AQA SCIENCE B1A

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  • Created by: Amy Hatch
  • Created on: 17-04-11 14:52

B1A 1.1 RESPONDING TO CHANGE

Hormones, secreted by special glands, are chemicals that control internal processes in the body.

The nervous system responds to changes in the environment

  • receptor cells detect stimuli such as 
    • light
    • sound
    • temperature
  • impulses from the receptor travels along the sensory neurone
  • the brain then co-ordinates a response
  • impulses from the brain travel back along motor neurones to the effector

RECEPTOR > SENSORY NEURONE > CO-ORDINATOR > MOTOR NEURONE > EFFECTOR

B1A 1.2 REFLEX ACTION

  • Reflexes are reactions to change that happen unconsciously
  • Reflex actions include pulling your hand away from a hot object to protect your body

a reflex arc (http://scienceaid.co.uk/biology/humans/images/reflexarc.png)

  • the receptor detects the change then an impulse travels along a sensory neurone to the spinal chord, not the brain
  • it then passes over a synapse and along a relay neurone, then straight back to the effector along the motor neurone
  • this reaction is very quick and requires no conscious thought 

detailed structure of a synapse (http://scienceaid.co.uk/biology/humans/images/synapse.png)

Impulses travel synapses by sacs containing chemicals passing the gap which starts another impulse on the relay neurone.

B1A 1.3 THE MENSTRUAL CYCLE

  • the menstrual cycle is controlled by hormones
  • once a month, the pituitary gland secretes FSH
    • this makes eggs mature in the ovary
    • it stimulates the secretion of oestrogen from the ovaries
      • this causes the womb lining to thicken
      • it stimulates the pituitary gland to produce LH
        • this stimulates the release of the matured egg 

B1A 1.4 ARTIFICIAL CONTROL OF FERTILITY

THE CONTRACEPTIVE PILL

  • contain mainly oestrogen
    • oestrogen inhibits the release of FSH
    • without FSH no eggs can mature
  • must be taken regularly
  • can cause health problems

FERTILITY TREATMENTS

  • fertility drugs containing FSH can be taken 
    • this stimulates eggs to mature in the ovary
    • also triggers the release of oestrogen
    • can result in many babies
  • IVF treatments remove eggs from the ovaries and fertilize them with sperm in a test tube
    • good if fallopian tubes are damaged
    • expensive
    • low success rate
  • raises ethical questions about interfering with god's plan and what to do with extra embryos

B1A 1.5 CONTROLLING CONDITIONS

WATER AND IONS

  • if too much water moves in or out of cells they could be damaged
  • you lose water in sweat, urine and when you breath out
  • you lose salt in sweat and urine
  • kidneys control water and salt levels

TEMPERATURE

thermoregulation (http://scienceaid.co.uk/biology/humans/images/thermoregulation.jpg)

BLOOD SUGAR

  • blood sugar levels must be kept constant
  • controlled by the pancreas
    • secretes insulin

2.1 DIET AND EXERCISE

  • a healthy diet consists of:
    • carbohydrates
    • proteins
    • fats 
    • vitamins
    • minerals
    • fibre
    • water
    • the right amount of energy
  • if your diet isn't balanced you will become malnourished
  • in rich countries such as the UK, there are not many malnourished people, but some don't get the right amount of energy

ENERGY

  • the amount energy a person needs depends on:
    • gender
    • age
    • amount of exercise they do
    • the temperature of where they live
    • their metabolic rate
      • this is affected by proportion of fat to muscle and your genes

2.2 WEIGHT PROBLEMS

  • BMI = WEIGHT / (HEIGHT)2

OBESITY

  • if you take in more energy than you use,

Comments

Krissie

loving these notes :)

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