summary about the Endocrine System

1. The Endocrine System
Human Anatomy & Physiology

2. Endocrine System Overview

3. • Endocrine system acts with nervous
system
of body cells
• Influences metabolic activities via
hormones transported in blood
• Responses are slower but longer lasting
than nervous system responses
• Endocrinology: study of hormones
and endocrine organs
Endocrine System Overview

4. Endocrine System
Controls and integrates body processes
Regulation of cellular metabolism
and energy balance
Mobilization of body defenses
Reproduction
Growth and
development
Maintenance of electrolyte, water,
and nutrient balance of blood

5. Types of Glands
Exocrine glands
• Produce non-hormonal
substances (examples:
sweat, saliva)
• Have ducts to carry secretions
to membrane surface
Endocrine glands
• Produce hormones
• Lack ducts
Secretions
Duct
Surface
Gland lumen

6. Types of Glands
Blood in
capillaries
Hormones
being secreted
into blood
Exocrine glands
• Produce non-hormonal
substances (examples:
sweat, saliva)
• Have ducts to carry secretions
to membrane surface
Endocrine glands
• Produce hormones
• Lack ducts

7. Endocrine System Overview
Pancreas
Gonads (ovaries)
Placenta
Organs with
exocrine and
endocrine
functions
Pineal gland
Adrenal glands
Pituitary gland
Trachea
Parathyroid glands
(on posterior side
of thyroid)
Thyroid gland Hypothalamus

8. Other tissues and organs
that produce hormones:
• Adipose cells
• Thymic cells
Endocrine System Overview
Adipose cell

9. Other tissues and organs
that produce hormones:
• Adipose cells
• Thymic cells
Endocrine System Overview
Duodenum
Small
intestine
Stomach
Jejunum
Ileum
Heart
Kidneys

10. Long-distance chemical
signals that travel in blood
or lymph
Chemicals that exert
effects on the same cells
that secrete them
Locally acting chemicals
that affect cells nearby
without affecting those
that secrete them
Chemical Messengers
Hormones Autocrines Paracrines
Autocrine and paracrine hormones are not
considered part of endocrine system

11. Hormone Chemical Structure

12. Hormone Chemical Structure
Amino acid-based hormones Steroids
• Amino acid derivatives,
peptides, and proteins
• Synthesized from cholesterol
• Gonadal and adrenocortical
hormones
Two main classes of hormones:
A possible third class, eicosanoids, is considered a hormone by some
scientists, but most classify it as a paracrine.

13. Action of Hormones

14. Action of Hormones
Target cell
Target cell
Hormones alter
target cell activity.
Blood vessel Hormone
Secreting cell
Receptor

15. Action of Hormones
Stimulate synthesis
of enzymes or other
proteins
Induce secretory activity
Activate or
deactivate
enzymes
Stimulate mitosis
Alter plasma membrane permeability
and/or membrane potential by
opening or closing ion channels
Hormone action on target cells may be to:

16. Action of Hormones
1. Water-soluble hormones
(all amino acid-based hormones
except thyroid hormone)
• Act on plasma membrane receptors
• Act via G protein second messengers
• Cannot enter cell
2. Lipid-soluble hormones
(steroid and thyroid hormones)
• Act on intracellular receptors
that directly activate genes
• Can enter cell
Hormones act in one of two ways,
depending on their chemical nature and receptor location.

17. Amino acid-based hormones, except thyroid
hormone, exert effects through second
messenger systems.
Second Messenger Systems

18. Second Messenger Systems
1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone)
Cyclic
AMP
PIP2-
calcium

19. Cyclic AMP (cAMP) Signaling Mechanism
1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone)
Receptor
Hormone
Cytoplasm
G protein complex
(stimulatory)
Adenylate cyclase
AC
ATP cAMP
Adenosine
triphosphate
PKA
Protein kinase
Phosphorylation cascade
Phosphodiesterase
(stops signal
transduction pathway)
-AMP
PDE4 PDE4i
activates Amplification effect

20. PIP2-Calcium Signaling Mechanism
Protein
kinase C
Phosphorylation
of target proteins
Phospholipase C
G protein coupled
receptor
IP3/Ca2+
channel
Ca2+
Ca2+
Ca2+
Ca2+ Ca2+
Ca2+
Ca2+ Ca2+
Ca2+
Protein kinase
Cellular
response
1. Water-soluble hormones (all amino acid-based hormones except thyroid hormone)
DAG
(diacylglycerol)
(Inositol trisphosphate) IP3
Hormone
PIP2
Calmodulin

