This comprehensive Grade 12 IEB Life Sciences summary explains the endocrine system, covering the functions of major glands like the hypothalamus, pituitary, thyroid, and adrenal glands. It discusses key hormones, target organs, and processes like homeostasis and negative feedback mechanisms. Ideal...
CHEMICAL COORDINATION
the slow
,
prolonged process of communicating information by way of hormones secreted by the endocrine glands .The
endocrine system works with the nervous
system what is an endocrine gland -
hormones which
A vascular ductless
, gland that secretes
HORMONES AND TARGET ORGANS are carried in the bloodstream to their target organs .
crichly supplied will blood Vessels
> what is a hormone ?
An organic chemical substance usually a protein but sometime a sterold secreted by an endocrine gland and carriedIn the
, ,
blood stream to its target organs ,
where It regulates metabolic reaction .
↳ hormones do not last long in the body as they are broken down by enzymes
- What is a target organ ?
Hormones are carried In the blood throughout the body they only
,
affect certain cells . The specific cells that respond to a
given
hormone have receptor sites for that hormone . These cells are known as target tissue or target organs
ENDOCRINE GLANDS IN THE BODY
&
>
hypothalamus
Hypothalamus
brain above the
7. -
part of pituitary gland
Functions :
canterior pituitare
· controls the autonomic nervous system
posterior
pituitary
>
· controls the functioning of the pituitary gland
·
Its neurons secrete the hormone ADH (anti-diuretic hormones which is a neurohormone
what happens to the ADH ?
↳ ADH is passed down the nerve fibres and is stored in the posterior pituitary gland ,
when hormones from the
anterior pituitary gland are needed the hypothalamus secretes releasing factor into the blood which is carried to the
pituitary gland instructing It to produce and release hormones
↳ When ADH are needed from the posterior pituitary gland ,
nerve impulses from the hypothalamus cause the stored
hormones to be released into the bloodstream
2 .
Bitwitary Gland <hypophysis)
-
Master gland as it controls the release of hormones from other glands , located in
small bony cavity called the turkish saddle .
Anterior large and made
:
of secretory cells .
↳What hormones are secreted
O Thyroid stimulating hormone (TSH) stimulates thyroid to secrete thyroxin
:
② follicle stimulating hormone (FSH) : Stimulates Gametogenisis (Male and Female
③ Lutenizing hormone (CH) stimulates :
ovulation and formation of corpus luteum
① Prolactin stimulates production of
:
milk in the female mammary glands after the birth of the baby and maternal instrict
⑤ Adrenocorticotropic hormone (ACTH) :
Stimulates advenal cortex to secrete cortisone and aldosterone
⑧ Interstitial cell stimulating hormone (ICSH) : Stimulates the testes to secrete testosterone
⑦ Growth hormone (GH) or (STH) promotes skeletal
:
and muscular growth by stimulating synthesis of proteins
,
, ↳ growth disorders can occur :
> in prepubertal children :
·
hypersecretion overdevelopment :
of the skeleton ,
known as gigantisism , rare and normally caused by a tumor on the
pituitary gland .
·
hyposecretion : under development of the skeleton ,
known as pituitary dwarfism (different from genetic dwarfism) caused
by disease of anterior lobe of pituitary Suffers tend to be very short (91-122cm) but with normal proportions ,
They are not mentally retarded ,
but sexually immature ·
Can be treated with Injections of Synthetic STH produced
by genetically engineered bacteria .
> in adults :
· hypersecretion enlarged : hands
, jawbone and brow structures
,
called acromegaly . Because It is an adult bones
,
can only
thicken as growth plates are no longer active .
Posterior :
small and mainly made of neurons .
↳ The osmoreptors picks up change osmolarity of the blood . Nerve impulses stimulate posterior
hypothalamus , containing ,
in
lobe to secrete ADH also known as vasopressin ADH .
is responsible for conservation of water when the body is dehydrated by amoung
Other things increasing the permeability of the distal convoluted tubule in the nephron facilitating reabsorption of water into the
blood so that It is not excreted .
↳ disorders :
> lack of ADH Secretion causes diabetes insipidus , this condition is characterised by loss of large amounts of dilute urine
(5-10 liters a day) unrelated to sugar .
,
3 .
Thyrod Glamecrete restmadsbyromanoputar
NOTE :
>
Iodine is an essential element needed for production of thyroxin it is found in seafood ,
sea salt and lodised salt
,
A goltre may develop If Iodine levels are low .
Function
· increased basal metabolic rate (the amount of energy needed to function while at rest )
. It does this by controlling the rate
of cellor reproduction (ATP production
&espiration
:) CoHi280 +
Oc =
CO2 +
H20 + ATP
·
promotes normal functioning of the heart
·
promotes normal functioning of the nervous system It increases nervous activity ,
sharpness alertness and reflexes
,
,
of disorders
Types
:
hypothyroidism too little thyroxin-low metabolic rate
:
o
↳ in children : results in cretinism ·
Child does not
grow physically and has immature sexual development and mental retardation
↳
In adults :
myxoedema-mental and physical sluggishness ,
low BP low heart rate and low respiratory rate
·
hyperthyroidism :
too much thyroxin-high metabolic rate
↳
high body temperature and extreme sweating
↳ Increased heart rate ,
BP and respiratory rate
↳ muscle tremors and nervousness
↳ Swollen thyroid gotre (different to previously mentioned) -
exopthalmic goitre
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