The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neural control center for all endocrine systems.

1. The Endocrine System
Presented by : Jagruti Marathe

2. • Exocrine glands secrete their products into
ducts.
– Sudoriferous (sweat) glands
– Sebaceous (oil) glands
– Mucous glands
– Digestive glands
None of these are hormones!
Endocrine is NOT Exocrine

3. • Endocrinology is the study of ductless glands or
tissues and their hormonal products
• Endocrine gland – composed of a prominent
parenchyma of secretory cells, connective tissue,
blood vessels and nerves.
• Endocrine glands are ductless and secrete their
products directly into the blood.
– Can include any group of cells that secrete a hormone.
A Little Endocrine :

4. The endocrine system is made up of glands and the
hormones they secrete. Although the endocrine
glands are the primary hormone producers, the brain,
heart, lungs, liver, skin, thymus, gastrointestinal
mucosa, and placenta also produce and release
hormones.

5. The primary endocrine glands are the pituitary (the
master gland), pineal, thyroid, parathyroid, islets of
Langerhans, adrenals, ovaries in the female and testes
in the male.
The function of the endocrine system is the
production and regulation of chemical substances
called hormones.

6. • Endocrine glands secrete hormones.
– Do not have ducts
– Secrete their hormones directly into the
interstitial fluid that surrounds them.
– The hormones then diffuse into the blood stream
through capillaries and are carried to target cells
throughout the body.
Endocrine Glands

7. Endocrine Glands & Organs
• Classic Glands
– Pituitary
– Thyroid
– Parathyroid
– Islets of Langerhans
– Adrenal Glands
– Gonads
– Placenta
• Organs w/ Endocrine
Functions
– Brain
– Heart
– Liver
– GI Tract
– Kidneys
– Adipose (fat)

8. Endocrine Glands/Organs

9. HORMONE
A hormone is a chemical transmitter.
It is released in small amounts from glands,
and is transported in the bloodstream to
target organs or other cells.
Hormones are chemical messengers,
transferring information and instructions from
one set of cells to another.
Hormones regulate growth, development,
mood, tissue function, metabolism, and sexual
function.

10. HORMONE
Hyposecretion or hypersecretion of
any hormone can be harmful to the
body. Controlling the production
of hormones can treat many
hormonal disorders in the body.

11. Hormones…
The endocrine system and nervous system work together to help maintain
homeostasis… balance.
The hypothalamus is a collection of specialized cells located in the brain, and is the
primary link between the two systems.
It produces chemicals that either stimulate or suppress hormone secretions of the
pituitary gland.
The pituitary gland has 2
lobes…

12. • Chemical messenger is any substance
produced by a cell that plays a physiological
role in the control of the activity of a another
cell.
• Hormone is any substance elaborated by one
cell to regulate another cell and may be
delivered in an endocrine, paracrine,
autocrine or pheromonal route.
But what about all those neuro messengers?
Chemical Messenger Classifications

13. Secretions from the anterior pituitary
gland…
Growth Hormone (GH): essential for the
growth and development of bones, muscles,
and other organs. It also enhances protein
synthesis, decreases the use of glucose, and
promotes fat destruction.

14. Secretions from the anterior
pituitary gland…
Adrenocorticotropin
(TRŌ pun) (ACTH):
essential for the
growth of the
adrenal cortex.
Thyroid-Stimulating
Hormone (TSH):
essential for the growth
and development of the
thyroid gland.

15. Secretions from the anterior
pituitary gland…
It stimulates the
growth ovarian
follicles in the female
and the production of
sperm in the male.
Follicle-Stimulating
Hormone (FSH): is a
gonadotropic hormone.

16. Secretions from the anterior
pituitary gland…
Luteinizing
Hormone (LH): is a
gonadotropic
hormone
stimulating the
development of
corpus luteum in
the female ovarian
follicles and the
production of
testosterone in the
male.
The yellow corpus luteum
remains after ovulation; it
produces estrogen and
progesterone.

17. Secretions from the anterior
pituitary gland…
Prolactin (PRL):
stimulates the
development and
growth of the
mammary glands
and milk production
during pregnancy.
The sucking motion of the baby stimulates
prolactin secretion.

18. Secretions from the anterior
pituitary gland…
Melanocyte-stimulating
hormone (MSH): regulates skin
pigmentation and promotes
the deposit of melanine in the
skin after exposure to sunlight

19. Antidiuretic
Hormone (ADH):
stimulates the
reabsorption of
water by the
renal tubules.
Hyposecretion
of this hormone
can result in
diabetes
insipidus.
Secretions from the posterior lobe of
the pituitary gland…

20. Oxytocin: stimulates
the uterus to contract
during labor, delivery,
and parturition. A
synthetic version of
this hormone, used
to induce labor, is
called Pitocin. It also
stimulates the
mammary glands to
release milk.
Secretions from the posterior lobe of
the pituitary gland…

21. Secretions from the pineal gland…
The pineal gland is pine-cone-shaped
and only about 1 cm in diameter.
Melatonin: communicates
information about
environmental lighting
to various parts of the
body. Has some effect
on sleep/awake cycles
and other biological
events connected to
them, such as a lower
production of gastric
secretions at night.

