypothalamus = “master nerve control center”



nervous system
receives information from nerves around body
about internal conditions
releasing hormones: regulates release of hormones
from pituitary
 Pituitary gland = “master gland”


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endocrine system
secretes broad range
of “tropic” hormones
regulating other
glands in body
hypothalamus
posterior
pituitary
anterior
Hypothalamus
 Hypothalamus integrates endocrine &
nervous systems
 Hormone releasing cells in hypothalamus
are specialized neurons – they can
synthesize hormones, release hormones
and they can conduct nerve impulses
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Hypothalamus
 Therefore these cells receive signals
from other nerve cells that trigger them
to release hormones to the bloodstream
 Hypothalamus has 2 sets of
neurosecretory cells
1)
2)
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Produces hormones of posterior pituitary
The other set produce releasing
hormones that regulate the anterior
pituitary
Pituitary Gland
 Posterior pituitary – stores & secretes
hormones made by the hypothalamus.
Both hormones act directly on muscles
and kidneys (rather than affecting other
endocrine glands)
 Anterior Pituitary – produce their own
hormones, several act on other
endocrine glands
AP Biology
tropic hormones = target endocrine glands
hypothalamus
thyroid-stimulating
hormone
(TSH)
Thyroid gland
Adrenal
cortex
posterior antidiuretic
pituitary hormone
(ADH)
anterior
pituitary
gonadotropic
hormones:
folliclestimulating
hormone (FSH)
& luteinizing
hormone (LH)
Kidney
tubules
Muscles
of uterus
Melanocyte
in amphibian
Bone
and muscle
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Testes
Ovaries
Mammary
glands
in mammals
Pituitary Gland Videos
 http://www.youtube.com/watch?v=Vae5
CcaPN_8
AP Biology
Homology in hormones
What does this tell you about these hormones?
How could these hormones have different effects?
same gene family
gene duplication?
prolactin
mammals
milk
production
AP Biology
birds
fat
metabolism
fish
amphibians
salt &
water
balance
metamorphosis
& maturation
growth
hormone
growth
& development
Feedback
Female reproductive cycle
egg
matures &
is released
(ovulation)
estrogen
builds up
uterus lining
corpus
luteum
ovary
progesterone
FSH & LH
maintains
uterus lining
pituitary
gland
hCG
yes
pregnancy
GnRH
hypothalamus
AP Biology
fertilized egg
(zygote)
no
corpus luteum breaks down
progesterone drops
menstruation
corpus
luteum
progesterone
maintains
uterus lining
AP Biology
tropic hormones = target endocrine glands
hypothalamus
posterior
pituitary
anterior
pituitary
Thyroid gland
Kidney
tubules
Muscles
of uterus
Adrenal
cortex
Melanocyte
in amphibian
Bone
and muscle
AP Biology
Testes
Ovaries
Mammary
glands
in mammals