1. Chapter 16:
The Endocrine System

2. Arnold Adolph Berthold 1803 – 1861 Founder of Endocrinology

3. Berthold’s Experiment in Roosters….
Castration &
Reimplantation
of testis
Castration
Castration &
Transplantation
of testis

4. Berthold’s Conclusion...
-A secretory, blood-borne product of the transplanted testes
is responsible for the normal development of the birds in the
second and third group
Today, it is called TESTOSTERONE
-’problem’: no one knows why Berthold did the experiment in
the first place…. No clear rationale for it.

5. Pineal gland Hypothalamus Pituitary gland Thyroid gland
Figure 16.1: Location of the major endocrine organs of the body, p. 605.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
(on dorsal aspect
of thyroid gland)
Thymus gland
Adrenal glands
Pancreas
Ovary
(female)
Testis
(male)

6. Extracellular fluid Hormone DAG 1 4 5 Active protein kinase C 2 GTP 3
Figure 16.3: PIP second-messenger mechanism of amino acid-based hormones, p. 608.
Extracellular fluid
Hormone
DAG 1 4 5
Active
protein
kinase C 2
GTP 3
GTP
PIP2
Receptor Gq
Inactive
protein
kinase C
GTP
GDP
IP3
Catecholamines
TRH
ADH
GnRH
Oxytocin
Phospholipase C
Triggers responses
of target cell 5
Endoplasmic
reticulum 6
Cytoplasm
Ca2+
Ca2+-calmodulin

7. Steroid hormone Cytoplasm Steroid hormone Receptor- chaperonin complex
Figure 16.4: Direct gene activation mechanism of steroid hormones, p. 609.
Steroid
hormone
Cytoplasm
Steroid
hormone
Receptor-
chaperonin
complex
Receptor-hormone
complex
Molecular
chaperones
Hormone
response
elements
Binding
Transcription
Chromatin
mRNA
mRNA
Nucleus
New protein
Ribosome
Translation

8. Figure 16.5: Three types of endocrine gland stimuli, p. 612.
Capillary blood contains low
concentration of Ca2+, which
stimulates… 1
Preganglionic SNS fiber stimulates
adrenal medulla cells… 1
The hypothalamus secretes
hormones that…
Hypothalamus
Capillary
(low Ca2+ in blood)
Thyroid gland
(posterior view)
CNS
(spinal cord) 2
…stimulate
the anterior
pituitary gland
to secrete
hormones
that…
Parathyroid
glands
Preganglionic
SNS fiber
Pituitary
gland
Medulla of
adrenal
gland
Thyroid
gland
Adrenal
cortex
Gonad
(Testis)
Parathyroid
glands
PTH 2
…secretion of parathyroid
hormone (PTH) by parathyroid
glands
Capillary 2
…to secrete catecholamines 3
…stimulate other endocrine glands
to secrete hormones
(a)
Humoral
(b)
Neural
(c)
Hormonal

9. paraventricular nuclei
Figure 16.6: Relationships of the pituitary gland and hypothalamus, p. 613.
Hypothalamic
neurons in the
paraventricular nuclei
Neurons
in the ventral
hypothalamus
Hypothalamic
neurons in the
supraoptic nuclei
Infundibulum
(connecting stalk)
Superior
hypophyseal
artery
Hypothalamic-
hypophyseal tract
Hypophyseal portal system
• Primary capillary
plexus
Neurohypophysis
(storage area for
hypothalamic
hormones)
• Hypophyseal
portal veins
• Secondary capillary
plexus
Posterior
lobe
Anterior lobe
Secretory cells of
adenohypophysis
Venule
Oxytocin
ADH
TSH, FSH, LH,
ACTH, GH, PRL
Inferior
hypophyseal
artery
Venule

10. Figure 16.7: Metabolic actions of growth hormone (GH), p. 615.
Hypothalamus
secretes growth
hormone – releasing
hormone (GHRH), and
somatostatin (GHIH)
Inhibits GHRH release
Stimulates GHIH release
Feedback
mechanism
Anterior
pituitary
Inhibits GH synthesis
and release
Key:
Growth hormone
Increases, stimulates
Direct effects
Reduces, inhibits
Initial stimulus
Liver and
other tissues
Physiological response
Result
Insulin-like growth
factors (IGFs)
Anti-insulin
actions
Indirect
growth-promoting
actions
Extraskeletal
effects
Carbohydrate
metabolism
Skeletal effects
Fat
Increased protein
synthesis, and
cell growth and
proliferation
Increased cartilage
formation and
skeletal growth
Increased blood
glucose and other
anti-insulin effects
Increased
lipolysis

