Chapter 40: pp. 735 - 754
Hormones &
Endocrine Systems
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(Caterpillar): © Doug Wechsler/Animals Animals/Earth Scenes; (Moth): © Richard Kolar/Animals
Animals/Earth Scenes
1
Outline
 Endocrine Glands
 Pheromones
 Steroid Hormones
 Peptide Hormones
 Hypothalamus and Pituitary Gland
 Other Endocrine Glands and Hormones
 Thyroid
 Parathyroid
 Adrenal
 Pancreas
 Gonads
2
Endocrine Gland
• The endocrine system functions differently from
the nervous system.
• An endocrine system consists of glands that
coordinate body activities through hormones
• Chemical signals are used between individuals,
between body parts, and between cells
• Both the nervous system and the endocrine
system rely on negative feedback mechanisms.
3
The Human Endocrine System
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HYPOTHALAMUS
Releasing and inhibiting hormones:
regulate the anterior pituitary
PITUITARY GLAND
Posterior Pituitary
Antidiuretic (ADH):
water reabsorption by kidneys
Oxytocin: stimulates uterine
contraction and milk letdown
Anterior Pituitary
Thyroid stimulating (TSH):
stimulates thyroid
Adrenocorticotropic (ACTH):
stimulates adrenal cortex
Gonadotropic (FSH, LH): egg and
sperm production; sex hormone
production
PINEAL GLAND
Melatonin: controls
circadian and circannual
Prolactin (PL): milk production
Growth (GH): bone growth, protein
synthesis, and cell division
PARA THYROIDS
Parathyroid hormone (PTH):
raises blood
parathyroid glands
(posterior surface
of thyroid)
THYROID
Thyroxine (T 4) and triiodothyronine
(T3): increase metabolic rate;
regulates growth and development
Calcitonin: lowers blood calcium level
THYMUS
Thymosins: production and
maturation of T
lymphocytes
ADRENAL GLAND
Adrenal cortex
Glucocorticoids (cortisol):
raises blood glucose level;
stimulates breakdown of protein
Mineralocorticoids (aldosterone):
reabsorption of sodium and
excretion of potassium
Sex hormones: reproductive organs
and bring about sex characteristics
PANCREAS
Adrenal medulla
Epinephrine and norepinephrine:
active in emergency situations;
raise blood glucose level
Glucagon: raises blood
glucose level and
promotes glycogen
breakdown
Insulin: lowers blood
glucose level and
promotes glycogen
buildup
testis
(male)
GONADS
Testes
Androgens (testosterone):
male sex characteristics
Ovaries
Estrogens and progesterone:
female sex characteristics
ovary (female)
4
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Modes of Action of the Nervous and
Endocrine Systems
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liver cell
liver
insulin
receptor
b. Reception of insulin, a hormone
axon of
nerve fiber
pancreas
arteriole
vesicle
axon terminal
neurotransmitter
receptor
a. Reception of a neurotransmitter
6
Chemical Signals
• Pheromones
– Chemical signals that work at a distance between
individuals
– A woman’s axillary extract can alter another
woman’s menstrual cycle
• Hormones
– Chemical signals that work
• At a distance between organs, or
• Locally between adjacent cells
7
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Target Cell Concept
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nontarget cell
receptors
target cells
hormone
capillary
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Action of Hormones
 Hormones
 Chemical signals produced by one cell that
regulate the metabolism of other cells
 Steroid Hormones
Can cross cell membranes
 Peptide Hormones
Most bind to receptor in plasma membrane
 First Messenger
Causes internal release of cAMP
 Second Messenger
10
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Peptide Hormone
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capillary
1. Hormone binds to a
receptor in the plasma
membrane.
peptide hormone
(first messenger)
activated receptor protein
enzyme
2. Binding leads to
activation of an
enzyme that changes
ATP to cAMP.
plasma
membrane
ATP
cAMP
(second messenger)
3. cAMP activates an
enzyme cascade.
4. Many molecules of
glycogen are broken
down to glucose,
which enters the
bloodstream.
glucose
(leaves cell
and goes
to blood)
glycogen
13
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Steroid Hormone
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steroid
hormone
1. Hormone diffuses
through plasma
membrane because
it is lipid soluble.
plasma
membrane
cytoplasm
nuclear
pore
nucleus
2. Hormone binds
to receptor inside
nucleus.
protein
DNA
receptor
protein
mRNA
3. Hormone-receptor
complex activates
gene and synthesis
of a specific mRN
molecule.
ribosome
mRNA
4. mRNA moves to
ribosomes, and protein
synthesis occurs.
