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Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 9
The Endocrine System
Slides 9.1 – 9.22
Lecture Slides in PowerPoint
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Endocrine System
 Second messenger system of the body
 Uses chemical messages (hormones)
that are released into the blood
 Hormones control several major
processes
 Reproduction
 Growth and development
 Mobilization of body defenses
 Maintenance of much of homeostasis
 Regulation of metabolism
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Slide
Hormone Overview
 Hormones are produced by specialized
cells
 Cells secrete hormones into
extracellular fluids (blood)
 Blood transfers hormones to target sites
 These hormones regulate the activity of
other cells
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Slide
The Chemistry of Hormones
 Amino acid-based hormones
 Proteins
 Peptides
 Amines
 Steroids – made from cholesterol
 Prostaglandins (local hormones) –
made from highly active lipids in cell
membranes.
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Mechanisms of Hormone Action
 Hormones affect only certain tissues or
organs (target cells or organs)
 Target cells must have specific protein
receptors
 Hormone binding influences the working of
the cells
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Effects Caused by Hormones
 Hormone means “to arouse”. They
alter cellular activity by increasing or
decreasing a normal cellular process.
 1. Changes in plasma membrane
permeability or electrical state
 2. Synthesis of proteins, such as
enzymes
 3. Activation or inactivation of
enzymes
 4. Stimulation of mitosis
 5. Promotion of secretory activity
Slide
Steroid Hormone Action
 Diffuse through the plasma membrane
of target cells
 Enter the nucleus
 Bind to a specific protein within the
nucleus
 Bind to specific sites on the cell’s DNA
 Activate genes that result in synthesis of
new proteins
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Slide
Steroid
hormone
Extracellular fluid
Plasma
membrane
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Cytoplasm
Receptor
protein
Receptorhormone
complex
Nucleus
Figure 16.3, step 1
Steroid
hormone
Extracellular fluid
Plasma
membrane
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Cytoplasm
Receptor
protein
Receptorhormone
complex
2 The receptor-
Nucleus
hormone complex enters
the nucleus.
Figure 16.3, step 2
Steroid
hormone
Extracellular fluid
Plasma
membrane
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Cytoplasm
Receptor
protein
Receptorhormone
complex
2 The receptor-
Nucleus
Hormone
response
elements
DNA
hormone complex enters
the nucleus.
3 The receptor- hormone
complex binds a hormone
response element (a
specific DNA sequence).
Figure 16.3, step 3
Steroid
hormone
Extracellular fluid
Plasma
membrane
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Cytoplasm
Receptor
protein
Receptorhormone
complex
2 The receptor-
Nucleus
Hormone
response
elements
DNA
mRNA
hormone complex enters
the nucleus.
3 The receptor- hormone
complex binds a hormone
response element (a
specific DNA sequence).
4 Binding initiates
transcription of the
gene to mRNA.
Figure 16.3, step 4
Steroid
hormone
Plasma
membrane
Extracellular fluid
1 The steroid hormone
diffuses through the plasma
membrane and binds an
intracellular receptor.
Cytoplasm
Receptor
protein
Receptorhormone
complex
2 The receptor-
Nucleus
Hormone
response
elements
DNA
mRNA
hormone complex enters
the nucleus.
3 The receptor- hormone
complex binds a hormone
response element (a
specific DNA sequence).
4 Binding initiates
transcription of the
gene to mRNA.
5 The mRNA directs
protein synthesis.
New protein
Figure 16.3, step 5
Steroid Hormone Action
Figure 9.1a
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Slide
Nonsteroid Hormone Action
 Hormone binds to a membrane receptor
 Hormone does not enter the cell
 Sets off a series of reactions that
activates an enzyme
 Catalyzes a reaction that produces a
second messenger molecule
 Oversees additional intracellular
changes to promote a specific response
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Slide
1 Hormone (1st messenger)
Extracellular fluid
binds receptor.
Receptor
Hormones that
act via cAMP
mechanisms:
Epinephrine
ACTH
FSH
LH
Glucagon
PTH
TSH
Calcitonin
Cytoplasm
Figure 16.2, step 1
1 Hormone (1st messenger)
Extracellular fluid
binds receptor.
