Endocrine System
Chemical control
The Primary Function
The Endocrine system is
the system in the body
responsible for...
“the production and
secretion of hormones
that travel in the blood
stream and trigger target
cells or target organs to
respond/act in order to
maintain homeostasis.”
Endocrine system comprises
three main parts:
1. THE ENDOCRINE GLANDS – Organs that
produce/store and secrete the hormones
2. THE HORMONES – The chemical substances
produced in an endocrine gland which target
specific cells by acting as a messenger in the body.
3. THE TARGET CELLS/ORGANS – The cells/organs
that respond to the chemical messages
What hormones do……
Hormones help control biochemical reaction in a
target cell in three different ways:
1. A hormone can increase the rate at which other
substances enter or leave the cell
2. It can stimulate a target cell to synthesize
enzymes, proteins, or other substances
3. It can prompt a target cell to activate or
suppress existing cellular enzymes.
The Endocrine Glands
Produce the
hormones
Many glands in
various locations
throughout the body
Co-ordinated by the
Pituitary Gland which
responds to
information from the
hypothalamus
Hypothalamus
Hypothalamus links the nervous and
endocrine systems
Constantly checking the internal
environment
If conditions change – it secrets
hormones that act upon the pituitary
gland
The pituitary gland responds to
information from the hypothalamus.
Pituitary Gland
Pituitary gland receives a message from
the hypothalamus.
Pituitary gland responds by secreting
other hormones or producing less
hormones.
These hormones act on the function of
other endocrine glands or directly on
target cells.
Target Cells:
Hormones produced in very small amounts and
travel through the blood, reaching all body cells.
But not all cells are affected. Only TARGET cells and
these are hormone specific.
Different hormones have different chemical
structures – that is their shape varies.
Target cells have receptors which only fit the shape
of their specific hormone.
A Quick Point!!
The Endocrine Glands secrete hormones into
extracellular fluid and then by diffusion these
move into the surrounding tissue.
A hormone
producing and
secreting cell
belonging to
some endocrine
gland
The Endocrine Glands
1. Pineal gland (not
assessed)
A Gland in the brain that
secretes melatonin, a
hormone that may help
regulate when you sleep at
night and when you wake
in the morning.
The Endocrine Glands
2. Pituitary Gland
Prolactin - which activates milk
production in breastfeeding women
Thyrotropin - which stimulates the
thyroid gland to produce thyroid (or
TSH)
Corticotropin - which stimulates the
adrenal gland to produce adrenaline
Endorphins - chemicals that act on
the nervous system and reduce
feelings of pain.
Antidiuretic hormones - which
helps control the balance of water in
the body
Oxytocin - which triggers the
contractions of the uterus in a woman
having a baby.
Examples of Hormones - ADH
Remember
those
Osmoreceptors?
Antidiuretic hormone (ADH) is a hormone chiefly
responsible for maintaining water levels in your
blood.
The Endocrine Glands
3. Thyroid Gland
The Thyroid Gland produces
the hormones thyroxine
and triiodothyronine.
These hormones control the rate
at which cells burn fuels from
food to produce energy.
Examples of Hormones -
Thyroxine
Thyroxine’s principle function is to stimulate
the consumption of oxygen and thus the
metabolism of all cells and tissues in the body.
The Endocrine Glands
4. Thymus (not
assessed)
Produces Thymosins and T-
lymphocytes which are
white blood cells that fight
infections and destroy
abnormal cells.
Functions to support the
immune system in
childhood but shrinks when
body is fully developed.
The Endocrine Glands
5. Adrenal Glands
Glands located on top of each
kidney. The adrenal glands
produce many hormones;
Aldosterone a hormone that
controls salt and water
balance
in the body, and Adrenaline
a
hormone that increases blood
pressure and heart rate when
the body experiences stress.
Plus Cortisol, Progesterone
and Oestrogen and
Noradrenalin.
The Endocrine Glands
6. Pancreas
An organ with many functions
including an endocrine function.
It produces and secretes
hormones Insulin and
Glucagon
which work together to regulate
blood sugar levels.
The7.Endocrine
Ovaries
Glands
A female sex organ that
produces Oestrogen and
Progesterone.
8. Testes
A male sex organ that
produces testosterone,
progesterone and
oestrogen.
ACTIVITY
Identify location of the
major endocrine glands in
the body and label them.
COMPARING &
CONTRASTING THE
NERVOUS & ENDOCRINE
SYSTEMS
Choose a side!
For each of the following
statements chose the side of
the room that identifies with
your answer
THE NERVOUS SYSTEM USES
CHEMICALS/HORMONES OR ELECTRICAL IMPULSES?
