Download Endocrine System

Chapter 9
The Endocrine
System
Lecture Presentation by
Patty Bostwick-Taylor
Florence-Darlington Technical College
© 2015 Pearson Education, Inc.
The Endocrine System
 Second controlling system of the body
 Nervous system is the fast-control system
 Uses chemical messengers (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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Hormone Overview
 Hormones are produced by specialized cells
 Cells secrete hormones into extracellular fluids
 Blood transfers hormones to target sites
 These hormones regulate the activity of other cells
 Endocrinology is the scientific study of hormones
and endocrine organs
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The Chemistry of Hormones
 Hormones are classified chemically as
 Amino acid–based, which includes:
 Proteins
 Peptides
 Amines
 Steroids—made from cholesterol
 Prostaglandins—made from highly active lipids that
act as local hormones
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Hormone Action
 Hormones affect only certain tissues or organs
(target cells or target organs)
 Target cells must have specific protein receptors
 Hormone binding alters cellular activity
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Hormone Action
Hormones arouse cells, or alter cellular activity.
Typically, one or more of the following occurs:
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
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The Chemistry of Hormones
 Hormones act by two mechanisms:
1. Direct gene activation
2. Second-messenger system
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Direct Gene Activation (Steroid Hormone
Action)
1. Steroid hormones diffuse through the plasma
membrane of target cells
2. Steroid hormones enter the nucleus
3. Steroid hormones bind to a specific protein within
the nucleus
4. Hormone-receptor complex binds to specific sites
on the cell’s DNA
5. Certain genes are activated that result in…
6. Synthesis of new proteins
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Figure 9.1a Mechanisms of hormone action.
Steroid
hormone
Slide 1
Nucleus
Cytoplasm
1
Receptor
protein
2
3
Hormone-receptor
complex
4
DNA
5
mRNA
New
protein
Plasma
membrane
of target
cell
(a) Steroid hormone action
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6
Second-Messenger System (Nonsteroid
Hormone Action)
1. Hormone (first messenger) binds to a membrane
receptor
2. Activated receptor sets off a series of reactions
that activates an enzyme
3. Enzyme catalyzes a reaction that produces a
second-messenger molecule (such as cyclic AMP,
or cAMP)
4. Oversees additional intracellular changes to
promote a specific response in the target cell
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Figure 9.1b Mechanisms of hormone action.
Slide 1
Nonsteroid
hormone (first
messenger)
Cytoplasm
Enzyme
ATP
1
2
Receptor
protein
Plasma
membrane
of target cell
3
Second
cAMP messenger
4
Effect on cellular function,
such as glycogen
breakdown
(b) Nonsteroid hormone action
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Control of Hormone Release
 Hormone levels in the blood are maintained mostly
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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Endocrine Gland Stimuli
 The stimuli that activate endocrine glands fall into
three major categories:
1. Hormonal
2. Humoral
3. Neural
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Hormonal Stimuli of Endocrine Glands
 Most common stimulus
 Endocrine organs are activated by other hormones
 Example:
 Anterior pituitary hormones travel to target glands,
such as the thyroid gland, to prompt the release of a
particular hormone, such as thyroid hormone
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Figure 9.2a Endocrine gland stimuli.
(a) Hormonal stimulus
1 The hypothalamus secretes
hormones that…
Hypothalamus
2 …stimulate
the anterior
pituitary
gland to
secrete
hormones
that…
Thyroid
gland
Anterior
pituitary
gland
Adrenal Gonad
cortex
(testis)
3 …stimulate other endocrine
glands to secrete hormones
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Humoral Stimuli of Endocrine Glands
 Changing blood levels of certain ions and nutrients
stimulate hormone release
 Humoral indicates various body fluids, such as blood
and bile
 Examples:
 Parathyroid hormone and calcitonin are produced in
response to changing levels of blood calcium levels
 Insulin is produced in response to changing levels of
blood glucose levels
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Figure 9.2b Endocrine gland stimuli.
