Endocrine system

“The will to achieve is important,
But the will to prepare is vital.”
GOOD MORNING


Review of the
Anatomy and Physiology
of the
Endocrine system
Jerard Lloyd B. Domingo,Student Nurse
President Ramon Magsaysay State University
College of Nursing

Endocrinology
• the study that deals with secretion of
chemical messengers that affect a gland
or a target cell.
• Chemical Messengers – both produced
by the nervous and endocrine system.
• Gland - is an organ consisting of
epithelial cells that is specialized for
secretion.

4 Classes of Chemical messengers
1. Autocrine Chemical Messengers
- messengers that stimulates the cell that
originally secreted it and sometimes
nearby cells of the same type.
Ex: WBC secretion during infection. These
WBC can stimulate or inhibit (influence
the activity with the same type) the
production of WBC if there’s an
infection.

4 classes of Chemical messengers
2. Paracrine Chemical Messengers
• secreted by one cell type but affect neighboring
cells of different type.
• they are secreted in the cellular fluid and not in the
bloodstream.
• Example: When histamine (a paracrine chemical
messenger) is released by the WBC during allergic
reactions which stimulates vasodilation in nearby
blood vessels.

3. Neurotransmitters – are chemical messengers
secreted by neurons that activated an adjacent
cells.
*adjacent cells – located in the axon of a neuron,
glandular, or muscle cell.
• Neurotransmitters are released in the synaptic
cleft.
• Neurotransmitters are also considered as a
Paracrine Chemical Messenger but it is in a
separated category.

4. Endocrine Chemical Messengers
• Released and secreted into the bloodstream
by a certain gland or cells.
• The chemical messenger that affect cells that
are distant from their source (hormones).
• Endocrine means to screte within.
• (endo – within, krino – secrete)

Endocrine vs. Exocrine
Endocrine
• Secreted via
bloodstream to the
effector organ.
• Pituitary Gland
secretes hormones
that controls the
release of other
hormones.
Exocrine
• Have ducts that
carries secretion to
the outside of the
body.
• Example: saliva,
breast milk, digestive
system

Functions of the Endocrine System
1. Metabolism – regulates the rate of metabolism, the
sum of chemical changes in tissue. Example:
Glucose breakdown rate.
2. Control of food intake and digestion –regulates the
level of satiety (fullness) and the breakdown of food
into individual nutrients.
3. Tissue development – Endocrine system influences
the development of tissues such as those of the
nervous system. Example: Growth Hormone
stimulates the growth of tissues including the bones
and muscles.

4. Ion Regulation – endocrine system
regulates the solute concentration of
blood.
5. Water Balance – endocrine system
regulates the water balance by
controlling the solutes in blood.
6. Heart rate and Blood Pressure
Regulation - Helps body to prepare for a
physical activity.

7. Controls blood Glucose and Other
Nutrients
8. Control of Reproductive Function –
different hormones that contributes to
reproduction.
9. Uterine contractions and Milk Release
–uterine contractions during delivery
and milk release from breasts.
10. Immune System Regulation – ES
controls production of immune cells.

10 functions of Endocrine System
1. M
2. COFIAD
3. TD
4. IR
5. WB
6. HRBPR
7. CBGON
8. CORF
9. UCMR
10. ISR

Chemical Nature of Hormones
Cell membrane is a selectively permeable
phospholipid bilayer that excludes most water
soluble but allowslipid soluble molecules to pass
thriugh. (does not allow water soluble molecules)
 Steroid hormones – derived from cholesterol
Thyroid hormones – derived from Amino Acid
thyrosine.
Other hormones are Amino acid derivatives,
peptides and proteins.

Chemical Nature of Hormones
1. Lipid Soluble Hormones - nonpolar, include steroid
hormones, thyroid hormones, Fatty acid derivative
hormones such as certain eicosanoids.
 It is insoluble in water based fluids such as plasma of
blood.
 Lipid soluble hormones travels to the bloodstream and
attach to binding proteins for protection and transport.
 Lipid Soluble Hormones are degraded slowly and are more
rapidly eliminated from the circulation.

Lifespan: Few days to several weeks.
Without the binding proteins would quickly
diffuse out of the capillary and be degraded
by enzymes of the kidneys and lungs and
eliminated by the kidneys.
*Hydrolytic enzymes can metabolize LSH and
the breakdown products are excreted in the
urine or as bile.
1. Lipid Soluble Hormones

2. Water Soluble Hormones
• Polar molecules
• Include protein hormones, peptide, and
amino acid derivatives.
• It can dissolve in blood (WSH circulate in the
blood as free hormones).
*Free Hormones can dissolved directly in the
blood and delivered in the target tissue
without attaching to a binding protein.