G protein (GS)
Receptor
GDP
Hormones that
act via cAMP
mechanisms:
Epinephrine
ACTH
FSH
LH
Glucagon
PTH
TSH
Calcitonin
2 Receptor
activates G
protein (GS).
Cytoplasm
Figure 16.2, step 2
1 Hormone (1st messenger)
binds receptor.
Adenylate cyclase
Extracellular fluid
G protein (GS)
Receptor
GDP
Hormones that
act via cAMP
mechanisms:
Epinephrine
ACTH
FSH
LH
Glucagon
PTH
TSH
Calcitonin
2 Receptor
activates G
protein (GS).
3 G protein
activates
adenylate
cyclase.
Cytoplasm
Figure 16.2, step 3
1 Hormone (1st messenger)
binds receptor.
Adenylate cyclase
Extracellular fluid
G protein (GS)
Receptor
GDP
Hormones that
act via cAMP
mechanisms:
Epinephrine
ACTH
FSH
LH
Glucagon
PTH
TSH
Calcitonin
2 Receptor
activates G
protein (GS).
3 G protein
activates
adenylate
cyclase.
4 Adenylate
cyclase
converts ATP
to cAMP (2nd
messenger).
Cytoplasm
Figure 16.2, step 4
1 Hormone (1st messenger)
binds receptor.
Adenylate cyclase
Extracellular fluid
G protein (GS)
5 cAMP acti-
vates protein
kinases.
Receptor
GDP
Hormones that
act via cAMP
mechanisms:
Epinephrine
ACTH
FSH
LH
Glucagon
PTH
TSH
Calcitonin
2 Receptor
activates G
protein (GS).
3 G protein
activates
adenylate
cyclase.
4 Adenylate
cyclase
converts ATP
to cAMP (2nd
messenger).
Active
protein
kinase
Triggers responses of
target cell (activates
enzymes, stimulates
cellular secretion,
opens ion channel,
etc.)
Cytoplasm
Inactive
protein kinase
Figure 16.2, step 5
Nonsteroid Hormone Action
Animation
Figure 9.1b
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Slide
Control of Hormone Release
 Hormone levels in the blood are
maintained by negative feedback
 A stimulus or low hormone levels in the
blood triggers the release of more
hormone
 Hormone release stops once an
appropriate level in the blood is reached
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Slide
Overview of the Endocrine System
•Control of Endocrine Secretion
• Humoral (fluid) stimuli
• E.g., blood level of Ca2+ directly
controls parathyroid hormone and
calcitonin release
• Hormonal stimuli
• E.g., thyroid stimulating hormone
triggers thyroid hormone release
• Neural stimuli
• E.g., epinephrine release from
adrenal gland
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Hormonal Stimuli of Endocrine Glands
 Endocrine glands
are activated by
other hormones –
hormonal
stimulus
Figure 9.2a
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Slide
Humoral Stimuli of Endocrine Glands
 Changing blood
levels of certain
ions stimulate
hormone release –
humoral stimuli
Figure 9.2b
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Slide
Neural Stimuli of Endocrine Glands
 Nerve impulses
stimulate hormone
release – neural
stimuli
 Most are under
control of the
sympathetic nervous
system
Figure 9.2c
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Slide
Nervous System Modulation
• The nervous system modifies the stimulation
of endocrine glands and their negative
feedback mechanisms
• Example: under severe stress, the hypothalamus
and the sympathetic nervous system are
activated
• As a result, body glucose levels rise
Location of Major Endrocrine Organs
Figure 9.3
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Slide
• Pituitary Gland
• Small, pea size gland. Very mighty
gland, that is actually two glands in
one, the anterior and posterior
pituitary.
• Buried deep in the cranial cavity in a
depression in the sphenoid bone
called the sella tursica.