Chemicals/Hormones Electrical Impulses
THE NERVOUS SYSTEM USES
CHEMICALS/HORMONES OR ELECTRICAL IMPULSES?
Electrical Impulses
THE ENDOCRINE SYSTEM HAS A SYSTEM OF NERVES
OR HORMONES TO TRANSPORT MESSAGES?
Nerves Hormones
THE ENDOCRINE SYSTEM HAS A SYSTEM OF NERVES
OR HORMONES TO TRANSPORT MESSAGES?
Hormones
THE NERVOUS SYSTEM RESPONSES ARE
FAST OR SLOW?
Fast Slow
THE NERVOUS SYSTEM RESPONSES ARE
FAST OR SLOW?
Fast
THE ENDOCRINE SYSTEM USES
CHEMICALS/HORMONES OR ELECTRICAL IMPULSES?
Chemicals/Hormones Electrical Impulses
THE ENDOCRINE SYSTEM USES
CHEMICALS/HORMONES OR ELECTRICAL IMPULSES?
Chemicals/
Hormones
THE NERVOUS SYSTEM RESPONSES
OFTEN LAST A LONG OR SHORT TIME?
Long Short
THE NERVOUS SYSTEM RESPONSES
OFTEN LAST A LONG OR SHORT TIME?
Short
A MESSAGE IN THE ENDOCRINE SYSTEM CAN
ONLY FOLLOW ONE PATH OR TAKE MANY PATHS?
Follow one path Take many paths
A MESSAGE IN THE ENDOCRINE SYSTEM CAN
ONLY FOLLOW ONE PATH OR TAKE MANY PATHS?
Take many paths
THE NERVOUS SYSTEM HAS A SYSTEM OF NERVES
OR HORMONES TO TRANSPORT MESSAGES?
Nerves Hormones
THE NERVOUS SYSTEM HAS A SYSTEM OF NERVES
OR HORMONES TO TRANSPORT MESSAGES?
Nerves
RESPONSES FROM THE ENDOCRINE SYSTEM COME
FROM ONE PART OF THE BODY OR THROUGHOUT
THE BODY?
One part of the Throughout the
body body
RESPONSES FROM THE ENDOCRINE SYSTEM COME
FROM ONE PART OF THE BODY OR THROUGHOUT
THE BODY?
Throughout the
body
THE ENDOCRINE SYSTEM RESPONSES
OFTEN LAST A LONG OR SHORT TIME?
Long Short
THE ENDOCRINE SYSTEM RESPONSES
OFTEN LAST A LONG OR SHORT TIME?
Long
A MESSAGE IN THE NERVOUS SYSTEM CAN ONLY
FOLLOW ONE PATH OR TAKE MANY PATHS?
Follow one path Take many paths
A MESSAGE IN THE NERVOUS SYSTEM CAN ONLY
FOLLOW ONE PATH OR TAKE MANY PATHS?
Follow one path
THE ENDOCRINE SYSTEM RESPONSES
ARE FAST OR SLOW?
Fast Slow
THE ENDOCRINE SYSTEM RESPONSES
ARE FAST OR SLOW?
Slow
RESPONSES FROM THE NERVOUS SYSTEM COME
FROM ONE PART OF THE BODY OR THROUGHOUT
THE BODY?
One part of the Throughout the
body body
RESPONSES FROM THE NERVOUS SYSTEM COME
FROM ONE PART OF THE BODY OR THROUGHOUT
THE BODY?
One part of the
body
ACTIVITY
Comparison of endocrine and nervous system
Nervous Endocrine
Type of message Electrical (nerve Chemical
impulses) and (hormones)
chemical
(neurotransmitte
rs)
Speed of FAST! Slow…..
response (stimulus and (seconds to
age dependent days)
but approx. 750
msec)
Duration of Stops quickly Can continue for
response weeks
Area of effect Targeted and General and
specific widespread
Method of Neurons Blood stream
Transport
PLANTS HAVE HORMONES TOO!
Auxin
Produced – Shoot, root and bud
apical meristems
Functions - Stem elongation,
promotion of vascular tissue
growth, suppression of lateral
buds, influences responses to light
and gravity
Gibberellins
Produced – Apical region of roots
and shoots
Functions – Stem and internode
elongation, mobilisation of enzymes
during seed germination, flowering
and fruit growth
Gibberellin suppressant Paclobutrazol
Ethene (aka Ethylene)
Produced – Leaves, stems and young fruit
Functions – Controls leaf, flower and fruit fall, retards
lateral bud elongation, hastens fruit ripening