• Some WSH are quite large so they diffuse
slowly in tissue spaces of an organ.
• Some WSH are too small, to avoid being
filtered out in the blood, they need to attach
to a binding protein.
• WSH are short half lives because they are
rapidly degraded by enzymes calles proteases
in the bloodstream.

• Some hormone target cells destroy WSH or
take up the hormone through endocytosis to
terminate their effect.
*Endocytosis - uptake of material through the
cell membrane by the formation of vesicles.
When a specific substance binds to a receptor
molecule, endocytosis is triggered and the
substance is transported into the cell. It is also
called the Receptor Mediated Endocytosis.

• Once the hormones are inside the target cell,
lysozomal enzymes degrade them and the target cells
recycles them to synthesize new proteins.
• Hormones with short-half lives are normally have
concentrations that change rapidly within the blood
and regulate activities that have a rapid onset and a
short duration.
• Some WSH are more stable to blood than others
because they are being modified (because protein and
peptide hormones have a carbon dioxide on them).
• Some WSH also attach to binding proteins and circulate
in the blood longer than free soluble hormones.

LSH and WSH in Medicine
• LSH such as steroids may be taken orally
because they can diffuse easily to the wall of
the intestine into the circulatory system.
• Ex: synthetic estrogen and progesterone-like
hormones in birth control pills and steroids
that reduce the severity of inflammation such
as PREDNISONE.

LSH and WSH in Medicine
WSH or protein hormones cannot
diffuse across the intestinal wall
because they are degraded easily to
individual amino acids before they are
transported in the intestinal wall.
Therefore, its normal structure is
destroyed and it’s physiological activity
or function is lost.

Control
of
Hormonal Secretions
Humoral, neural,
and hormonal.

Control by Humoral Stimuli
• Blood-borne Chemicals in the bloodstream that
stimulates the release of hormones.
• Humoral refers to the body fluids including blood.
• Sensitive to a particular chemical changes in the
body.
Example: An athlete just finished a long race during
a hot weather. So he may not be able to produce
urine for 12hrs after the race because of elevated
solute levels in the blood stimulates the release
of ADH to conserve water.

2. Control by Neural Stimuli
• Neurons release of NT into the synapse with the cells
that produce the hormone. NT stimulates the cells to
increase hormone secretion.
• *Autonomic Nervous System
1. Parasympathetic Stimulation – Secretes Acth
2. Sympathetic Stimulation – secretes NE.
*Sympathetic nervous system stimulates the release
of EPI and NE to increase HR, and increase Blood
Flow through exercising muscles. When the
exercise stops, the neural stimulation decreases
and also the secretion of EPI and NE decreases.

Neuropeptides
• Secreted by neurons which are chemical
messenger hormones.
• They stimulate hormone secretion from an
endocrine cells that are called “releasing
hormones”.
*Releasing hormones – term used for
hormones in the HYPOTHALAMUS.

3. Control by Hormonal Stimuli
• When a hormone is secreted and stimulates the
secretion of other hormones.
• Ex: Anterior Pituitary Gland Hormones are called
as “Tropic Hormones”.
*tropic hormones- stimulates the secretion of
other hormones.
Ex: Hypothalamus release hormones that
stimulates the secretion of APG to release tropic
hormones . The release of tropic hormones
stimulates the release of a target endocrine
glands to release its hormones.

Inhibition of Hormone Release
1. Humoral – hormones release is sensitive to the
presence of a humoral stimulus, there exists a
companion hormone that oppose with the
secreted hormone and counteract with the
secreted hormone’s action.
Example: To raise BP, the adrenal cortex releases
aldosterone in response to low blood pressure.
But if BP goes up, the atria of the heart releases
Atrial Natriuretic Peptide to lower BP. Therefore
Aldosterone and ANP work together tp maintain
homeostasis of Blood Pressure.

Inhibition of Hormone Release
2. Neural – secretion of an inhibitory
NEUROTRANSMITTER. (Endorphin, Serotonin,
glycine and GABA).
3. Hormonal – some hormones prevent the
secretion of other hormones which is a common
mode of regulation. Through the secretion of
inhibiting hormones from the hypothalamus .
Ex: TH can control their own blood levels by
inhibiting their anterior pituitary tropic hormone.
Without the original stimulus, less thyroid
hormone is released.

Regulation of Hormone Levels in Blood
1. Negative Feedback
2. Positive Feedback

1. Negative Feedback
“The self-limiting system”
The hormone secretion is inhibited by the
hormone itself once homeostasis is
maintained.
Ex: Thyroid hormone inhibits the secretion og
their releasing hormone from the
hypothalamus and their tropic hormone from
the pituitary gland.