• The pituitary gland (hypophysis) has
two major lobes
1. Anterior pituitary (lobe)
• Glandular tissue
2. Posterior pituitary (lobe):
• Nervous tissue
• Anterior Lobe:
• Releasing and inhibiting hormones
are carried to the anterior lobe from
the hypothalamus to control the
release of the many hormones it
secretes.
Hypothalamus
Hypothalamic neuron
cell bodies
Superior
hypophyseal artery
Hypophyseal
portal system
• Primary capillary
plexus
• Hypophyseal
portal veins
• Secondary
capillary
plexus
Anterior lobe
of pituitary
TSH, FSH,
LH, ACTH,
GH, PRL
1 When appropriately
stimulated,
hypothalamic neurons
secrete releasing and
inhibiting hormones
into the primary
capillary plexus.
2 Hypothalamic hormones
travel through the portal
veins to the anterior pituitary
where they stimulate or
inhibit release of hormones
from the anterior pituitary.
3 Anterior pituitary
hormones are secreted
into the secondary
capillary plexus.
(b) Relationship between the anterior pituitary and the hypothalamus
Figure 16.5b
• Called the master gland because it
exerts control over the thyroid gland,
adrenal cortex, ovarian follicles, and
the corpus luteum.
• Tropic hormones – hormones
whose target organs are other
endocrine glands.
Anterior Pituitary Hormones
• Growth hormone (GH)
• Thyroid-stimulating hormone (TSH) or
thyrotropin
• Adrenocorticotropic hormone (ACTH)
• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Prolactin (PRL)
• Growth hormone
• Speeds up the absorption of amino
acids which will be used to produce
new proteins. Accelerates fat
breakdown for energy use and
slows glucose breakdown.
• Major effects directed to the growth
of skeletal muscles and long bones
of the body.
Homeostatic Imbalances of Growth
Hormone
• Hypersecretion
• In children results in gigantism
• In adults results in acromegaly
• Hyposecretion
• In children results in pituitary dwarfism
Gigantism
Dwarfism
video
video
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• Prolactin
• During pregnancy
stimulates the
breast development
for milk production,
then after delivery,
stimulates breasts
to secrete milk.
• Adrenocorticotropic
Hormone (ACTH)
• Stimulates the
adrenal cortex to
increase in size
and to secrete its
hormone, cortisol
(hydrocortizone).
• Thyroid
Stimulating
Hormone (TSH)
• Stimulates the
thyroid gland
to secrete its
hormone,
thyroxine.
• Follicle-stimulating
hormone (FSH)
• Stimulates the
ovarian follicles to
develop. As the
follicles mature
produce estrogen,
and eggs are
readied for
ovulation.
• In the male
FSH
stimulates
sperm
development.
• Luteinizing hormone
• Triggers ovulation.
Causes the ruptured
follicle to produce
progesterone.
• In the male it
stimulates interstitial
cells to secrete
testosterone.
Pituitary-Hypothalamus Relationship
• Hypothalamus
• Actually produces ADH and Oxytocin
by specialized neurons, which then
passes down along the axons into the
posterior pituitary gland.
Pituitary-Hypothalamus Relationship
• Also produces substances called
releasing and inhibiting hormones.
These are produced in the
hypothalamus then go directly to the
anterior pituitary by way of
specialized blood capillaries.
Pituitary-Hypothalamus Relationship
• The combined nervous and endocrine
functions of the hypothalamus help it
to play a dominant role in regulating
many body functions, like
temperature, appetite, and thirst.
• Posterior lobe
• It is a downgrowth of the hypothalamus.
Nuclei in the hypothalamus produce 2
hormones (oxytocin and antidiuretic
hormone (ADH)) that travel down the
axons to the posterior pituitary, where
they are stored in the axon terminals
there.
1 Hypothalamic
Paraventricular
nucleus
Supraoptic
nucleus
Optic chiasma
Infundibulum
(connecting stalk)
Hypothalamichypophyseal
tract
Axon
terminals
Posterior
lobe of
pituitary
Hypothalamus
neurons
synthesize oxytocin
and ADH.
