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Endocrine System
Hormones
AP Biology
2007-2008
Regulation
 Why are hormones needed?
chemical messages from one
body part to another
 communication needed to
coordinate whole body
 homeostasis & regulation

 metabolism
 growth
 development
 maturation
 reproduction
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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
 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
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
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How do hormones act on target cells
 Lipid-based hormones

hydrophobic & lipid-soluble
 diffuse across membrane & enter cells
 bind to receptor proteins in cytoplasm & nucleus
 bind to DNA as transcription factors
 Protein-based hormones

hydrophilic & not lipid soluble




can’t diffuse across membrane
receptor proteins in cell membrane
trigger secondary messenger pathway
activate internal cellular response
 enzyme action, uptake or secretion of molecules…
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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)
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
Benefits of a 2° messenger system
signal
1
Activated adenylyl cyclase
receptor protein
2
Not yet
activated
amplification
4
3
GTP
amplification
cAMP
amplification
5
G protein
protein kinase
6
amplification
enzyme
Amplification!
7
FAST
response!
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amplification
product
Endocrine system
 Ductless
glands release
hormones into
blood
Duct glands = exocrine
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(tears,
salivary)
Major vertebrate hormones (1)
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Major vertebrate hormones (2)
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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
hypothalamus
thyroid-stimulating
hormone
(TSH)
Thyroid gland
posterior antidiuretic
pituitary hormone
(ADH)
anterior
pituitary
Kidney
tubules
Muscles
of uterus
Adrenal
cortex
gonadotropic
hormones:
folliclestimulating
hormone (FSH)
& luteinizing
hormone (LH)
Melanocyte
in amphibian
Bone
and muscle
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Testis
Ovary
Mammary
glands
in mammals
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
Hormones & Homeostasis
 Negative feedback Inhibition Hypothalamus

stimulus triggers
control mechanism
that inhibits further
change
 body temperature
 sugar metabolism
 Positive feedback

stimulus triggers
control mechanism
that amplifies effect
 lactation
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 labor contractions
–
Releasing hormones
(TRH, CRH, GnRH)
Inhibition
Anterior pituitary
Tropic hormones
(TSH, ACTH, FSH, LH)
Target glands
(thyroid, adrenal cortex, gonads)
Hormones
–
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
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
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)
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
thyroxine
Goiter
Iodine deficiency
causes thyroid to
enlarge as it tries to
produce thyroxine
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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
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fertilized egg
(zygote)
no
corpus luteum breaks down
progesterone drops
menstruation
corpus
luteum
progesterone
maintains
uterus lining
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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
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(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
Any Questions??
Robert Wadlow
1918-1940
8' 11"
AP Biology
2007-2008