bsu unversity russia

1. Endocrine system
• LECTURE

2. • Formation of multicell organisms in the
evolutionary development brought about the
need for some mechanisms that could establish
relationships between both individual cells in
tissues and individual organs in the body.
• In result of the evolutionary selection two
mechanisms of integration of elements into one
whole have been formed – mechanisms of neural
and humoral regulation.

3. What is the difference between nerve and
hormon control?

4. NERVOUS SYSTEM AND ENDOCRINE SYSTEM
The nervous system coordinates fast, precise
response. Electrical impulses generated by this
system are very rapid and of short duration
(milliseconds).
The endocrine system regulates metabolic
activity within the cells of organs and tissues. In
contrast to the nervous system, this system
coordinates activities that require longer duration
(hours, days) rather than speed.

5. Humoral regulation
• is a complex of physiological, biochemical and
biophysical mechanisms that change
conditions of individual cells, tissues, organs
and systems by acting through chemical
compounds in the internal environment of
the body.

6. Humoral regulation
• The concept of the internal environment was brought into
science by the famous French physiologist Claude Bernard.
He understood the internal environment as a complex of
biological fluids – blood, lymph and tissue fluid.
• Chemical substances that can participate in humoral
regulatory mechanisms fall into 3 classes:
1) water-soluble salts, or electrolytes;
2) products of metabolism, or metabolites;
3) biologically active substances including hormones.

7. MECHANISMS OF INTERCELLULAR
COMMUNICATION
• The maintenance of homeostasis requires the
coordination of cells, tissues, and organs.
Most communication between cells is
achieved by the release of chemical
messengers.

8. MECHANISMS OF INTERCELLULAR
COMMUNICATION
• Autocrine signaling occurs when a cell
regulates itself by the release of a chemical
messenger

9. MECHANISMS OF INTERCELLULAR
COMMUNICATION
• Paracrine communication involves cells that secrete
chemical transmitters locally into the surrounding
interstitial fluid; the target cells are near “neighbors”
and are reached by diffusion of the hormone rather
than by its transport in the blood.

10. MECHANISMS OF INTERCELLULAR
COMMUNICATION
• Neuroendocrine control is a hybrid of neural and
endocrine communication in which neurons release
a chemical transmitter (neurohormone) that is
carried to a distant site of action via the blood; for
example, the release of an antidiuretic hormone
from the axon terminals in the posterior pituitary
gland.

11. MECHANISMS OF INTERCELLULAR
COMMUNICATION
• Endocrine communication occurs by the
release of a chemical transmitter (hormone)
by specialized endocrine cells and is carried
to a distant site of action via the blood

12. ENDOCRINE SYSTEM

13. ENDOCRINE SYSTEM
The endocrine system carries out its effects
through the production of hormones, chemical
messengers that exert a regulatory effect on the
cells of the body, secreted from endocrine
glands, which are ductless structures.
Hormones are released directly into the blood.

14. THE MAJOR PROCESSES THAT ENDOCRINE SYSTEM
CONTROL AND INTEGRATE:
1. Reproduction
2. Growth and development
3. Maintenance of electrolyte, water, and
nutrient balance of the blood
4. Regulation of cellular metabolism and energy
balance
5. Mobilization of body defenses

15.  The Endocrine
Glands are the
organs of the
Endocrine System.
 They produce and
secrete (release)
Hormones.
 They are located all
over your body.
Endocrine glands

16. Copyright 2009, John Wiley & Sons, Inc.
Hormone Activity
• Hormones affect only specific target tissues
with specific receptors
• Receptors constantly synthesized and broken
down

17. Target tissue
Target tissue of a certain hormone is the tissue,
which contains the specific receptors of that
hormone

18. Hormone receptors
Definition:
Cell-associated recognition molecules which are protein in
nature.
Functional sites:
Two functional sites:
• Recognition site: It binds the hormone specifically.
• Signaling site: It couples hormone binding to intracellular
effect.

