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module B1 Understanding Ourselves


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OCR GCSE module B1 revision notes. key points

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module B1 Understanding Ourselves

  1. 1. Module B1 – Understanding Ourselves • Being fit is not the same as being healthy Healthy means being free of any infection or diseases Being fit is a measure of how well you can perform physical tasks Blood is pumped around the body under pressure. The heart contracts to pump the blood around the body. These contractions increase the pressure of the blood and it means the blood reaches all parts of the body. The blood leaves the heart under pressure through arteries, these split into thousands of capillaries which take blood to every cell in the body. The blood flows back to the heart through veins under lower pressure. The blood pressure is at its highest when the heart contracts – this is the systolic pressure (the top measurement in blood pressure readings). When the heart relaxes the pressure is at the lowest – this is the diastolic pressure (the bottom measurement in BP readings). As people get older blood pressure tends to get higher, other factors can also cause high blood pressure, these are: a diet high in salt; being overweight; drinking too much alcohol; being under stress; not doing enough exercise Respiration - The process of releasing energy from glucose, which happens in every cell. • The energy is used to build up larger molecules (like proteins); contract muscles; maintain body temperature. Aerobic respiration – needs plenty of oxygen Glucose + oxygen carbon dioxide + water (+ ENERGY) Anaerobic respiration – doesn’t use oxygen at all • The glucose is partially broken down and lactic acid is produced. Lactic acid builds up in the muscles and gets painful. Glucose lactic acid (+ENERGY) • Exercising increases breathing rate and heart rate. The breathing rate increases to get more oxygen into the blood and carbon dioxide out of the blood. Heart rate increases to deliver more oxygen and glucose to the muscles quicker. The pulse rate remains high after you stop exercising to help you recover. If you’re fit your pulse rate goes back to normal faster than if you’re unfit. A balanced diet supplies all your essential nutrients 1
  2. 2. Nutrients Functions Carbohydrates e.g. glucose, provide energy Fats Provide energy and act as an energy store Proteins Growth and repair of tissue (meat, fish ) Vitamins Various functions, e.g. vitamin C - scurvy Minerals Various functions, e.g. iron needed to make haemoglobin – prevents anaemia Water Needed to replace water lost through urinating, breathing, sweating Fibre Keeps the guts in-order, prevents constipation Children and teenagers need more protein for growth; older people need more calcium to prevent diseases like osteoporosis. Females need more iron to replace iron lost in menstrual blood. Active people need more protein for muscle development and carbohydrate for energy. Eating too much can lead to obesity – it is defined as being 20% or more over recommended body weight Eating too little can cause problems like kwashiorkor – characterised by a very swollen stomach and caused by eating too little protein. The recommended daily allowance of protein can be calculated by: RDA (g) = 0.75 X body mass (kg) Body mass index indicates if you’re under / overweight. BMI = body mass (kg) Height m 2 Body mass index Weight description Below 18.5 underweight 18.5 – 24.9 normal 25 – 29.9 overweight 30-40 Moderately obese Above 40 Severely obese 2
  3. 3. BMI isn’t always reliable, athletes have lots of muscle which weigh more than fat, and this can falsely elevate their BMI even though they’re not overweight. % body fat can be an alternative measurement. Digestion • Big molecules are broken down into smaller ones enabling nutrients from our food to pass into our blood. Physical digestion is chewing food and churning it bout in the stomach. Chemical digestion involves enzymes which break down the big molecules into smaller ones. • Carbohydrases break down carbohydrates into simple sugars like glucose and maltose; proteases convert proteins into amino acids; lipases convert fats into fatty acids and glycerol. The enzymes need to have the right conditions to work effectively, for example the pH in the stomach is very acidic which is ideal for proteases to work effectively. Infectious diseases • An infectious disease can be spread from person to person. They are caused by pathogens. Pathogens are micro-organisms. There are four types:  Fungi - e.g. athletes foot  Bacteria – e.g. cholera  Viruses – e.g. flu  Protozoa – e.g. dysentery • Malaria is an example of an infectious disease. It is caused by a protozoan, this is a parasite and the animal it infects is called the host. The mosquitoes are vectors – this means they carry the disease without getting it themselves. They pick up the malarial parasite when they feed on an infected animal. Every time the mosquito feeds on another animal it infects it by inserting the parasite into the animal’s blood vessels. 3
