Principles of Anatomy and Physiology

25/11/2019
Principles of Anatomy and Physiology

Principles of Anatomy and Physiology
Fifteenth Edition
Gerard Tortora and Bryan Derrickson
Chapter 18
The Endocrine System
Copyright ©2017 John Wiley & Sons, Inc. 2
Comparison of Control by the Nervous Comparison of Control by the Nervous and

and Endocrine Systems Endocrine Systems (1 of 2)
• The nervous and endocrine systems act together to
coordinate all systems of the body
Characteristic Nervous system Endocrine system
• The nervous system releases neurotransmitters; the Molecules Neurotransmitters released Hormones delivered to tissues
endocrine system releases hormones locally in response to nerve throughout body by blood.
impulses.
• Most hormones circulate through the blood and bind to Site of action Close to site of release, at Far from site of release
receptors on “target cells” synapse; binds to receptors in (usually); binds to receptors
postsynaptic membrane. on or in target cells.
• Neurotransmitters also bind to receptors on “target”
cells
Copyright ©2017 John Wiley & Sons, Inc. 3 Copyright ©2017 John Wiley & Sons, Inc. 4
Comparison of Control by the Nervous and Endocrine Glands (1 of 3)

Endocrine Systems (2 of 2)
• Exocrine glands secrete their products into ducts
Characteristic Nervous system Endocrine system
 None of these are hormones
Types of target cells Muscle (smooth, cardiac, and Cells throughout body.
skeletal) cells, gland cells, other  Exocrine glands include sudoriferous (sweat) glands,
neurons. sebaceous (oil) glands, mucous glands, digestive
Time to onset of Typically within milliseconds Seconds to hours or days.
action (thousandths of a second).
glands and several others throughout the body
Duration of action Generally briefer (milliseconds). Generally longer (seconds to
days).
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Endocrine Glands (2 of 3) Endocrine Glands (3 of 3)

• Endocrine glands secrete hormones • Certain organs and tissues that are not part of the
 Endocrine glands do not have ducts; instead they endocrine system also secrete hormones because they
secrete their hormones directly into the interstitial contain secreting cells
fluid that surrounds them • Secreting cells can be found in the hypothalamus,
• The hormones diffuse into the blood stream through thymus, pancreas, ovaries, testes, kidneys, stomach,
capillaries and are carried to target cells throughout liver, small intestine, skin, heart, adipose tissue and
the body placenta
• Endocrine glands include the pituitary, thyroid,
parathyroid, adrenal and pineal glands
Endocrine Gland Locations (1 of 2) Hormone Activity (1 of 9)

• Hormones traveling throughout the body will only
affect target cells that possess specific protein
receptors for the hormone
• Receptors are continually being synthesized and broken
down
• Receptors may be down-regulated in the presence of
high concentrations of hormone
• Receptors may be up-regulated in the presence of low
concentrations of hormone
Hormone Activity (2 of 9) Hormone Activity (3 of 9)

Hormones that don’t
circulate are local
hormones (paracrines).
Those that act on the same
cell that secretes them are
autocrines.
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• Hormones are either lipid-soluble (steroid hormones, Summary of Hormones by Chemical Class
thyroid hormones, nitric oxide) or water-soluble Lipid-Soluble
(amine hormones, peptide and protein hormones,
eicosanoid hormones) Chemical class Hormones Site of secretion
 Water-soluble hormones circulate freely in the Steroid hormones
Aldosterone is made up of hydrogen, carbon, and
Aldosterone, cortisol, androgens. Adrenal cortex.
Calcitriol (active form of vitamin Kidneys.
plasma oxygen.
D). Testosterone. Testes.

 Lipid-soluble hormones circulate bound to transport Estrogens, progesterone. Ovaries.
proteins

Water-soluble
Chemical class Hormones Site of secretion
Chemical class Hormones Site of secretion
Thyroid hormones T3 (triiodothyronine), T4 Thyroid gland (follicular
Amines Epinephrine, norepinephrine Adrenal medulla.
(thyroxine). cells). Norepinephrine is made up of CH, O H, HO, CH2, and
NH2. (catecholamines). Pineal gland.
Gas Nitric oxide (NO). Endothelial cells lining Melatonin. Mast cells in connective
Triiodothyronine, or T sub 3, is made up of iodine,
oxygen, carbon, and hydrogen. blood vessels. Histamine. tissues.
Serotonin. Platelets in blood.

