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Marieb’s Human
Anatomy and Physiology
Marieb w Hoehn
Chapter 16
Endocrine System
Lecture 14
Lecture Overview
• The Adrenal Glands
• The Pancreas
• Other Endocrine Tissues
• Stress and its effects
• Life-span changes
2
Location/Blood Supply of the Adrenal
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
3
Adrenal Glands
Figure from: Hole’s Human A&P, 12th edition, 2010
Adrenal cortex and medulla are functionally distinct
4
Hormones of the Adrenal Medulla
Epinephrine (80%) and Norepinephrine (20%)
• derived from amino acid tyrosine
• hormones of ‘fight or flight’ are called catecholamines
• release controlled by sympathetic nervous system
(neural control of hormone release)
• hormone releasing cells are considered equivalent to
postganglionic sympathetic neurons
• increases heart rate and blood pressure
• dilates respiratory airways
• promotes glycogenolysis and gluconeogenesis
• activates reticular formation
• increases metabolic rates
5
Adrenal Cortex and its Hormones
• Yellowish appearance of cortex is due to stored lipids,
especially cholesterol and various fatty acids
• Produces more than 25 steroid hormones
• Hormones of the Adrenal Cortex are…
–
–
–
–
Called adrenocortical steroids, or corticosteroids
Carried in blood by transcortins
Essential to life
Affect cellular metabolism by determining the nature and
concentration of cellular enzymes
– Not stored in cell
6
Adrenocortical Steroids - Aldosterone
Figure from: Hole’s Human A&P, 12th edition, 2010
• increases blood
volume and
pressure by
promoting
conservation of
sodium ions and
water (distal
tubules of kidney)
• Activated by 1)
the reninangiotensin system
and by 2) changing
concentrations of
of Na+ and K+
• Zona glomerulosa
Aldosterone is a mineralocorticoid
7
Adrenocortical Steroids - Glucocorticoids
Cortisol (hydrocortisone) – a glucocorticoid
•  protein synthesis,  protein catabolism
• increases fatty acid release (glucose-sparing effect)
• stimulates gluconeogenesis
• controlled by CRH from hypothalamus and ACTH from anterior
pituitary
Produced in the Zona
Fasciculata
Blood levels peak
shortly after arising in
morning
Glucocorticoids have
anti-inflammatory and
anti-immune effects
Figure from: Hole’s Human A&P, 12th edition, 2010
8
Anti-Inflammatory Effects of Steroids
Figure from: Hole’s Human A&P, 12th edition, 2010
Eicosanoids are important
paracrine factors that
mediate many processes in
the body, including:
- Inflammation
- blood vessel constriction
- blood clotting
- smooth muscle contraction
and relaxation
9
Adrenocortical Steroids - Androgens
Adrenal androgens (gonadocorticoids)
• supplement sex hormones from the gonads (release
stimulated slightly by ACTH; inhibitory stimulus
unknown). Mostly dehydroepiandrosterone (DHEA)
• may be converted to estrogen in the blood (♀)
• When secreted in normal amounts, neither adrenal
androgens or estrogens affect sexual characteristics (may
affect sex drive in ♀)
• Produced in the Zona Reticularis
• Tumors of this region can lead to androgenital
syndrome (masculinization)
10
Endocrine Pancreas
11
Figures from: Hole’s Human A&P, 12th edition, 2010
Cells of the Pancreatic Islets
• Alpha cells - Glucagon
• Beta cells – Insulin, amylin
• Delta cells
– Somatostatin (growth hormone-inhibiting hormone,
GH-IH)
• Suppresses release of insulin and glucagon
• Slows rates of food absorption
• F cells
– Pancreatic polypeptide (inhibits GB contractions –
exact physiological role is uncertain)
12
Insulin
Insulin decreases
blood glucose levels
by allowing cells to
take up glucose
from the blood
Binding enhances
glucose uptake
