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5.1.4 Hormonal
Communication
A Level Biology…read more

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The Endocrine System
· Made up of endocrine glands- a group of cells which are specialised to
secrete chemicals- hormones. These are secreted directly into the
bloodstream
· The pituitary gland:
-base of brain
-makes several hormones which, in turn, control the release of other
hormones
-close proximity to the hypothalamus ensures that the nervous and
hormonal responses of the body are closely linked and co-ordinated
· Exocrine glands produce other secretions outside the body or to
other surfaces of the body e.g. digestive enzymes (not secreted in the
bloodstream)…read more

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Hormones
· Chemical messengers which carry information from one part of the body to
another
· Most are proteins, can be: steroids, proteins, glycoproteins, polypeptides, amines
or tyrosine derivatives
· Secreted directly into the bloodstream when a gland is stimulated- can occur as
a result of a change in concentration of a particular substance e.g. blood glucose
concentration and can also occur as the result of another hormone or nerve
impulse
· Hormones diffuse out of the blood and bind to specific receptors for that
hormone, found on the membranes or in the cytoplasm in cells of target organs
target cells
· Once bound to the receptor, hormones stimulate the target cells to produce a
response…read more

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Type of hormone determines the
way it causes its effect on a
target cell
Non-Steroid Hormones
· Hydrophilic so cant pass directly through the cell membrane
· 2 stages
· They bind to specific receptors on the cell surface membrane of the
target cell which relay the message via a different receptor
molecule- second messenger
· This triggers a cascade reaction mediated by chemicals- second
messengers e.g. adrenaline…read more

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