19. Hormone receptors
Location:
Receptors may be:
• Intracellular receptors: (in the cytosol or in the
nucleus)
• Cell-membrane receptors: (in the plasma
membrane)

20. Biochemical classification of hormones
Hormones are classified into three biochemical
categories :
1. Steroids
2. Proteins/peptides
3. Amines

21. Steroid hormones
• Steroid hormones are produced by the adrenal cortex,
testes, ovaries and placenta.
• Synthesized from cholesterol, these hormones are lipid
soluble.
• They cross cell membranes readily and bind to receptors
found intracellularly.
• These hormones are transported in the blood bound to
proteins. Steroid hormones are not typically preformed and
stored for future use within the endocrine gland.
• Steroid hormones are absorbed easily by the
gastrointestinal tract and therefore may be administered
orally.

22. Protein/peptide hormones
• Protein/peptide hormones are derived from amino acids.
• These hormones are preformed and stored for future use in
membrane-bound secretory granules. When needed, they are
released by exocytosis.
• Protein/peptide hormones are water soluble, circulate in the
blood predominantly in an unbound form, and thus tend to
have short half-lives.
• Because these hormones are unable to cross the cell
membranes of their target tissues, they bind to receptors on
the membrane surface.
• Protein/peptide hormones cannot be administered orally
because they would be digested in the gastrointestinal tract.
Instead, they are usually administered by injection (e.g.,
insulin). Because small peptides are able to cross through
mucus membranes, they may be given sublingually or
intranasally.

23. Amine hormones
• Amine hormones include the thyroid hormones and the
catecholamines.
• The thyroid hormones tend to be biologically similar to the steroid
hormones. They are mainly insoluble in the blood and are transported
predominantly (>99%) bound to proteins.
• Thyroid hormones cross cell membranes to bind with intracellular
receptors and may be administered orally.
• Thyroid hormones have the unique property of being stored
extracellularly in the thyroid gland.
• The catecholamines are biologically similar to protein/peptide
hormones.
• Catecholamines are soluble in the blood and are transported in an
unbound form.
• Catecholamines do not cross cell membranes, they bind to receptors
on the membrane surface.
• Catecholamines are stored intracellularly in secretory granules for
future use.

24. Distinguishing Features of Steroid,
Protein/Peptide, and Amine Hormones

25. Functional classification of hormones
Hormones are classified into two
functional categories:
• Trophic hormones
• Nontrophic hormones

26. Trophic hormones
• A trophic hormone acts on another endocrine gland to
stimulate secretion of its hormone.
• For example, thyrotropin, or thyroid-stimulating
hormone (TSH), stimulates the secretion of thyroid
hormones. Adrenocorticotropin, or
adrenocorticotropic hormone (ACTH), stimulates the
adrenal cortex to secrete the hormone cortisol. Both
trophic hormones are produced by the pituitary gland;
in fact, many trophic hormones are secreted by the
pituitary. The pituitary gland is sometimes referred to
as the “master gland” because its hormones regulate
the activity of other endocrine glands.

27. Nontrophic hormones
• A nontrophic hormone acts on nonendocrine
target tissues.
• For example, parathormone released from
the parathyroid glands acts on bone tissue to
stimulate the release of calcium into the
blood. Aldosterone released from the cortical
region of the adrenal glands acts on the
kidney to stimulate the reabsorption of
sodium into the blood.

28. Mechanisms of hormone action
• Response depends on both hormone and target cell
• Lipid-soluble hormones bind to receptors inside target cells
• Water-soluble hormones bind to receptors on the plasma
membrane
– Activates second messenger system
– Amplification of original small signal
• Responsiveness of target cell depends on
– Hormone’s concentration
– Abundance of target cell receptors
– Influence exerted by other hormones
• Permissive, synergistic and antagonistic effects

29. Copyright 2009, John Wiley & Sons, Inc.
Lipid-soluble Hormones
(steroid and thyroid hormones)
Mechanisms of hormone action
act on receptors inside the cell, which directly
activate genes