21. 1. Lipid-soluble steroid hormones and
thyroid hormone can diffuse into
target cells and bind with intracellular
receptors.
2. Receptor-hormone complex enters
nucleus and binds to a specific
region of the DNA.
Intracellular Receptors: Direct Gene Activation
Lipid-soluble
hormone
2. Lipid-soluble hormones (steroid and thyroid hormones)
Cytoplasm
Nucleus
Plasma
membrane
Intracellular
receptor

22. Intracellular Receptors: Direct Gene Activation
Lipid-soluble
hormone
3. Receptor-hormone complex helps
initiate DNA transcription
to produce mRNA.
4. mRNA is then translated into
specific protein.
• Proteins synthesized have
various functions, e.g.: metabolic
activities, structural purposes,
or being exported from the cell.
2. Lipid-soluble hormones (steroid and thyroid hormones)
Cytoplasm
Nucleus
Plasma
membrane
Intracellular
receptor
New
protein

23. Hormone Release

24. Hormone Release
Blood levels of hormones
• Controlled by
negative feedback systems
• Levels vary only within narrow,
desirable range
• Hormone release is triggered by:
• Endocrine gland stimuli
• Nervous system modulation
Homeostasis
Correction:
↑ hormone
3
Imbalance:
trigger
Negative
feedback
4
Hormone
release
2
1

25. Endocrine Gland Stimuli
Humoral
stimuli
Neural
stimuli
Hormonal
stimuli
Endocrine glands are stimulated to synthesize and release
hormones in response to one of 3 stimuli:

26. Parathyroid Hormone (PTH)
Blood vessel
Ca2+
Low
blood
levels of
Ca2+
+
Changing blood levels of ions and nutrients directly stimulate secretion of hormones
PTH
Calcium is released into bloodstream
Rising
levels
of Ca2+
+

27. • Nerve fibers stimulate
hormone release
• Example: sympathetic
nervous system fibers
stimulate adrenal medulla
to secrete catecholamines
Neural Stimuli
CNS (spinal cord)
Medulla of
adrenal gland
Sympathetic
fibers
Capillary
Hormones
e.g., catecholamines

28. Hormonal Stimuli
© by Lecturio
Anterior
pituitary
+
+
+
+
+
+
• Hormones stimulate other
endocrine organs to release
their hormones.
• Example: hormones
of the hypothalamus
Hypothalamus

29. The nervous system can make adjustments to hormone
levels when needed. It can modify stimulation or inhibition
of endocrine glands.
The nervous system can override normal endocrine controls.
Nervous System Modulation

30. Target Cell Specificity

31. Target cells must have specific receptors to which hormones
bind. For example, ACTH receptors are found only on certain
cells of the adrenal cortex, but thyroxin receptors are found
on nearly all cells of the body.
Target Cell Specificity

32. Target Cell Specificity
Affinity (strength)
of binding between
receptor and hormone
Relative number
of receptors on/in
target cell
Blood levels
of hormone
Target cell activation depends on 3 factors:

33. Target Cell Specificity
The amount of hormone can influence
the number of receptors for that
hormone
• Up-regulation: target cells form
more receptors in response to low
hormone levels
• Down-regulation: target cells lose
receptors in response to high
hormone levels
• Desensitizes the target cells to
prevent them from overreacting
to persistently high levels of
hormone
Up-regulation
Down-regulation
Hormone
Target
cell
Hormone
receptor
Time
Time
Hormone Target
cell
Hormone receptor

34. Hormone Circulation
Blood vessel Free hormone
Endocrine cell
Hormones circulate in the blood
either free or bound.
• Steroids and thyroid hormone are
attached to plasma proteins.
• All others circulate without carriers.
Bound to
carrier proteins

35. Hormone Circulation
Blood vessel Free hormone
Endocrine cell
Concentration of circulating hormone
reflects:
• Rate of release
• Speed at which it is inactivated
and removed from the body
Bound to
carrier proteins

36. Degrading enzymes Liver
Kidneys
Hormone Circulation
Hormones can be removed from the blood by:

37. Half-life is the time required for the level of hormone
in blood level to decrease by half. It varies anywhere from a
fraction of a minute to a week, depending on the hormone.
Half-life of Hormone Activity

38. Onset of Hormone Activity
Hormones have different response times:
• Some responses are immediate.
• Some, especially steroids,
can take hours to days.
• Some are inactive until they
enter target cells.