22. Secretions from the pineal gland…
Serotonin: a
neurotransmitter that
regulates intestinal
movements and affects
appetite, mood, sleep, anger,
and metabolism.

23. Secretions of the thyroid gland…
Calcitonin: influences
bone and calcium
metabolism;
maintains a
homeostasis of
calcium in the blood
plasma
The thyroid gland plays a
vital role in metabolism
and regulates the body’s
metabolic processes.

24. Secretions of the thyroid gland…
Thyroxine (T4) and
triodothyronine (T3):
essential to BMR – basal
metabolic rate (the rate at
which a person’s body
burns calories while at rest);
influences physical/mental
development and growth
Hyposecretion of T3 and T4 = cretinism,
myxedema, Hashimoto’s disease
Hypersecretion of T3 and T4 = Grave’s disease,
goiter, Basedow’s disease

25. Secretions of the parathyroid gland…
The two pairs of
parathyroid glands are
located on the dorsal or
back side of the thyroid
gland. They secrete
parathyroid (PTH) which
plays a role in the
metabolism of phosphorus.
Too little results in
cramping; too much
results in osteoporosis or
kidney stones.

26. The islets of Langerhans…
The islets of Langerhans are small clusters of
cells located in the pancreas.

27. Secretions from the islets of
Langerhans… Beta cells secrete the
hormone insulin, which is
essential for the maintenance
of normal blood sugar levels.
Inadequate levels result in
diabetes mellitus.
Delta cells suppress
the release of
glucagon and
insulin.
Alpha cells
facilitate the
breakdown of
glycogen to
glucose. This
elevates the blood
sugar.

28. The adrenal glands…
The triangular-
shaped adrenal
glands are
located on the
top of each
kidney. The
inside is called
the medulla and
the outside layer
is called the
cortex.

29. Secretions from the
adrenal cortex…
Cortisol: regulates
carbohydrate, protein, and fat
metabolism; has an anti-
inflammatory effect; helps
the body cope during times of
stress
Hyposecretion results
in Addison’s disease;
hypersecretion
results in Cushing’s
disease
Corticosterone: like
cortisol, it is a
steroid; influences
potassium and
sodium metabolism

30. Secretions from the adrenal cortex…
Aldosterone: essential in regulating
electrolyte and water balance by
promoting sodium and chloride
retention and potassium excretion.
Androgens: several
hormones including
testosterone; they
promote the
development of
secondary sex
characteristics in
the male.

31. Secretions from the adrenal
medulla…
Dopamine is used
to treat shock. It
dilates the
arteries, elevates
systolic blood
pressure,
increases cardiac
output, and
increases urinary
output.

32. Secretions
from the
adrenal
medulla…
Epinephrine is also called adrenalin. It elevates
systolic blood pressure, increases heart rate and
cardiac output, speeds up the release of glucose
from the liver… giving a spurt of energy, dilates
the bronchial tubes and relaxes airways, and
dilates the pupils to see more clearly. It is often
used to counteract an allergic reaction.

33. Secretions from the
adrenal medulla…
Norepinephrine, like epinephrine, is released when
the body is under stress. It creates the underlying
influence in the fight or flight response. As a drug,
however, it actually triggers a drop in heart rate.

34. Secretions of the ovaries…
The ovaries produce
several estrogen hormones
and progesterone. These
hormones prepare the
uterus for pregnancy,
promote the development
of mammary glands, play a
role in sex drive, and
develop secondary sex
characteristics in the
female.
Estrogen is essential for the growth, development,
and maintenance of female sex organs.

35. The testes produce
the male sex
hormone called
testosterone. It is
essential for normal
growth and
development of the
male sex organs.
Testosterone is
responsible for the
erection of the
penis.
Secretions of the testes…

36. During pregnancy, the
placenta serves as an
endocrine gland.
Secretions of the placenta…
It produces
chorionic
gonadotropin
hormone,
estrogen, and
progesterone.