30. 1 Lipid-soluble
hormone
diffuses into cell
Blood capillary
Target cell
Transport
protein
Free hormone
1 Lipid-soluble
hormone
diffuses into cell
Blood capillary
Activated
receptor-hormone
complex alters
gene expression
Nucleus
Receptor
mRNA
DNA
Cytosol
Target cell
Transport
protein
Free hormone
2
1 Lipid-soluble
hormone
diffuses into cell
Blood capillary
Activated
receptor-hormone
complex alters
gene expression
Nucleus
Receptor
mRNA
Newly formed
mRNA directs
synthesis of
specific proteins
on ribosomes
DNA
Cytosol
Target cell
Transport
protein
Free hormone
Ribosome
2
3
1 Lipid-soluble
hormone
diffuses into cell
Blood capillary
Activated
receptor-hormone
complex alters
gene expression
Nucleus
Receptor
mRNA
Newly formed
mRNA directs
synthesis of
specific proteins
on ribosomes
DNA
Cytosol
Target cell
New proteins alter
cell's activity
Transport
protein
Free hormone
Ribosome
New
protein
2
3
4

31. Water-soluble hormones
- (all amino acid–based hormones except thyroid
hormone) act on receptors in the plasma
membrane. These receptors are usually coupled
via regulatory molecules called G proteins to
one or more intra- cellular second messengers
which mediate the target cell’s response.
Mechanisms of hormone action

32. Water-soluble
hormone
Receptor
G protein
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
1
Water-soluble
hormone
Receptor
G protein
cAMP
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP
1
2
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP
1
2
3 Activated
protein
kinases
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Activated
protein
kinases
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Activated protein
kinases
phosphorylate
cellular proteins
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP
1
2
4
3
Protein— P
ADP
Protein
ATP
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Activated
protein
kinases
Protein—
Second messenger
Activated adenylate
cyclase converts
ATP to cAMP
Activated protein
kinases
phosphorylate
cellular proteins
Millions of phosphorylated
proteins cause reactions that
produce physiological responses
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
P
ADP
Protein
ATP
ATP
1
2
4
3
5
Water-soluble
hormone
Receptor
cAMP serves as a
second messenger
to activate protein
kinases
G protein
Protein kinases
cAMP
Activated
protein
kinases
Protein—
Second messenger
Phosphodiesterase
inactivates cAMP
Activated adenylate
cyclase converts
ATP to cAMP
Activated protein
kinases
phosphorylate
cellular proteins
Millions of phosphorylated
proteins cause reactions that
produce physiological responses
Blood capillary
Binding of hormone (first messenger)
to its receptor activates G protein,
which activates adenylate cyclase
Adenylate cyclase
Target cell
P
ADP
Protein
ATP
ATP
1
2
6
4
3
5

33. ENDOCRINE GLANDS

34. Hypothalamus and Pituitary Gland
• Hypothalamus is a major link between
nervous and endocrine system
• Pituitary attached to hypothalamus by
infundibulum
• Pituitary gland is divided into two divisions:
– Anterior pituitary or adenohypophysis
– Posterior pituitary or neurohypophysis

35. Hypothalamus and Pituitary Gland

36. Copyright 2009, John Wiley & Sons, Inc.
Anterior pituitary
– Release of hormones stimulated by releasing and
inhibiting hormones from the hypothalamus
– Also regulated by negative feedback
– Hypothalamic hormones made by neurosecretory
cells transported by hypophyseal portal system
– Anterior pituitary hormones that act on other
endocrine systems called tropic hormones

37. Copyright 2009, John Wiley & Sons, Inc.
Hormones of the Anterior Pituitary
• Human growth hormone (hGH) or somatostatin
– Stimulates secretion of insulin-like growth factors (IGFs) that
promote growth, protein synthesis
• Thyroid-stimulating hormone (TSH) or thyrotropin
– Stimulates synthesis and secretion of thyroid hormones by
thyroid
• Follicle-stimulating hormone (FSH)
– Ovaries initiates development of oocytes, testes stimulates
testosterone production
• Luteinizing hormone (LH)
– Ovaries stimulates ovulation, testes stimulates testosterone
production

38. Copyright 2009, John Wiley & Sons, Inc.
Hormones of the Anterior Pituitary
• Prolactin (PRL)
– Promotes milk secretion by mammary glands
• Adrenocorticotropic hormone (ACTH) or
corticotropin
– Stimulates glucocorticoid secretion by adrenal
cortex
• Melanocyte-stimulating Hormone (MSH)
– Unknown role in humans