39. Duration of Hormone Activity
The duration of the response is usually
limited.
• It ranges from 10 seconds
to several hours.
• Effects may disappear rapidly
as blood levels drop, but some may
persist for hours at low blood levels.

40. Permissiveness Synergism
• One hormone cannot
exert its effects without
another hormone being
present.
• Example: Reproductive
hormones need thyroid
hormone to have effect.
• More than one hormone
produces the same
effects on a target cell,
causing amplification.
• Example: Glucagon and
epinephrine both cause
the liver to release
glucose.
Interaction of Hormones at Target Cells
Multiple hormones may act on the same target at the same time.
Antagonism
• One or more hormones
oppose the action of
another hormone.
• Example: Insulin
decreases blood
glucose levels while
glucagon increases
blood glucose levels.

41. The Hypothalamus

42. The Hypothalamus and Pituitary Gland
Pituitary gland
Hypothalamus
• The hypothalamus is
connected to the
pituitary gland
(hypophysis)
via a stalk called the
infundibulum.
• The pituitary secretes
at least 8 major
hormones.
Infundibulum
Thalamus

43. The Hypothalamus and Pituitary Gland
Hypothalamus
Infundibulum
Thalamus
Posterior pituitary:
composed of neural
tissue that secretes
neurohormones
Anterior pituitary

44. The Hypothalamus and Pituitary Gland
Anterior pituitary
Hypothalamus
Infundibulum
+ Posterior lobe
= Neurohypophysis
Thalamus
Posterior pituitary

45. The Hypothalamus and Pituitary Gland
Hypothalamus
Infundibulum
+ Posterior lobe
= Neurohypophysis
Thalamus
Posterior pituitary
Anterior pituitary
(adenohypophysis):
consists of glandular
tissue

46. The Hypothalamus and Pituitary Gland
Pituitary gland
• The hypothalamus is
connected to the
pituitary gland
(hypophysis)
via a stalk called the
infundibulum.
• The pituitary secretes
at least 8 major
hormones.
Hypothalamus

47. Posterior Pituitary-hypothalamic Relationships
Capillary
plexus
Hypothalamo-
hypophyseal
tract
Posterior
pituitary
gland
The posterior lobe is
neural tissue derived from
a downgrowth of the brain.
Hormones are stored in
axon terminals in the
posterior pituitary and are
released into the blood
when neurons fire.
• Paraventricular neurons
produce oxytocin (OT)
• Supraoptic neurons
produce antidiuretic
hormone (ADH) ADH release
OT release
Hypothalamus
Infundibulum
Pituitary gland
ADH release
OT release

48. Posterior Pituitary-hypothalamic Relationships
Hypothalamo-
hypophyseal
tract
Antidiuretic hormone (ADH)
Oxytocin (OT)
Hypothalamus
Infundibulum
Pituitary gland
Neurons of
supraoptic nucleus:
ADH production
Neurons of
paraventricular nucleus:
OT production
Posterior pituitary
(neural tissue)
Axon terminals

49. Posterior Pituitary and Hypothalamic Hormones
Paraventricular
neurons produce
oxytocin (OT)
Supraoptic
neurons produce
antidiuretic
hormone (ADH)
Posterior pituitary consists of axon terminals
of neurons from hypothalamic neurons:

50. Oxytocin Effects
• Stimulates uterine contractions
during childbirth
• Triggers milk ejection
• Acts as neurotransmitter in the brain
(PIP2-calcium second messenger
system)
Both positive feedback mechanisms
More oxytocin
needed
Uterine
contractions
3
Posterior
pituitary
Positive
feedback
4
Oxytocin
release
2
1

51. Antidiuretic Hormone (ADH)
Osmoreceptor cells
in hypothalamus
monitor solute concentration
Posterior pituitary:
release of ADH
Kidney tubules
reabsorb more water
and prevent urine formation
Inhibited by:
alcohol, diuretics
High concentrations
cause vasoconstriction
(ADH = vasopressin)
+
Triggered by:
• Solute concentration
= too high
• Pain
• Low blood pressure
• Drugs
+

