1. Chapter Opener 16
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2. Figure 16.1 Location of selected endocrine organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
(on dorsal aspect
of thyroid gland)
Thymus
Adrenal glands
Pancreas
Gonads
• Ovary (female)
• Testis (male)
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3. Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones.
Recall from Chapter 3 that
G protein signaling mechanisms
are like a molecular relay race.
Hormone
(1st messenger)
Receptor
G protein
Enzyme
2nd
messenger
Hormone (1st messenger) binds receptor. 1
Adenylate cyclase
Extracellular fluid
G protein (Gs)
cAMP
cAMP activates protein kinases. 5
GTP
Receptor
GTP
ATP
GDP
Inactive
protein
kinase
Active
protein
kinase
GTP
Triggers responses of
target cell (activates
enzymes, stimulates
cellular secretion,
opens ion channel, etc.)
Cytoplasm
Receptor activates G protein (Gs). 2
G protein activates adenylate cyclase. 3
Adenylate
cyclase converts
ATP to cAMP (2nd messenger). 4
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4. Cytoplasm Nucleus mRNA New protein
Figure Direct gene activation mechanism of lipid-soluble hormones.
Steroid
hormone
Extracellular
fluid
Plasma
membrane
The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1
Cytoplasm
Receptor
protein
Receptor-
hormone
complex
The receptor-
hormone complex enters the nucleus. 2
Receptor
Binding region
Nucleus
The receptor- hormone complex binds a specific DNA region. 3
DNA
Binding initiates transcription of the gene to mRNA. 4
mRNA
The mRNA directs protein synthesis. 5
New protein
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5. Figure 16.4 Three types of endocrine gland stimuli.
(a) Humoral Stimulus
(b) Neural Stimulus
(c) Hormonal Stimulus
Hormone release caused by altered
levels of certain critical ions or
nutrients.
Hormone release caused by neural input.
Hormone release caused by another
hormone (a tropic hormone).
CNS (spinal cord)
Hypothalamus
Capillary (low Ca2+
in blood)
Thyroid gland
(posterior view)
Parathyroid
glands
Anterior
pituitary
gland
Preganglionic
sympathetic
fibers
Thyroid
gland
Adrenal
cortex
Gonad
(Testis)
Medulla of
adrenal gland
Parathyroid
glands
PTH
Capillary
Stimulus: Low concentration of Ca2+ in
capillary blood.
Stimulus: Action potentials in preganglionic
sympathetic fibers to adrenal medulla.
Stimulus: Hormones from hypothalamus.
Response: Parathyroid glands secrete
parathyroid hormone (PTH), which
increases blood Ca2+.
Response: Anterior pituitary gland secretes
hormones that stimulate other endocrine glands
to secrete hormones.
Response: Adrenal medulla cells secrete
epinephrine and norepinephrine.
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6. Figure 16.4a Three types of endocrine gland stimuli.
Humoral Stimulus
Hormone release caused by altered
levels of certain critical ions or
nutrients.
Capillary (low Ca2+
in blood)
Thyroid gland
(posterior view)
Parathyroid
glands
Parathyroid
glands
PTH
Stimulus: Low concentration of Ca2+ in
capillary blood.
Response: Parathyroid glands secrete
parathyroid hormone (PTH), which
increases blood Ca2+.
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7. Figure 16.4b Three types of endocrine gland stimuli.
Neural Stimulus
Hormone release caused by neural input.
CNS (spinal cord)
Preganglionic
sympathetic
fibers
Medulla of
adrenal gland
Capillary
Stimulus: Action potentials in preganglionic
sympathetic fibers to adrenal medulla.
Response: Adrenal medulla cells secrete
epinephrine and norepinephrine.
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8. Figure 16.4c Three types of endocrine gland stimuli.
Hormonal Stimulus
Hormone release caused by another
hormone (a tropic hormone).
Hypothalamus
Anterior
pituitary
gland
Thyroid
gland
Adrenal
cortex
Gonad
(Testis)
Stimulus: Hormones from hypothalamus.
