The nervous system uses electrical impulses to enavle you to react quickly to your surroundings and coordinate what you do.
Cells called receptors detect stimuli (changes in the environment).
Like all animal cells, light receptor cells and other receptors have a nucleus, cytoplasm and cell membrane.
Impulses from receptors pass along sensory neurons to the brain or spinal cord (CNS). Impulses are sent along motor neurons from the brain (CNS) to the effector organs.
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B1 2.2 Reflex actions
Some responses to stimuli are automatic and rapid and are called 'relex actions'.
Reflex actions run everyday bodily functions and help you to avoid danger.
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B1 2.3 Hormones and the menstrual cycle
Hormones control the release of an egg from the ovary and the build-up of the lining of the womb in the menstrual cycle.
Some of the hormones involved are FSH from the pituitary gland and oestrogen from the ovary.
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B1 2.4 The artificial control of fertility
Hormones can be used to control fertility.
Oral contraceptives contain hormones, which stop FSH production so no eggs mature.
FSH can be used as a fertility frug for women, to stimulate eggs to mature in their ovaries. These eggs may be used in IVF treatments.
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B1 2.5 Controlling conditions
Humans need to maintain a constant internal environment, controlling levels of water, ions and blood sugar, as well as temperature.
Homeostasis is the result of the coordination of your nervous system, your hormones and your body organs.
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B1 2.6 Hormones and the control of plant growth
Plants are sensitive to light moisture and gravity.
Plant responses are brought about by plant hormones (auxin).
The responses of roots and shoots to stimuli such as ligt and gravity are the result of the unequal distribution of plant hormones.
We can use plant growth hormones as weed killers and as rooting hormones on cuttings.
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B1 2.7 Using hormones
There are benefits and problems associated with the use of hormones to control fertility and these must be evaluated carfully.
Plant hormones are very useful as weed killers but their use can damage the environment.
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