52. Anterior Pituitary-hypothalamic Relationships
Posterior
pituitary
gland
The hypothalamus secretes
releasing and inhibiting
hormones to the anterior
pituitary to regulate
hormone secretion.
Hypothalamus
Infundibulum
Pituitary gland
Anterior
pituitary
gland

53. The hypothalamus secretes releasing and
inhibiting hormones to the anterior pituitary
to regulate hormone secretion.
Pituitary-hypothalamic Relationships

54. Anterior Pituitary Hormones
All 6 hormones are peptide hormones.
LH FSH TSH PRL GH ACTH
• Luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)
• Thyroid-stimulating hormone (TSH)
• Prolactin (PRL)
• Growth hormone (GH)
• Adrenocorticotropic hormone (ACTH)

55. Anterior Pituitary Hormones
All but growth hormone (GH) activate target cells
via cAMP second messenger system.
LH FSH TSH PRL GH ACTH
• Luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)
• Thyroid-stimulating hormone (TSH)
• Prolactin (PRL)
• Growth hormone (GH)
• Adrenocorticotropic hormone (ACTH)

56. Anterior Pituitary Hormones
All but 2 are tropic hormones (tropins) that regulate
the secretion of other hormones.
LH FSH TSH PRL GH ACTH
• Luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)
• Thyroid-stimulating hormone (TSH)
• Prolactin (PRL)
• Growth hormone (GH)
• Adrenocorticotropic hormone (ACTH)

57. GH is also called somatotropin as it is
produced by somatotropic cells.
It has direct actions on metabolism
and indirect growth-promoting actions.
Growth Hormone (GH)

58. Growth Hormone (GH)
Fatty acids
• Tropic hormone, also called somatotropin
• Origin: somatotropic cells
• Function: direct actions on metabolism and indirect growth-promoting actions
Direct actions
on metabolism
Indirect
actions
on growth
• Glucose-sparing actions decrease rate
of cellular glucose uptake and metabolism
(anti-insulin effects)
• Triggers liver to break down glycogen
into glucose
• Increases blood levels of fatty acids
for use as fuel and encourages cellular
protein synthesis

59. Growth Hormone (GH)
Direct actions
on metabolism
Indirect
actions
on growth
• GH triggers liver, skeletal muscle, and bone
to produce insulin-like growth factors (IGFs)
• IGFs stimulate cellular uptake of nutrients to:
• Synthesize DNA and proteins
needed for cell division
• Form of collagen
• Deposit of bone matrix
• GH stimulates most cells to enlarge and divide
(major targets: bone and skeletal muscle)
• Tropic hormone, also called somatotropin
• Origin: somatotropic cells
• Function: direct actions on metabolism and indirect growth-promoting actions
IGF-1 release

60. Growth Hormone (GH) Regulation of Secretion
GH release or
inhibition is chiefly
regulated by
hypothalamic
hormones on
somatotropic
cells.
Hypothalamus
GHRH
Pituitary
GH
+
GHIH/SST
GH
IGF-I
Liver
+
Stomach
Ghrelin
GH in blood
Glucose
(hypoglycemia)
Amino acids

61. Negative Feedback Loop for TSH
Stimulates
Inhibits
Thyroid gland
Thyroid hormones
Target cells
Anterior pituitary
TSH (Thyrotropin)
Hypothalamus
↑ Thyroid
hormones
GHIH
TRH (Thyrotropin-releasing hormone)

62. • Also called corticotropin
• Origin: corticotropic cells
• Precursor: pro-
opiomelanocortin
• Function: stimulates
adrenal cortex to release
corticosteroids
Adrenocorticotropic Hormone (ACTH)
Anterior pituitary
Adrenal cortex
ACTH
Corticosteroid
Hypothalamus
CRH

63. • Internal and external
factors that alter release
of CRH include fever,
hypoglycemia,
and stressors
Adrenocorticotropic Hormone (ACTH)
Anterior pituitary
Adrenal cortex
ACTH
Corticosteroid
Hypothalamus
CRH