11. Colloid-filled follicles Hyoid bone Follicle cells Epiglottis
Figure 16.8: Gross and microscopic anatomy of the thyroid gland, p. 620.
Colloid-filled
follicles
Hyoid bone
Follicle cells
Epiglottis
Thyroid cartilage
Internal carotid
artery
External carotid
artery
Superior thyroid
artery
Common carotid
artery
Inferior thyroid
artery
Isthmus of
thyroid gland
Trachea
Left subclavian
artery
Brachiocephalic
artery
Left lateral lobe
of thyroid gland
Aorta
Parafollicular cell
(a)
(b)

12. Figure 16.11: The parathyroid glands, p. 624.
Pharynx
(posterior
aspect)
Thyroid
gland
Capillary
Parathyroid
glands
Chief
cells
Esophagus
Trachea
Oxyphil
cells
(a)
(b)

13. Hypocalcemia (low blood calcium) stimulates parathyroid glands Key:
Figure 16.12: Effect of parathyroid hormone on bone, the intestine, and the kidneys, p. 625.
Hypocalcemia (low blood
calcium) stimulates
parathyroid glands
Key:
= Ca2+ ions
= PTH molecules
Rising Ca2+ in
blood inhibits
PTH release
PTH release from
parathyroid glands
PTH:
Bone
Activates
osteoclasts;
calcium and
phosphate
ions released
into blood
Intestine
Increases
calcium
absorption
from food
Promotes activation
of vitamin D
Kidney
Increases
calcium
reabsorption
Blood-
stream

14. Figure 16.13: Microscopic structure of the adrenal gland, p. 626.
Capsule
Zona
glomerulosa
Adrenal
gland
Zona
fasciculata
• Medulla
• Cortex
Zona
reticularis
Kidney
Adrenal
medulla
(a)
(b)

15. Figure 16.16: Stress and the adrenal gland, p. 631.
Short term
Stress
More prolonged
Hypothalamus
CRH (corticotropin-
releasing hormone)
Nerve impulses
Spinal cord
Corticotroph
cells of
anterior
pituitary
To target in blood
Preganglionic
sympathetic
fibers
Adrenal
cortex
ACTH
Adrenal
medulla
Short-term
stress response
Mineralocorticoids
Glucocorticoids
1. Increased heart rate
2. Increased blood pressure
3. Liver converts glycogen to glucose
and releases glucose to blood
4. Dilation of bronchioles
5. Changes in blood flow patterns
leading to decreased digestive
system activity and reduced
urine output
6. Increased metabolic rate
Catecholamines
(epinephrine
and norepinephrine)
Long-term stress response
1. Retention of sodium and
water by kidneys
2. Increased blood volume
and blood pressure
1. Proteins and fats
converted to glucose
or broken down for
energy
2. Increased blood glucose
3. Suppression of immune
system

16. Homeostasis: Normal blood glucose level (about 90 mg/100 ml)
Figure 16.18: Regulation of blood glucose levels by insulin and glucagon, p. 633.
Stimulates
glucose uptake
by cells
Insulin
Tissue cells
Stimulates
glycogen
formation
Pancreas
Glycogen
Glucose
Blood
glucose
falls to
normal
range
Liver
Stimulus:
Rising blood
glucose level
Imbalance
Homeostasis: Normal blood glucose level (about 90 mg/100 ml)
Imbalance
Stimulus:
Declining blood
glucose level
Blood
glucose
rises to
normal
range
Pancreas
Glucose
Stimulates
glycogen
breakdown
Glycogen
Glucagon
Liver

18. Figure 16.1: Modified to emphasize the relationship between the adrenal glands and the testes and ovaries.
Testes & Ovaries
These gamete producing glands produce the lion’s share of sex hormone for each sex. Ovaries are in females and Testes are in males. There is, however, an important role for the adrenal glands…
Adrenal glands
Ovary
(female)
Testis
(male)