37. The mucosa
of the pyloric
area of the
stomach
secretes the
hormone
gastrin, which
stimulates the
production of
gastric acid
for digestion.
Secretions of the gastrointestinal
mucosa…

38. The mucosa of
the duodenum
and jejunum
secretes the
hormone
secretin, which
stimulates
pancreatic juice,
bile, and
intestinal
secretion.
Secretions of the gastrointestinal
mucosa…

39. The thymus gland has
two lobes, and is part
of the lymphatic
system. It is a
ductless gland, and
secretes thymosin.
This is necessary for
the Thymus’ normal
production of T cells
for the immune
system.
Secretions of the
thymus…

40. • Neurotransmitters are released
by neurons and travel only
across the synaptic
cleft/neuromuscular junction
• Neuromodulators are released
by neurons to affect other
neurons but are not
immediately taken up or
metabolized like NTs
• Neurohormones are hormones
produced by a nerve cell and
released into the blood to reach
their target cells

41. • The nervous and endocrine systems act
together to coordinate all systems of the body.
Control by the Nervous and Endocrine
Systems

44. • Endocrine where the messenger is blood-
borne.
• Neuroendocrine where the hormone
released by a nerve is blood borne.
• Paracrine where the released hormone
diffuses to adjacent target cells through the
immediate extracellular space.
• Autocrine where the hormone may feedback
to the cell of origin to regulate it’s own
release.
Hormone Delivery Review

45. • Neuromodulator is a hormone that modulates
the response of a neuron to a neurotransmitter
or other hormone. (all act as NM- feedback
loops)
• Pheromone is a chemical messenger released to
the exterior of one animal to stimulate a
response in another member of the same
species.
• Chalones (K-lone) are putative cellular mitotic
inhibitors
• Growth factors are mitogenic peptides which
may later become known as hormones.
Continued

46. Hormones are either:
• Lipid-soluble
– Steroid hormones, thyroid hormones, nitric oxide (NO)
• Water-soluble
– Amine hormones, peptide and protein hormones,
eicosanoid hormones
• Water-soluble hormones circulate freely in the plasma;
Lipid-soluble hormones circulate bound to transport
proteins.
Hormone Activity
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

47. Credit: Dr. Michael Ormsbee, Florida State University

48. Where Do Hormones Come From?
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

49. Where Do Hormones Come From?
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

50. 1. Hormones affect cellular synthesis and
secretion of other hormones within other
endocrine glands and neurons.
2. Hormones affect anabolic and catabolic
processes.
3. Hormones affect contraction, relaxation, and
metabolism of muscle.
Physiological Role of Hormones

51. 4. Hormones control reproductive processes
such as gondal differentiation, maturation, and
gametogenesis.
5. Hormones stimulate and inhibit cellular
proliferation, thus affecting growth. Hormones
regulate cell division and differentiation of the
fertilized egg.
Continued

52. 6. Hormones regulate the excretion and
reabsorption of inorganic cations and ions.
7. Hormones have a permissive action on other
hormones
8. Hormones play an important part in animal
behavior.
Continued Some More

53. Short answer: RECEPTORS
• Receptors (proteins or glycoproteins) provide
specificity for hormone-cell interaction.
• Receptors may be components of the cell
membrane or they may by cytosolic or
nuclear receptors. (steroid/thyroid/vitamin d)
• Cells do not possess receptors for all
hormones but rather have a limited number
of receptor types.
How Do Hormones Exert Their Influence??

54. • Hormones traveling throughout the body will
only affect target cells that possess specific
protein receptors.
• Receptors are continually being synthesized
and broken down.
• Receptors may be down-regulated in the
presence of high concentrations of hormone.
• Receptors may be up-regulated in the
presence of low concentrations of hormone.
Hormone Activity
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

55. Lipid-soluble
hormones bind to
receptors within
target cells.
Mechanisms of Hormone Action

56. Water-soluble hormones
bind to receptors on the
exterior surface of the
target cell.
Mechanisms of Hormone Action

57. How a target cell responds to a hormone is
based on:
– The hormone’s concentration in the blood
– The number of hormone receptors on the target
cell
– Influences exerted by other hormones
– Some hormones work more effectively when a
second hormone is present to assist them
(synergistic effect).
– Some hormones oppose the action of others
(antagonistic effect).
Mechanisms of Hormone Action

58. Hormones are secreted in short bursts when
needed.
Secretion is regulated by:
– Signals from the nervous system
– Chemical changes in the blood
– Other hormones
Control of Hormone Secretion
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

59. Most hormone regulation
is achieved via negative
feedback.
Control of Hormone Secretion

60. A few hormones operate
via positive feedback.
Control of Hormone Secretion

62. Interactions Animation:
Control of Hormone Secretion
 Hormonal Cycles

63. • NT’s are chemical messengers released from
neurons into the synapse between the nerve
and its effector cells
• Secretory cells, muscle cells, or other neurons.
• Usually act in a paracrine fashion
• Many peptide hormones that function in a
classical sense are also synthesized in specific
neurons and may function as NT’s.
Neurotransmitters (NT)

64. NT’s that diffuse beyond the synapse and enter
the blood stream are termed Neurohormones.
– i.e. Dopamine
NT’s act very rapidly in comparison to
neuromodulators which exert a more sustained
response.
Neuromodulatory hormones may originate from
non-neuronal sources
– i.e. corticosteroids, androgens, estrogens.
Neurohormones