Chapter 45.
Endocrine System
Hormones
AP Biology
2004-2005
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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2004-2005
growth hormones
Regulation & Communication
 Animals rely on 2 systems for regulation

endocrine system
 ductless gland which secrete
chemical signals directly into blood
 chemical travels to target tissue
 slow, long-lasting response

nervous system
 system of neurons, central
nerve system
 transmits “electrical” signal to
target tissue
 fast, short-lasting response
AP Biology
2004-2005
Regulation by chemical messengers
 Neurotransmitters released by neurons
 Hormones release by endocrine glands
Endocrine gland
Axon
Neurotransmitter
Hormone
carried
by blood
Receptor
proteins
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Target cell
2004-2005
Classes of Hormones
 Protein-based hormones

polypeptides
 small proteins: insulin, ADH

glycoproteins
 large proteins + carbohydrate: FSH, LH

amines
 modified amino acids: epinephrine, melatonin
 Lipid-based hormones

steroids
 modified cholesterol: sex hormones,
aldosterone
AP Biology
2004-2005
How do hormones act on target cells
 Lipid-based hormones
lipid-soluble
 diffuse across membrane & enter cells

 bind to receptor proteins in cytoplasm &
then this hormone-receptor complex moves
into nucleus
 bind to receptor proteins in nucleus

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bind to DNA as transcription factors
2004-2005
Action of steroid (lipid) hormones
Cytoplasm
S
Steroid
S hormone
Blood plasma
S
1
Protein
carrier
Plasma membrane
1 Steroid hormone (S) passes
2
through plasma membrane.
2
Inside target cell, the steroid
hormone binds to a specific
receptor protein in the
cytoplasm or nucleus.
3
Hormone-receptor complex
enters nucleus & binds to DNA,
causing gene transcription
4
Protein synthesis is induced.
5
Protein is produced.
2004-2005
4
S
DNA
Nucleus
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3
mRNA
5 Protein
How do hormones act on target cells
 Protein-based hormones

hydrophilic & not lipid
soluble
Signal molecule
Cell surface receptor
enzyme
 can’t diffuse across
cAMP
membrane

trigger secondary (2°)
messenger pathway
G protein
ATP
 transmit “signal” across
membrane
 “signal transduction”
 usually activates a series of
2° messengers
 multi-step “cascade”

Nucleus
activate cellular response
 enzyme action, uptake or
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Target
protein
secretion of molecules, etc.
Cytoplasm
2004-2005
Action of protein hormones
1
Protein
hormone
activates
enzyme
G protein
cAMP
Receptor
protein
3
2
ATP
GTP
Cytoplasm
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activates
enzyme
activates
enzyme
4
Produces an action
protein
messenger
cascade
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Action of epinephrine (adrenalin)
Liver cell
1
Epinephrine
activates
adenylyl cyclase adrenal gland
G protein
Receptor
protein
cAMP
2
3
ATP
GTP
activates
protein kinase-A
activates
phosphorylase
4
released
to blood
Cytoplasm
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Glycogen
Glucose
2004-2005
Benefits of a 2° messenger system
1
Signal molecule
Receptor protein
Activated adenylyl cyclase
Not yet
activated
2 Amplification
4 Amplification
3
GTP
cAMP
5
G protein
Protein kinase
6 Amplification
Amplification!
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Enzyme
7 Amplification
Enzymatic product
2004-2005
Endocrine system
 Ductless
glands release
hormones into
blood
Duct glands = exocrine
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(tears,
salivary)
2004-2005
Major vertebrate hormones (1)
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2004-2005
Major vertebrate hormones (2)
AP Biology
2004-2005
Endocrine & Nervous system links
 Hypothalamus = “master control center”



nervous system
receives information from nerves around body
about internal conditions
regulates release of hormones from pituitary
 Pituitary gland = “master gland”


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endocrine system
secretes broad range
of hormones
regulating other
glands
2004-2005
Hypothalamus
Thyroid-stimulating
Antidiuretic
Hormone
Posterior
hormone
(TSH)
pituitary (ADH)
Thyroid gland
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
2004-2005
Homology in hormones
What does this tell you about these hormones?
same gene family
prolactin
mammals
milk
production
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birds
fat
metabolism
fish
amphibians
salt &
water
balance
metamorphosis
& maturation
growth
hormone
growth
& development
2004-2005
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)
Hormones2004-2005
–
Regulating blood sugar levels
beta islet cells
pancreas
- triggers
release of
glucose by
liver
- stimulates
appetite
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- triggers uptake
of glucose by
body cells
- triggers
storage in liver
- depresses
appetite
pancreas
alpha islet cells
2004-2005
Regulating blood osmolarity
If amount of
dissolved
material in
blood too
high, need to
dilute blood
Dehydration
Osmotic concentration
of blood increases
Negative
feedback
Osmoreceptors
Negative
feedback
ADH synthesized
in hypothalamus
ADH
Increased
water
retention
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Lowers
blood
volume
& pressure
Reduced
urine
volume
ADH released from
posterior pituitary
into blood
Increased
vasoconstriction
leading to higher
blood pressure
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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
2004-2005
Goiter
Iodine deficiency
causes thyroid to
enlarge as it tries to
produce thyroxine
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2004-2005
Thyroxine secretion rate
Homology in hormones
–35
Thyroxine stimulates metamorphosis in amphibians
TRH
TSH
Thyroxine
TRH rises
–30
–25
–20
–15
–10
–5
0
+5
+10
Days from emergence of forelimb
AP Biology
2004-2005
Regulating blood calcium levels
Thyroid
Low blood Ca++
–
Negative
feedback
Increased absorption
of Ca++ from intestine
due to PTH activation
of Vitamin D
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Parathyroids
Parathyroid
hormone (PTH)
Reabsorption of Ca++ &
excretion of PO4
Increased blood Ca++
Osteoclasts
dissolve CaPO4
crystals in
bone, releasing
Ca++
2004-2005
Hormonal regulation of insect development
Neurosecretory cells
Brain hormone
Juvenile hormone
Low amounts
Prothoracic
gland
Molting hormone
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Larval molt
Pupal molt
Adult molt
2004-2005
Any Questions??
AP Biology
2005-2006