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Keywords
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Paracrines
Exocrine glands
Endocrine glands
Pancreas
 Islets of Langerhans
 Insulin
 Glucagon
Thymus
 Thymosins
Adrenal glands
 Adrenaline
 Noradrenaline
 Aldosterone
 Cortisol
Thyroid
 Thyroxine
Parathyroid
 Parathyroid hormone
 Hypothalamus
 Pituitary gland
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Growth hormone (GH)
Prolactin
Oxytocin
Antidiuretic hormone
(ADH)
Follicle stimulating hormone
(FSH)
Luteinising hormone (LH)
Thyroid stimulating
hormone (TSH)
Adrenocorticotropic
hormone (ACTH)
The endocrine system
 The endocrine system is comprised of a group of
ductless glands that secrete chemical messenger
substances, called hormones, into the
bloodstream.
 It works in conjunction with the nervous system
 It is responsible for the long-term regulation of
many bodily functions. It works to maintain
homeostasis through negative feedback loops
The endocrine system
 The endocrine system
includes the
 Pituitary gland
 Thyroid & parathyroid
 Thymus
 Adrenal glands
 Pancreas
 Gonads (ovaries and
testes).
Endocrine glands
Excocrine glands
 secrete substances into a
duct that carries the
secretion to the surface
of the body or to one of
the body’s cavities eg.
sweat glands, glands of
the alimentary canal
 have ducts
Endocrine glands
 secrete substances into
the extracellular fluid
that surrounds the cells
making up the gland.
The secretion then
usually passes into the
capillaries to be
transported by the blood
 are ductless
Hormones
Hormones are:
1. Chemical messengers
2. Secreted by endocrine glands
3. Are either proteins, amines (small molecules
derived from amino acids) or steroids (derived
from cholesterol)
4. Carried in the bloodstream to target specific cells
and organs
5. Change the way in which cells function
6. Act over the long-term – days, weeks, months
Paracrines
 Cells can communicate
with other cells in the
same tissue by secreting
paracrines that diffuse
to adjacent cells
 Paracrines are secreted
by all cells, unlike
hormones which are
secreted by specialised
cells
How hormones work
 Hormones are only able to influence cells
that have the correct receptor. Hormone
receptors are specific.
 Saturation of the receptors can also occur
 The combination of the hormone with a
receptor causes a secondary messenger
substance to diffuse through the cell and
activate particular enzymes within the cell
How hormones work
Amplification
 One hormone molecule
can effect thousands of
enzymes by enzyme
amplification
 The hormone triggers a
cascade effect in which
the number of reacting
molecules involved is
increased for each step
along the metabolic
pathway
Hormone clearance
 Once the hormone has
produced the wanted
effect, it gets broken
down in the liver and
kidneys and then
excreted in the bile or
urine
The hypothalamus
 The hypothalamus
regulates most hormonal
activity in the body
 It is located at the base of
the brain
 The hypothalamus can
secrete releasing factors
to stimulate hormone
secretion or inhibiting
factors to slow down
hormone secretion
The hypothalamus
 These releasing and
inhibiting factors are
themselves hormones
 many important bodily
functions such as body
temp, water balance and
heart rate
 Many of the functions of
the hypothalamus are
carried out through the
pituitary gland
The pituitary gland
 The pituitary gland is located just
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under the hypothalamus
The pituitary gland consists of an
anterior lobe and a posterior
lobe. The lobes function separately
The hypothalamus directly controls
the activity of the pituitary gland
Many of the hormones released by
the pituitary gland in turn regulate
the activity of other endocrine
glands.
The pituitary gland is often referred
to as the master gland.
Anterior lobe of the pituitary
The anterior lobe of the
pituitary releases
numerous hormones:
1. Growth Hormone
(GH) stimulates body
growth
2. Prolactin works to
initiate and maintain
milk secretion in
females
Anterior lobe of the pituitary
3.
Thyroid stimulating
hormone (TSH)
stimulates production
and release of hormones
from the thyroid gland
4. Adrenocorticotropic
hormone (ACTH)
controls production and
release of some of the
hormones from the
adrenal glands
Anterior lobe of the pituitary
5.