(b) Humoral stimulus
1 Capillary blood contains low
concentration of Ca2+, which
stimulates…
Capillary
(low Ca2+
in blood)
Thyroid gland
(posterior view)
Parathyroid
glands
Parathyroid
glands
PTH
2 …secretion of parathyroid
hormone (PTH) by parathyroid
glands)
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Neural Stimuli of Endocrine Glands
 Nerve impulses stimulate hormone release
 Most are under the control of the sympathetic
nervous system
 Examples:
 The release of norepinephrine and epinephrine by
the adrenal medulla
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Figure 9.2c Endocrine gland stimuli.
(c) Neural stimulus
1 Preganglionic sympathetic
fiber stimulates adrenal medulla
cells…
CNS (spinal cord)
Preganglionic
sympathetic fibers
Medulla of
adrenal
gland
Capillary
2 …to secrete catecholamines
(epinephrine and norepinephrine)
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Major Endocrine Organs
 Pituitary gland
 Thyroid gland
 Parathyroid glands
 Adrenal glands
 Pineal gland
 Thymus gland
 Pancreas
 Gonads (ovaries and testes)
 Hypothalamus
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Figure 9.3 Location of the major endocrine organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
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Major Endocrine Organs
 Some glands are purely endocrine
 Anterior pituitary, thyroid, adrenals, parathyroids
 Endocrine glands are ductless glands
 Hormones are released directly into blood or lymph
 Other glands are mixed glands, with both endocrine
and exocrine functions (pancreas, gonads)
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Pituitary Gland and Hypothalamus
 Pituitary gland is the size of a pea
 Hangs by a stalk from the hypothalamus in the brain
 Protected by the sphenoid bone
 Has two functional lobes
 Anterior pituitary—glandular tissue
 Posterior pituitary—nervous tissue
 Often called the “master endocrine gland”
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Pituitary Gland and Hypothalamus
 Hypothalamus produces releasing and inhibiting
hormones
 These hormones are released into portal circulation,
which connects hypothalamus to anterior pituitary
 Hypothalamus also makes two hormones: oxytocin
and antidiuretic hormone
 Carried to posterior pituitary via neurosecretory cells
for storage
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Figure 9.4 Hormones released by the posterior lobe of the pituitary and their target organs.
Optic
chiasma
Axon
terminals
Hypothalamic
neurosecretory
cells
Hypothalamus
Arterial blood supply
Posterior lobe
Capillary bed
Venous drainage
Anterior lobe
of the pituitary
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ADH
Oxytocin
Kidney tubules
Mammary glands
Uterine muscles
Posterior Pituitary and Hypothalamic
Hormones
 Oxytocin
 Stimulates contractions of the uterus during labor,
sexual relations, and breastfeeding
 Causes milk ejection (let-down reflex) in a
breastfeeding woman
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Posterior Pituitary and Hypothalamic
Hormones
 Antidiuretic hormone (ADH)
 Inhibits urine production (diuresis) by promoting
water reabsorption by the kidneys
 In large amounts, causes vasoconstriction of
arterioles, leading to increased blood pressure (the
reason why ADH is known as vasopressin)
 Alcohol inhibits ADH secretion
 Diabetes insipidus results from ADH hyposecretion
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Hormones of the Anterior Pituitary
 Six anterior pituitary hormones
 Two affect nonendocrine targets:
1. Growth hormone
2. Prolactin
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Hormones of the Anterior Pituitary
 Four stimulate other endocrine glands to release
hormones (tropic hormones):
1.
2.
3.
4.
Thyroid-stimulating hormone (thyrotropic hormone)
Adrenocorticotropic hormone
Follicle-stimulating hormone
Luteinizing hormone
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Hormones of the Anterior Pituitary
 Characteristics of all anterior pituitary hormones
 Protein (or peptides) structure
 Act through second-messenger systems
 Regulated by hormonal stimuli
 Regulated mostly by negative feedback
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Figure 9.5 Hormones of the anterior pituitary and their major target organs.