64. Gonadotropins (FSH and LH)
Male testes Female ovaries
+
Anterior
pituitary
Hypothalamus
GnRH
LH, FSH
Sex hormones
+
Testosterone
Estradiol
progesterone
+ +
LH and FSH
both absent
from blood in
prepubertal
boys and girls

65. • Origin: prolactin
cells of anterior
pituitary
• Function:
stimulates milk
production in
females role in
males not well
understood
Prolactin (PRL)
Hypothalamus
Pituitary
Breast
TRH
Dopamine/PIH
PRL
Breast milk production
+
• Mechanical
stimulus
• Increased
estrogen
levels
(suckling)

66. Prolactin (PRL)
Increased estrogen levels stimulate PRL
Reason behind breast swelling and tenderness during menstrual cycle
Rising blood levels toward end of pregnancy
Suckling stimulates PRL release and promotes continued milk production

67. Thyroid Gland

68. Isthmus:
median mass
connecting two
lateral lobes
Thyroid Gland Location and Structure
Follicles:
hollow sphere of epithelial follicular cells
that produce glycoprotein thyroglobulin
Butterfly-shaped gland in anterior neck on the trachea, just inferior to larynx, that consists of:

69. Thyroid Gland Location and Structure
Colloid: fluid of follicle lumen containing
thyroglobulin plus iodine; precursor to
thyroid hormone
Parafollicular cells:
produce hormone
calcitonin
Butterfly-shaped gland in anterior neck on the trachea, just inferior to larynx, that consists of:

70. Location and Structure
PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46700.html, CC BY 4.0, cropped
Parafollicular cell
Colloid-containing
follicle
Follicle cells
(cuboidal epithelium)

71. Thyroid Hormone (TH)
T4 (thyroxine) T3 (triiodothyronine)
Both are iodine-containing amine hormones.

72. Thyroid Hormone (TH)
Target cell
T4
T3
T3
T3
T3
Gene
transcription
Increases basal metabolic
rate and heat production
calorigenic
DNA
Receptor

73. Thyroid Hormone (TH)
Regulates tissue growth
and development
Maintains blood pressure
Critical for normal skeletal and
nervous system development
and reproductive capabilities
Increases adrenergic receptors
in blood vessels

74. Synthesis of Thyroid Hormone (TH)
Follicular cell Colloid
Blood
vessel

75. Iodide
Thyroglobulin
Lumen
Iodine (oxidized
iodide)
MIT
DIT
T4
T3
Lysosome
T4
T3
Golgi
apparatus
Synthesis of Thyroid Hormone (TH)
Bloodstream
ER
Thyroxine-binding
globulins (TBGs)
Tyrosine (part of thyroglobulin)

76. T4 and T3 are transported by thyroxine-binding globulins (TBGs).
• Both bind to target receptors, but T3 is 10 times more active than T4.
• Peripheral tissues have enzymes needed to convert T4 to T3.
• Enzymes remove one iodine atom from thyroxine.
Thyroid Hormone (TH) Transport and Regulation

77. Negative Feedback Control
Hypothalamus
Anterior pituitary
Thyroid gland
TSH
T3 + T4
↑ TH levels
GHIH
Dopamine
↑ Cortisol
↑ Iodide
↓ TH levels
TRH
+ +
+
+
+

78. • Produced by parafollicular (C)
cells in response to high Ca2+
levels
• Antagonist to parathyroid
hormone (PTH)
Calcitonin
Parafollicular cell
Colloid-containing
follicle
Follicle cells
(cuboidal epithelium)

79. No known physiological role in
humans at normal physiological
levels, but at higher-than-normal
doses:
• Inhibits osteoclast activity and
prevents release of Ca2+ from
bone matrix
• Stimulates Ca2+ uptake and
incorporation into bone matrix
Calcitonin
Parafollicular cell
Colloid-containing
follicle
Follicle cells
(cuboidal epithelium)

80. Calcitonin
Thyroid gland
Intestine
Bone
Kidney
Blood vessel
Ca2+
Calcitonin
Inhibits Ca2+
reabsorption in the
kidney (excreted
in the urine)
Promotes deposition
of Ca2+ into bones
(inhibits osteoblasts
and stimulates
osteoclasts)
Lowers Ca2+
levels in the blood
Inhibits Ca2+
absorption by
the intestines

