Biology B1

Fitness and Health
1. Blood Pressure
  1. Measured in millimetres of mercury (mmHg)
  2. Stylostic pressure is the maximum pressure the heart produces Diastolic pressure is the blood pressure between heartbeats
  3. Can be increased by: stress, high alcohol intake, smoking and being overweight
    1. Can be decreased by: regular exercise and eating a balanced diet
  4. High blood pressure can cause blood vessels to burst. It can cause damage to the brain (stroke) and to the kidneys
    1. Low blood pressure can cause dizziness, fainting (because the blood supply to the brain is reduced) and poor circulation to other areas such as the fingers and toes.
2. Fitness and Health
  1. Fitness is the ability to do physical activity
    1. Health is being free from diseases such as those caused by bacteria and viruses.
  2. General level of fitness can be measured by your cardiovascular efficiency
  3. Fitness can be measured for different activities
    1. Strength - by the amount of weights lifted
    2. Flexibility - by the amount of joint movement
    3. Stamina - by the time of sustained exercise
    4. Agility - by changing direction many times
    5. Speed - by a sprint race
      1. Therefore, you can be very fit for a sprint race but not perform well in a marathon (stamina)
    6. Ways of measuring fitness should be evaluated to check effectiveness in particular situations
3. Smoking
  1. Smoking can increase blood pressure in a number of ways
    1. Carbon monoxide in smoke causes blood to carry less oxygen. This means the heart rate increases so that the tissues receive enough oxygen
      1. Carbon monoxide decreases the oxygen-carrying capacity of blood
        It combines with haemoglobin, preventing it from combining with oxygen, so less oxygen is carried
    2. Nicotine in cigarette smoke directly increases heart rate
4. Diet and Heart Disease
  1. Heart disease is caused by a restricted blood flow to the heart muscle
    1. The risk is increased by having a high level of saturated fat in the diet, which leads up to a build-up of cholesterol (a plaque) in arteries
      1. Also increased by having high levels of salt, which can increase blood pressure
  2. It is essential to be able to interpret data showing links between the amount of saturated fat eaten ,the build-up of cholesterol and the incidence of heart disease
  3. The narrowing of the arteries (caused by plaques in the coronary arteries) can reduce blood flow to the heart
    1. The plaques also make blood clots or thrombosis more likely to happen, which will also block the artery
      1. Remember: It is the blood vessel into the heart muscle that is blocked, not the blood flowing into the heart!
Human Health and Diet
1. A Balanced Diet
  1. It is important for good health to eat a balanced diet
    1. A balanced diet contains the correct amounts of chemicals found in food
      1. Three of these are: carbohydrates (made of simple sugars such as glucose), proteins (made up of amino acids), fats (made up of fatty acids and glycerol
    2. A balanced diet varies according to factors including age, gender, level of activity, religion, being vegetarian or vegan, or because of medical issues such as food allergies
  2. If you eat too much fat or carbohydrates they are stored in the body
    1. Carbohydrates are stored in the liver as glycogen or converted into fats
    2. Fats are stored under the skin and around the organs as adipose tissue
    3. Although proteins are essential for growth and repair, they cannot be stored in the body
      1. Although proteins cannot be stored in the body, some amino acids can be converted by the body into other amino acids
2. Protein Intake
  1. Proteins are needed for growth and so it is important to eat the correct amount
    1. This is called the estimated average daily requirement (EAR)
      1. It can be calculated using this formula: EAR in g = 0.6 x body mass in kg
        Example: Sue has a mass of 72.5kg. Her EAR is 0.6 x 72.5 = 43.5 g/day
      2. The EAR is only an estimated figure based on an average person
        It may be affected by factors such as body mass, age, pregnancy or breast-feeding
  2. Too little protein in the diet causes kwashiorkor. This is more common in developing countries due to overpopulation and lack of money to improve agriculture