Releasing hormones
secreted into portal
circulation
Hypothalamus
Anterior pituitary
Posterior pituitary
Hypophyseal
portal system
Adrenocorticotropic
hormone (ACTH)
Growth hormone (GH)
Bones and muscles Prolactin (PRL) Follicle-stimulating
hormone (FSH)
and luteinizing
Mammary
hormone (LH)
glands
Testes or ovaries
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Thyrotropic
hormone (TH)
Thyroid
Adrenal cortex
Hormones of the Anterior Pituitary
 Growth hormone (GH)
 General metabolic hormone
 Major effects are directed to growth of skeletal
muscles and long bones
 Plays a role in determining final body size
 Causes amino acids to be built into proteins
 Causes fats to be broken down for a source of
energy
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Hormones of the Anterior Pituitary
 Growth hormone (GH) disorders
 Pituitary dwarfism results from hyposecretion of GH
during childhood
 Gigantism results from hypersecretion of GH during
childhood
 Acromegaly results from hypersecretion of GH
during adulthood
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Figure 9.6 Disorders of pituitary growth hormone.
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This individual exhibiting gigantism (right)
stands 8 feet, 1 inch tall. The pituitary dwarf
(left) is 2 feet, 5.37 inches tall.
Hormones of the Anterior Pituitary
 Prolactin (PRL)
 Stimulates and maintains milk production following
childbirth
 Function in males is unknown
 Adrenocorticotropic hormone (ACTH)
 Regulates endocrine activity of the adrenal cortex
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Hormones of the Anterior Pituitary
 Thyrotropic hormone (TH), also called thyroidstimulating hormone (TSH)
 Influences growth and activity of the thyroid gland
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Hormones of the Anterior Pituitary
 Gonadotropic hormones
 Regulate hormonal activity of the gonads
 Follicle-stimulating hormone (FSH)
 Stimulates follicle development in ovaries
 Stimulates sperm development in testes
 Luteinizing hormone (LH)
 Triggers ovulation of an egg in females
 Stimulates testosterone production in males
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Thyroid Gland
 Found at the base of the throat
 Consists of two lobes and a connecting isthmus
 Produces two hormones:
1. Thyroid hormone
2. Calcitonin
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Figure 9.7a The thyroid gland.
Thyroid
cartilage
Epiglottis
Common
carotid artery
Isthmus of
thyroid gland
Trachea
Brachiocephalic
artery
Left subclavian
artery
Left lobe of
thyroid gland
Aorta
(a) Gross anatomy of the thyroid gland, anterior view
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Thyroid Gland
 Thyroid hormone
 Major metabolic hormone
 Controls rate of oxidation of glucose to supply body
heat and chemical energy
 Needed for tissue growth and development
 Composed of two active iodine-containing hormones
 Thyroxine (T4)—secreted by thyroid follicles
 Triiodothyronine (T3)—conversion of T4 at target
tissues
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Figure 9.7b The thyroid gland.
Colloid-filled
Follicle cells
follicles
Parafollicular cells
(b) Photomicrograph of thyroid gland
follicles (380×)
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Thyroid Gland
 Thyroid hormone disorders
 Goiters
 Thyroid gland enlarges because of lack of iodine
 Salt is iodized to prevent goiters
 Cretinism
 Caused by hyposecretion of thyroxine
 Results in dwarfism during childhood
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Figure 9.8 Woman with an enlarged thyroid (goiter).
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Thyroid Gland
 Thyroid hormone disorders (continued)
 Myxedema
 Caused by hypothyroidism in adults
 Results in physical and mental sluggishness
 Graves’ disease
 Caused by hyperthyroidism
 Results in increased metabolism, heat intolerance,
rapid heartbeat, weight loss, and exophthalmos
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Figure 9.9 The exophthalmos of Graves’ disease.
