Biology B1a

Key Points from B1 in the AQA Core Course

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Hormones

  • Secreted by glands
  • Chemicals that help control and co-ordinate processes in your body
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The Nervous system

  • Uses electrical impulses so you can react with your surroundings
  • Receptors detect stimuli
  • Impulses from receptors pass along sensory neurones to the brain
  • Impulses sent from the brain along motor neurones to effector organs
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Reflex Actions

  • Some responses to stimuli are automatic and rapid
  • A relay neurone connects the sensory and motor neurone
  • Relay neurone often found in the spinal cord
  • Called the reflex arc
  • The electrical impulse in the relfex arc bypasses the concious areas of your brain
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The Menstrual Cycle

  • Controlled by hormones
  • Pituitary Gland releases FSH - stimulates eggs to mature in the ovaries and stimulates ovaries to produce oestrogen
  • Oestrogen - stimulates lining of the womb to thicken. Also stimulates pituitary gland to produce LH
  • LH - Stimulates the release of a mature egg
  • 28 days - lining of the womb thickens
  • 14 days in egg released
  • If fertilised pregnancy takes place
  • Not fertilised - egg and lining shed from womb (period)
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Controlling Fertility

  • Hormones
  • Oral contrceptives stop production of FSH ( no eggs mature)
  • FSH used as fertility drug to stimulate eggs to mature
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Controlling Conditions

  • Humans need to maintain constant internal environment
  • water and ions (like salt) - Kidneys play important role, nerves and hormones control concentration of urine form kidneys
  • blood sugar - concentration of glucose in yoru body kept constant by hormones made by the pancreas
  • temperature - sweat to cool down, shiver to warm up, nervous system controls this
  • Homeostasis - is coordination of CNS, Hormones and Organs
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Diet and Exercise

  • Healthy diet - carbohydrates, proteins, fats, vitamins, minerals, fibre, water
  • Balnced diet - right amount of each food
  • Different people need different amounts of energy
  • too much - too fat - too little - too thin
  • If you do little exercise you don't need as much food. More exercise = more food
  • Metabolic rate - the rate at which all chemical reactions in the cells of the body take place
  • Exercise increases your metabolic rate
  • Could be affected by factors inherited from your parents
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Weight Problems

  • Obesity - take in more energy than you use=excess stored as fat
  • Serious health problems - Arthritis, Diabetes, high blood pressure, heart disease
  • Starvation - muscles waste away, immune system can't work properly.
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Cholesterol

  • Made in the liver
  • We need cholesterol for our cell membranes, sex hormones and to deal with stress
  • High levels increase risk of heart disease or diseased blood vessels
  • Cholesterol levels depend on two factors - the way your liver works (inherited) and the amount of fat in your diet
  • Carried around body by lipoproteins
  • LDL (low-density lipoproteins) are 'bad'
  • HDL are 'good'
  • Need to get a balance in blood for healthy heart
  • Fats - Saturated- raise cholesterol; Mono-unsaturated -reduce cholesterol; Polyunsaturated - best at reducing levels
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Drugs

  • Change chemical processes in the body
  • Harmful
  • Cannabis causes psychological problems
  • very addictive
  • cause serious health problems
  • Alcohol - gets to your nervous system and slow down reactions
  • Smoking - nicotine is addictive; Tar is a carcinogen - cancer causing;
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Pathogens

  • Bacteria - single cell, genetic material is not in the nucleus, has cytoplasm surrounded by cell membrane and cell wall.
  • Some bacteria are useful
  • Reproduce once inside the body - produce toxins
  • Virus - smaller than bacteria, protein coat surrounding genetic material
  • Virus - takes over your cells and reproduces damaging and destroying them
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Defence Mechanisms

  • Passive immunity - Skin - acts as a barrier; Platelets - in your blood, form a scab when barrier is damaged; Mucus - traps pathogens, in your respiratory system; Stomach acid - destroys pathogens
  • Active Immunity - White blood cells - ingests pathogens, makes antibodies and antitoxins
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Antibiotics

  • can kill bacteria without harming your cells
  • No effect on a virus
  • Antibiotic resistant bacteria - as a result of natural selection. (MRSA)
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Vaccination

  • Vaccines - made of dead or weakened form of the disease causing microbes
  • Gives white blood cells chance to develop the antibodies to fight the infection without you getting ill
  • White Blood Cells can then respond rapidly if you meet the live pathogens
  • Can be used to fight bacterial (tetanus, diptheria) and viral (polio, measles, mumps and rubella) diseases.
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