Chemical class Hormones Site of secretion Chemical class Hormones Site of secretion
Peptides and All hypothalamic releasing and inhibiting Hypothalamus. Eicosanoids Prostaglandins, leukotrienes. All cells except red
proteins hormones. Oxytocin, antidiuretic hormones. Posterior pituitary. blood cells.
Growth hormone, thyroid-stimulating Anterior pituitary.
Oxytocin is made up of glutamine, A leukotriene or LTB4 is made up of HO,
isoleucine, asparagine, tyrosine, O H, and COOH.
cysteine, sulfur, proline, leucine, glycine,
and NH2.
hormone, adrenocorticotropic hormone,
follicle-stimulating hormone, luteinizing Pancreas.
hormone, prolactin, melanocyte-stimulating Parathyroid glands.
hormone. Thyroid gland
Insulin, glucagon, somatostatin, pancreatic (parafollicular cells).
polypeptide. Stomach and small
Parathyroid hormone. intestine
Calcitonin. (enteroendocrine
Gastrin, secretin, cholecystokinin, GIP cells).
(glucose-dependent insulinotropic peptide). Kidneys.
Erythropoietin. Leptin. Adipose tissue.
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Mechanisms of Hormone Action (2 of 5) Mechanisms of Hormone Action (3 of 5)

Responses to the same hormone may vary depending on Lipid-soluble hormones
the hormone itself and the target cell bind to receptors within
The response may be: target cells
 Synthesis of new molecules
 Changing permeability of the cell membrane
 Stimulating transport of a substance into or out of
the cell
 Altering the rate of metabolic actions
 Causing contraction of smooth or cardiac muscle
Mechanisms of Hormone Action (4 of 5) Mechanisms of Hormone Action (5 of 5)

Water-soluble hormones How a target cell responds to a hormone is based on:
bind to receptors on the  The hormone’s concentration in the blood
exterior surface of the
target cell  The number of hormone receptors on the target cell
 Influences exerted by other hormones
 Some hormones work more effectively when a
second hormone is present to assist them
(synergistic effect)
 Some hormones oppose the action of others
(antagonistic effect)
Control of Hormone Secretion (1 of 3) Control of Hormone Secretion (2 of 3)

Hormones are secreted in short bursts when needed • Most hormone
Secretion is regulated by: regulation is achieved via
negative feedback
 Signals from the nervous system
• Only a few hormones
 Chemical changes in the blood operate via positive
 Other hormones feedback.
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Hypothalamus and Pituitary Gland (5 of 14) Hypothalamus and Pituitary Gland (6 of 14)
Hormones and Cells of the Anterior Pituitary Hypothalamic
Hypothalamic inhibiting
Hormone Secreted by releasing hormone
hormone (suppresses secretion)
(stimulates secretion)
Hypothalamic releasing Hypothalamic inhibiting
Luteinizing hormone Gonadotrophs Gonadotropin- —
Hormone Secreted by hormone (stimulates hormone (suppresses
(LH) releasing hormone
secretion) secretion)
(GnRH).
Growth hormone Somatotrophs Growth hormone- Growth hormone-inhibiting
Prolactin (PRL) Lactotrophs Prolactin-releasing Prolactin-inhibiting hormone
(GH) also known as releasing hormone hormone (GHIH), also known
hormone (PRH) * (PIH), which is dopamine.
somatostatin. (GHRH), also known as somatostatin.
as somatostatin. Adrenocorticotropic Corticotrophs. Corticotropin-releasing —
hormone (ACTH), hormone (CRH).
Thyroid-stimulating Thyrotrophs Thyrotropin-releasing Growth hormone-inhibiting
also known as
hormone (TSH), hormone (TRH). hormone (GHIH).
Corticotropin
also known as
thyrotropin Melanocyte- Corticotrophs. Corticotropin-releasing Dopamine.
stimulating hormone (CRH).
Follicle-stimulating Gonadotrophs Gonadotropin-releasing —
hormone (MSH)
hormone (FSH) hormone (GnRH).
Negative feedback loops
control the secretions of
thyrotrophs,
gonadotrophs, and
corticotrophs
• Human growth hormone (hGH) is the most plentiful

