b5 Health, Disease and the Development of Medicines

• Health can be described as a state of both physical and mental wellbeing. 
• What is the role of the immune system?

  To detect and destroy pathogens 
• What is a pathogen?

  A microorganism that can cause disease 
• Four main ways that pathogens can spread :

  1. Through the air - Diseases such as influenza and measles can spread via tiny droplets of saliva that we expel when we cough or sneeze.
  2. Contaminated water - Diseases such as cholera can spread through water sources contaminated by the diarrhoea of infected people. 
  3. Contaminated food - Diseases such as salmonella are spread by eating food which has been infected with salmonella, and then not cooked properly.
  4. Direct contact - Athlete's foot is spread by walking barefoot on surfaces contaminated with the fungi. 
• Give three ways we can reduce the spread of infectious disease?

  isolating people who are infected + vaccination and improved hygiene
• How viruses spread and multiply :

  1. Viruses can pass between humans via the air, contaminated food or water, or by direct contact.
  2. As they can't reproduce themselves, viruses have to enter one of our cells, and then use it to create multiple copies of the virus itself.
  3. Once there are lots of copies, the viruses cause the cell to burst, and then go on to infect neighbouring cells. 
• How can measles be spread between people?

  Via droplets in air when an infected person coughs or sneezes
• What are the symptoms of measles?

  Fever (feeling hot and cold) + Red skin rash
• Which two ways can HIV be spread between people?

  Exchange of bodily fluids 

  Sexual contact 
• Infection with the HIV virus can lead to AIDS, this is where the immune system is so weak that the person can catch unusual infections. 
• What type of organism does Tobacco Mosaic Virus (TMV) infect? 

  plants ( mainly tomato and tobacco plants)
• What is the main symptom of Tobacco Mosaic Virus (TMV)?

  Patches of the leaves get discoloured 
• The terms STD and STI both mean basically the same thing. 

  STD - Sexually Transmitted Disease 

   STI   - Sexually Transmitted Infection
• Cholera - key information

  1. Pathogen - Vibrio cholerae bacterium
  2. Transmission - through contaminated water or food
  3. Symptoms - severe diarrhea, vomiting, dehydration
  4. Treatment - supportive care, rehydration, and antibiotics in severe cases
  5. Prevention - access to a clean water supply, proper sanitation, and vaccination
• Stomach ulcers - key information

  1. Pathogen - Helicobacter pylori bacterium
  2. Transmission - oral transmission, through contaminated food or water
  3. Symptoms - stomach pain, nausea, vomiting, bloating
  4. Treatment - antibiotics, medications to reduce stomach acid
  5. Prevention - good hygiene practices, avoiding contaminated food and water, and treating infections promptly
• Tuberculosis (TB) - key information

  1. Pathogen - Mycobacterium tuberculosis bacterium
  2. Transmission - airborne, through droplets released when infected people cough
  3. Symptoms - cough, weight loss, fever, fatigue, lung damage
  4. Treatment - long-term antibiotics
  5. Prevention - TB vaccine (BCG), good ventilation and hygiene, and isolation of infected patients
• Pencillin is the first antibiotic to be produced
• Chalara ash dieback - key information

  1. Pathogen - Hymenoscyphus fraxineus fungus
  2. Transmission - airborne spores, often through wind
  3. Symptoms - wilting, dieback of leaves, wounds on the bark
  4. Treatment - no treatment available
  5. Prevention - removing infected trees, restricting movement of ash trees, promoting diversity in tree populations
• 1. The organisms that cause malaria are a type of protist.
  2. They are transported between hosts by mosquitoes. 
  3. The symptoms include recurrent fevers and headaches, and in extreme cases it can be fatal.
• Suggest three ways we might try to reduce the spread of malaria?

  Destroy the mosquito breeding sites 

  Kill the mosquito with insecticides 

  Use mosquito nets
• An antibody on the other hand is a protein produced by our white blood cells that binds to specific antigens. This acts as a signal to our immune system to destroy the antigen
• How does skin help to defend against disease?

  It covers the body, physically preventing pathogens from entering and It secretes oils and antimicrobial substances that kill pathogens
• The cells that line the trachea, bronchi and bronchioles have tiny hair-like projections that waft the mucus and pathogens away from the lungs. 

  What are these structures called? 

  Cilia
• What substance does the stomach produce to kill pathogens? 

  hydrochloric acid
• What is the role of the immune system? 

  To locate and destroy pathogens that enter the body
• Phagocytes are a special type of white blood cell. 
• Stages of phagocytosis -

  1. Phagocytosis is carried out by a special type of white blood cell called a phagocyte. 
  2. The first step is for the phagocyte to track down a pathogen, and then bind to it. 
  3. The phagocyte's membrane will then surround the pathogen and engulf it.
  4. Finally, enzymes inside the phagocyte break down the pathogen in order to destroy it.
• What do antitoxins do?

  Bind and neutralise the toxins produced by bacteria 
• Benefit of widespread vaccination

  Widespread vaccination campaigns can prevent outbreaks of disease (epidemics). This is because if a large enough portion of the population is vaccinated, it makes the spread of disease from person to person unlikely.

  As a result, the whole population becomes protected - not just those who are immune.
• What are the potential drawbacks of vaccines? 

  They don't always give full immunity to the disease  and They can (in rare cases) cause severe reactions such as seizures . Lastly, They can cause mild symptoms such as fever or a sore arm
• What does the term 'efficacy' mean?

  How well a drug produces the desired effect 
• What does the term 'toxicity' mean?

  How harmful a drug is e.g. how many side effects 
• What does the term 'dosage' mean?

  How much of the drug is required to give the desired effect
• Stages of drug development :

  1. Stage 1 - Test the drug on human cells and tissues.
  2. Stage 2 - Test the drug on live animals.
  3. Stage 3a - Test the drug on healthy volunteers to find the maximum dosage before side effects occur.
  4. Stage 3b - Test the drug on patients that suffer from the relevant disease, to find the optimum dosage. 
• Patients in clinical trials are often given a placebo.

  What is a placebo?

  A substance or treatment that contains no active drug
• Medical trials often use placebos, and are double-blind. 

  Why is it important for medical trials to be double-blind?

  It helps to avoid any bias by the patients or researchers. If patients know they received the drug, then they may be more likely to report side effects. If researchers know who has been given the real drug, then they may pay closer attention to those patents, and document their symptoms more carefully. 
• Risk factors usually fall into one of two categories

  1. Aspects of a person's lifestyle.
  2. Substances in the person's body or environment .
• Obesity can be caused by a poor diet and lack of exercise. Obesity itself can then go on to cause type II diabetes. 
• How is someone's BMI calculated?

  mass (kg) divided by height (m2)
• Anticoagulants (such as Warfarin) are medicines that help prevent blood clots, which makes heart attacks and strokes less likely.