15
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Human Endocrine System
• Endocrine glands
– Ductless glands that secrete hormones directly into
the bloodstream
• Most endocrine hormones are peptides
• Only gonads and adrenal cortex produce steroid hormones
– Effects of hormones are moderated in two ways
• Negative feedback opposes release
• Antagonistic hormones oppose each other’s actions
18
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Hypothalamus and Pituitary Gland
 Hypothalamus regulates internal environment
 Acts through autonomic system
 Also controls glandular secretions of pituitary gland
 Posterior Pituitary
 Antidiuretic Hormone (ADH)
 Controlled by negative feedback
 Oxytocin
 Controlled by positive feedback
 Anterior Pituitary
 Hypothalamus controls by producing
 Hypothalamic-releasing hormones, and
 Hypothalamic-inhibiting hormones
20
Hypothalamus and the Pituitary
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hypothalamus
1. Neurosecretory cells produce
hypothalamic-releasing and
hypothalamic-inhibiting hormones.
2. These hormones are secreted into
a portal system.
1. Neurosecretory cells produce ADH
and oxytocin.
optic
chiasm
2. These hormones move down
axons to axon endings.
portal system
4. The anterior pituitary secretes
its hormones into the bloodstream,
whereby they are then delivered to
specific cells, tissues, and glands.
3. When appropriate, ADH and
oxytocin are secreted from axon
endings into the bloodstream.
Posterior pituitary
Kidney tubules:
antidiuretic
hormone (ADH)
Smooth muscle
in uterus:
oxytocin
3. Each type of hypothalamic
hormone either stimulates or
inhibits production and secretion
of an anterior pituitary hormone.
Mammary glands:
oxytocin
Anterior pituitary
Mammary glands:
prolactin (PRL)
Thyroid:
thyroid-stimulating
hormone (TSH)
Bones, tissues:
growth hormone
(GH)
Adrenal cortex:
adrenocorticotropic
hormone (ACTH)
Ovaries, testes:
gonadotropic
hormones (FSH, LH)
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Anterior Pituitary Hormones
 Anterior pituitary hormones that affect other glands:
 Thyroid-Stimulating Hormone (TSH)
 Adrenocorticotropic Hormone (ACTH)
 Gonadotropic Hormones
 Anterior pituitary hormones that do NOT affect other
glands
 Prolactin (PRL)
 Melanocyte-Stimulating Hormone (MSH)
 Growth Hormone (GH)
22
Effect of Growth Hormone
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a.
b.
a: © AP/Wide World Photos; b: © Ewing Galloway, Inc.
23
Acromegaly
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Age 9
Age 16
Age 33
Age 52
From Clinical Pathological Conference, "Acromegaly, Diabetes, Hypermetabolism, Proteinura and Heart Failure", American Journal of Medicine, 20 (1956) 133. Reprinted with permission from
Excerpta Medica Inc.
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Thyroid Glands
• Composed of large number of follicles filled with
– Triiodothyronine (T3), and
– Thyroxine (T4)
• Thyroid hormones increase metabolic rate
• Thyroid-induced abnormalities
– Simple goiter - Poor hormone production
– Cretinism - Poor thyroid development
– Myxedema - Hypothyroidism
– Exophthalmic goiter - Hyperthyroidism
25
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Abnormalities of the thyroid
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affected eye
a. Simple goiter
b. Congenital hypothyroidism
c. Exophthalmic goiter
a: © Bruce Coleman, Inc./Alamy; b: © Medical-on-Line/Alamy; c: © Dr. P. Marazzi/Photo Researchers, Inc.
27
Calcitonin
• Regulates blood calcium level (in part)
• Secreted by thyroid gland when blood calcium level
rises
• Brings about deposit of calcium in the bones
• Low calcium level in blood stimulates the release of
parathyroid hormone (PTH)
– Parathyroid hormone causes
• Phosphate level in blood to decrease, and
• Calcium level in blood to increase
– Insufficient production of parathyroid hormone leads to
tetany
28
Regulation of Blood Calcium Level
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calcitonin
Thyroid gland
secretes
calcitonin
into blood.
Bones
take up Ca2+
from blood.
Blood Ca2+
lowers.
Homeostasis (normal blood Ca2+)
Blood Ca2+
rises.
Parathyroid
glands
release PTH
into blood.
activated
vitamin D
parathyroid
hormone
(PTH)
Intestines
absorb Ca2+
from digestive
tract.
Kidneys
reabsorb Ca2+
from kidney
tubules.
Bones
release Ca2+
into blood.
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Adrenal Glands
• Paired – One sits atop each kidney (ad-renal)
• Each consists of outer cortex and inner
medulla
– Inner portion, the adrenal medulla
• Produces
– Epinephrine, and
– Norepinephrine
• Short-term response to stress (fight or flight)
– Outer portion, adrenal cortex
• Produces
– Mineralocorticoids, and
– Glucocorticoids
• Long-term response to stress
30
Adrenal Glands
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stress
hypothalamus
spinal cord
(cross section)
neurosecretory
cells produce
hypothalamicreleasing
hormone
path of nerve
impulses
epinephrine
Glucocorticoids
Protein and fat metabolism
instead of glucose
breakdown.
neuron
cell body
sympathetic fibers
Stress Response:
Long Term
anterior
pituitary
secretes
ACTH
ACTH
Reduction of inflammation;
immune cells are
suppressed.