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Thyroid Gland
 Calcitonin
 Decreases blood calcium levels by causing calcium
deposition on bone
 Antagonistic to parathyroid hormone
 Produced by parafollicular cells found between the
follicles
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Figure 9.7b The thyroid gland.
Colloid-filled
Follicle cells
follicles
Parafollicular cells
(b) Photomicrograph of thyroid gland
follicles (380×)
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Parathyroid Glands
 Tiny masses on the posterior of the thyroid
 Secrete parathyroid hormone (PTH)
 Stimulates osteoclasts to remove calcium from bone
 Hypercalcemic hormone (increases blood calcium
levels)
 Stimulates the kidneys and intestine to absorb more
calcium
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Figure 9.10 Hormonal controls of ionic calcium levels in the blood.
Calcitonin
Calcitonin
stimulates
calcium salt
deposit in bone.
Thyroid gland
releases calcitonin.
Stimulus
Rising blood
Ca2+ levels
BALANCE
Calcium homeostasis of blood:
9–11 mg/100 ml
BALANCE
Stimulus
Falling blood
Ca2+ levels
Thyroid
gland
Osteoclasts
degrade bone
matrix and release
Ca2+ into blood.
Parathyroid
glands
PTH
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Parathyroid
glands release
parathyroid
hormone (PTH).
Adrenal Glands
 Sit on top of the kidneys
 Two regions:
1. Adrenal cortex—outer glandular region has three
layers that produce corticosteroids
 Mineralocorticoids are secreted by outermost layer
 Glucocorticoids are secreted by middle layer
 Sex hormones are secreted by innermost layer
2. Adrenal medulla—inner neural tissue region
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Figure 9.11 Microscopic structure of the adrenal gland.
Adrenal
gland
Capsule
Mineralocorticoidsecreting area
Adrenal gland
• Medulla
• Cortex
Cortex
Kidney
Adrenal
cortex
Sex hormone–
secreting area
Medulla
Kidney
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Glucocorticoidsecreting area
Adrenal
medulla
Hormones of the Adrenal Cortex
 Mineralocorticoids (mainly aldosterone)
 Produced in outer adrenal cortex
 Regulate mineral content in blood, particularly
sodium and potassium ions
 Regulate water and electrolyte balance
 Target organ is the kidney
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Hormones of the Adrenal Cortex
 Release of aldosterone is stimulated by:
 Humoral factors (fewer sodium ions or too many
potassium ions in the blood)
 Hormonal stimulation (ACTH)
 Renin and angiotensin II in response to a drop in
blood pressure
 Aldosterone production is inhibited by atrial
natriuretic peptide (ANP), a hormone produced by
the heart when blood pressure is too high
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Figure 9.12 Major mechanisms controlling aldosterone release from the adrenal cortex.
