Endocrine System
Hormones
AP Biology
2007-2008
Ch. 34 Warm-Up
1. What type of behavior in animals might
be triggered by cold temperatures?
2. What type of behaviors might be
triggered in hot temperatures?
3. List 2 examples of negative feedback.
List 2 examples of positive feedback.
4. What is the main type of chemical
messenger in the endocrine system? The
nervous system?
AP Biology
34.2 The Vertebrate Endocrine
System
 Animal cells communicate with one
another by way of a variety of shortrange and long-range chemical signals
 Animal cells communicate with
adjacent cells through gap junctions
and by releasing molecules that bind to
receptors in or on other cells
AP Biology
Mechanisms of Intercellular Signaling
 Only neurons secrete neurotransmitters, which
diffuse across the synaptic cleft to the target cell
 Many cells secrete local signaling molecules –
such as prostaglandins released by injured cells
– which affect only neighboring cells
 Animal hormones are secreted into interstitial
fluid, enter the blood, and are distributed
throughout the body
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Types of
Intercellular
Signaling
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Pheromones
(other signaling
molecule)
Hormones
Local
Regulators
(other signaling
molecule)
Chemical signal Chemical signal
from 1
from endocrine Chemical signal
individual to
gland through from one cell to
another
blood to target an adjacent cell
individual
cell
Eg. ant trail; sex
phermones
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Eg. peptide,
steroid
hormones
Eg. cytokines,
growth factors,
nitric oxide (NO)
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 rely on 2 systems for regulation

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

nervous system
 system of neurons
 transmits “electrical” signal &
release neurotransmitters to
target tissue
 fast, short-lasting response
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Regulation by chemical messengers
 Neurotransmitters released by neurons
 Hormones release by endocrine glands
endocrine gland
neurotransmitter
axon
hormone
carried by blood
receptor proteins
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receptor proteins
target cell
Lock & Key
system
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
 Protein-based hormones

hydrophilic & not lipid soluble




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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…
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Table 34-1 p588
Types of Hormones
Peptide
Steroid
• Water-soluble
• Bind to receptors on
•
•
•
•
plasma membrane &
triggers signal
transduction pathway
Affects protein activity
already present in cell
Rapid response
Short-lived
Eg. oxytocin, insulin,
epinephrine
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• Lipid-soluble
• Enters cell & binds to
•
•
•
•
intracellular receptors
Causes change in gene
expression (protein
synthesis)
Slower response
Longer life
Eg. androgens
(testosterone), estrogen,
progesterone, cortisol
DISCOVERY VIDEO: ENDOCRINE
SYSTEM
https://www.youtube.com/watch?v=HrMi4Gi
kWwQ
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From Signal Reception to
Response
Signal
Reception
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Signal
Transduction
Cellular
Response
Action of lipid (steroid) hormones
 Intracellular Receptors
 Steroid hormones are made from
cholesterol and can diffuse across the
plasma membrane
 Most steroid hormones form a
hormone-receptor complex that binds
to a promoter inside the nucleus and
alters the expression of specific genes
AP Biology
1
A steroid hormone
molecule is moved from
blood into interstitial fluid
bathing a target cell.
2 Being lipid
soluble, the
hormone
easily
diffuses
across the
cell’s plasma
membrane.
The
resulting
mRNA moves
into the
cytoplasm and
is transcribed
into a protein.
5
gene product
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3 The hormone
diffuses through the
cytoplasm and nuclear
envelope. It binds with
its receptor in the
nucleus.
receptor
4
The
hormone–
receptor
complex
hormone–
receptor triggers
complex transcription of a
specific
gene.
Figure 34-3a p589
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)
Action of protein hormones
 Large amine, peptide and protein
hormones bind to a receptor at the
plasma membrane
 Binding triggers formation of a second
messenger (molecule that relays signal
into cell)
Enzyme converts ATP to cAMP
 cAMP activates a cascading series of
reactions

