Infection and response

• What is health?

  The state of physical and mental wellbeing
• What are communicable diseases?

  Diseases that can be spread from person to person or between animals and people. They can be caused by pathogens and can be described as contagious or infectious. Examples include measles and malaria
• What are non-communicable diseases?

  Diseases that cannot be spread between people or between animals and people. They generally last for a long time and get worse slowly. Example include asthma, cancer and coronary heart disease
• What's the problem with a weak immune system?

  You have an increased chance of suffering from communicable diseases (e.g. the flu) because the body is less likely to be able to defend itself against the pathogen that causes the disease
• What can some types of cancer be triggered by?

  Infection by certain viruses

  E.g. the hepatitis virus can cause long-term infections in the liver which increases the chance of getting liver cancer. Also, infection with HPV can cause cervical cancer
• What are asthma sufferers in danger of?

  Their symptoms becoming worse - immune system reactions in the body caused by infection by a pathogen can trigger allergic reactions (e.g. skin rashes) or worsen the symptoms of asthma
• How can be mental health problems be triggered?

  When someone is suffering from severe physical body problems, especially if they have an impact on their ability to do normal activities or affect their life expectancy
• What factors can affect you health?

  1) Balanced diet - provides your body with everything it needs

  2) Stress - being constantly under lots of stress can lead to health issues

  3) Life situation - having easy access to medicine or things that can prevent illness e.g. buy healthy food or condoms to prevent catching an STD
• What are risk factors?

  Things that are linked to an increase in your chance of contracting a disease

  E.g. smoking, obesity, drinking, exposure to radiation
• Smoking as a risk factor

  Causes cardiovascular disease, lung disease and lung cancer. It damages the walls of arteries and the cells in the lining of the lungs
• Obesity as a risk factor

  Causes Type 2 diabetes - makes the body less sensitive to insulin
• Drinking as a risk factor

  Drinking too much alcohol causes liver disease, affects brain function and damages the nerve cells in the brain
• Exposure to radiation as a risk factor

  Cancer can be caused by exposure to ionising radiation, a carcinogen (something that causes cancer)
• What are benign tumours?

  Tumour grows until there's no more room

  The tumour stays in once place (usually in a membrane)

  Isn't dangerous or cancerous
• What are malignant tumours?

  Tumours grow and spread to nearby healthy tissues - invading these tissues forms secondary tumours

  Cells can break off and spread to other parts of the body via the bloodstream

  Is dangerous and cancerous - can be fatal
• Risk factors for cancer

  Smoking - lung, mouth, bowel, stomach and cervical cancer

  Obesity - bowel, liver and kidney cancer

  UV exposure - skin cancer

  Viral infection - infection with hepatitis B/C can increase the risk of developing liver cancer
• Human Cost of Disease

  1) Millions of deaths

  2) Lower quality of life

  3) Shorter lifespan

  4) Effect of disease spreads to family members & relatives
• Financial Cost of Disease

  1) Cost to the NHS of researching & treating these diseases is huge

  2) Families may have to move or adapt their home to help a family member with a disease

  3) If a family member has to give up work or dies, the family's income will be reduced

  4) Reduction in the number of people able to work can also affect a country's economy
• How do viruses make you ill?

  They invade healthy cells and replicate inside them. The cells will burst and release all the copies of the virus
• What are protists?

  Single-celled eukaryotes
• What are parasites?

  Protists that live in or inside other organisms and cause damage. They are transferred by a vector
• How can pathogens be spread?

  1) Water - drinking/bathing in dirty water e.g. cholera

  2) Air - breathing it in or the spreading of droplets from coughs or sneezes e.g. the flu

  3) Direct contact - touching contaminated surfaces e.g. athlete's foot
• Measles

  Virus spread by droplets from a sneeze or a cough

  Symptoms: red skin rash and a fever

  It can sometimes lead to pneumonia or encephalitis (a brain infection)

  Can be vaccinated against
• HIV

  Virus spread by sexual contact or by exchanging bodily fluids e.g. sharing needles when taking drugs

  Symptoms: flu-like symptoms for a few weeks

  Antiretroviral drugs stop the HIV virus replicating

  The virus attacks immune cells

  If the immune system is badly damaged, it can't cope with other infections or cancer - the virus at this stage is known as AIDS
• Tobacco Mosaic Virus (TMV)

  Virus that affects many species of plants e.g. tomatoes

  Symptoms: a mosaic pattern on the leaves - parts of the leaves become discoloured

  The discolouration prevents the plant from photosynthesising as well, thus the virus affects growth
• Rose Black Spot

  Fungus that causes purple/black spots to appear on leaves of rose plants - the leaves then turn yellow and fall off

  Inhibits the process of photosynthesis and growth

  Spread via the environment e.g. water or wind

  Treatment: fungicides and stripping the plant of its affected leaves and then burning the leaves so the virus doesn't spread
• Malaria

  Caused by a protist

  Mosquitoes are vectors that acquire the malarial protist from feeding on infected animals

  Each time a mosquito feeds on another animal, it infects it by inserting the protist into the blood vessels

  Symptoms: repeating episodes of fever - can be fatal

  Insecticides and mosquito nets help prevent malaria
• Salmonella

  Bacteria that causes food poisoning by producing toxins

  Symptoms: fever, stomach cramps, vomiting and diarrhoea

  Caused by eating food contaminated with salmonella e.g. uncooked chicken

  In the UK, most chickens are vaccinated against salmonella
• Gonorrhoea

  Bacterial disease

  Sexually transmitted disease (STD) caused by sexual contact e.g. unprotected sex

  Symptoms: pain when urinating; thick yellow/green discharge from the vagina/penis

  Originally treated with penicillin - now some strains have become resistant to it

  Treatment with antibiotics and using barrier methods of contraception (e.g. condoms) help prevent the spread of it
• Reducing/Preventing the spread of diseases

  1) Being hygienic e.g. washing hands before preparing food or after sneezing

  2) Destroying vectors e.g. vectors that are insects are killed by insecticides or destroying their habitats

  3) Isolating infected individuals e.g. quarantine for people with communicable diseases

  4) Vaccination - vaccinating against communicable diseases stops them from being developed then passed on
• What is a vector?

  Organisms that spread disease
• The skin as a defence

  Acts as a barrier to pathogens

  Secretes antimicrobial substances which kill pathogens
• Hairs and mucus as a defence

  In your nose, they trap particles that contain pathogens
• The trachea & bronchi as a defence

  Secrete mucus which traps pathogens
• Cilia as a defence

  Hair-like structures which waft the mucus up to the back of your throat where it can be swallowed (and used to trap pathogens)
• The stomach as a defence

  Produces hydrochloric acid which kills pathogens that make it farther than the mouth
• Phagocytes - white blood cells

  Engulf foreign cells (microbes etc) and digest them
• B-lymphocytes - white blood cells

  Recognise foreign antigens on cells and produce antibodies to lock onto the antigens so that the cells can be located and destroyed

  The antibodies are specific to that type of antigen - they form a lock and key connection
• T-lymphocytes - white blood cells

  Produce antitoxins that neutralise any toxins produced by bacteria
• What are antibodies?

  Y-shaped proteins that are produced by B-lymphocytes