2 Oxytocin and ADH are
Inferior
hypophyseal artery
transported along the
hypothalamic-hypophyseal
tract to the posterior
pituitary.
3 Oxytocin and ADH are
stored in axon terminals
in the posterior pituitary.
4 Oxytocin and ADH are
Oxytocin
ADH
released into the blood
when hypothalamic
neurons fire.
(a) Relationship between the posterior pituitary and the hypothalamus
Figure 16.5a
• Oxytocin
• Stimulates
the uterus to
contract
during labor.
• Causes the
glandular
cells in breast
to release
milk into the
ducts.
• Posterior Pituitary
• Antidiuretic hormone (ADH)
• accelerates the reabsorption of
water from urine in the kidney
tubules to the blood.
• Therefore its purpose is to help keep
fluid in the body and to decrease urine
volume. Hyposecretion of ADH
results in “diabetes insipidus” a
condition in which large volumes of
urine are formed.
Thyroid Gland
• Consists of two lateral lobes
connected by a median mass called
the isthmus.
Figure 16.8
• Thyroid Gland
• Secretes two thyroid hormones T4
and T3. T4 is more abundant but T3
is more potent.
• Both hormones require iodine
connected to peptide groups as
part of their structure.
Thyroid Hormone
• Major metabolic hormone
• Increases metabolic rate and heat
production
• Plays a role in
• Maintenance of blood pressure
• Regulation of tissue growth
• Development of skeletal and nervous
systems
• Reproductive capabilities
• Hyperthyroidism
• Generally results from tumor of
thyroid gland.
• increases metabolic rate of all cells,
weight loss, intolerance to heat,
rapid heart rate, irritable, nervous,
increased appetite, protrusion of
eyeballs (exopthalmos). Called
Graves Disease.
Figure 16.10
• Hypothyroidism
• decreases metabolic rate.
• Lack of iodine results in lower
thyroxine levels which causes the
pituitary to increase TSH. This
calls for more thyroxine from the
thyroid, so the thyroid gland
enlarges (called a goiter), but
without iodine it can only make the
peptide part of the molecule.
• Hypothyroidism in the young
causes cretinism; retarded
growth, sexual development, and
mental retardation. In adults
causes myxedema; decreased
mental and physical vigor, weight
gain, loss of hair, and swelling,
low body temperature (feels
cold), dry skin.
• Also secretes the hormone
calcitonin. Calcitonin decreases the
concentration of calcium in the blood
by causing it to be deposited in the
bones, preventing hypercalcemia.
• Parathyroid Glands
• 4 small glands
located on the
back of the thyroid
gland.
• Secretes
parathyroid
hormone (PTH).
• The most important regulator of blood
calcium ion concentration.
• Does the opposite of calcitonin. It will
increase the concentration of calcium
in the blood by increasing osteoclastic
activity which breaks down bone
matrix releasing calcium into the
blood.
• If calcium levels fall too low, muscles
go into uncontrolable spasms called
tetany.
• Hyperparathyroidism causes
excess PTH production, which
causes excess osteoclastic activity in
the bone, leaving the person with
severe osteoporosis.
• Adrenal Glands
• Sits on top of each kidney.
• Two separate glands
• Adrenal cortex -outer part
• Adrenal medulla - inner part
• Adrenal Cortex
• Hormones secreted by the cortex
are called corticoids.
• 3 layers to cortex from outer to
inner…
»Outer zone
»Middle zone
»Inner zone
• Outer zone secretes
mineralocorticoids, chiefly
aldosterone, which increases
sodium and decreases potassium
in the blood. Since water follows
sodium aldosterone regulated both
water and electrolyte balance.
• Middle zone secretes
glucocorticoids, chiefly cortisol
or cortisone. Resists long-term
stressors by increasing blood
glucose (gluconeogenesis).
• Cortisol also helps maintain normal
blood pressure.
• It also has an antiinflammatory
effect, antiimmunity effect, and
antiallergy effect.
• Stress causes the adrenal cortex to
increase secretion of glucocorticoids.