Brain, kidneys, liver,
RBCs are insulin
independent
Insulin release is
also affected by the
ANS
Figure from: Martini, Anatomy & Physiology,
Prentice Hall, 2001
13
Glucagon
Figure from: Martini, Anatomy
& Physiology, Prentice Hall,
2001
Raises blood glucose levels
by:
- stimulating breakdown of
stored molecules
- increasing release and
formation of glucose
14
Insulin and Glucagon
Figure from: Hole’s Human A&P, 12th edition, 2010
Example of a humoral stimulus
(glucose) for hormone secretion
15
Pineal Gland
Pinealocytes synthesize melatonin from serotonin
16
Melatonin
• regulates circadian rhythms - daily changes in
physiological processes that follow a regular pattern
Light (eyes) → retina → hypothalamus → reticular formation

 melatonin  pineal  sympathetic fibers  spinal cord
• may control onset of puberty (melatonin levels
decline at puberty)
• helps regulate female reproductive cycle
• may protect CNS against free radicals (antioxidant)
17
Other Endocrine Glands
Reproductive Glands
• ovaries secrete estrogen and progesterone
• testes secrete testosterone
• placenta secretes estrogen, progesterone, and
gonadotropins, e.g., hCG
Thymus Gland
• secretes thymosins
• promotes development of T-lymphocytes
Heart
• secretes natriuretic peptides (ANP, BNP)
- Natri = sodium; uretic = in the urine
- promote loss of water and Na+ at the kidney
- secreted when atria/ventricles are stretched
- inhibit renin release
- inhibit secretion of ADH and aldosterone
18
Other Endocrine Glands
• Adipose Tissue
– Leptin
• After eating, adipose tissue absorbs glucose and lipids
• Peptide hormone, leptin, is released
• Binds to receptors in hypothalamus (esp. arcuate and paraventricular
nuclei)
–
–
–
–
–
Alters levels of other substances in brain
Increased sympathetic activity
Decreased insulin secretion
Permissive effect on GnRH (effects on reproductive function)
Sense of satiety and suppression of appetite
• Levels are normal in most obese individuals; receptors or cellular
pathways may be defective
– Resistin
• Reduces insulin sensitivity throughout body (insulin antagonist)
• May be one of the ‘missing links’ between obesity and diabetes
– TNF - in obese people, inhibits glut4 protein; activates
stress hormones
19
Stress
Types of Stress
• physical stress
• psychological
(emotional) stress
(Stress is any condition,
physical or emotional, that
threatens homeostasis)
Stress Response (General
Adaptation Syndrome [GAS])
• hypothalamus triggers
sympathetic impulses to
various organs
• epinephrine is released
• cortisol is released to
promote longer-term
responses
Three general phases of the GAS
in response to stress A R E:
• Alarm phase
• Resistance phase
• Exhaustion phase
21
Responses to Stress
Exhaustion
-  lipid reserves
-  production of glucocorticoids
- electrolyte imbalance
- damage to vital organs
22
Figure from: Hole’s Human A&P, 12th edition, 2010
GH Abnormalities
Figure from: Hole’s Human A&P, 12th edition, 2010
Growth Hormone Ups and Downs
• Gigantism - hypersecretion of GH in children
• Acromegaly – hypersecretion of GH in adults
• Dwarfism – hyposecretion of GH in children
Age 9
Age 16
Age 33
Age 52
23
Diabetes (= Overflow)
• Diabetes Mellitus (DM)
– Hyposecretion or hypoactivity of insulin
– Three P’s of Diabetes Mellitus (mellitum = honey)
• Polyuria (increased urination)
• Polydipsia (increased thirst)
• Polyphagia (increased hunger)
– Hyperglycemia, ketonuria, glycosuria
• Renal Glycosuria
– excretion of glucose in the urine in detectable amounts
– normal blood glucose concentrations or absence of
hyperglycemia
• Diabetes Insipidus (insipidus = tasteless)
