Transcript Chapter 45.
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
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
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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 (peptide)-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 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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Paracrine Regulators
Paracrine regulation occurs in most organs
-Growth factors are proteins that promote growth and
cell division in specific organs
-Epidermal GF = Skin
-Nerve GF = Neurons
-Insulin-like GF = Bone -Cytokines = Immune system
The endothelium of blood vessels is a rich source of
paracrine regulators
-Nitric oxide (NO) which promotes vasodilation
-Endothelin which stimulates vasoconstriction
Prostaglandins-A diverse group of fatty acids that are
produced in almost every organ regulate a variety of
functions including inflammation
-Synthesis is inhibited by nonsteroidal anti-inflammatory
drugs (NSAIDs) such as aspirin and ibuprofen
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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
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
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
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”
Anterior pituitary (adenohypophysis) -Appears glandular
-Posterior pituitary (neurohypophysis) -Appears
hypothalamus
fibrous
endocrine system
posterior
secretes broad range of “tropic”
hormones regulating other glands pituitary
anterior
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in body
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 Anterior Pituitary
The hypothalamus and the anterior pituitary
are partially controlled by the very
hormones whose secretion they stimulate
-This is termed negative feedback or
feedback inhibition
Positive feedback is uncommon because it
causes deviations from homeostasis
-One example is the control of ovulation
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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
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
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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Anterior Pituitary Disorders
Growth hormone stimulates growth of
muscles and connective tissue
-It also promotes the production of insulinlike growth factors
-Stimulate cell division in the epiphyseal
growth plates, and thus bone elongation
Gigantism is caused by an excessive
secretion of growth hormone in a child
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Anterior Pituitary Disorders
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