anterior pituitary hormone
• It is released in bursts every few hours by
somatotrophs
• Their activity is controlled by two hypothalamic
hormones: growth hormone-releasing hormone
(GHRH) and growth hormone-inhibiting hormone
(GHIH)
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Summary of the Principal Actions of Anterior Pituitary
In summary, the anterior pituitary gland secretes: Hormones
 Human growth hormone (hGH) Hormone Target Tissues Principal Actions
 Thyroid-stimulating hormone (TSH) Growth hormone (GH),
A diagram shows the liver and
other tissues. Stimulates liver, muscle, cartilage, bone, and other
also known as tissues to synthesize and secrete insulin-like
 Follicle-stimulating hormone (FSH) somatotropin growth factors (IGFs), which in turn promote
growth of body tissues. GH acts directly on target
 Luteinizing hormone (LH) cells to enhance lipolysis and decrease glucose
uptake.
 Prolactin (PRL) Thyroid-stimulating
A diagram shows the thyroid
gland. Stimulates synthesis and secretion of thyroid
hormone (TSH), also hormones by thyroid gland.
 Adrenocorticotropic hormone (ACTH) known as thyrotropin
 Melanocyte-stimulating hormone (MSH)
Hormone Target Tissues Principal Actions Hormone Target Tissues Principal Actions
A diagram shows an ovary and A diagram shows mammary
Follicle-stimulating testis. In females, initiates development of oocytes and Prolactin (PRL) glands in the breasts. Together with other hormones, promotes milk
hormone (FSH) induces ovarian secretion of estrogens. production by mammary glands.
In males, stimulates testes to produce sperm.
A diagram shows an ovary and A diagram shows the adrenal

Luteinizing testis. In females, stimulates secretion of estrogens and Adrenocorticotropic cortex. Stimulates secretion of glucocorticoids (mainly
hormone (LH) progesterone, ovulation, and formation hormone (ACTH), Cortisol) by adrenal cortex.
of corpus luteum. In males, stimulates testes to also known as
produce testosterone. corticotropin
A diagram show the brain.
Melanocyte- Exact role in humans is unknown but may influence
stimutating brain activity; when present in
hormone (MSH) excess, can cause darkening of skin.
Summary of Posterior Pituitary Summary of Posterior Pituitary

Hormones (1 of 2) Hormones (2 of 2)
Hormone and Hormone and

Control of Secretion Principal Actions Control of Secretion Principal Actions
Target Tissues Target Tissues
Oxytocin (OT) Neurosecretory cells of Stimulates contraction of smooth Antidiuretic Neurosecretory cells of Conserves body water by decreasing
Diagrams show the uterus
and mammary glands. hypothalamus secrete OT in muscle cells of uterus during hormone hypothalamus secrete ADH urine volume; decreases water loss
response to uterine distension childbirth; stimulates contraction of (ADH) or in response to elevated blood through perspiration; raises
and stimulation of nipples. myoepithelial cells in mammary vasopressin osmotic pressure, blood pressure by constricting
glands to cause milk ejection. Diagram shows the
kidneys, sudoriferous or dehydration, loss of blood arterioles.
sweat glands, and
arterioles.
volume, pain, or stress;
inhibitors of ADH secretion
include low blood osmotic
pressure, high blood volume,
and alcohol.
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Thyroid Gland (1 of 8) Thyroid Gland (5 of 8)

The thyroid gland is a Thyroid hormones:
butterfly-shaped gland  Increase basal metabolic rate (BMR)
located inferior to the larynx
and anterior to the trachea  Help maintain normal body temperature
 It has right and left  Stimulate protein synthesis
lateral lobes connected  Increase the use of glucose and fatty acids for ATP
by an isthmus production
• Some glands also  Upregulate beta (β) receptors that attach to
have a pyramidal catecholamines
lobe projecting from
the isthmus  Work with hGH and insulin to accelerate body growth
Thyroid Gland (7 of 8) Thyroid Gland (8 of 8)