81. Parathyroid Gland

82. • 4 - 8 tiny yellow-brown
glands embedded in a
posterior surface of the
thyroid.
• Contain oxyphil cells
(function not clear) and
parathyroid cells, which
secrete parathyroid
hormone (PTH), or
parathormone
Parathyroid Gland
Hyoid bone
Thyroid
cartilage
Cricoid
cartilage
Right
parathyroid
glands
Left
parathyroid
glands

83. • 4 - 8 tiny yellow-brown glands
embedded in the posterior
aspect of thyroid
• Contain oxyphil cells (function
not clear) and parathyroid cells,
which secrete parathyroid
hormone (PTH)
Parathyroid Gland
Oxyphil cells
Blood vessel
Parathyroid
(chief) cell

84. • PTH is the most important
hormone in Ca2+ homeostasis
• Secreted in response to
low blood levels of Ca2+
• Inhibited by rising levels
of Ca2+
• Target organs: skeleton,
kidneys, and intestine
Parathyroid Hormone (PTH)
Oxyphil cells
Blood vessel
Parathyroid
(chief) cell

85. Parathyroid Hormone (PTH)
Parathyroid glands (located on the back of the thyroid gland)
Intestine
Bone
Kidney
Blood vessel
Ca2+
Ca2+
Ca2+
Rising
levels
of Ca2+
Low
blood
levels of
Ca2+
PTH
Vitamin D
PTH
+ +

86. Functions of Parathyroid Hormone (PTH)
Parathyroid glands (located on the back of the thyroid gland)
Intestine
Bone
Kidney
Blood vessel
Ca2+
Ca2+
Ca2+
PTH
Vitamin D
PTH

87. Adrenal Gland

88. Adrenal Gland
Adrenal gland
Adrenal cortex
3 layers of glandular
tissue that synthesize
and secrete several
different hormones
Nervous tissue that
is part of sympathetic
nervous system
Paired, pyramid-shaped organs
atop kidneys (suprarenal glands)
Adrenal medulla
Superior surface of kidney

89. • Produces over 24 different hormones
collectively called corticosteroids.
• Steroid hormones are not stored in cells.
• The rate of release depends on the
rate of synthesis.
Adrenal Cortex
Adrenal gland
Superior surface of kidney
Adrenal
cortex
Adrenal
medulla

90. Adrenal Cortex
PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46684.html, CC BY 4.0, cropped
Adrenal medulla
Three layers of cortical cells produce different corticosteroids.
Zona glomerulosa Mineralocorticoids
Zona fasciculata Glucocorticoids
Zona reticularis Gonadocorticoids

91. Adrenal Cortex Mineralocorticoids
K+ (potassium)
• Sets resting membrane
potential of cells
Na+ (sodium)
• Affects ECF volume, blood
volume, blood pressure,
and levels of other ions
(K+, H+, HCO3 , and Cl )
Function: regulate electrolyte concentrations in ECF
primarily Na+ (sodium) and K+ (potassium)

92. Adrenal Cortex Mineralocorticoids
Aldosterone
↑ Na+ reabsorption
↑ K+ elimination
by kidneys
Results in increased
blood volume
and blood pressure

93. Effects of aldosterone are short-lived.
It stimulates synthesis and activation of
Na+/K+ ATPase transport pumps, where
Na+ is exchanged for K+.
Adrenal Cortex Mineralocorticoids

94. Adrenal Cortex Mineralocorticoids
Aldosterone
NKA
3 Na+
2 K+
Aldosterone effects
within the cell
Synthesis and
activation of
the ATPase
Sodium-potassium
pump

95. Aldosterone Secretion
Renin-
angiotensin-
aldosterone
mechanism
Plasma
concentration
of K+
ACTH
Atrial natriuretic
peptide
Factors that regulate aldosterone secretion:

96. Factors that Regulate Aldosterone Secretion: RAAM
↓ Blood pressure
Renin
Angiotensinogen
(plasma protein)
Angiotensin II
↑ Aldosterone secretion
Release
Cleaves off
parts of
Triggers
cascade

97. Factors that Regulate Aldosterone Secretion
↑ Aldosterone secretion
↑ Aldosterone secretion
ACTH
↓ Aldosterone secretion
High blood
pressure
↑ K+ plasma concentration

98. Adrenal Cortex Glucocorticoids
Glucocorticoids
Maintain blood pressure
by increasing action of
vasoconstrictors
Keep blood glucose
levels constant
Influence metabolism of
most cells and help us
resist stressors