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A peptide hormone
1 molecule,
glucagon,
diffuses from blood into
interstitial fluid bathing
the plasma membrane
of a liver cell.
unoccupied glucagon
receptor at target cell’s
plasma membrane
cyclic
AMP
ATP
+ Pi
2
Glucagon binds
with a receptor.
Binding activates an
enzyme that catalyzes
the formation of
cyclic AMP from ATP
inside the cell.
4
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Cyclic AMP
activates another
enzyme in the cell.
3
The enzyme activated by
cyclic AMP activates another
enzyme, which in turn
activates another kind that
catalyzes the breakdown of
glycogen to its glucose
monomers.
5
The enzyme
activated by
cyclic AMP
also inhibits
glycogen
synthesis.
Figure 34-3b p589
signal-transduction pathway
Action of protein hormones
1
protein
hormone
P
signal
plasma membrane
binds to receptor protein
activates
G-protein
activates enzyme
cAM
P
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
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
Epinephrine: one hormone  many effects
1.Liver cells break 2.Blood vessels to
down glycogen and skeletal muscles
dilate
AP Biology release glucose
3.Blood vessels
to intestines
constrict
Benefits of a 2° messenger
system1
signal
Activated adenylyl cyclase
receptor protein
2
Not yet
activated
amplification
4
3
GTP
amplification
cAMP
amplification
5
G protein
protein kinase
6
amplification
Amplification!
enzyme
Cascade multiplier!
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FAST
response!
7
amplification
product
Maintaining homeostasis
hormone 1
lowers
body condition
gland
high
specific body condition
low
raises
body condition
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gland
hormone 2
Negative Feedback
Model
Nervous System Control
Feedback
Controlling Body Temperature
nerve signals
hypothalamus
dilates surface
blood vessels
sweat
high
body temperature
(37°C)
low
hypothalamus
constricts surface shiver
blood vessels
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nerve signals
Endocrine System Control
Feedback
Regulation of Blood Sugar
islets of Langerhans
insulin
beta islet cells
liver stores
glycogen
body
cells take
up sugar
from blood
pancreas
liver
high
blood sugar level
(90mg/100ml)
low
triggers
hunger
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liver
releases
glucose
liver
pancreas
glucagon
islets of Langerhans
alpha islet cells
reduces
appetite
Diabetes Mellitus
 Type I diabetes (10%):deficiency of insulin
Insulin-dependent
 Autoimmune disorder  beta cells of
pancreas destroyed

 Type II diabetes (90%): failure of target
cells to respond to insulin
Non-insulin dependent
 Insulin produced  cells don’t respond
(defect in insulin receptor or response
pathway)
 Risk factors: obesity, lack of exercise
AP Biology

BIOFLIX: HOMEOSTASIS – BLOOD
SUGAR
https://massasoit.instructure.com/courses/902777/pages/biofli
x-homeostasis-regulating-blood-sugar
AP Biology
Endocrine System Control
Blood Osmolarity
osmoreceptors in
hypothalamus
Feedback
ADH
increased
water
reabsorption
pituitary
increase
thirst
nephron
high
blood osmolarity
blood pressure
nephron
adrenal
gland
low
increased
water & salt
reabsorption
JuxtaGlomerular
Apparatus
nephron
(JGA)
renin
aldosterone
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angiotensinogen
angiotensin
RAAS (Renin Angiotensin Aldosterone System
 Handwritten Tutorials

https://www.youtube.com/watch?v=PDE
2qdS2ZvY
 https://www.youtube.com/watch?v=bY6
IWVgFCrQ
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ANIMATION: Hormones and target cell
receptors
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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
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birds
fat
metabolism
fish
amphibians
salt &
water
balance
metamorphosis
& maturation
growth
hormone
growth
& development
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
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
The Hypothalamus and Pituitary
Gland
hypothalamus
anterior
lobe of
pituitary
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posterior
lobe of
pituitary
Posterior Pituitary Function
 Secretory neurons of the hypothalamus
make two hormones that move through
axons into the posterior pituitary,
which releases them
 Antidiuretic hormone (ADH) affects
certain kidney cells
 Oxytocin (OT) triggers muscle
contractions during childbirth
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Cell bodies of
secretory neurons
in hypothalamus
synthesize ADH or
oxytocin.
1
The ADH or
oxytocin moves
downward inside the
axons of the secretory
neurons and
accumulates in the
axon terminals.
2
Action potentials
trigger the release of
these hormones,
which enter blood
capillaries in the
posterior lobe of the
pituitary.
3
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Blood
vessels carry
hormones to
the general
circulation.
4
Figure 34-5 p591
Regulating metabolism
 Hypothalamus

