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Hormones and the Endocrine System: (1) WRP- Coordination and Response…
Hormones and the Endocrine System
: (1) WRP- Coordination and Response Avantika
Hormones and Endocrine Glands:
Hormones
are
chemical substances
produced by
glands
and carried by the
blood
, which alters the activity of the
target organ
.
Hormones either
speed up or slow down the activity of an organ.
Endocrine glands
are glands which produce specific hormones. They
do not have duct
and are often known as duct less glands.
Endocrine system
: Transmission of chemicals, Transmission via blood, Slow transmission, Hormones dispersed throughout the body, long term effects.
How are hormones secreted by the endocrine glands?
1) A stimulus affects the endocrine gland. Hormone is secreted.
2) Hormone reaches the target organ through blood stream.
3) Hormones are specific. Receptor cells on the membrane of the target organ recognise the hormone.
4) Target organ brings about an appropriate response.
Functions of hormones:
Regularising
Maintaining
Coordination
Development of the body
Metabolism
Thyroid gland:
Present in
front of the neck
.
Produces the hormone
Thyroxine
Role of Thyroxine:
It has a
stimulatory effect on the metabolic rate of the body cells.
Controls the
level of activity.
Promotes skeletal growth
.
Helps in the normal development of the brain.
Pituitary gland:
Attached to the
base of the brain
.
Produces
many hormones
.
Produces
FSH
:
Follicle Stimulating Hormone
. It
matures follicles in the ovaries.
Produces
LH
:
Luteinising Hormone
. It
induces ovulation.
It also produces the
human growth hormone
.
Adrenal glands:
Present at the
back of abdominal cavity, above both the kidneys.
It has a zone called the "
Adrenal Medulla
". This medulla
receives nerves from the brain and produces the hormone Adrenaline.
Adrenaline has some obvious effects on our body:
In response to stressful situations,
nerve impulses are sent from brain to the adrenal gland
, which
releases the hormone adrenaline.
Its presence causes
breathing
to become
faster and deeper.
The
heart beats faster, leading to an increase in the pulse rate
Pupils
dilate
, making them look more
black
.
These all effects make us more able to react quickly and strongly in dangerous situations (fight or flight situations).
The pancreas:
Is an endocrine and an exocrine gland
Insulin and Glucagon
are produced in the
islets
of langerhans.
Insulin
controls the
levels of glucose in blood.
Glucagon
converts the
glycogen in the liver to glucose.
Reproductive organs:
Ovaries
Produces
Oestrogen
(This
thickens the lining of uterus
).
Testes
Produces
Testosterone
. Plays a part in the
development of secondary sexual characteristics.