The Endocrine System
Contents
2
Hormone
Endocrine & exocrine
Undercativity of the
pituitary gland
glands
Types of hormones
Functions of hormones
The endocrine glands
in the human
Hypothalamus
Pituitary gland
Glands, Hormones &
Functions
Overactivity of the
pituitary gland
Diabetes mellitus
Feedback mechanism
of hormonal control
Hormonal Vs Nervous
Communication
 Similarities
 Differences
Hormone
hormone: a substance (chemical
message) produced by an endocrine
gland secreted directly into and
transported by the blood stream to other
parts (target organs) of the body where it
evokes a response.
3
Endocrine & exocrine glands
4
endocrine gland: ductless gland secretions (hormones) delivered directly
into bloodstream e.g. pituitary, thyroid,
parathyroid, pancreas, adrenal, ovary
and testis.
exocrine gland: a gland which delivers its
secretion through a tube or duct - does
not depend on blood stream - e.g. liver,
pancreas, sweat glands and salivary
glands.
Types of hormones
Protein or protein-like nature e.g. insulin
– attach to proteins on the surface
membranes of their target organs and
cause a response.
 Steroids e.g. oestrogen (similar structure
to cholesterol) – enters the cells of the
target organ – affects the nucleus and
caused the cell to produce specific
proteins – a slower response.

5
Function of hormones
to regulate the activities of the various body
systems e.g. cell metabolism (blood
sugar levels – insulin)
6
The endocrine
glands in the
human
7
The endocrine
glands in the
human
8
Thyroid and Parathyroid location
9
Hypothalamus
Monitors the blood – pH, temperature,
hormone levels
 Hormones released by hypothalamus
travel to pituitary and cause it to release
hormones.
 Produces TRH (thyroid releasing
hormone) which stimulates the pituitary
to release TSH.

10
Position of
hypothalamus
and pituitary
gland
11
Pituitary gland
Releases hormones that control other
glands e.g. TSH (thyroid stimulating
hormone) stimulates the thyroid gland to
release thyroxine, which increases cell
metabolism.
 Releases hormones that control other
organs e.g. growth hormone

12
Glands, Hormones & Functions
13
Under activity of the pituitary gland
If the pituitary of a child does not produce
enough growth hormone – this person
will not grow = a pituitary dwarf.
 Can be cured with growth hormone
injections (must be given before normal
growth stops)

14
Over activity of the pituitary gland
If the pituitary of a child produces too
much growth hormone – this person will
grow very large = a pituitary giant – often
due to a pituitary tumour).
 Can be stopped by removing the tumour
(will not reduce growth that has already
taken place)

15
Diabetes mellitus
diabetes mellitus: sugar in urine and
excessive urine production caused by an
inadequate production of insulin by the
pancreas.
Affected people can monitor their blood
sugar levels and inject themselves with
insulin when their sugar levels are rising.
16
17
Hormonal Vs Nervous
Communication
SIMILARITIES
18

Both provide a means of communication
within the body.

Both involve the transmission of a
message, which is triggered by a
stimulus and produces a response.
Similarities continued
19

The target organs of a hormone are
equivalent to a nerve's effector.

Both involve chemical transmission - the
transmission of the message across the
synapse is achieved by acetylcholine
(chemical messenger), which is
equivalent to a hormone in the endocrine
system.
Hormonal Vs Nervous
Communication – Differences
Chemical substance sent
through blood stream
Responses usually slow
Hormones carried to all
parts of the body
Responses often
widespread - involving
many target organs
Responses may continue
over a long time
20
Action potential sent
along nerve fibre
Response usually rapid
Impulse transmitted to
specific destinations
Responses may be
localised - involving
only one muscle
Responses usually rapid
and short-lived
END
21