39. Copyright 2009, John Wiley & Sons, Inc.
Negative Feedback Regulation

40. Copyright 2009, John Wiley & Sons, Inc.
Posterior pituitary
– Does not synthesize hormones
– Stores and releases hormones made by the
hypothalamus
• Transported along hypothalamohypophyseal tract
– Oxytocin (OT)
– Antidiuretic hormone (ADH) or vasopressin

41. Copyright 2009, John Wiley & Sons, Inc.
Oxytocin (OT)
– During and after delivery of baby affects uterus
and breasts
– Enhances smooth muscle contraction in wall of
uterus
– Stimulates milk ejection from mammary glands

42. Copyright 2009, John Wiley & Sons, Inc.
Antidiuretic Hormone (ADH)
– Decreases urine production by causing the kindeys to
return more water to the blood
– Also decreases water lost through sweating and
constriction of arterioles which increases blood pressure
(vasopressin)

43. Copyright 2009, John Wiley & Sons, Inc.
Thyroid Gland
• Located inferior to larynx
• 2 lobes connected by isthmus
• Thyroid follicles produce thyroid hormones
– Thyroxine or tetraiodothyronine (T4)
– Triiodothyronine (T3)
• Both increase BMR, stimulate protein synthesis, increase use of
glucose and fatty acids for ATP production
• Parafollicular cells or C cells produce calcitonin
– Lowers blood Ca2+ by inhibiting bone resorption

44. Copyright 2009, John Wiley & Sons, Inc.
Thyroid Gland

45. Thyroid hormone has many metabolic effects in
the body:
Growth and maturation
• Perinatal lung maturation
• Normal skeletal growth
Neurological
• Normal fetal and neonatal brain development
• Regulation of neuronal proliferation and differentiation, myelinogenesis, neuronal outgrowth,
and synapse formation
• Normal CNS function in adults
Sympathetic nervous system function
• Increase in the number of b-adrenergic receptors
• Increase in heart rate
• Tremor
• Sweating
Cardiovascular system
• Increase in heart rate
• Increase in myocardial contractility
• Increase in cardiac output
Metabolism
• Increase in basal metabolic rate
Stimulation of all metabolic pathways, both anabolic and catabolic • Increase in carbohydrate
utilization
• Increase in oxygen consumption
• Increase in heat production

46. Copyright 2009, John Wiley & Sons, Inc.
Control of thyroid hormone secretion
– Thyrotropin-releasing hormone (TRH) from
hypothalamus
– Thyroid-stimulating hormone (TSH) from anterior
pituitary
– Situations that increase ATP demand also increase
secretion of thyroid hormones

47. Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
Anterior
pituitary
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
Anterior
pituitary
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
TSH released into
blood stimulates
thyroid follicular cells
Thyroid
follicle
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
Anterior
pituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
T3 and T4
released into
blood by
follicular cells
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
TSH released into
blood stimulates
thyroid follicular cells
Thyroid
follicle
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
Anterior
pituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
4 T3 and T4
released into
blood by
follicular cells
Elevated
T3inhibits
release of
TRH and
TSH
(negative
feedback)
TRH, carried
by hypophyseal
portal veins to
anterior pituitary,
stimulates
release of TSH
by thyrotrophs
TSH released into
blood stimulates
thyroid follicular cells
Thyroid
follicle
Low blood levels of T3
and T3 or low metabolic
rate stimulate release of
Hypothalamus
Anterior
pituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
5
4

48. Parathyroid glands
Function is to control metabolism of calcium
– Necessary for normal nerve and muscle function, blood
clotting, healthy bones and teeth
• Located in back of thyroid gland (in neck)
• Usually 4
• Hormone released is parathormone (PTH)
• Undersecretion of parathormone results in nerve
disorders, brittle bones and clotting problems

49. Copyright 2009, John Wiley & Sons, Inc.
Adrenal Glands
• Located at the top of each kidney
• There are 2 structurally and
functionally distinct regions
– Adrenal cortex
Hormons:
Mineralocorticoids affect mineral homeostasis
Glucocorticoids affect glucose homeostasis
(cortisol)
Androgens have masculinzing effects
– Adrenal medulla
Hormons:
• Epinephrine
• Norepinephrine
Modified sympathetic ganglion of autonomic
nervous system
Intensifies sympathetic responses