Follicle stimulating
hormone (FSH)
 In females it stimulates the
development of the follicle
that contains the egg.
 In males it controls the
production and
maturation of sperm
6. Luteinising hormone (LH)
 In females it works to bring
about ovulation
 In males it stimulates cell
in the testes to secrete
male sex hormone
Posterior lobe of the pituitary
 The 2 lobes function
separately
 The posterior lobe is
not a true gland
because it does not
secrete any
substances. It is
controlled by
neurons from the
hypothalamus
Posterior Lobe of the pituitary
The posterior lobe of the pituitary releases the
hormones:
1. Oxytocin is a hormone that stimulates
contractions of the uterus
2. Antidiuretic hormone (ADH) causes the
kidney to remove water from urine that is
forming and the water is returned to the
bloodstream. ADH helps to retain fluid in the
body
Hypothalamus & pituitary gland
How the hypothalamus & pituitary gland function
(3 minutes)
 http://bcs.whfreeman.com/thelifewire/content/chp42
/4202s.swf
The pineal gland
 The pineal gland
produces melatonin and
is involved in the
regulation of the
Circadian rhythm.
 It is affected by sunlight.
 The thyroid gland is located
in the neck just below the
larynx
 The main hormone secreted
is thyroxine, made from an
amino acid and iodine
 Thyroxine controls
metabolism and brings about
the release of energy
 Thyroxine is released in
response to thyroid
stimulating hormone from
the anterior of the pituitary
Thyroid gland
The parathyroid glands
 There are 4 pararthyroid
glands
 These are embedded in
the rear of the thyroid
gland
 They secrete parathyroid
hormone which controls
calcium and phosphate
levels in the blood
The thymus
 The thymus is located
in the chest just above
the heart and behind
the sternum
 It secretes a group of
hormones called
thymosins which
influence the
maturation of disease
fighting cells called tlymphocytes
The adrenal glands
 There are 2 adrenal
glands that are located
above each kidney
 Each adrenal gland has
an inner adrenal
medulla and an outer
adrenal cortex
Hormones produced by the
adrenal medulla include:
1. Adrenaline has an effect
similar to the
sympathetic nervous
system and helps to
prepare the body for
flight-fight responses
2. Noradrenalin has
similar effects to
adrenaline. In particular,
it influences the rate and
force of the heartbeat
Adrenal Medulla
Adrenal cortex
A number of hormones are
produced in the adrenal
cortex. They are called
corticosteriods. Two
main ones are:
Aldosterone acts on the
kidneys to reduce the
amount of salt and
increase the amount of
potassium in the urine
2. Cortisol promotes
normal metabolism to
help the body withstand
stress
1.
The pancreas
 The pancreas lies
just below the
stomach and
alongside the
duodenum
 It is both an
exocrine gland and
an endocrine gland
 The exocrine part secretes
digestive enzymes
 The endocrine part is
contained within clusters of
cells called islets of
Langerhans
 The islets secrete 2
important hormones,
insulin and glucagon
1. Insulin reduces the
amount of glucose in
the blood.
2. Glucagon acts in the
opposite way to
insulin, and increases
blood sugar levels
The pancreas
Gonads: testes and ovaries.
1. Androgens are the main sex
hormones produced by the
testes. They are responsible
for the development and
maintenance of male sex
characteristics
2. Oestrogens and
progesterone are the female
sex hormones produced by
the ovaries. They are
responsible for the
development and
maintenance of female sex
characteristics
The gonads
YouTube clips
Bozeman Science
The endocrine system
13 minutes
5 star
https://www.youtube.com/watch?v=S_vQZDH9hY&list=TLiZ7pOKGMaMtrV6dQFIRlq
snzIvMMaf-G
YouTube clips
 http://www.e-
learningforkids.org/Courses/Liquid_Animation/Body_
Parts/Endocrine_System/endocrine_object.swf
 http://bcs.whfreeman.com/thelifewire/content/chp42
/4202s.swf
 http://www.phys.unsw.edu.au/biosnippets/biosnippet
s_container2.swf