Biology - B1.2 - Coordination and Control

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B1.2.1 - Responding to Change

  • The nervous systems has receptors, found in sense organs, to detect stimuli
  • The stimuli stimulates the receptors, causing electrical impulses to pass along neurons (contained in nerves) to the brain, which coodinates a response
  • The brain and spinal cord = central nervous system (CNS)
  • Effector organs may be muscles or glands - mucscles contract, glands secrete chemicals
  • Stimulus - Receptors - Sensory neurons - CNS/Relay neurone - Motor neurons - Effector organs - Response
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B1.2.2 - Reflex Actions

  • STIMULUS -> RECEPTOR -> SENSORY NEURON -> CNS -> RELAY NEURON -> NOTOR NEURON -> EFFECTOR -> RESPONSE
  • Gap between two neuron = SYNAPSE
  • Sequence from receptor - effector = reflex arc
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B1.2.3 - Hormones and the Menstrual Cycle

  • FSH - follicle stimulating hormone, made in the pituitary gland, causes egg to mature and oestrogen to be produced
  • OESTROGEN - produced by the ovaries, inhibits the further production of FSH, stimulates the production on LH, stimluates development of the womb lining to recieve a fertilised egg
  • LH - lutenising hormone, made by the pituitary galnd, stimluates the mature egg to be released from the ovary (ovulation)
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B1.2.4 - The Artificial Control of Fertility

  • Contraceptive pill may contain oestrogen and progesterone - some are progesterone-only and have fewer side effects - they prevent the production of FSH so eggs can't mature
  • FSH and LH can be given to women who can't produce mature eggs - fertility treatment
  • Contraceptive pill - adv: reduce family size = reduced poverty, pregnancies can be planned, disadv: side effects, some object for ethical/religious reasons
  • Fertility treatment - adv: help infertile couples having IVF, IVF help couples have babies, disadv:expensive, some think it's unethical-particularly for older women, extra embryos may be stored or destroyed
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B1.2.5 - Controlling Conditions

  • Body carefully controls internal conditions, eg. water and ion content, temperature, blood sugar level
  • Water - leaves when we breathe out and sweat, excess lost in urine(produced by kidneys)
  • Ion - leaves in sweat and urien
  • Temperature - must be kept constant, otherwise enzymes denature
  • Blood sugar - energy source for cells and controlled by the pancreas
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B1.2.6 - Hormones and the Control of Plant Growth

  • Plants sensitive to light, gravity and moisture
  • Shoots grow towards light - phototropism
  • Roots grow down (gravity and water) - gravitropism
  • AUXIN - hormone that controls phototropism and gravitropism
  • Unequal distribution of auxin = unequal growth - results in bending of shoots or roots
  • Plant growth hormones can be used as weed killers and to stimluate root growth
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B1.2.7 - Using Hormones

  • Hormones In Women
    -  used to prevent unwanted pregancies or plan for babies
    -  used to help get pregnant
    -  used for older women to get pregnant - egg donor is given hormones to produce extra eggs
    -  can lead to side effects
  • Hormones In Plants
    -  used by farmers and gardeners
    -  weedkillers used to kill unwanted plants
    -  before cuttings are taken, hormones are used to encourage root growth
    -  used to ripen fruit
    -  can damage environment eg. weedkillers may harm useful plants
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