99. Adrenal Cortex Glucocorticoids
Glucocorticoids
Cortisol (hydrocortisone) Corticosterone
Cortisone
Only glucocorticoid in
significant amounts in
humans

100. Adrenal Cortex Regulation of Secretion
CRH ACTH
Stress
Metabolic
effects
Cortisol
HPA axis Anterior
pituitary
Hypothalamus
Adrenal
gland
Kidney
+
+
+
+
+
+

101. Adrenal Cortex Actions of Cortisol
Formation of glucose
from fats and proteins
Rise in blood pressure
Enhances vasoconstriction
Gluconeogenesis
Metabolic effects
Cortisol

102. Adrenal Cortex Actions of Cortisol
• Depress cartilage and bone formation
• Inhibit inflammation by decreasing release of inflammatory chemicals
• Depress immune system
• Disrupt normal cardiovascular, neural, and gastrointestinal functions
Excessive levels of glucocorticoids

103. Glucocorticoid drugs can control
symptoms of many inflammatory diseases
(arthritis, allergies) but can also cause
undesirable effects.
Adrenal Cortex Actions of Cortisol

104. Adrenal Cortex Gonadocorticoids
Adrenal
cortex
Weak androgens (male sex hormones) are converted
to testosterone in tissue cells, some to estrogens.
May contribute to:
• Onset of puberty and appearance
of secondary sex characteristics
• Sex drive in women
• Source of estrogens in
postmenopausal women

105. Medullary chromaffin cells synthesize
catecholamines: epinephrine (80%)
and norepinephrine (20%)
Adrenal Medulla
Effects of catecholamines
• Vasoconstriction
• Increased heart rate
• Increased blood glucose levels
• Blood diverted to brain, heart,
and skeletal muscle
20%
80%

106. Adrenal Medulla
© by Lecturio
Both hormones have basically same effects, but:
Epinephrine is more a stimulator of metabolic
activities (Example: bronchial dilation,
and blood flow to skeletal muscles and heart).
Norepinephrine has more of an influence
on peripheral vasoconstriction and blood
pressure.
Responses to stressors are brief,
unlike adrenal cortical hormones.
Adrenal medulla

107. Pineal Gland

108. The pineal gland is a small gland that is hanging from the
roof of the third ventricle.
Pinealocytes secrete melatonin, derived from serotonin.
Pineal Gland

109. Pineal Gland
Pineal gland
Pinealocytes
secrete melatonin.
Third ventricle

110. Pineal Gland
Day/night cycles
Timing of sexual maturation
and puberty
Production of antioxidant and
detoxification molecules in cells
Physiological processes that show
rhythmic variations (body
temperature, sleep, appetite)
Melatonin may affect:

111. Other Endocrine Organs

112. The pancreas is a triangular gland located
partially behind the stomach.
It has both exocrine and endocrine cells.
Other Endocrine Organs Pancreas

113. Other Endocrine Organs Pancreas
© by Lecturio
Lobules
Head
Body
Tail
Pancreatic
duct
Common
bile duct
Duodenal
papilla

114. Pancreas
Acinar cells (exocrine)
produce enzyme-rich juice for digestion
Pancreatic islets (islets of Langerhans)
contain endocrine cells
Alpha () cells Beta () cells
Produce glucagon
(hyperglycemic hormone)
Produce insulin
(hypoglycemic hormone)

115. Pancreatic Islets
PhilSchatz, Anatomie, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, cropped
The alpha and beta cells appear as little islands among the acinar cells.
Alpha cells
Beta cells
Exocrine acinus

116. Extremely potent hyperglycemic agent
• Triggered by decreased blood glucose
levels, rising amino acid levels,
or sympathetic nervous system
Pancreatic Islets Glucagon
PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited
Splenic artery
Glucagon release:
alpha cells of pancreas release glucagon

117. Raises blood glucose levels
by targeting liver to:
• Break down glycogen into glucose
(glycogenolysis)
• Synthesize glucose from lactic
acid and other noncarbohydrates
(gluconeogenesis)
• Release glucose into the blood
Pancreatic Islets Glucagon
PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited
Glucagon release:
alpha cells of pancreas release glucagon
Splenic artery