– Hyposecretion or hypoactivity of ADH
– Polyuria
– Polydipsia
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Hormone Summary Table I – Pituitary Hormones
Tissue
Origin
Destination
Action on Target Tissue
Control of Release1
anterior
pituitary
males: seminiferous
tubules of testes;
females: ovarian
follicle
males: sperm production
females: follicle/ovum maturation
Gonadotropin Releasing
Hormone (GnRH)
LUETINIZING
HORMONE (LH)
anterior
pituitary
In males: interstitial
cells in testes;
in females: mature
ovarian follicle
males: testosterone secretion
females: ovulation
Gonadotropin Releasing
Hormone (GnRH)
T
THYROID
STIMULATING
HORMONE (TSH)
anterior
pituitary
thyroid
secrete hormones
Thyrotropin Releasing
Hormone (TRH)
G
GROWTH
HORMONE (GH)
anterior
pituitary
bone, muscle, fat
growth of tissues
Growth Hormone Rleasing
Hormone (GHRH)
A
ADRENOCORTICOTROPIC HORMONE
(ACTH)
anterior
pituitary
adrenal cortex
secrete adrenal hormones
Corticotropin Releasing
Hormone (CRH)
P
PROLACTIN (PRL)
anterior
pituitary
mammary glands
produce milk
Prolactin Releasing Hormone
(PRH)
ANTI-DIURETIC
HORMONE (ADH)
(VASOPRESSIN)
posterior
pituitary
Collecting ducts of
kidneys
reabsorption of water; increases blood
pressure
increase in osmolarity of
plasma or a decrease in blood
volume
OXYTOCIN (OT)
posterior
pituitary
uterine smooth
muscle; breast
contraction during labor; milk letdown
Stretching of uterus; infant
suckling
Name
FOLLICLE
STIMULATING
HORMONE (FSH)
Se(x)
26
Hormone Summary Table II
Tissue
Name
Origin
Destination
Action on Target Tissue
Control of Release
TRIIODOTHYRONINE
(T3) & THYROXINE
(T4)
Thyroid (follicular
cells)
all cells
increases rate of metabolism (BMR)
Thyroid Stimulating Hormone
(TSH)
Thyroid (C cells)
Intestine, bone,
kidney
Decreases plasma [Ca2+]
( intestinal absorp of Ca;  action of
osteoclasts;  excretion of Ca by kidney
 plasma [Ca2+]
Parathyroids
Intestine, bone,
kidney
Increases plasma [Ca2+]
( intestinal absorp of Ca;  action of
osteoclasts;  excretion of Ca by kidney
 plasma [Ca2+]
cardiac muscle,
arteriole and
bronchiole smooth
muscle,
diaphragm, etc
increases heart rate and blood pressure...
(fight or flight)
Sympathetic Nervous System
CALCITONIN
PARATHYROID
HORMONE (PTH)
EPINEPHRINE/
NOREPINEPHRINE
(Catecholamines)
Adrenal Medulla
ALDOSTERONE
(Mineralocorticoids)
Adrenal Cortex
Kidneys; sweat
glands; salivary
glands; pancreas
reabsorption of water and Na (increases blood
pressure) and excretion of K
(mineralocorticoid)
Angiotensin II
 plasma [Na+]
 plasma [K+]
CORTISOL
(Glucocorticoids)
Adrenal Cortex
all cells
Diabetogenic; anti-inflammatory
(glucocorticoid)
ACTH
INSULIN
β-cells of
Pancreatic Islets
all cells, liver and
skeletal muscle
pushes glucose into cells from blood, glycogen
formation (decreases blood glucose)
 plasma [glucose]
SNS
GLUCAGON
α-cells of
pancreatic Islets
liver and skeletal
muscle
breakdown of glycogen (increase in blood
glucose)
 plasma [glucose]
TESTOSTERONE
Testes
secondary sex
organs
development and maintenance
LH
ESTROGEN
Ovaries
secondary sex
organs
development at puberty and maintenance
throughout life
LH
NATRIURETIC
PEPTIDES
atria and ventricles
of heart
increased excretion of sodium and water from
kidneys,  blood volume,  blood pressure
Stretching of atria and ventricles
adrenal cortex,
kidneys
27
Review
• Reaction to stress occurs in three stages
– Short term
• Alarm or “fight or flight”
• Reactions similar to sympathetic stimulation
• Mediated by hormones of the adrenal medulla
– Long term
• Resistance
• Long-term raising of blood glucose
• Mediated by hormones of the adrenal cortex
– Exhaustion
• Failure of compensatory mechanisms
28