Endocrine System
ACCESS.
HUMAN BIOLOGY.
Clare Hargreaves-Norris
Introduction to the endocrine system
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The endocrine system is in charge of body processes that
happen slowly, such as cell development, digestion, excretion,
and sexual activity.
Faster processes like breathing and body movement are
monitored by the nervous system.
The nervous and endocrine systems are separate. However
they are both Major Regulatory Systems.
However, they often work together to help the body function
properly.
The endocrine system is made up of a series of endocrine
glands.
Endocrine glands are positioned around the body.
Endocrine glands secrete hormones.
Clare Hargreaves-Norris
What is an endocrine gland?
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An endocrine gland has no duct linking it to
another part of the body.
It is sometimes called a ductless gland.
These glands produce hormones.
The hormones are released directly into
the blood stream to be carried around the
body.
Clare Hargreaves-Norris
The endocrine glands of the body.
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Hypothalamus
Pituitary
Thyroid
Thymus
Para-thyroid
Pancreas - islets of Langerhans
Adrenals
Gonads
Clare Hargreaves-Norris
What is a hormone?
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A hormone is a chemical messenger.
Hormones are produced by endocrine glands.
Hormones are secreted into the blood stream.
They then travel along to their target organ.
Hormones are specific.
This means that they carry out one type of
reaction.
Therefore there is only a certain place for them to
travel.
Clare Hargreaves-Norris
How does the body know when to
produce hormones?
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The hypothalamus controls the endocrine system.
The hypothalamus is located in the brain.
The hypothalamus detects when the body needs a
particular hormone.
The hypothalamus then stimulates the pituitary
gland to bring about the production of the
necessary hormone.
When the hormone levels in the body reaches the
required level, the hypothalamus is stimulated by
a process called negative feedback; it then
stimulates the pituitary to inhibit any further
production of the hormone.
Clare Hargreaves-Norris
Diagram of the endocrine glands
Clare Hargreaves-Norris
Hypothalamus
The hypothalamus controls the
endocrine and autonomic nervous
systems.
 It secretes hormones such as;
growth hormone-releasing hormone
(GHRH) and many others.
 Hormones are released into the
blood supply.
 They travel directly to the anterior
lobe of the pituitary gland where
they can bring about their affects.
 It has an effect on many of the
Pituitary Hypothalamus
body’s functions such as: pituitary
gland secretions, autonomic nervous
system, body temperature,
metabolism and water balance.
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Clare Hargreaves-Norris
Pituitary gland
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Pituitary
Hypothalamus
The pituitary gland is often
referred to as the master
endocrine gland.
It is situated in the base of the
brain.
It has two sections, both of
which have different functions.
The anterior lobe is stimulated
by the release of chemicals from
the hypothalamus.
The posterior lobe is stimulated
by nervous control from the
hypothalamus.
Clare Hargreaves-Norris
Hormones Produced By The Anterior Pituitary Gland
Hormone
Target
Function
Somatotrophin
Hard tissues
of the body
Causes growth in children and
maintains size in adults.
Thyroid stimulating
hormone (TSH)
Thyroid gland
Regulates the metabolism and
the break down of fat.
Adrenocorticotrophin
(ADH)
Adrenal cortex
Stimulates adrenal cortex to
secrete corticosteroids.
Follicle stimulating
hormone (FSH)
Gonads
Stimulates secretion of
oestrogen (controlling
maturation of ovaries) & sperm.
Lutenising hormone
(LH)
Gonads
Stimulates secretion of
progesterone, forming corpus
luteum in the ovaries and
preparing the breasts for
lactation during pregnancy.
Clare Hargreaves-Norris
Hormones Produced By The Posterior Pituitary Gland
Hormone
Target
Function
Anti-diuretic
hormone
(vasopressin)
Kidneys
Controls water balance within
the body.
Oxytocin
Pregnant uterus Stimulates contraction of the
uterus in childbirth.
Clare Hargreaves-Norris
Pituitary gland disorders
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Over secretion of the anterior pituitary:
– may result in excess growth hormone,
somatotrophin, resulting in Gigamtism
(excessive height) or Acromagaly (over large
hands, feet and face.
Under secretion of the anterior pituitary:
– may result in too little growth hormone,
somatotrophin, resulting in dwarfism
(abnormally short stature).
Clare Hargreaves-Norris
Pineal gland
Pea-sized mass of nerve tissue.
 Functions as a gland, secreting
the hormone Melatonin.
 Melatonin communicates
information about
environmental lighting to
various parts of the body.
 More melatonin is produced
during darkness.
Hypothalamus Light entering the eye inhibits
Pituitary gland
the production of melatonin.
Pineal gland
 Seasonal Affective Disorder
(SAD) is thought to be due to
over production of Melatonin.
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Clare Hargreaves-Norris
Thyroid gland
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The thyroid gland
is situated in the
front of the neck.
It controls
metabolism (the
speed at which the
body’s cells work).
Thyroid gland
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Parathyroid gland
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There are 4 small
parathyroid glands.
There are 2 parathyroid
glands embedded in the
posterior surface of each
lobe of the thyroid gland.
The parathyroid glands
control the calcium levels
within the body.
Clare Hargreaves-Norris
Hormones Produced By The Thyroid Gland
Hormone
Target
Function
Thyroxide
Triiodothyronine
Cells and
tissues
Regulates the
metabolism, increases
urine production, breaks
down proteins and
increases glucose uptake
by the cells.
Hormones Produced By The Parathyroid Gland
Hormone
Parathormone
Target
Function
Increases the amount of
calcium in the blood.
Clare Hargreaves-Norris
Thyroid Gland Disorders
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Thyrotoxicosis: Over secretion of the thyroid.