Decreased Na+ or
increased K+ in
blood
Stress
Hypothalamus
Decreased
blood volume
and/or blood
pressure
Corticotropinreleasing
hormone
Anterior pituitary
ACTH
Kidney
Renin
Indirect
stimulating
effect via
angiotensin
Increased
blood pressure
or blood volume
Heart
Atrial natriuretic
peptide (ANP)
Angiotensin II
Direct
stimulating
effect
Inhibitory
effect
Mineralocorticoidproducing part of
adrenal cortex
Enhanced secretion
of aldosterone targets
kidney tubules
Increased absorption
of Na+ and water;
increased K+ excretion
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Increased blood
volume and
blood pressure
Hormones of the Adrenal Cortex
 Glucocorticoids (including cortisone and cortisol)
 Produced by middle layer of adrenal cortex
 Promote normal cell metabolism
 Help resist long-term stressors by increasing blood
glucose levels (hyperglycemic hormone)
 Anti-inflammatory properties
 Released in response to increased blood levels of
ACTH
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Hormones of the Adrenal Cortex
 Sex hormones
 Produced in the inner layer of the adrenal cortex
 Small amounts are made throughout life
 Mostly androgens (male sex hormones) are made,
but some estrogens (female sex hormones) are also
formed
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Adrenal Glands
 Adrenal cortex disorders
 Addison’s disease
 Results from hyposecretion of all adrenal cortex
hormones
 Bronze skin tone, muscle weakness, burnout,
susceptibility to infection
 Hyperaldosteronism
 May result from an ACTH-releasing tumor
 Excess water and sodium are retained, leading to
high blood pressure and edema
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Adrenal Glands
 Adrenal cortex disorders (continued)
 Cushing’s syndrome
 Results from a tumor in the middle cortical area of the
adrenal cortex
 “Moon face,” “buffalo hump” on the upper back, high
blood pressure, hyperglycemia, weakening of bones,
depression
 Masculinization
 Results from hypersecretion of sex hormones
 Beard and male distribution of hair growth
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Hormones of the Adrenal Medulla
 Produces two similar hormones: (catecholamines)
1. Epinephrine (adrenaline)
2. Norepinephrine (noradrenaline)
 These hormones prepare the body to deal with
short-term stress (“fight or flight”) by:
 Increasing heart rate, blood pressure, blood glucose
levels
 Dilating small passageways of lungs
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Figure 9.11 Microscopic structure of the adrenal gland.
Adrenal
gland
Capsule
Mineralocorticoidsecreting area
Adrenal gland
• Medulla
• Cortex
Cortex
Kidney
Adrenal
cortex
Sex hormone–
secreting area
Medulla
Kidney
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Glucocorticoidsecreting area
Adrenal
medulla
Figure 9.13 Roles of the hypothalamus, adrenal medulla, and adrenal cortex in the stress response.
Short term
Stress
More prolonged
Hypothalamus
Releasing hormones
Nerve impulses
Spinal cord
Corticotropic cells of
anterior pituitary
Preganglionic
sympathetic
Adrenal fibers
medulla
ACTH
Adrenal
cortex
Mineralocorticoids Glucocorticoids
Short-term stress response
1. Increased heart rate
Catecholamines
2. Increased blood pressure
(epinephrine and
3. Liver converts glycogen
norepinephrine)
to glucose and releases
glucose to blood
4. Dilation of bronchioles
5. Changes in blood flow
patterns, leading to
increased alertness and
decreased digestive and
kidney activity
6. Increased metabolic rate
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Long-term stress response
1. Retention of sodium 1. Proteins and fats
and water by kidneys
converted to
2. Increased blood
glucose or broken
volume and blood
down for energy
pressure
2. Increased blood
sugar
3. Suppression of
immune system
Pancreatic Islets
 Pancreas
 Located in the abdomen, close to stomach
 Mixed gland, with both endocrine and exocrine
functions
 The pancreatic islets produce hormones
 Insulin—produced by beta cells
 Glucagon—produced by alpha cells
 These hormones are antagonists that maintain blood
sugar homeostasis
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Figure 9.14a Pancreatic tissue.
Stomach
Pancreas
(a)
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Figure 9.14b Pancreatic tissue.
Exocrine
cells of
pancreas
(b)
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Pancreatic
islets
Figure 9.14c Pancreatic tissue.
Exocrine
cells of
pancreas
Alpha (𝛂)
cells
Capillaries
(c)
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Cord of beta (𝛃) cells
secreting insulin into
capillaries
Pancreatic Islets
 Insulin
 Released when blood glucose levels are high
 Increases the rate of glucose uptake and metabolism
by body cells
 Glucagon
 Released when blood glucose levels are low
 Stimulates the liver to release glucose to blood, thus
increasing blood glucose levels
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Homeostatic Imbalance
 Diabetes mellitus
 Occurs in the absence of insulin
 Blood sugar levels increase dramatically
 Blood glucose is lost in the urine; water follows
 Three cardinal signs:
1. Polyuria
2. Polydipsia
3. Polyphagia
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Figure 9.15 Regulation of blood glucose levels by a negative feedback mechanism involving pancreatic hormones.