Summary of Thyroid Gland Hormones
Hormone and
Control of secretion Principal actions
Hormone and source
Control of secretion Principal actions
source Calcitonin (CT) High blood Ca2+ levels stimulate secretion; Lowers blood levels of Ca2+
T3 (triiodothyronine) Secretion is increased by thyrotropin- Increase basal metabolic rate; from low blood Ca2+ levels inhibit secretion. and HP042+ by inhibiting bone
and T4 (thyroxine) or releasing hormone (TRH), which stimulates stimulate synthesis of parafollicular resorption by osteoclasts and
thyroid hormones release of thyroid-stimulating hormone proteins; increase use of by accelerating uptake of
cells
from follicular cells (TSH) in response to low thyroid hormone glucose and fatty acids for A diagram shows a thyroid calcium and phosphates
A diagram shows a thyroid follicle,
levels, low metabolic rate, cold, pregnancy, ATP production; increase
follicle with parafollicular into bone extracellular
surrounded by follicular cells and cells next to the blood
blood vessels. and high altitudes; TRH and TSH secretions lipolysis; enhance vessels. matrix.
are inhibited in response to high thyroid cholesterol excretion;
hormone levels; high iodine level accelerate body growth;
suppresses T3/T4 secretion. contribute to development of
nervous system.
Adrenal Glands (11 of 13) Adrenal Glands (12 of 13)

Summary of Adrenal Gland Hormones Adrenal cortex hormones
Adrenal cortex hormones
Hormone and Source Control of Secretion Principal Actions
Androgens (mainly ACTH stimulates secretion. Assist in early growth of axillary
dehydroepiandrosterone, and pubic hair in both sexes; in
Mineralocorticoids (mainly Increased blood K+ level and Increase blood levels of Na+ or DHEA) from zona females, contribute to libido
aldosterone) from zona angiotensin II stimulate and water; decrease blood reticularis cells and are source of estrogens
glomerulosa cells secretion level of K+. A diagram shows the adrenal cortex, an
outer layer of the adrenal gland.
after menopause.
Glucocorticoids (mainly ACTH stimulates release; Assist in early growth of axillary
cortisol) from zona corticotropin-releasing and pubic hair in both sexes; in
fasciculata cells hormone (CRH) promotes ACTH females, contribute to libido
secretion in response to stress and are source of estrogens
and low blood levels of after menopause.
glucocorticoids.
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Adrenal Glands (13 of 13) Pancreatic Islets (4 of 8)

Adrenal medulla hormones Summary of Pancreatic Islet Hormones

Glucagon from alpha Decreased blood level of glucose, Raises blood glucose level by
Epinephrine and Sympathetic preganglionic Enhance effects of sympathetic cells of pancreatic exercise, and mainly protein accelerating breakdown of
norepinephrine from neurons release acetylcholine, division of autonomic nervous islets meals stimulate secretion of glycogen into glucose in liver
chromaffin cells which stimulates secretion. system (ANS) during stress. A diagram shows an alpha cell, close
somatostatin and insulin inhibit (glycogenosis), converting
A diagram shows the adrenal medulla, at the to the outer layer near the acini.
center of the adrenal gland. secretion. other nutrients into glucose in liver
(gluconeogenesis), and
releasing glucose into blood.
Pancreatic Islets (5 of 8) Pancreatic Islets (6 of 8)
Hormone and Source Control of Secretion Principal Actions Hormone and Source Control of Secretion Principal Actions
Insulin from beta cells Increased blood level of glucose, Lowers blood glucose level by Somatostatin from Pancreatic polypeptide inhibits Inhibits secretion of insulin and
of pancreatic islets acetylcholine (released by accelerating transport delta cells of secretion. glucagon; slows absorption
A diagram shows a beta cell, one of
many that make up the majority of the
parasympathetic vagus nerve of glucose into cells, converting pancreatic islets of nutrients from gastrointestinal
pancreatic islets. fibers), arginine and leucine (two glucose into glycogen (glycogenesis), A diagram shows a delta cell, one of
several at scattered intervals.
tract.
amino acids), glucagon, GIP, GH, and decreasing glycogenolysis and
and ACTH stimulate secretion; gluconeogenesis; increases
somatostatin inhibits secretion. lipogenesis and stimulates
protein synthesis.
Pancreatic Islets (7 of 8) Pancreatic Islets (8 of 8)

