infection and response

• Benign tumor

  Growth of abnormal cells which are found in one area, contained within a membrane, do not invade or spread to other parts of the body
• Malignant tumor

  Malignant cells invade neighboring tissues, move into the bloodstream, spread to different parts of the body and form new tumors (secondary tumors)
• Malignant tumor cells are classed as a cancer
• Risk factors for developing cancer

  • Genetic (e.g. certain types of breast cancer, prostate cancer, cancer of the large intestine)
  • Lifestyle (e.g. lung cancer linked to smoking, skin cancer linked to UV exposure, mouth and throat cancer linked to alcohol)
  • Environmental (e.g. radon, a radioactive gas that increases risk of lung cancer)
• Radon releases ionizing radiation that damages DNA in cells, causing uncontrolled cell division leading to cancer
• Communicable diseases

  Diseases that can be spread from person to person
• Non-communicable diseases

  Diseases that cannot be passed from person to person
• Diseases can cause ill health, which is defined as the state of physical and mental well-being
• Ill health can be caused by communicable and non-communicable diseases, poor diet, high levels of stress, and other life situations
• People with a defective immune system


  Are much more likely to suffer from infectious diseases
• Infection with HPV

  Can cause cervical cancer
• Infection with a pathogen


  Can trigger an allergy such as asthma or dermatitis
• Physical illness (arthritis)

  Can lead to mental illness (depression)
• Non-communicable disease

  Diseases not spread from person to person, instead caused by risk factors
• Cigarette smoking

  Increased risk of lung cancer
• Determining correlation

  1. Plot scatter graph

  2. Look for positive/negative correlation
• Correlation does not prove causation
• Causal mechanism

  Scientific explanation for how a risk factor could cause a disease
• Cigarette smoke contains carcinogens that damage DNA and increase cancer risk
• Sampling

  • Selecting a group to investigate rather than the whole population
  • Need large, random sample to avoid bias
• Sampling from only one town may not represent the entire population
• Pathogen


  Microorganisms that cause infectious disease
• Types of pathogens


  • Bacteria
  • Viruses
  • Protists
  • Fungi
• Bacteria


  • Reproduce very rapidly under ideal conditions
  • Can divide every 20 minutes
  • Release harmful chemicals called toxins that damage tissues and make us feel ill
• Viruses


  • Cannot be produced by themselves
  • Can only reproduce inside a host cell
  • Invade host cell, reproduce inside, then cause the cell to burst open and die
• Ways pathogens are spread

  • Airborne (e.g. influenza)
  • Waterborne (e.g. cholera)
  • Direct contact (e.g. HIV)
• Reducing the spread of pathogens

  1. Practicing basic hygiene (e.g. handwashing)

  2. Providing clean drinking water

  3. Reducing direct contact between individuals (e.g. using condoms)

  4. Isolating highly infectious patients

  5. Vaccination
• Many bacterial diseases can kill us
• Viruses are very damaging to cells as they reproduce inside cells by inserting their dna into the cells nucleus which instructs the nucleus to reproduce more viruses until the cell burts open and dies
• Immune system


  Protects us against pathogens
• White blood cells


  Involved in the immune system
• Phagocytosis


  The process of white blood cells ingesting and destroying pathogens
• How white blood cells destroy pathogens using antibodies

  1. White blood cells produce antibodies

  2. Antibodies stick to pathogens

  3. This triggers the pathogens to be destroyed
• Antibodies


  • Extremely specific to the antigen of the pathogen
  • Can remain in the blood for a long time to protect against future infection
• How white blood cells protect against toxins

  1. White blood cells produce antitoxins

  2. Antitoxins stick to pathogen

  3. Prevents toxins from damaging cells
• Skin

  • Forms a protective layer covering the body
  • Outer layer of dead cells is difficult for pathogens to penetrate
  • Produces an oily substance called sebum which can kill bacteria
  • Can scab over when damaged to prevent pathogens entering
• Openings in the body not covered by skin

  • Nostrils
  • Mouth
• Nose

  • Contains hair and mucus to trap pathogens before they enter the breathing system
• Trachea and bronchi

  • Covered with tiny hair-like structures called cilia
  • Cilia are covered in mucus which traps pathogens and moves them upwards towards the throat to be swallowed
• Stomach

  • Contains hydrochloric acid which kills pathogens before they can enter the digestive system further