Response: Anterior pituitary gland secretes
hormones that stimulate other endocrine glands to secrete hormones.
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9. Figure The hypothalamus controls release of hormones from the pituitary gland in two different ways.
Posterior Pituitary:
Anterior Pituitary:
Paraventricular nucleus
Hypothalamus 1
Hypothalamic neurons
synthesize oxytocin or antidiu-
retic hormone (ADH).
Hypothalamus
Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
Posterior lobe
of pituitary
Anterior lobe
of pituitary
Optic chiasma
Superior
hypophyseal
artery
Supraoptic
nucleus
Infundibulum
(connecting stalk)
Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit rele-
ase of hormones made in the anterior pituitary. 2
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. 1
Oxytocin and ADH are
transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. 2
Inferior
hypophyseal
artery
Hypothalamic-
hypophyseal
tract
Hypophyseal
portal system
In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. 3
Axon terminals
Oxytocin and ADH are stored
in axon terminals in the
posterior pituitary. 3
• Primary capillary
plexus
A portal
system is two capillary plexuses
(beds) connected by veins.
• Hypophyseal
portal veins
Posterior lobe
of pituitary
• Secondary
capillary plexus
Oxytocin
ADH 4
When associated hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
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10. Paraventricular nucleus
Figure The hypothalamus controls release of hormones from the pituitary gland in two different ways. (1 of 2)
Posterior Pituitary:
Paraventricular nucleus
Hypothalamus 1
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
Posterior lobe
of pituitary
Optic
chiasma
Supraoptic
nucleus
Infundibulum
(connecting stalk) 2
Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.
Inferior
hypophyseal
artery
Hypothalamic-
hypophyseal
tract
Axon terminals 3
Oxytocin and ADH are stored in axon terminals in the posterior pituitary.
Posterior lobe
of pituitary 4
Oxytocin
ADH
When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
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11. they stimulate or inhibit
Figure The hypothalamus controls release of hormones from the pituitary gland in two different ways. (2 of 2)
Anterior Pituitary:
Hypothalamus
Hypothalamic
neurons synthesize
GHRH, GHIH, TRH,
CRH, GnRH, PIH.
Anterior lobe
of pituitary
Superior
hypophyseal
artery
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. 1 2
Hypothalamic hormones travel through portal veins to the anterior pituitary where
they stimulate or inhibit
release of hormones made in the anterior pituitary.
Hypophyseal
portal system
• Primary capillary
plexus 3
A portal system is two capillary plexuses (beds) connected by veins.
In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation.
• Hypophyseal
portal veins
• Secondary
capillary plexus
GH, TSH, ACTH,
FSH, LH, PRL
Anterior lobe
of pituitary
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12. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (1 of 4)
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13. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (2 of 4)
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14. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (3 of 4)
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15. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (4 of 4)
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16. Figure 16.6 Growth-promoting and metabolic actions of growth hormone (GH).
Hypothalamus
secretes growth
hormone–releasing
hormone (GHRH), and
GHIH (somatostatin)
Feedback
Inhibits GHRH release
Stimulates GHIH release
Anterior
pituitary
Inhibits GH synthesis
and release
Growth hormone (GH)
Indirect actions
(growth-
promoting)
Direct actions
(metabolic,
anti-insulin)
Liver and
other tissues
Produce
Insulin-like growth
factors (IGFs)
Effects
Effects
Fat
metabolism
Carbohydrate
metabolism
Skeletal
Extraskeletal
Increases, stimulates
Reduces, inhibits
Increased protein
synthesis, and
cell growth and
proliferation
Initial stimulus
Increased cartilage
formation and
skeletal growth
Increased
fat breakdown
and release
Increased blood
glucose and other
anti-insulin effects
Physiological response
Result
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17. Figure 16.7 Disorders of pituitary growth hormone.
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18. Figure 16.8 Regulation of thyroid hormone secretion.
Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
Thyroid
hormones
Stimulates
Target cells
Inhibits
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19. Figure 16.9 The thyroid gland.