2. Positive Feedback
 “The self propagating system”
 Stimulates further secretion of the of the
original hormone.
 Ex: prolonged estrogen stimulation promotes
a release of the anterior pituitary hormone
responsible for stimulating ovulation.

• Hormones exert their actions by binding to proteins
called “receptors”.
• A hormone can stimulate only the cells that have the
receptor for that hormone.
• *receptor site – a portion of the receptor molecule
where a hormone binds and exert their actions
(stimulation or inhibition).
• *specificity – tendency of each type of hormone to
bind to one type of receptor.
Ex: Insulin bind to insulin receptors only and not to
Thyroid Hormone receptors. But some hormones
such as EPINEPHRINE can bind to a family of
receptors with the similar structure to it.

• Hormone receptors have a high affinity for the
hormones to bind for them, only a small
concentration of a given hormone is needed
to activate a significant number of receptors.
• *Affinity – a liking for or an attraction to
something.

Classes of Receptors
1. Nuclear Bound Receptors
2. Membrane Bound Receptors

1. Nuclear Bound Receptors
• LSH bound to NBR
• LSH are relatively small and non-polar. Non-polar
molecules can freely across the cell membrane.
• Nuclear bound receptors are most often found in the
cell nucleus (activated) and in the cytoplasm (inactive
form).
• When hormones bound to NR, hormone receptor
complex is formed.
• Hormone receptor complex interacts in the DNA in the
nucleus or with cellular enzymes to regulate the
transcription of particular genes in the target tissue.
(occurs up to several minutes or hours).

• *Transcription – first step in gene expression and it
takes place in the nucleus of the cell. DNA
determines the structure of mRNA through
transcription.
Thyroid Hormones and Steroid Hormones bind to
Nuclear Bound Receptors.
*Non-polar molecules – a molecule that carries a
neutral charge , there’s an equal sharing of electrons
between atoms of the molecule.
*Polar molecule – a molecule that carries a charge,
there’s an unequal sharing or a transfer of electrons
between atoms of the molecule.

Membrane Bound Receptors
• These are proteins extended to the cell
membrane (outside).
• Water Soluble Hormones bind to Membrane
Bound Receptors.
• Since Water soluble Hormones are polar
molecules, they bind to MBR.
• When the WSH bounded on the MBR outside,
the hormone receptor complex initiates a
response inside the cell.

Actions of Nuclear Receptors
• LSH stimulates protein synthesis.
1. LSH diffuse inside the cell membrane to bind
with Nuclear Receptor to form Hormone
Receptor Complex.
2. HRC binds to the DNA for Protein synthesis (in
the ribosome).
*HRC – has hormone response elements.
*Hormone Response Elements – receptors that
bind to specific nucleotide sequence in DNA.
*LSH and Nuclear receptor forms a transcription
factor.

*transcription factor – regulates the transcription
of mRNA.
3. Newly formed mRNA moves to the cytoplasm
and translated into a specific proteins at the
ribosome.
4. The new proteins produces the hormone effect
on the target cell. (stimulates the gland
secretion or inhibition of hormones or
formation of new structures in the body).
Example: Testosterone stimulates the synthesis of
CHON that are responsible for male secondary
sex characteristics such as the formation of the
muscle mass and the typical male body
structure.

After the synthesis of new protein
molecules in response to hormonal
stimuli normally have a latent period of
several hours for the LSH to bind with its
receptor. During the latent period, mRNA
and new proteins are synthesized.
Hormone Receptor Complex are
degraded to limit the length of time
hormones influence the cells activities
and slowly return to their previous
functional states.

Membrane Bound Receptors
and Signal Amplification
Cell membrane contains proteins, which are
embedded in the phospholipid bilayer.
Membrane Bound Receptors are examples of
membrane proteins.
MBR activates proteins in 2 ways:
1.Some receptors alter the activity of G-Proteins
at the inner surface of the cell membrane.
2. Other receptors directly alter the activity of
intracellular enzymes.

These activation of the G-Proteins or
intracellular enzymes elicits responses in
cells, including the production of
molecules called as “second messengers”
*second messengers – a molecule produced inside the
cell once a ligand binds to its Membrane bound
receptor.
*second messenger system – activates the set of
responses inside the cell in response to the hormone.
Example: When a ligand binds to the Membrane Bound
Receptor, cAMP (a second messenger) is produced.
cAMP- cyclic adenosine monophosphate.