  4. 4. • Some places have higher incidences of disease than others – this is generally the case in poorer, hot countries. • The body has three main ways of keeping out pathogens. o The skin – provides an effective barrier against micro-organisms, if it gets damaged the blood clots quickly to seal cuts to keep micro-organisms out. o The digestive system – the stomach produces hydrochloric acid which kills most micro-organisms that get in that way. o The respiratory system – lined with mucus and cells with cilia (little hairs) which catch dust and bacteria before they reach the lungs. Preventing and treating infectious disease • Immune system: o White blood cells engulf foreign cells and digest them; they produce anti toxins to deal with any poisons produced by the invading micro-organism; they produce antibodies which are specific to the invading micro-organism (antigen). If the person is infected again by the same micro-organism the white blood cells will quickly produce the antibodies to kill it – the person is naturally immune to the pathogen and won’t get ill. • Immunisation stops you getting infections E.g. polio, measles = active immunity, the immune system makes its own antibodies after being stimulated by a pathogen. Usually permanent. Passive immunity – you use antibodies made by another organism, e.g. passed on from mother to baby through breast milk. Only temporary. • Antibiotics – get rid of bacterial infections. They kill bacteria or fungi without killing your own body cells. They DO NOT KILL VIRUSES. 4
  5. 5. Other disorders These things can cause disorders: • Vitamin deficiency – e.g. scurvy – lack of vitamin C • Mineral deficiency – e.g. anaemia - lack of iron • Genetic inheritance - e.g. red-green colour blindness; haemophilia • Body disorders – e.g. cancer; diabetes Drugs are developed to treat diseases but they need to be tested first. Often computer models are used first, then they are tested on human tissues, then on animals – British law states this should be on two different live mammals. After this the drug is tested on humans in a clinical trial, if it works and there are no harmful side effects the drug is put on the market for sale. Drugs: use and harm • Drugs can be beneficial or harmful • Drugs can cause addiction and users suffer withdrawal symptoms if they don’t get the drug. It is not just illegal drugs that cause addiction. • Tolerance – the body gets used to having the drug and you need a higher dose to give the same effect. • Depressants – e.g. alcohol, temazepam. They decrease the activity of the brain. Slows down reactions. 5
  6. 6. • Stimulants – e.g. nicotine, ecstasy, caffeine. They increase the activity of the brain. They make you feel alert and awake • Painkillers – e.g. asprin, reduces the number of painful stimuli at the nerve endings near an injury. Local anaesthetics act differently as though the painful stimuli still happen they are blocked. • Performance enhancers – e.g. anabolic steroids, they help build muscle and allow athletes to train harder – they’re banned by sports organisations. Testosterone is an example. • Hallucinogens – e.g. cannabis, LSD. They distort what is seen by altering the pathways that nerve impulses normally travel along. • Some drugs are illegal: • Class A – heroin, LSD, ecstasy and cocaine • Class B – amphetamines (speed). Become class A if injected. • Class C – cannabis, anabolic steroids, tranquillisers Smoking and alcohol • Smoking Burning them produce four main things: 1. Carbon monoxide – stops haemoglobin carrying as much oxygen, can lead to small baby at birth 2. Nicotine – stimulant drug, makes smoking addictive 3. Particulates – little particles that irritate the airways 6
  7. 7. 4. Tar – contains chemicals, carcinogens • Smoking causes all sorts of illnesses: 1. Disease of the heart and blood vessels leading to heart attacks and strokes. 2. Lung, throat, mouth and oesophagul cancer 3. Severe loss of lung function leading to diseases like emphysema and bronchitis, Alcohol is a depressant drug • Reduces the activity of the nervous system • Makes people feel less inhibited • Too much can cause death of liver cells – cirrhosis • Alcohol can cause dehydration • Being drunk leads to impaired judgement, poor balance, poor coordination, slurred speech, blurred vision, sleepiness. Receptors – The Eye • Cornea – refracts light into the eye • Iris – controls how much light enters the pupil (the hole in the middle) • Lens – focuses the light onto the retina • Retina – the light sensitive part, its covered in receptors called rods and cones which detect light. 7
  8. 8. • Rods – more sensitive in dim light but can’t sense colour • Cones – sensitive to colours but not so good in dim light (red / green colour blindness is due to a lack of certain cone cells). • Optic nerve – carries impulses from the receptors to the brain • How light gets into the eye: light from the object is refracted into the eye by the cornea, the lens refracts the light a bit more to focus it on your retina. • Long sighted – unable to focus on near objects because the cornea or lens doesn’t bend the light enough or the eyeball is too short. This means images of near objects are bought into focus behind the retina. • Short sighted – unable to focus on distant objects because the cornea or lens bends the light too much or the eyeball is too long. This means the images of distant objects are brought into focus in front of the retina. • Binocular vision – two eyes work together. The brain uses small differences between what each eye sees to judge distances and how fast things are moving. • Monocular vision – eyes have totally separate views, e.g. turkeys and lizards. They have a wider field of vision but can’t judge depth or speed. Organisms with monocular vision are more likely to notice predators. Neurones and reflexes • Neurones transmit information around the body. The nervous system is very quick – it uses electrical impulses. 8