Mineralocorticoids
Sodium ions and water
are reabsorbed by kidney.
norepinephrine
Blood volume and
pressure increase.
Stress Response:
Short Term
Heartbeat and blood
pressure increase.
glucocorticoids
Blood glucose level rises.
mineralocorticoids
Muscles become
energized.
adrenal medulla
adrenal cortex
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Glucocorticoids
• Cortisol
– Raises blood glucose level
– Promotes breakdown of muscle proteins to amino
acids
– Promotes metabolism of fatty acids
– Counteracts inflammatory response
32
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Mineralocorticoids
 Aldosterone
 Promotes two renal functions:
Absorption of sodium, and
Excretion of potassium
 Renin-angiotensin-aldosterone system
Raises blood pressure
Angiotensin II constricts arterioles
Aldosterone causes kidneys to reabsorb sodium (causing
water retention)
 Atrial natriuretic hormone (ANH) is antagonistic
to aldosterone
34
Regulation of Blood Pressure and
Volume
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atrial natriuretic
hormone (ANH)
Kidneys excrete
Na+ and water
in urine.
Heart secretes
atrial natriuretic
hormone (ANH)
into blood.
Blood pressure
lowers.
Homeostasis (normal blood pressure)
Blood pressure
rises.
Kidneys secrete
renin into blood.
Kidneys
reabsorb Na+
and water from
kidney tubules.
renin
angiotensin
I and II
aldosterone
Adrenal cortex
secretes
aldosterone
into blood.
35
Addison Disease
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a.
b.
a: © Custom Medical Stock Photos; b: © NMSB/Custom Medical Stock Photos
36
Cushing Syndrome
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(Both): Atlas of Pediatric Physical Diagnosis, Second Edition by Zitelli & Davis, 1992. Mosby-Wolfe Europe Limited, London, UK
37
Pancreas
• Made up of exocrine and endocrine tissue
– Endocrine Portion of the Pancreas:
• Consists of pancreatic islets
• Produce and secrete
– Insulin
» Secreted during high blood glucose level
» Stimulates uptake of glucose by cells
– Glucagon
» Secreted during low blood glucose level
» Stimulates liver to break down glycogen
– Exocrine Portion of the Pancreas:
• Secretes enzymes and buffers into intestine
38
Regulation of Blood Glucose Level
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insulin
Liver stores
glucose from
blood as
glycogen.
Pancreatic islet
of Langerhans
Muscle cells
store glycogen
and build protein.
After eating,
pancreas
secretes insulin
into blood.
Adipose tissue
uses glucose
from blood
to form fat.
Blood glucose
level lowers.
Homeostasis (normal blood glucose)
Before eating,
pancreas secretes
glucagon into
blood.
Liver breaks
down glycogen
to glucose.
Glucose enters
blood.
Pancreatic islet
of Langerhans
Adipose tissue
breaks down fat.
glucagon
© Peter Arnold, Inc./Alamy
39
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Other Endocrine Glands
• Gonads
– Testes
• Produce testosterone
• Secondary sex characteristics
– Ovaries
• Produce estrogen and progesterone
• Reproduction
• Secondary sex characteristics
41
The Effects of Anabolic Steroid Use
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balding in men and women;
hair on face and chest in
women
'roid mania–
delusions and hallucinations;
depression upon withdrawal
deepening of voice in women
severe acne
breast enlargement in men
and breast reduction in women
high blood cholesterol and
atherosclerosis; high blood
pressure and damage to heart
liver dysfunction
and cancer
kidney disease and
retention of fluids,
called "steroid bloat"
reduced testicular
size, low sperm count,
and impotency
in women, increased
size of ovaries;
cessation of ovulation
and menstruation
stunted growth in
youngsters by prematurely halting fusion
of the growth plates
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Other Endocrine Glands
 Pineal Gland
 Produces melatonin
 Involved in Circadian rhythms
 Thymus Gland
 Secrete thymosins
 Aid in differentiation of lymphocytes
 Prostaglandins
 Produced within cells
 Not distributed in blood
43
Melatonin Production
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a. experimental
b. winter
6 P.M.
6 A.M.
c. summer
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44
Review
 Endocrine Glands
 Pheromones
 Steroid Hormones
 Peptide Hormones
 Hypothalamus and Pituitary Gland
 Other Endocrine Glands and Hormones
 Thyroid
 Parathyroid
 Adrenal
 Pancreas
 Gonads
45