The MBR Responses
1. When WSH (ligand-first mesenger) binds to a
membrane bound receptor.
2. The binding of a ligand and a MBR binds, G-protein
activities may be altered or Intracellular enzymes
activities are directly altered.
3. When G-proteins or intracellular enzymes are
activated, second messengers are produced (cAMP).
4. The second messengers elicits cellular processes
inside the cell in response to the hormone.
*this mechanism was usually employed by WSH because
they cannot pass the cell membrane. Also, LSH can
bind to MBR which is consistent with actions via MBR.

MBR that activates G-proteins
G-proteins consists of three sub-units:
1. Alpha (α) – binds to guanine nucleotides.
2. Beta (β)
3. Gamma (ƴ)
*in an inactive state, the guanine diphosphate
(GDP) is bound to the α subunit of each
G-Protein.
*in an active state, guanine triphosphate (GTP) is
bound to the α subunit.

1. After a hormone (WSH) binds to a receptor, the
receptor changes shape.
2. as a result, the receptor binds to the G-protein on the
inner surface cell membrane, and GDP is released
from the α subunit.
3. GTP binds to the α subunit that activates it.
4. The G-proteins separate from the receptor on the
outside cell , and the activated α subunit separates
from the β and ƴ subunit.
5. The activated α subunit can alter the activity of
hormones within the cell membrane that produces
cellular responses.

6. After a short time, the activated α subunit is
turned off because the G protein removes
the phosphate group from the GTP, which
converts it to GDP.
7. Then the α subunit recombines with the β
and ƴ subunit.
*thus, the α subunit is called as “GTPase”.

G-Proteins that Interact with Adenate Cyclase
1. Activated α subunits of G-proteins can alter the
activity of enzymes inside the cell. The α
subunit can influence the rate of cAMP
formation by activating or inhibiting adenylate
cyclase.
*Adenylate Cyclase – an enzyme that converts ATP
to cAMP (a second messenger).
2. cAMP binds with protein kinases and activates
it.
*protein kinases – enzymes that regulate the
activity of other enzymes (increase or decrease
its activity).

3. The amount of time cAMP is present to produce a
respose in a cell is limited time only because of an
enzyme in the cytoplasm called *phospodiesterase
which breaks down cAMP to AMP.
*once cAMP levels drop, the enzymes in the cell are no
longer stimulated.
*cAMP elicit many responses in the body.
For example: The hormone glucagon binds to receptors
on the surface hepatocytes (liver cells) activating in G-
Proteins and causing an increase in cAMP synthesis,
which stimulates the activity of enzymes that break
down glycogen into glucose for release in the liver
cells..
G-Proteins that Interact with Adenate Cyclase

Signal Amplification
• Nuclear receptors work by activating protein
synthesis, which for some hormones could take up
to several hours. However, some hormones
stimulates the synthesis of second messengers can
produce an almost instantaneous response
because the second messenger influences existing
enzymes.
• Each receptor produces thousands of secondary
messengers leading to a cascade effect and
ultimately the amplification of the hormonal
signal. It is efficient because a single hormone
can activate an enormous amount of final product
to conduct cell processes.

• It is the “Army of Molecules”
• Produces the “Cascade Effect”
*Cascade Effect – the combination of a hormone
with a membrane bound receptor activates G-
proteins. The G-proteins, in turn, activates many
inactive adenylate cyclases enzymes that will
cause the synthesis of large number of cAMP
molecules.
The large number of cAMP molecules activates
many inactive protein kinase enzymes, which
produce a rapid amplified response.

• Example 1: Epinephrine (adrenaline) is effective
in a fight or flight situation is that it can turn on
the target cell responses within a few seconds.
• Example 2: pregnancy maintenance is mediated
by steroids, long acting hormones, which is
reflected by the fact that pregnancy is a long
term process.
• *Therefore, it is important that our bodies have
hormones that can function over differing time
scales.

Endocrine Glands
Their Hormones

Endocrine System
• Endocrine glands are ductless glands that secretes
hormones in the interstitial fluid.
• The richest blood supply in the body are the
endocrine glands specifically the adrenal glands
and thyroid gland.
• Pancreas is both an exocrine and an endocrine
gland. (there’s a part that secretes hormones, and
other part na nagsesecrete ng digestive enzymes).
• Portions of the ovaries and testes secretes
hormones, but other parts of the ovaries and
testes produce oocytes (female repro cells) or
sperm cells (male repro cells).

Pituitary and Hypothalamus
•NOT YET DONE PO 

Endocrine system

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Endocrine system

Similar to Endocrine system (20)

More from JerardLloyd

More from JerardLloyd (13)

Recently uploaded

Recently uploaded (20)

Endocrine system