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B1.2 Nerves and hormones

The nervous system enables humans to react to their surroundings and coordinate their behaviour.

o Any change in your surroundings e.g. temperature, visual, sound etc. is potentially a detectable stimulus to one
of you sensory organs e.g. skin, eyes, ears etc. The stimulus might be chemical,…

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o a chemical is then released at the synapse between a relay neurone and motor neurone in the central
nervous system, causing impulses to be sent along a motor neurone to the organ (the effector) that brings
about the response,
The effector is either a muscle or a gland, a…

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Hormones regulate the functions of many organs and cells
Several hormones are involved in the menstrual cycle of a woman and hormones are involved in promoting the release
of an egg:
The follicle stimulating hormone (FSH) is secreted by the pituitary gland and causes eggs to mature in the

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Plants are sensitive to light, moisture and gravity:
Their shoots grow towards light and against the force of gravity,
Their roots grow towards moisture and in the direction of the force of gravity.
Plants produce hormones to coordinate and control growth:
Auxin is a plant hormone that controls the growth…





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