  9. 9. • The central nervous system coordinates information – it consists of the brain, spinal cord. A change in the environment (a stimulus) is detected by sensory neurones which carry the information from receptors (e.g. light receptors in the eye) to the CNS. The CNS sends the information to an effector (muscle or gland) along a motor neurone. The job of the CNS is to coordinate the information. • Reflex actions stop you injuring yourself. The conscious brain isn’t involved instead the sensory neurone often joins to a relay neurone in the spinal cord which links directly to the motor neurone. Reflex actions often have a protective role so you don’t get hurt. Homeostasis - Maintaining a constant internal environment • Body temperature - kept at about 37OC • Too hot o Hairs lie flat o Lots of sweat which transfers heat from you to the environment as it evaporates, this cools you down. o Blood vessels close to the surface of the skin widen, this means more blood flows near to the surface and radiates more heat into the surroundings. o If you get too hot you may get dehydrated – heat stroke – death • Too cold o Hairs stand on end to trap an insulating layer of air which helps keep you warm o Very little sweat is produced 9
  10. 10. o Blood vessels near the surface of the skin constrict o You shiver o If your body temperature drops too low you can get hypothermia - death • How do you measure body temperature? o Use a clinical thermometer or temperature sensitive strip or digital thermometer. Place in ear, mouth or anus, these are areas that are nearest in temperature to the internal organs. Hormones - Chemical messengers sent in the blood - Produced in endocrine glands - The glands release hormones directly into the blood - They travel all over the body but only affect particular organs called target organs - They travel at the speed of blood, this is SLOWER than the nervous system • Ovaries (females) – produce oestrogen, promotes female secondary characteristics (extra hair on underarms and pubic area, hips widen, development of breasts, periods start) • Testes (males) – produce testosterone, promotes male secondary characteristics (extra hair on face and body, muscles develop, penis and testicles enlarge, sperm production, deepening of voice). • Pancreas – produces insulin for the control of blood sugar, 10
  11. 11. • Hormones are also used in contraception and fertility treatment, e.g. the Pill Controlling blood sugar • Insulin controls blood sugar levels • Blood glucose level too high = insulin added • Blood glucose level too low = no insulin added • In diabetes the pancreas stops making enough insulin • If the blood sugar levels rise too much it can cause death. The problem can be controlled by: o Avoiding foods rich in carbohydrate o Injecting insulin – before meals, removes glucose from the blood as soon as it enters the blood from the gut where the carb rich food is being digested. This stops the level of glucose in the blood from getting too high. This is an effective treatment however the person also needs to eat sensibly after injecting insulin or the blood sugar level could drop dangerously low. • Monitoring blood sugar levels – glucose-monitoring device, prick their finger to get a drop of blood for the machine to check. Genes and chromosomes • Found in the nucleus which contains 46 chromosomes arranged in 23 pairs. Chromosomes are divided into different regions called genes. A gene is a short length of a chromosome, which is quite a long length of DNA. DNA is a double helix, coiled into a double spiral. 11
  12. 12. • Genes are responsible for certain characteristics, e.g. eye colour, nose shape, ear lobe shape, blood type. There are variations in the genes that give different versions of the same characteristics, e.g. blue or brown eyes. Genetic variation is caused by: GENES • Sexual reproduction – shuffling chromosomes • Mutations – occasionally a gene may mutate and produce a new characteristic, increasing variation ENVIRONMENT • Scars • Spoken language Most characteristics are due to a mixture of genes and the environment. E.g. height determined by your genes but whether you get it depends on your environment, growth can be stunted if you have a poor diet. Genes, chromosomes and genetic disorders • Chromosomes determine whether you’re male or female • The 23rd pair determine whether you’re male or female 12
  13. 13. • All men have an X and a Y chromosome. XY. The Y chromosome causes male characteristics. • All women have two X chromosomes, XX. The XX combination causes female characteristics. • Only dominant characteristics are seen, e.g. brown eyes are dominant over blue eyes • Mutations are changes to genes • It can happen spontaneously, though the chances can be increased by nuclear radiation, X rays, UV light also exposure to certain chemicals called mutagens, e.g. cigarette smoke. • Mutations are usually harmful, if a mutation occurs in reproductive cells the offspring may develop abnormally or die. If the mutation occurs in body cells the mutant cells may start to multiply in an uncontrolled way or invade other parts of the body = cancer. • Occasionally mutations may be beneficial giving an organism a survival advantage. • Genetic disorders are caused by faulty genes: • e.g. cystic fibrosis – disorder of cell membranes, the body produces a lot of thick, sticky mucus in the air passages and pancreas 13
  14. 14. • red / green colour blindness – lack of certain cone cells in retina. • Sickle cell anaemia – funny shaped red cells, get stuck in blood vessels, causing shortage of oxygen. Causes pain, anaemia possibly a stroke or heart attack 14