Hyoid bone
Colloid-filled
follicles
Thyroid cartilage
Epiglottis
Follicular cells
Superior thyroid
artery
Common carotid
artery
Inferior thyroid
artery
Isthmus of
thyroid gland
Trachea
Left subclavian
artery
Left lateral
lobe of thyroid
gland
Aorta
Parafollicular cells
Gross anatomy of the thyroid gland, anterior view
Photomicrograph of thyroid gland
follicles (145x)
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20. Figure 16.9a The thyroid gland.
Hyoid bone
Thyroid cartilage
Epiglottis
Superior thyroid
artery
Common carotid
artery
Inferior thyroid
artery
Isthmus of
thyroid gland
Trachea
Left subclavian
artery
Left lateral
lobe of thyroid
gland
Aorta
Gross anatomy of the thyroid gland, anterior view
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21. Figure 16.9b The thyroid gland.
Colloid-filled
follicles
Follicular cells
Parafollicular cells
Photomicrograph of thyroid gland
follicles (145x)
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22. Table 16.2 Major Effects of Thyroid Hormone (T4 and T3) in the Body (1 of 2)
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23. Table 16.2 Major Effects of Thyroid Hormone (T4 and T3) in the Body (2 of 2)
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24. Figure 16.10 Synthesis of thyroid hormone.
Thyroid follicular cells
Colloid
Thyroglobulin is synthesized and discharged into the follicle lumen. 1
Tyrosines (part of thyroglobulin
molecule)
Capillary
Iodine is attached to tyrosine in colloid, forming DIT and MIT. 4
Golgi
apparatus
Rough ER
Thyro-
globulin
colloid
Iodine
Iodide is oxidized to iodine. 3
DIT
MIT
Iodide (I−)
Iodide (I–) is trapped (actively transported in). 2 T4
Iodinated tyrosines are linked together to form T3 and T4. 5 T3
Lysosome T4
Thyroglobulin colloid is endocytosed and combined with a lysosome. 6 T3
Lysosomal enzymes cleave T4 and T3 from thyroglobulin and hormones diffuse into bloodstream. 7 T4
Colloid in
lumen of
follicle T3
To peripheral tissues
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25. Figure 16.11 Thyroid disorders.
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26. Figure 16.12 The parathyroid glands.
Pharynx
(posterior
aspect)
Capillary
Parathyroid
cells
(secrete
parathyroid
hormone)
Thyroid
gland
Parathyroid
glands
Esophagus
Oxyphil
cells
Trachea
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27. Figure 16.12a The parathyroid glands.
Pharynx
(posterior
aspect)
Thyroid
gland
Parathyroid
glands
Esophagus
Trachea
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28. Figure 16.12b The parathyroid glands.
Capillary
Parathyroid
cells
(secrete
parathyroid
hormone)
Oxyphil
cells
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29. Figure 16.13 Effects of parathyroid hormone on bone, the kidneys, and the intestine.
Hypocalcemia
(low blood Ca2+)
PTH release from
parathyroid gland
Osteoclast activity
in bone causes Ca2+
and PO43- release
into blood
Ca2+ reabsorption
in kidney tubule
Activation of
vitamin D by kidney
Ca2+ absorption
from food in small
intestine
Ca2+ in blood
Initial stimulus
Physiological response
Result
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30. Figure 16.14 Microscopic structure of the adrenal gland.
Hormones
secreted
Capsule
Zona
glomerulosa
Aldosterone
Zona
fasciculata
Adrenal gland
• Medulla
Cortex
• Cortex
Cortisol
and
androgens
Kidney
Zona
reticularis
Medulla
Adrenal
medulla
Epinephrine
and
norepinephrine
Drawing of the histology of the
adrenal cortex and a portion of
the adrenal medulla
Photomicrograph (115x)
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31. Figure 16.14a Microscopic structure of the adrenal gland.