Uptake of glucose from
blood is enhanced in
most body cells
Insulin-secreting cells
of the pancreas activated;
release insulin into the
blood
Pancreas
Insulin
Tissue cells
Glucose Glycogen
Elevated blood
sugar level
Liver takes up
glucose and stores
as glycogen
Stimulus
Blood
glucose level
(e.g., after
eating four
jelly doughnuts)
Stimulus
Blood glucose
level (e.g., after
skipping a meal)
Blood glucose rises
to homeostatic
set point; stimulus
for glucagon
release diminishes
Liver breaks
down glycogen
stores and
releases glucose
to the blood
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Blood glucose
falls to homeostatic
set point; stimulus
for insulin release
diminishes
Low blood sugar level
Glucagon-releasing
cells of pancreas
activated; release
glucagon into blood
Glucose Glycogen
Liver
Glucagon
Pineal Gland
 Located posterior to the third ventricle of the brain
 Secretes melatonin
 Helps establish the body’s sleep/wake cycles as well
as biological rhythms
 Believed to coordinate the hormones of fertility in
humans
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Figure 9.3 Location of the major endocrine organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
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Thymus Gland
 Located posterior to the sternum
 Largest in infants and children
 Produces thymosin
 Matures some types of white blood cells
 Important in developing the immune system
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Gonads
 Ovaries
 Produce eggs
 Produce two groups of steroid hormones:
1. Estrogens
2. Progesterone
 Testes
 Produce sperm
 Produce androgens, such as testosterone
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Figure 9.3 Location of the major endocrine organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
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Hormones of the Ovaries
 Estrogens
 Stimulate the development of secondary female
characteristics
 Mature female reproductive organs
 With progesterone, estrogens also
 Promote breast development
 Regulate menstrual cycle
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Hormones of the Ovaries
 Progesterone
 Acts with estrogen to bring about the menstrual cycle
 Helps in the implantation of an embryo in the uterus
 Helps prepare breasts for lactation
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Hormones of the Testes
 Produce several androgens
 Testosterone is the most important androgen
 Responsible for adult male secondary sex
characteristics
 Promotes growth and maturation of male
reproductive system
 Required for sperm cell production
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Table 9.1 Major Endocrine Glands and Some of Their Hormones (1 of 5).
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Table 9.1 Major Endocrine Glands and Some of Their Hormones (2 of 5).
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Table 9.1 Major Endocrine Glands and Some of Their Hormones (3 of 5).
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Table 9.1 Major Endocrine Glands and Some of Their Hormones (4 of 5).
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Table 9.1 Major Endocrine Glands and Some of Their Hormones (5 of 5).
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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
 Produces hormones that maintain pregnancy
 Some hormones play a part in the delivery of the
baby
 Produces human chorionic gonadotropin (hCG) in
addition to estrogen, progesterone, and other
hormones
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Table 9.2 Hormones Produced by Organs Other Than the Major Endocrine Organs (1 of 3).
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Table 9.2 Hormones Produced by Organs Other Than the Major Endocrine Organs (2 of 3).
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Table 9.2 Hormones Produced by Organs Other Than the Major Endocrine Organs (3 of 3).
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Developmental Aspects of the Endocrine
System
 In the absence of disease, efficiency of the
endocrine system remains high until old age
 Decreasing function of female ovaries at
menopause leads to such symptoms as
osteoporosis, increased chance of heart disease,
and possible mood changes
© 2015 Pearson Education, Inc.
Developmental Aspects of the Endocrine
System
 Efficiency of all endocrine glands gradually
decreases with aging, which leads to a generalized
increase in incidence of:
 Diabetes mellitus
 Immune system depression
 Lower metabolic rate
 Cancer rates in some areas
© 2015 Pearson Education, Inc.