Biology - B1.2 - Coordination and Control - Revision Cards in GCSE Biology

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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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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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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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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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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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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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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