118. Pancreatic Islets Glucagon
Beta
cell
Glucagon
Hypoglycemia, GIP, amino acids
Alpha
cell
Brain
• Food intake ↓
• Appetite ↓
• Satiety ↑
Pancreas
• Insulin
secretion ↑
Liver
• Glucose production ↑
• Glucose breakdown ↓
• Lipid breakdown ↑
• Lipid production ↓
• Ketone body production ↑
• Amino acid breakdown ↓
Brown
adipose tissue
• Resting
energy
expenditure ↑
Heart
• Heart rate (↑)
• Contractility (↑)

119. • Secreted when blood glucose
levels increase
• Synthesized as proinsulin that is
then modified
Pancreatic Islets Insulin
PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited
Splenic artery
Insulin release:
beta cells of pancreas release insulin

120. Pancreatic Islets Insulin
Beta
cell
Insulin
Enhances membrane
transport of glucose
into fat and muscle cells
Inhibits conversion of
amino acids or fats to glucose
Smooth ER
Rough ER
Inhibits breakdown of
glycogen to glucose
Liver
Mitochondria

121. Pancreatic Islets Insulin
Beta
cell
Insulin
Plays a role in neuronal development,
learning, and memory
Binding to tyrosine kinase enzyme
receptor triggers cell to increase
glucose uptake

122. Insulin also triggers cells to:
• Catalyze oxidation of glucose
for ATP production: first priority
• Polymerize glucose to form
glycogen
• Convert glucose to fat
(particularly in adipose tissue)
Pancreatic Islets Insulin
PhilSchatz, Anatomy, https://philschatz.com/anatomy-book/contents/m46685.html, CC BY 4.0, edited
Insulin release:
beta cells of pancreas release insulin
Splenic artery

123. Pancreatic Islets Insulin
Beta
cell
Insulin
Catalyze oxidation of glucose
for ATP production: first priority
Convert glucose to fat
(particularly in adipose tissue)
Polymerize glucose to form glycogen

124. Pancreatic Islets Insulin
Factors that influence insulin release
Elevated blood glucose
levels: primary stimulus
Rising blood levels of
amino acids and fatty
acids
Hormones glucagon,
epinephrine, growth
hormone, thyroxine,
glucocorticoids
Somatostatin and
sympathetic nervous
system inhibit insulin
release
Release of acetylcholine
by parasympathetic
nerve fibers

125. The Gonads and Placenta
• Maturation of reproductive organs
• Appearance of secondary sexual
characteristics
• With progesterone, causes breast
development and cyclic changes
in uterine mucosa
• Initiates maturation of male
reproductive organs
• Causes appearance of male secondary
sexual characteristics and sex drive
• Necessary for normal sperm production
• Maintains reproductive organs
in functional state
Progesterone Testosterone
Estrogen
Estrogen Progesterone
Gonads
Ovaries (female) Testes (male)

126. The Placenta secretes estrogens, progesterone,
and human chorionic gonadotropin (hCG)
Placenta

127. Most endocrine organs operate well until old age, however:
• ↓ GH (muscle atrophy)
• ↓ TH (lower basal metabolic rates)
• = PTH (lack of estrogen in older women
makes them more vulnerable to
bone-demineralizing effects of PTH)
• ↓ Glucose tolerance
• Ovaries: become unresponsive to
gonadotropins (estrogen deficiency)
• ↓ Testosterone (effect is not
usually seen until very old age)
Endocrine Function throughout Life

128. In a Nutshell
 The endocrine system acts with the
nervous system. It coordinates and
integrates the activity of body cells.
 Hormones act by binding to specific
target cells and altering cell activity.
 There are several endocrine glands
throughout the body, which secrete
specific hormones and target specific
cells.

129. In a Nutshell
 The pituitary gland secretes 8 different
hormones: 2 posterior pituitary
hormones and 6 anterior pituitary
hormones.
 The thyroid gland secretes thyroid
hormone (metabolic regulator).
 The parathyroid secretes parathyroid
hormone (Ca2+ levels).

130. In a Nutshell
 The adrenal gland secretes hormones
responsible for several different body
activities (regulation of blood pressure
and stress response).
 The pineal gland secretes the hormone
melatonin (circadian rhythm).
 Other organs in the body with
endocrine function include the
pancreas, gonads, and placenta.