2. Introduction
• Endocrine system a control system of ductless glands that secrete hormones.
• There are 2 types of hormones:
• Steroidal &
• Non-steroidal
• The multiple hormone systems play a key role in regulating almost all body
functions, including:
• Homeostasis
• Metabolism,
• Growth & development,
• Water & electrolyte balance,
• Reproduction &
• Behaviour.
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5. Types of Glands
1. Exocrine Glands
• Release their secretions through a
duct.
• These include :
• Sweat glands
• Salivary glands
• Pancreatic glands
• Mammary glands
Endocrine Glands
• Glands which have no duct.
• Release their secretions into the
ECF or into the blood.
• This include:
• Pituitary (AP & PP)
• Thyroid, Parathyroid
• Adrenal (cortex & medulla)
• Pancreas & Gonads
• Endocrine system consists
of gland, hormone,
transport, receptor, and
target cells.
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6. Chemical classification of Hormones
1. Amines
• Hormones that are derived
from tyrosine.
• T4 & T3
• AD, NA
2. Peptides /proteins
• Hormones that are chains of
</>100 amino acids.
• ADH, Oxytocin,
• Insulin & human
growth hormone (GH).
3. Steroids
- Hormones that are lipids (cholesterol)
• Adrenal cortex (cortical
steroids)
• Gonads (sex steroids)
4. Eicosanoids
- Hormones that are lipids (FA).
• Prostaglandins
• Prostacyclins
• Thromboxanes
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7. Hormone receptor and MoA
• Events developed after
complex formation are
changes on:
• Ion channel.
• Enzymatic activities.
• G protein & 2nd
messengers.
• Gene expression &
protein synthesis.
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8. Hormone secretion control
• Hormone secretions are controlled by 4 methods:
1. Negative feedback mechanism (most hormones)
2. Positive feedback mechanism (LH- surge)
3. Neural control
• Secretion of OT, ADH, AD, NA
4. Circadian rhythm (periodic variations)
• Secretion of Sex hormones
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9. Hypothalamus
• Is part of the diencephalon &about 5
gm.
• It plays most important role in
controlling homeostasis.
• It is the main brain structure
involved in regulating hormonal
levels in the body.
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11. APG and PPG
ADH (vasopressin)
• Regulate body water &
BP by reabsorption of
water & vasoconstriction
of arteries and arterioles
• Oxytocin: contract
endometrial & breast
SM.
• Secretion from the gland
controlled by nerve signals.
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• The AP lobe receives
hormones (RH & IH) from
the HT.
• No nerve fibers are
terminated in to APG.
• Secretion process is
regulated by blood born
hormones.
13. Growth hormones
• Promotes tissue growth by stimulating liver to
produce IGF-I/Somatomedin-C
• Promote protein synthesis
• Increase DNA transcription
• Increase mRNA production
• Enhance amino acids into cell & reduce protein
catabolism.
• Increase protein sparing, not used as energy.
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14. Thyroid gland
• The largest endocrine gland
in the body.
• Positioned on the neck just
below the Larynx & has 2
lobes with one on either side
of the trachea.
• It produce hormones T3
(triiodothyronine) & T4
(thyroxine).
• T3 & T4 increase the
metabolic activity of the
body’s cells.
Function of the thyroid hormones
1. Calorigenic action
↑O2 consumption
↑Metabolic rate on CHO,
protein and Fat
Body growth: promotes
growth of bone, teeth and nerve
tissue in children
3. Effect on NS/CNS
Promotes growth and maturation
of nerve tissue, synaptic
development.
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15. Calcitonin
• A hormone that is produced by the parafollicular cells (C-cells) of
the thyroid.
• Produced by the thyroid & contributes to the regulation of blood
ca+2 levels.
• Thyroid cells produce calcitonin in response to high ca+2 levels in
the blood:
• Decreases the concentration of ca+2 in the blood.
• This hormone will stimulate movement of calcium into the bone
structure.
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16. Parathyroid gland
• Are 4 glands located on the
thyroid gland having
butterfly-shaped.
• Functions: Regulate the
body's calcium &
phosphorus levels.
• Secrete PTH [parathyroid
hormone], which
• Causes release of ca+2 from
bone to ECF.
• ↓ Osteoblasts (production
of bone) &
• ↑ Osteoclasts (removal of
bone).
• Signals the kidneys to
reabsorb ca+2 .
• Signals the small intestine to
absorb more ca+2
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18. Adrenal glands
• Triangular-shaped glands located on
top of the kidneys.
• They regulate many essential
functions in the body, including:
– biochemical balances that
influence:
• Athletic training &
• General stress response.
• Produce hormones like:
– Aldosteron
– Cortisol
– Androgens
• Produces chemicals like:
– AD, NA
– Dopamine
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19. Adrenal Cortex
1. Mineralocorticoids
(Aldosterone)
– regulate the salt & water
balance, leading to the increase
of BV & BP.
2. Glucocorticoids (Cortisol)
– raise blood glucose level,
stimulates breakdown of
protein.
3. Sex Hormones (Androgen)
– stimulates reproductive organs
& brings on sex characteristics.
Adrenal Medulla
• The effects of these hormones
provide a short-term
response to stress.
• Impulses from HT, spinal cord &
SNS fibers go to the adrenal
medulla,
• Then it releases hormones:
– Epinephrine
– Norepinephrine
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Adrenal glands
20. Pancreas
• It is both an exocrine & an
endocrine organ.
• As an exocrine organ; it is
considered to be part of the
GIT.
• It produces digestive enzymes
to be released into the SI.
• Aid food digestion to
absorbable.
• Endocrine function.
• Secret Insulin & glucagon
• They are secreted by islet cells
released into the bloodstream.
• Groups of endocrine cells
(Islets of Langerhans) secrete
two hormones.
1. Beta cells [β]
• secrete Insulin
1. Alpha cells [∂]
• secrete Glucagon.
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21. • Insulin
• Lower blood sugar levels
by allowing the sugar to
flow into cells.
• Glucagon
• Raise blood sugar levels
by causing glucose to be
released into the
circulation from its storage
sites.
• Insulin & glucagon act in an
opposite but balanced fashion
to keep blood sugar levels
stable.
1. On Carbohydrate
• blood glucose level by:
• Converting into glycogen
• Facilitate cells uptake
• Converting to fats & stored in the
adipose tissue
2. On Protein
– Promotes amino acid uptake by cells
and inhibits proteins breakdown.
3. On Cortisol
– Anti-cortisol effect =blood glucose by:
• inhibiting gluconeogenesis &
• activating glucose uptake
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Insulin metabolic Effects