50. Copyright 2009, John Wiley & Sons, Inc.
Pineal Gland
• Attached to roof of 3rd ventricle of brain at
midline
• Masses of neuroglia and pinealocytes
• Melatonin – amine hormone derived from
serotonin
• Appears to contribute to setting biological
clock
• More melatonin liberated during darkness
than light

51. Copyright 2009, John Wiley & Sons, Inc.
􏰒􏰒 Pancreas 􏰒 􏰒􏰒􏰒􏰒􏰒 􏰒􏰒 􏰒􏰒􏰒􏰒􏰒􏰒􏰒􏰒 􏰒􏰒􏰒
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Is both exocrine and endocrine gland
• Roughly 99% of cells produce digestive enzymes
• Endocrine function of pancreas is performed by the islets
of Langerhans. Human pancreas contains about 1 to 2
million islets.
• Pancreatic islets or islets of Langerhans consist of four types
of cells:
– Alpha or A cells secrete glucagon – raises blood sugar
– Beta or B cells secrete insulin – lowers blood sugar
– Delta or D cells secrete somatostatin – inhibits both insulin and
glucagon
– F cells secrete pancreatic polypeptide – inhibits somatostatin,
gallbladder contraction, and secretion of pancreatic digestive enzymes

52. Pancreas

53. Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
1
GLUCAGON
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
GLUCAGON
1
2 Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
GLUCAGON
1
2
3
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
GLUCAGON
1
2
3
4
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
GLUCAGON
1 5
2
3
4
INSULIN
Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULINGLUCAGON
1 5
2
3
4
6 Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
Blood glucose level falls
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
Insulin acts on various
body cells to:
• accelerate facilitated
diffusion of glucose
into cells
• speed conversion of
glucose into glycogen
(glycogenesis)
• increase uptake of
amino acids and increase
protein synthesis
• speed synthesis of fatty
acids (lipogenesis)
• slow glycogenolysis
• slow gluconeogenesis
If blood glucose continues
to fall, hypoglycemia
inhibits release of
insulin
Blood glucose level falls
Glucagon acts on
hepatocytes
(liver cells) to:
• convert glycogen
into glucose
(glycogenolysis)
• form glucose from
lactic acid and
certain amino acids
(gluconeogenesis)
Glucose released
by hepatocytes
raises blood glucose
level to normal
If blood glucose
continues to rise,
hyperglycemia inhibits
release of glucagon
Low blood glucose
(hypoglycemia)
stimulates alpha
cells to secrete
High blood glucose
(hyperglycemia)
stimulates beta cells
to secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
8

54. Copyright 2009, John Wiley & Sons, Inc.
Ovaries and Testes
• Ovaries produce 2 estrogens (estradiol and estrone)
and progesterone
– With FSH and LH regulate menstrual cycle,
maintain pregnancy, prepare mammary glands for
lactation, maintain female secondary sex
characteristics
• Testes produce testosterone – regulates sperm
production and maintains male secondary sex
characteristics

55. QUESTIONS
1. The humoral regulation.
2. Types of intercellural cell communication (autocrine, paracrine, endocrine, neurocrine).
3. The endocrine system. Functions. Endocrine glands.
4. Chemical hormone classification. Amine Hormones, Peptide and Protein Hormones, Steroid
Hormones (Structures, Synthesis).
5. Distinguish between a trophic and a nontrophic hormone.
6. Feedback Control of Hormone Secretion.
7. The two primary mechanisms by which hormones carry out their effects:
a) Plasma Membrane Receptors and Second-Messenger Systems: Adenylate Cyclase–cAMP
Second Messenger System
b) Intracellular Receptors and Direct Gene Activation.
7. The Pituitary Gland and Hypothalamus.
8. The Thyroid Gland.
9. The Parathyroid Glands.
10. The Adrenal Glands.
11. The Pineal Gland.
12. Other Endocrine Glands and Tissues: Pancreas, Gonads and Placenta.