Secretion of insulin and
Hormone and Source Control of Secretion Principal Actions glucagon are controlled by
Pancreatic polypeptide Meals containing protein, fasting, Inhibits somatostatin secretion, negative feedback
from F cells of exercise , and acute gallbladder contraction, and
pancreatic islets hypoglycemia stimulate secretion of pancreatic digestive
A diagram shows an F cell, close to acini.
secretion; somatostatin and enzymes.
elevated blood glucose level
inhibit secretion.
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Growth Factors (1 of 2) Growth Factors (2 of 2)

Summary of Selected Growth Factors
Growth factor Comment
Growth factor Comment Nerve growth factor (NGF) Produced in submandibular (salivary) glands and hippocampus of
Epidermal growth factor (EGF) Produced in submaxillary (salivary) glands; stimulates proliferation brain; stimulates growth of ganglia in embryo; maintains
of epithelial cells, fibroblasts, neurons, and astrocytes; suppresses sympathetic nervous system; stimulates hypertrophy and
some cancer cells and secretion of gastric juice by stomach. differentiation of neurons.
Platelet-derived growth factor Produced in blood platelets; stimulates proliferation of neuroglia, Tumor angiogenesis factors Produced by normal and tumor cells; stimulate growth of new
(PDGF) smooth muscle fibers, and fibroblasts; appears to have (TAFs) capillaries, organ regeneration, and wound healing.
role in wound healing; may contribute to atherosclerosis Transforming growth factors Produced by various cells as separate molecules: TGF-alpha has
development. (TGFs) activities similar to epidermal growth factor; TGF-beta inhibits
Fibroblast growth factor (FGF) Found in pituitary gland and brain; stimulates proliferation of many proliferation of many cell types.
cells derived from embryonic mesoderm (fibroblasts, adrenocortical
cells, smooth muscle fibers, chondrocytes, and endothelial cells);
stimulates formation of new blood vessels (angiogenesis).
Focus on Homeostasis: The Endocrine Endocrine Disorders (1 of 2)

System
• Pituitary gigantism and acromegaly are caused by
excess secretion of growth hormone
• Goiter is caused by a reduction in the production of
thyroid hormone
• Graves disease (with associated exophthalmos)
develops due to excess thyroid hormone
• Cushing’s syndrome is caused by excess secretion of
glucocorticoids
Endocrine Disorders (2 of 2)
Copyright ©2017 John Wiley & Sons, Inc. 53

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25/11/2019

Principles of Anatomy and Physiology

Copyright ©2017 John Wiley & Sons, Inc. 2

Comparison of Control by the Nervous Comparison of Control by the Nervous and

Comparison of Control by the Nervous and Endocrine Glands (1 of 3)

Endocrine Glands (2 of 3) Endocrine Glands (3 of 3)

Endocrine Gland Locations (1 of 2) Hormone Activity (1 of 9)

Hormone Activity (2 of 9) Hormone Activity (3 of 9)

Hormone Activity (4 of 9) Hormone Activity (5 of 9)

D). Testosterone. Testes.

Hormone Activity (6 of 9) Hormone Activity (7 of 9)

Hormone Activity (8 of 9) Hormone Activity (9 of 9)

Mechanisms of Hormone Action (2 of 5) Mechanisms of Hormone Action (3 of 5)

Mechanisms of Hormone Action (4 of 5) Mechanisms of Hormone Action (5 of 5)

Control of Hormone Secretion (1 of 3) Control of Hormone Secretion (2 of 3)

• Human growth hormone (hGH) is the most plentiful

 Melanocyte-stimulating hormone (MSH)

A diagram shows an ovary and A diagram shows the adrenal

Summary of Posterior Pituitary Summary of Posterior Pituitary

Hormone and Hormone and

Thyroid Gland (1 of 8) Thyroid Gland (5 of 8)

Thyroid Gland (7 of 8) Thyroid Gland (8 of 8)

Adrenal Glands (11 of 13) Adrenal Glands (12 of 13)

Adrenal Glands (13 of 13) Pancreatic Islets (4 of 8)

Hormone and Source Control of Secretion Principal Actions

Pancreatic Islets (5 of 8) Pancreatic Islets (6 of 8)

Pancreatic Islets (7 of 8) Pancreatic Islets (8 of 8)

Growth Factors (1 of 2) Growth Factors (2 of 2)

Focus on Homeostasis: The Endocrine Endocrine Disorders (1 of 2)

Copyright ©2017 John Wiley & Sons, Inc. 53

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