  3. Proteins from meat and fish are called first-class proteins
    1. They contain all the essential amino acids that cannot be made by the human body
    2. Plant proteins are called second-class proteins as they do not contain all the essential amino acids
3. Overweight or Underweight?
  1. To work out if a person is overweight or underweight you calculate their body mass index (BMI)
    1. BMI = mass in kg / (height in m)2
      1. Example: Tom is 170cm tall and has a mass of 80kg. 170cm = 1.7 m. BMI = 80 / 1.7 squared = 27.7
  2. A BMI of more than 30 means the person is obese, 25-30 is overweight, 20-25 is normal, less than 20 is underweight
  3. Some people may become ill as they choose to eat less than they need. This may be caused by low self-esteem, poor self-image or a desire for what they think is perfection
Staying Healthy
1. Malaria
  1. Malaria is caused by a protozoan called Plasmodium which feeds on human red blood cells
    1. Plasmodium is carried by mosquitoes, which are vectors
      1. Vectors are not affected by the disease
    2. It is transmitted to humans by mosquito bites
    3. Plasmodium is a parasite and humans are its host. A parasite is an organism that feeds on another living organism, causing it harm
  2. Knowledge of the mosquito's life cycle has helped stop the spread of malaria (by draining stagnant water, putting oil on the water surface and spraying insecticide). This knowledge has also helped to develop new treatments
2. Cancers
  1. Change in lifestyle and diet can reduce the risk of some cancers
    1. Not smoking reduces the risk of lung cancer
    2. Using sunscreen reduces the risk of skin cancer
  2. Benign tumour cells such as warts divide slowly and are harmless
    1. Cancers are malignant tumours: the cells display uncontrolled growth and may spread
  3. Ways of interpreting data on cancer and survival/mortality rates should be considered
3. The Fight Against Illness
  1. Pathogens (disease causing organisms) produce the symptoms of an infectious disease by damaging the body's cells or producing waste products called toxins
  2. The body protects itself by producing antibodies
    1. These lock onto antigens on the surface of pathogens such as a bacterium. This kills the pathogen
    2. White blood cells produce antibodies resulting in active immunity. This can be a slow process but has a long-lasting effect
      1. Vaccinations using antibodies from another human or animal result in passive immunity, which has a quick but short-term effect
        Each pathogen has its own antigens so a specific antibody is needed for each pathogen
        The process of immunisation is also called vaccination
        It starts with injecting a harmless pathogen carrying antigens
        The antigens trigger a response by white blood cells, producing the correct antibodies
        Memory cells (a type of T-lymphocyte cell) remain in the body, providing long-lasting immunity to that disease
        Immunisation carries a small risk to the individual, but it avoids the potentially lethal effect of the pathogen, as well as decreasing the risk of spreading the disease
4. Treatments and trials
  1. Antibiotics (against bacteria and fungi) and antiviral drug are specific in their action
    1. Antibiotics destroy pathogens, antiviral drugs slow down pathogen's development
  2. New treatments are tested using animals, human tissue and computer models before human trials. Some people object to causing suffering in animals in such tests
The Nervous System
1. How Do Eyes Work
  1. Light rays are refracted (bent) by the cornea and lens
  2. The retina contains light receptors. Some are sensitive to different colours
  3. Binocular vision helps to judge distance by comparing the images from each eye; the more different they are, the nearer the object
  4. Accommodation is where the eye can focus light from distant or near objects by altering the shape of the lens
  5. The ciliary muscles relax and the suspensory ligaments tighten (so the lens has a less rounded shape) to focus on distant objects
    1. The ciliary muscles contract and the suspensory ligaments slacken (so the lens regains a more rounded shape due to its elasticity) to focus on near objects
2. Faults In Vision
  1. Red-green colour blindness is caused by a lack of specialised cells in the retina
    1. Long or short sight are caused by the eyeball or lens being the wrong shape
      1. In long sight, the eyeball is too short or the lens is too thin, so the image is focused behind the retina
      2. In short sight, the eyeball is too long or the lens is too rounded so the lens refracts light too much, so the image would be focused in front of the retina
        Corneal surgery or a lens in glasses or contact lenses corrects long and short sight. A convex lens is used to correct long sight, a concave lens to correct short sight
3. Nerve Cells
  1. Nerve cells are called neurones. Nerve impulses pass along the axon
  2. What happens in a reflex action is shown by a reflex arc. The links in a reflex arc are: stimulus-->receptor-->sensory neurone-->central nervous system-->motor neurone-->effector-->response
  3. The pathway for a spinal reflex is: receptor-->sensory neurone-->relay neurone-->motor neurone-->effector
  4. Neurones are adapted by being long, having branched endings (dendrites) to pick up impulses and having an insulator sheath
    1. The gap between neurones is called a synapse.
      1. The arrival of an impulse triggers the release of a transmitter substance, which diffuses across the synapse. The transmitter substance binds with receptor molecules in the membrane of the next neurone causing the impulse to continue

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