– Symptoms include: Tachycardia (rapid heart beat),
sweating, tremor, anxiety, increased appetite, weight
loss, heat intolerance.
– May also present with goitre (neck swelling) and
exophthalmos (protruding eyes).
Myxoedema: Under secretion of the thyroid:
– Symptoms include: Dry, coarse skin, oedema (water
retention), alopecia, loss of energy and appetite, weight
gain, intolerance to cold, and mental dullness. inability to
keep warm and mental dullness.
- May be congenital (cretinism).
Clare Hargreaves-Norris
Parathyroid Disorder.
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Hypercalcaemia: Over secretion of the
parathyroid glands results in high calcium levels.
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Hypercalcaemia may lead to Osteitis Fibrosa Cystica
(areas of bone tissue replaced by cavities that fill with
fibrous tissue, thus causing brittle and deformed bone.
Hypocalcaemia: Under secretion of the
parathyroid glands results in a low calcium levels.
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Hypocalcaemia may lead to Tetany (convulsive –
involuntary - muscle contractions).
Clare Hargreaves-Norris
Adrenal (Supra Renal) Glands.
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Adrenal glands are
located one on top of
each kidney.
There are two parts
to each gland:
Adrenal cortex - outer
part of the gland
Adrenal medulla inner part of the gland
Clare Hargreaves-Norris
Hormones Produced By The Adrenal Cortex
Hormone
Target
Function
Glucocorticoids
(cortisone and cortisol).
Blood sugar and
the liver
•Controls metabolism of
carbohydrates and proteins within
the body.
•Converts protein into glycogen for
storage in the liver and increases
blood sugar levels.
Mineralocorticoids
(aldosterone).
Water content of
the tissues
•Regulates the salt and water
balance within the tissues.
•Regulates the mineral (sodium and
potassium) content of the body
fluids.
Sex hormones (androgen Gonads
and oestrogen).
Controls development and
functioning of the sex organs and
secondary sex characteristics.
Clare Hargreaves-Norris
Hormones Produced By The Adrenal Medulla
Hormone
Target
Function
Adrenalin
In-conjunction with
sympathetic
nervous system
Prepares the body for fight or
flight by working with the
sympathetic nervous system i.e.
heart rate increases, blood is
brought to muscles, pupils dilate
and digestion slows down.
Noradrenalin
Circulatory system
Contracts the blood vessels and
raises the blood pressure.
Clare Hargreaves-Norris
Adrenal (Suprarenal) Gland Disorders.
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Over secretion by the adrenal cortex may result in:
– Cushing’s syndrome (weight gain, reddening of face and neck,
excessive facial/body hair, high blood pressure, osteoporosis,
raised blood glucose and sometimes mental disturbance).
– Virilism (female development of excessive body hair, muscle
bulk, deep voice and male psychological characteristics).
– Muscular paralysis, ulcers and adrenal tumours.
Under secretion of the adrenal cortex may results in:
– Addison’s disease (muscular weakness, weight loss, low blood
pressure, anaemia, hyper-pigmentation and mental lethargy).
– Water loss from the body.
– Lowered pH levels of the blood.
Over secretion of the adrenal medulla causes:
– Hypertension (high blood pressure).
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Increased metabolic rate.
Under secretion of adrenal medulla causes:
– Hypotension (low blood pressure)
– Lower metabolic rate.
Clare Hargreaves-Norris
Islets of Langerhans
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Islets of Langerhans
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The Islets of Langerhans
are found in clusters,
irregularly distributed
throughout the pancreas.
There are three types of
hormone secreting cells in
the islets:
Alpha cells which produce
glucagon.
Beta cells which produce
insulin.
Delta cells which produce
somatostatin.
Clare Hargreaves-Norris
Homones Secreted by the Islets of Langerhans.
Hormone
Target
Function
Glucagon
Blood sugar
Raises blood sugar levels by converting
glycogen to glucose in the liver.
Insulin
Blood sugar
Controls the metabolism of carbohydrates
and lowers blood sugar levels by converting
glucose to glycogen in the liver._
Somatostatin
Regulates Alpha and Beta cells.
Clare Hargreaves-Norris
Islets of Langerhans disorder
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Under secretion of the islets of
Langerhans may result in diabetes
mellitus - a high blood sugar level due to a
shortage of insulin.
Clare Hargreaves-Norris
Gonads
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The gonads are the testes in the
male and the ovaries in the female.
The testes produce the male sex
hormones (androgens) such as
testosterone.
Testosterone stimulates the
development of the secondary male
sexual characteristics (deeper voice,
body hair and muscular development).
The ovaries produce oestrogen and
progesterone.
Ovaries control the menstrual cycle
including the production of ova (eggs)
and pregnancy.
Ovaries also produce small quantities
of androgens.
Clare Hargreaves-Norris
Hormones Produced By The Gonads
Hormone
Target
Function
Oestrogen
Secondary sex
characteristics in
females
Causes development of female
reproductive system, breast
development and regulates the
menstrual cycle.
Progesterone
Structures relating
to pregnancy
Maintains pregnancy, involved in the
development of the placenta and
prepares breasts for lactation.
Androgens
Secondary sex
characteristics in
males
Causes development of male
reproductive system and secondary
male characteristics such as beard
growth.
Clare Hargreaves-Norris
Disorders of the ovaries
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Under secretion by the ovaries may
result in Stein-leventhal syndrome
(polycystic ovaries).
Symptoms include enlarged ovaries with
numerous cysts, irregular menstruation,
weight gain and the development of excess
hair growth.
Polycystic ovaries are capable of secreting
large amounts of androgens.
Clare Hargreaves-Norris