TRH = TSH-releasing hormone
 Anterior Pituitary

TSH = thyroid stimulating hormone
 Thyroid


produces thyroxine hormones
metabolism & development







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bone growth
mental development
metabolic use of energy
blood pressure & heart rate
muscle tone
digestion
reproduction
tyrosine
+
iodine
thyroxines
Goiter
Iodine deficiency causes thyroid to enlarge as it
tries to produce thyroxine
+
tyrosine
+
iodine
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✗
✗
thyroxines
Endocrine System Control
Feedback
Regulation of Blood Calcium
calcitonin
 kidney
reabsorption
of Ca++
thyroid
Ca++ deposited
in bones
high
blood calcium level
 Ca++ uptake
in intestines
(10 mg/100mL)
low
activated Vitamin D
bones
release Ca++
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 kidney
reabsorption
of Ca++
parathyroid
parathyroid hormone (PTH)
Control of Anterior Pituitary
 Hormones from the hypothalamus control the
release of anterior pituitary hormones
 Releasing hormones encourage secretion of
hormones by target cells
 Inhibiting hormones reduce secretion of
hormones by target cells
 Releasing and inhibiting hormones are secreted
into the stalk that connects the hypothalamus to
the pituitary
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Anterior Pituitary Function
 The anterior pituitary produces
hormones of its own:
Adrenocorticotropic hormone (ACTH)
 Thyroid-stimulating hormone (TSH)
 Follicle stimulating hormone (FSH)
 Luteinizing hormone (LH)
 Prolactin (PRL)
 Growth hormone (GH)

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Take-Home Message: How do the
hypothalamus and pituitary gland interact?
 Some secretory neurons of the hypothalamus
make hormones (ADH, OT) that move through
axons into the posterior pituitary, which releases
them.
 Other hypothalamic neurons produce releasers
and inhibitors that are carried by the blood into
the anterior pituitary. These hormones regulate
the secretion of anterior pituitary hormones
(ACTH, TSH, LH, FSH, PRL, and GH).
AP Biology
34.10 The Gonads
 Gonads are the primary reproductive
organs that produce gametes (eggs and
sperm)
 Vertebrate gonads produce sex
hormones, steroid hormones that
control sexual development and
reproduction
Testes produce testosterone
 Ovaries produce estrogens and
AP Biology progesterone

Control of Sex Hormone Secretion
 The hypothalamus and anterior pituitary control
secretion of sex hormones by gonads
 The hypothalamus produces gonadotropinreleasing hormone (GnRH), which causes the
anterior pituitary to secrete follicle-stimulating
hormone (FSH) and luteinizing hormone (LH)
 FSH and LH are “gonadotropins” that cause
gonads to produce and secrete sex hormones
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Control of Sex Hormone Secretion
Hypothalamus
GnRH
Anterior Pituitary
FSH, LH
Gonads
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Sex hormones
Female hormones
 FSH & LH



released from pituitary
stimulates egg development & hormone release
peak release = release of egg (ovulation)
 Estrogen



released from ovary cells around developing egg
stimulates growth of lining of uterus
decreasing levels causes menstruation
 Progesterone



AP Biology
released from “corpus luteum” in ovaries
 cells that used to take care of developing egg
stimulates blood supply to lining of uterus
decreasing levels causes menstruation
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
Fertilization
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LH
Menstrual cycle

