Biology B1a
Key Points from B1 in the AQA Core Course
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- Created by: Zoey Vickers
- Created on: 04-06-09 19:06
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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