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Endocrine System
Hormones
AP Biology
2006-2007
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
 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
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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
Insect metamorphosis

Figure 45.1
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Is regulated by hormones
Three Key Events in Hormone Function
 Three Key Events
Reception
 Signal transduction
 Response

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Classes of Vertebrate Hormones
 Three major classes of molecules
function as hormones in vertebrates
Proteins and peptides
 Amines derived from amino acids
 Steroids

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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

Non polar amines
 Modified nonpolar amino acids: thyroxine
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How do hormones act on target cells
 Protein-based
SECRETORY
CELL
Hormone
molecule
hormones

VIA
BLOOD
Signal receptor
TARGET
CELL
Signal
transduction
pathway
OR
Cytoplasmic
response
DNA
Nuclear
response
NUCLEUS
hydrophilic & not
lipid soluble
 can’t diffuse across
membrane
 trigger secondary
messenger pathway
 activate cellular
response
 enzyme action, uptake or
secretion of molecules…
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Action of protein hormones
1
Protein
hormone
activates
enzyme
G protein
cAMP
Receptor
protein
3
2
ATP
GTP
activates
enzyme
activates
enzyme
cytoplasm
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4
Produces an action
protein
messenger
cascade
How do hormones act on target cells
 Lipid-based
SECRETORY
CELL
hormones

hydrophobic &
lipid-soluble
Hormone
molecule
VIA
BLOOD
 diffuse across
membrane & enter
cells
 bind to receptor
proteins in
cytoplasm & nucleus
 bind to DNA as
transcription factors
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TARGET
CELL
Signal
receptor
Signal
transduction
and response
DNA
mRNA
NUCLEUS
Synthesis of
specific proteins
Action of lipid (steroid) hormones
cytoplasm
steroid hormone
S
S
S
1
2
blood
protein
carrier
receptor protein
4
S
3
DNA
nucleus
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mRNA
5 protein
plasma membrane
Multiple Effects
 The same hormone may have different
effects on target cells that have



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Different receptors for the hormone
Different signal transduction pathways
Different proteins for carrying out the
response
Action of epinephrine (adrenalin)
liver cell
1
epinephrine
activates
adenylyl cyclase adrenal gland
G protein
cAMP
receptor
protein
2
3
ATP
GTP
activates
protein kinase-A
activates
phosphorylase
4
cytoplasm
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glycogen
glucose
released
to blood
Epinephrine: Multiple Effects
 The hormone epinephrine

Has multiple effects in mediating the
Different receptors
different cell responses
body’s response to short-term stress
Epinephrine
Epinephrine
Epinephrine
a receptor
b receptor
b receptor
Glycogen
deposits
Vessel
constricts
(a) Intestinal blood
vessel
Figure 45.4a–c
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Vessel
dilates
(b) Skeletal muscle
blood vessel
Different intracellular proteins
Glycogen
breaks down
and glucose
is released
from cell
(c) Liver cell
different cell responses
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
Paracrine Signaling by Local Regulators
 Paracrine signaling

Various types of chemical signals elicit
responses in nearby target cells
 Local regulators have various functions and
include




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Cytokines – important in immune response
Growth factors – stimulate cell proliferation
and differentiation
Nitric oxide – (NO) relaxes neighboring smooth
muscles causing vasodialation
Prostaglandins – important in semen and in
immune response promote fever and
inflammation
Fig. 11-5ab
Local signaling
Electrical signal
along nerve cell
triggers release of
neurotransmitter
Target cell
Secreting
cell
Local regulator
diffuses through
extracellular fluid
(a) Paracrine signaling
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Neurotransmitter
diffuses across
synapse
Secretory
vesicle
Target cell
is stimulated
(b) Synaptic signaling
The major human endocrine glands
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Ovary
(female)
Testis
(male)
Figure 45.6
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Major human endocrine glands and some of
their hormones
Table 45.1
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Major human endocrine glands and some of
their hormones
Table 45.1
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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
Relation Between the Hypothalamus and
Pituitary Gland
 The hypothalamus, a region of the lower
brain

Contains different sets of neurosecretory
cells
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Relation Between the Hypothalamus and
Pituitary Gland
 Some of these cells produce direct-acting
hormones

That are stored in and released from the
posterior pituitary, or neurohypophysis
Hypothalamus
Neurosecretory
cells of the
hypothalamus
Axon
Posterior
pituitary
HORMONE
Figure 45.7
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TARGET
Anterior
pituitary
ADH
Kidney tubules
Oxytocin
Mammary glands,
uterine muscles
Other hypothalamic cells produce
tropic hormones
 That are secreted into the blood and transported
to the anterior pituitary or adenohypophysis
Tropic Effects Only
FSH, follicle-stimulating hormone
LH, luteinizing hormone
TSH, thyroid-stimulating hormone
ACTH, adrenocorticotropic hormone
Neurosecretory cells
of the hypothalamus
Nontropic Effects Only
Prolactin
MSH, melanocyte-stimulating hormone
Endorphin
Portal vessels
Nontropic and Tropic Effects
Growth hormone
Hypothalamic
releasing
hormones
(red dots)
HORMONE
TARGET
Figure 45.8
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FSH and LH
Testes or
ovaries
TSH
Thyroid
Endocrine cells of the
anterior pituitary
Pituitary hormones
(blue dots)
ACTH
Prolactin
MSH
Endorphin
Adrenal
cortex
Mammary
glands
Melanocytes
Pain receptors
in the brain
Growth hormone
Liver
Bones
 The anterior pituitary