Controlled by
interaction of
4 hormones egg development
FSH & LH
 estrogen
 progesterone
FSH
ovulation = egg release

corpus luteum
estrogen
progesterone
lining of uterus
AP Biology
days 0
7
14
21
28
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Sex Hormones and Puberty
 Sex hormone production increases
during puberty, the period of
development when reproductive organs
mature and secondary sexual traits
appear
 Secondary sexual traits are traits that
differ between the sexes, but do not
have a direct role in reproduction
AP Biology
Take-Home Message:
What are sex hormones?
 Sex hormones are steroid hormones that influence the
development of sexual traits and reproduction. Production
of sex hormones increases at puberty.
 In both sexes, gonads secrete sex hormones in response to
anterior pituitary hormones (FSH and LH), which are in turn
released in response to a hypothalamic releasing hormone.
 A male’s testes secrete mainly testosterone, and a
female’s ovaries secrete mainly estrogens and
progesterone.
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Sex & Growth Hormones
 Large scale body
changes

how do they work
 turn genes on
 start new processes
in the body by
turning genes on
that were lying
“dormant”
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Pituitary gland hormones
 Sex & reproductive hormones

FSH
 follicle stimulating hormone
 stimulates egg & sperm production

LH
 luteinizing hormone
 stimulates ovaries & testes
 prepares uterus for fertilized egg

oxytocin
 stimulates childbirth contractions
 releases milk in nursing mothers

prolactin
 milk production in nursing mothers
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hormones
hormones
Everyone’s doing it, so
Ask Questions!!
AP Biology
2006-
Multiple Hormone Receptors
 Most cells have receptors for multiple
hormones, and the effect of one
hormone can be enhanced or opposed
by another one
 Example: Skeletal muscle hormone
receptors

AP Biology
Glucagon, insulin, cortisol, epinephrine,
estrogen testosterone, growth hormone,
somatostatin, thyroid hormone and
others
Actions of Hormones
 https://www.wisconline.com/learn/natural-science/lifescience/ap13704/the-actions-ofhormones
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34.13 Invertebrate Hormones
 Genes for hormone receptors and enzymes
involved in hormone synthesis evolved over time
 We can trace the evolutionary roots of the
vertebrate endocrine system in invertebrates
 Cnidarians (e.g. sea anemones) and mollusks
(e.g. sea slugs) have receptors that resemble
those that bind vertebrate hormones
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Hormones and Molting
 Some hormones are unique to
invertebrates
 Example: ecdysone, a steroid hormone
that controls molting in arthropods
Hormone-secreting neurons in the brain
respond to signals such as light and
temperature
 Mechanisms differ in crustaceans and
insects

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Control of Molting in Crabs
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Take-Home Message: What types of
hormones do invertebrates produce?
 Some invertebrate hormones are
homologous to those in vertebrates.
Cnidarians and annelids have receptors
that resemble those that bind vertebrate
hormones.
 Invertebrates also make hormones with
no vertebrate counterpart. Hormones
that control molting in arthropods are an
example.
AP Biology
Any Questions??
Robert Wadlow
1918-1940
8' 11"
AP Biology
2009-2010
Effects of stress on a body
Stress
Nerve
Spinal cord
signals
(cross section)
Hypothalamus
Releasing
hormone
Nerve
cell
Anterior pituitary
Blood vessel
adrenal medulla
secretes epinephrine
& norepinephrine
Nerve cell
ACTH
Adrenal
gland
Adrenal cortex
secretes
mineralocorticoids
& glucocorticoids
Kidney
(A) SHORT-TERM STRESS RESPONSE
Effects of epinephrine and norepinephrine:
1. Glycogen broken down to glucose;
increased blood glucose
2. Increased blood pressure
3. Increased breathing rate
4. Increased metabolic rate
5. Change in blood flow patterns, leading
to increased alertness & decreased
digestive & kidney activity
AP Biology
(B) LONG-TERM STRESS RESPONSE
Effects of
mineralocorticoids:
Effects of
glucocorticoids:
1. Retention of
sodium ions &
water by kidneys
1. Proteins & fats broken
down & converted to
glucose, leading to
increased blood
glucose
2. Increased blood
volume & blood
pressure
2. Immune system
suppressed