Cushing’s Syndrome
• Excessive cortisol production leads to
swollen “moon face” and a “buffalo
hump” of fat on the upper back. Also
results in high blood pressure,
hyperglycemia and severe depression
of the immune system.
Figure 16.15
Addison’s Disease
• Hyposecretion of all the adrenal
cortex hormones. Characterized by a
strange bronze tone of the skin.
Electrolyte and water loss, muscle
weakness, suppressed immune
system, lessened ability to cope with
stress.
• Inner zone secretes small
amounts of sex hormomes,
chiefly testosterone. These are
weak and insignificant
functionally in the male, but,
stimulates the female sex drive
in the female.
• Adrenal Medulla
• Secretes epinephrin (adrenalin)
and norepinephrin (collectively
called catecholamines). Chief
hormones that respond to stress
quickly. Fight or flight response.
• Adrenal medulla stimulated by
sympathetic nerve fibers. When
stimulated it literally squirts
epinephrine and norepinephrine
into the blood stream to deal with
brief, short-term stressful situations.
• Both an endocrine and exocrine
gland.
• Pancreatic Islets
• or islets of Langerhans are little
clumps of cells within the pancreas.
Two types, alpha and beta cells.
• Alpha cells secrete hormone called
glucagon, beta cells secrete insulin.
• Glucagon accelerates process called
gycogenolysis, which breaks
glycogen into glucose, which raises
blood glucose levels.
• Insulin decreases blood glucose
concentrations, by accelerating its
movement out of the blood and into
the cells.
• Hypoglycemia - lower than normal
glucose in the blood.
• Hyperglycemia - higher than
normal glucose in the blood.
Stimulates glucose uptake by cells
Tissue cells
Insulin
Pancreas
Stimulates
glycogen
formation Glucose Glycogen
Blood
glucose
falls to
normal
range.
Liver
Stimulus
Blood
glucose level
Stimulus
Blood
glucose level
Blood
glucose
rises to
normal
range.
Pancreas
Liver
Glucose Glycogen
Stimulates
glycogen Glucagon
breakdown
Figure 16.18
• Diabetes melitis
• Type I - Pancreas secrete too little
insulin so glucose stays in the
blood instead of entering the cells,
creating high blood glucose levels.
• Type II - (insulin independent)
results from abnormality of the
insulin receptors on the cell
membranes of cells. Also results in
high glucose levels.
• Glucose that spills out into the urine
is called glycosuria.
• Pineal Gland
• Small pine-cone shaped gland in the
roof of the third ventricle. Secretes
melatonin. Pineal gland sometimes
called the “third eye” because...
• … it receives sensory info from the
optic nerves. It uses this info
regarding changing light levels to
adjust the levels of melatonin, high at
night and low during the day.
• Melatonin therefore might regulate the
bodies internal clock.
• Thymus
• Hormone thymosin that plays an
important role in the development and
function of the bodies immune
system.
• Female Sex Glands
• Ovaries
• Ovarian follicles secrete
estrogen, which is involved in
the development of the
secondary female sex
characteristics and initiation of
the menstrual cycle.
• The corpus luteum mainly
secretes progesterone but some
estrogen also.
• Male Sex Glands
• The interstitial cells of the testes
produce testosterone, the
masculinizing hormone. Causes
development of male secondary sex
characteristics.
Other Hormone-Producing Tissues and
Organs
 Parts of the small intestine
 Parts of the stomach
 Kidneys
 Heart
 Many other areas have scattered
endocrine cells
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• Placenta
• a temporary endocrine gland. During
pregnancy it produces chorionic
gonadotropins. Also produces
estrogen and progesterone.
Endocrine Function of the Placenta
 Produces hormones that maintain the
pregnancy
 Some hormones play a part in the
delivery of the baby
 Produces HCG in addition to estrogen,
progesterone, and other hormones
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Developmental Aspects of the Endocrine
System
 Most endocrine organs operate smoothly
until old age
 Menopause is brought about by lack of
efficiency of the ovaries
 Problems associated with reduced estrogen
are common
 Growth hormone production declines with age
 Many endocrine glands decrease output with
age
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