B1.2 Coordination & Control Key Points

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B1 2.1 Responding to change

  • 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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