Is a true-endocrine gland
 The tropic hormones of the
hypothalamus

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Control release of hormones from the
anterior pituitary
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
Negative Feedback Model
hormone 1
lowers
body condition
gland
high
specific body condition
low
raises
body condition
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gland
hormone 2
2005-2006
Nervous System Control
Body Temperature
Feedback
nerve signals
brain
sweat
dilates surface
blood vessels
high
body temperature
low
brain
constricts surface shiver
blood vessels
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nerve signals
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Endocrine System Control
Blood Sugar
Feedback
insulin
liver stores
sugar
body
cells take
up sugar
from blood
pancreas
high
reduces
appetite
liver
blood sugar level
low
triggers
hunger
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liver
releases
sugar
liver
pancreas
glucagon
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Body cells
take up more
glucose.
Insulin
 Maintenance of glucose homeostasis
Beta cells of
pancreas are stimulated
to release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Rising blood glucose
level (for instance, after
eating a carbohydraterich meal)
Blood glucose level
declines to set point;
stimulus for insulin
release diminishes.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes.
Figure 45.12
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Liver breaks
down glycogen
and releases
glucose into
blood.
STIMULUS:
Dropping blood glucose
level (for instance, after
skipping a meal)
Alpha cells of pancreas
are stimulated to release
glucagon into the blood.
Glucagon
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Diabetes Mellitus
 Diabetes mellitus, perhaps the bestknown endocrine disorder
Is caused by a deficiency of insulin or a
decreased response to insulin in target
tissues
 Is marked by elevated blood glucose
levels

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2005-2006
Types of Diabetes
 Type I diabetes mellitus (insulin-dependent
diabetes)

Is an autoimmune disorder in which the
immune system destroys the beta cells of the
pancreas
 Type II diabetes mellitus (non-insulindependent diabetes)

Is characterized either by a deficiency of
insulin or, more commonly, by reduced
responsiveness of target cells due to some
change in insulin receptors
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2005-2006
Adrenal Hormones: Response to
Stress
 The adrenal glands
Are adjacent to the kidneys
 Are actually made up of two glands: the
adrenal medulla and the adrenal cortex

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2005-2006
Adrenal Hormones: Response to
Stress
 The adrenal medulla secretes
epinephrine and norepinephrine

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Hormones which are members of a
class of compounds called
catecholamines
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Adrenal Hormones: Response to
Stress
 These hormones
Are secreted in response to stressactivated impulses from the nervous
system
 Mediate various fight-or-flight
responses

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2005-2006
Adrenal Hormones: Response to
Stress
 Hormones from the adrenal cortex
Also function in the body’s response to
stress
 Fall into three classes of steroid
hormones

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2005-2006
Adrenal Hormones: Response to
Stress
 Glucocorticoids, such as cortisol

Influence glucose metabolism and the
immune system
 Mineralocorticoids, such as aldosterone

Affect salt and water balance
 Sex hormones

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Are produced in small amounts
2005-2006
Stress and the adrenal gland
Stress
Spinal cord
(cross section)
Nerve
signals
Hypothalamus
Releasing
hormone
Nerve
cell
Anterior pituitary
Blood vessel
Adrenal medulla
secretes epinephrine
and norepinephrine.
Nerve cell
Adrenal cortex
secretes
mineralocorticoids
and glucocorticoids.
ACTH
Adrenal
gland
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
Figure 45.13a,b
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5. Change in blood flow patterns, leading to
increased alertness and decreased digestive
and kidney activity
(b) Long-term stress response
Effects of
mineralocorticoids:
1. Retention of sodium
ions and water by
kidneys
2. Increased blood
volume and blood
pressure
Effects of
glucocorticoids:
1. Proteins and fats
broken down and
converted to glucose,
leading to increased
blood glucose
2. Immune system may
be suppressed
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Endocrine System Control
Blood Osmolarity
Feedback
ADH
increased
water
reabsorption
pituitary
increase
thirst
nephron
high
blood osmolarity
blood pressure
adrenal
gland
low
increased
water & salt
reabsorption
nephron
renin
aldosterone
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angiotensinogen
angiotensin
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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
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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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++
Feedback
Female reproductive cycle
egg
matures &
is released
(ovulation)
estrogen
builds up
uterus lining
corpus
luteum
ovary
progesterone
FSH & LH
maintains
uterus lining
fertilized egg
(zygote)
HCG
yes
pituitary
gland
pregnancy
GnRH
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hypothalamus
no
corpus luteum breaks down
progesterone drops
menstruation
corpus
luteum
progesterone
maintains
2005-2006
uterus lining