Summary
GRADE 11/12 IEB ENDOCRINE SYSTEM SUMMARY
In this summary, I cover all sections of the endocrine system, broken down in their various hormones. (IEB syllabus)
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-THE Endocrine System
the endocrine system
: is made up of
glands that produce & secrete hormones directly into the blood .
The role of the endocrine system is to control & coordinate the life processes in the body in response
to
changes in the internal
& external environments in such a
way that a constant internal environment
is maintained ( homeostasis ) .
life processes :
growth & development ,
chemical reactions in the
body ( metabolism )
,
the balance of water & salts
in the
body Cosmo regulation ) as well as reproduction .
- endocrine system :
system made up of
glands that produce & secrete hormones
directly into the bloodstream .
^
Secrete : to release or give off .
-
gland :
group of cells that are specialised to
produce & secrete a specific chemical substance . Cie hormone )
'
endocrine gland : a ductless gland that secretes its hormone directly into BS
É
•
hormone chemical substance that is produced in into the BS by endocrine
very small
:
secreted amounts glands .
•
target organ :
organ that responds to a hormone secreted by an endocrine gland .
Nervous system vs Endocrine system
• '
consists of neurons consists of glands
-
-
info transmitted in the form of nerve impulses information transmitted in the form of hormones
I
•
nerve impulses travel
along nerve fibres hormones travel in the blood
' -
info travels info
very quickly travels
slowly
'
>
affects the action of effectors (muscles gland) affects the action of target organ
>
'
effect of nerve impulse does not last effect of last for time
very long . a hormone can a
long
-
hypothalamus :
part of the brain that acts as an endocrine gland secreting hormones that either stimulate or
suppress the
release of hormones by the pituitary gland .
-
:
ADH hormone produced by the
hypothalamus which is stored in the pituitary gland ; allows more water to be re -
absorbed into the blood from the kidneys , reducing the volume of water lost in urine .
I
pituitary gland : endocrine gland at the base of the brain ; also known as the master gland because it produces
the secretion of other hormones
hormones that regulate .
-
thyroid gland :
endocrine
gland at the front of the neck that releases
thyroxine , a hormone .
&
'
: in the abdomen
pancreas organ that functions as both exocrine endocrine glands ; secretes the hormones
insulin and glucagon .
'
islets of Langerhans : clusters of cells in the pancreas that secrete the hormones glucagon
& insulin which
regulate
the blood glucose concentration .
, Locations & functions of endocrine glands :
' * ADH =
anti diuretic hormone
the
hypothalamus
-
located in the centre of the brain ,
below cerebrum .
activates & controls the autonomic nervous
system .
diuretic is the ability to conserve water
produces hormones that either stimulate of hormones from the
or inhibit the release
pituitary gland .
-
Front
functions secrete releasing factors Anterior pituitary gland
:
which stimulate the
- back
-
1 water con =
ADH
nerve impulses stimulate the posterior pituitary gland
- .
.
& responsible for the production of ADH Cret by posterior pg ) regulates the amount of water in the blood .
I
É
'
2 ' ' '
the pituitary gland :
master gland located at the base of the cranium turkish saddle is linked to
hypothalamus by a thin stalk .
Anterior growth hormone ; thyroid stimulating hormone CTSH ) ; Follicle stimulating hormone CFSH ) ; Luteinizing
hormone ( LH ) ; prolactin É adrenocorticotropic hormone CACTH )
Posterior anti diuretic hormone CADH )
-
& oxytocin .
3
Thyroid gland :
located in the lower front part of the neck ,
infront of trachea & below larynx
shaped like a
butterfly & has a L & R lobe ( connected by a narrow band of tissue .
)
secretes hormones that control the
body 's metabolism ( Thyroxine )
Thyroxine : inc metabolic rate / promotes normal functioning of the heart promotes normal
functioning of NS
* iodine is essential for production of metabolism *
thyroxine over stimulation
more
thyoroxine =
.
.
'
Lack of iodine development of
goitre C.
swelling of the
thyroid gland due to malfunction of the gland )
=
a
4 Pancreas :
an
elongated organ located in the abdomen behind the stomach .
1. exocrine :
secretes digestive enzymes into small intestines .
2. endocrine : secretes hormones into the blood .
Chas islets of Langerhans) .
blood
* normal
glucose levels : 70 80mg 1dL of blood
-
islets of Langerhans
.
:
Alpha cells ( d)
1- :
secrete which raises the concentration of in blood liver
glucagon -
glucose the by causing cells in the
to break down glycogen into glucose .
2 Beta cells (B) : which secrete insulin of in the blood
which lowers the concentration glucose by causing cells in the body
. -
to absorb glucose from blood & convert it into
glycogen / fat .
& is stored in fatty (adipose) tissue .
5 Adrenal gland : located on top of each kidney .
>
consists of : outer medulla & inner medulla .
6
Gonads :
are the
organs that produce reproductive cells cgamates) .
produce hormones that determines the development of secondary sexual characteristics .
synthetic growth hormone ; small bodies
1-
disproportionate heads .
2. too much
hyper secretion (giantism)
C
very tall ; caused by tumor in the
pituitary gland crave ) .
in adults ( acromegaly)
:
hyper secretion
bone continue to grow in size
?
enlarged hands
, jawbone & brows
usually affects middle aged adults .
( posterior)
g) Anti -
diuretic hormone :
Osmo
regulation
target organ :
kidney
result :
regulation of H2O levels .
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