The endocrine system

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The endocrine system
Hormones are molecules secreted by an endocrine gland directly into the body. They act as
chemical messengers carrying a signal from the endocrine gland to a specific target organ or
tissue.
The endocrine system
another communication system in the body
uses blood circulation to transport its signals
blood transports all over the body
any signal released into the blood will be transported through the body
the signals released are hormones
hormones are released from endocrine glands
Endocrine glands are glands that secrete hormones directly into the blood. Endocrine glands are
ductless- they consists of a group of cells that produce and release the hormone straight into the
blood capillaries.
Exocrine glands are glands that secrete molecules into a duct that carries the molecules to where
they are used. Examples include: salivary glands, sweat glands etc.
Targeting the signal
cells receiving a hormone must have specific complementary receptor on their plasma
membrane
every hormone is different: a hormone can travel around in the blood without affecting cells in
the body that do not have the correct receptor
Target cells are those that possess a specific receptor on their plasma membrane.
The shape of the receptor is complementary to the shape of the hormone molecule
Damilola Fasoyiro A2 Biology
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Many target cells together form a tissue
Hormones
There are two types of hormones:
Protein and peptide hormones - (insulin and glucagon), and derivatives and of amino
acids- (adrenaline)
Steroid hormones ­ (sex hormones)
These hormones work in different ways
proteins are not soluble in the phospholipid membrane and do not enter the cell
steroid can pass through the membrane and enter the cell to have a direct effect on the DNA in
the nucleus
The action of adrenaline
Adrenaline is an amino acid derivative:…read more

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Increase heart rate
Cause general vasoconstriction to raise blood pressure
Stimulate conversion of glycogen to glucose
Dilate the pupils
Increase mental awareness
Inhibit the action of the gut
Cause body hair to erect
The adrenal cortex
uses cholesterol to produce certain steroid hormones
roles in the body:
Mineralocorticoids (e.g. aldosterone) help to control the concentrations of sodium and
potassium in the blood
Glucocorticoids (e.g.…read more

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