Capsule
Zona
glomerulosa
Zona
fasciculata
Adrenal gland
• Medulla
Cortex
• Cortex
Kidney
Zona
reticularis
Medulla
Adrenal
medulla
Drawing of the histology of the
adrenal cortex and a portion of
the adrenal medulla
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32. Figure 16.14b Microscopic structure of the adrenal gland.
Hormones
secreted
Capsule
Zona
glomerulosa
Aldosterone
Zona
fasciculata
Cortisol
and
androgens
Zona
reticularis
Adrenal
medulla
Epinephrine
and
norepinephrine
Photomicrograph (115x)
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33. water; increased K+ excretion
Figure Major mechanisms controlling aldosterone release from the adrenal cortex.
Primary regulators
Other factors
Blood volume
and/or blood
pressure
K+ in blood
Stress
Blood pressure
and/or blood
volume
Hypo-
thalamus
Heart
Kidney
CRH
Direct
stimulating
effect
Anterior
pituitary
Renin
Initiates
cascade
that
produces
ACTH
Atrial natriuretic
peptide (ANP)
Angiotensin II
Inhibitory
effect
Zona glomerulosa
of adrenal cortex
Enhanced
secretion
of aldosterone
Targets
kidney tubules
Absorption of Na+ and
water; increased K+ excretion
Blood volume
and/or blood pressure
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34. Figure 16.16 The effects of excess glucocorticoid.
Patient before onset.
Same patient with Cushing’s
syndrome. The white arrow shows
the characteristic “buffalo hump” of
fat on the upper back.
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35. Table 16.3 Adrenal Gland Hormones: Summary of Regulation and Effects
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36. Figure 16.17 Stress and the adrenal gland.
Short-term stress
Prolonged stress
Stress
Nerve impulses
Hypothalamus
CRH (corticotropin-
releasing hormone)
Spinal cord
Corticotropic cells
of anterior pituitary
Preganglionic
sympathetic
fibers
To target in blood
Adrenal cortex
(secretes steroid
hormones)
Adrenal medulla
(secretes amino acid–
based hormones)
ACTH
Catecholamines
(epinephrine and
norepinephrine)
Mineralocorticoids
Glucocorticoids
Short-term stress response
Long-term stress response
• Heart rate increases
• Kidneys retain
sodium and water
• Proteins and fats converted
to glucose or broken down
for energy
• Blood pressure increases
• Bronchioles dilate
• Blood volume and
blood pressure
rise
• Liver converts glycogen to glucose and releases
glucose to blood
• Blood glucose increases
• Immune system
supressed
• Blood flow changes, reducing digestive system activity
and urine output
• Metabolic rate increases
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37. Pancreatic islet •  (Glucagon- producing) cells •  (Insulin-
Figure Photomicrograph of differentially stained pancreatic tissue.
Pancreatic islet
•  (Glucagon-
producing)
cells
•  (Insulin-
producing)
cells
Pancreatic acinar
cells (exocrine)
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38. BALANCE: Normal blood glucose level (about 90 mg/100 ml)
Figure Insulin and glucagon from the pancreas regulate blood glucose levels.
Stimulates glucose
uptake by cells
Insulin
Tissue cells
Stimulates
glycogen
formationw
Pancreas
Glucose
Glycogen
Blood
glucose
falls to
normal
range.
Liver
IMBALANCE
Stimulus
Blood
glucose level
BALANCE: Normal blood glucose level (about 90 mg/100 ml)
Stimulus
Blood
glucose level
IMBALANCE
Blood
glucose
rises to
normal
range.
Pancreas
Glucose
Glycogen
Liver
Stimulates
glycogen
breakdown
Glucagon
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39. Table 16.4 Symptoms of Insulin Deficit (Diabetes Mellitus)
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40. Table Selected Examples of Hormones Produced by Organs Other Than the Major Endocrine Organs (1 of 2)
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41. Table Selected Examples of Hormones Produced by Organs Other Than the Major Endocrine Organs (2 of 2)
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42. Closer Look 16.1
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43. System Connections 16.1
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