Natural Barriers to Microorganisms • Skin • Chemicals in tears • Sweat • Stomach acid • In suitable conditions (such as inside the body) microorganisms can reproduce rapidly.
Infectious Diseases • Microorganisms may enter the body and cause illness before the immune system can destroy them. • Symptoms of a disease are caused by: • Damage done to cells by the microorganisms • Poisons (toxins) they produce
White Blood Cells • Our immune system defends against the invading microorganisms • White Blood Cells can destroy microorganisms by: • engulfing and digesting them • by producing antibodies
Antibodies • A different antibody is needed to recognise each different type of microorganism • Once the body has made the antibody to recognise a particular microorganism, it can make that antibody again very quickly, therefore protecting against that particular microorganism.
Vaccinations • Vaccinations provide protection from microorganisms by establishing antibodies before infection • Vaccination contains a usually safe form of a disease-causing microorganism
Herd Immunity • To prevent epidemics of infectious diseases, it is necessary to vaccinate a high percentage of a population • http://www.immunisation.nhs.uk/About_Immunisation/Science/Herd_immunity_-_animation
Whose Choice? • Vaccination can never be completely safe, since individuals have varying degrees of side effects from a vaccine • Conflict between a person’s right to choose and what will benefit the society as a whole
Influenza (Flu) & HIV • New vaccines against Flu need to be developed regularly as the virus changes quickly • Difficult to develop a vaccine against HIV because this virus damages the immune system and has a high mutation rate
Antibiotics • Kills bacteria and fungi, but not viruses • Over time may become resistant to antibiotics • Random changes (mutations) in the genes of microorganisms sometimes lead to varieties which are less affected by the antibiotic
Reduce Antibiotic Resistance • Only use antibiotics when necessary. Not when you have the flu or common cold as these are viruses. • Always complete the full course of antibiotics.
Drug Testing • First tests for safety and effectiveness involve: • Human cells grown in lab • Animals • Second tests are carried out with humans: • On healthy volunteers to test for safety • On people with the illness to test for safety and effectiveness
Blind Trial:Patients do not know which group they are in Double Blind Trial:Patients and Doctors do not know who is in each grouphttp://www.youtube.com/watch?v=aSP2OMiFxhg&feature=PlayList&p=06CAD7DA2E77F66F&playnext=1&playnext_from=PL&index=32
Placebo • A “fake” drug that does nothing. Eg: a sugar (glucose) tablet. • Compares the new drug to see if it does any better than nothing. • Patients don’t know which pill they have taken though • Placebos are not commonly used in Human trials as they are unethical
Arteries • Thick outer wall. Thick layers of muscles and elastic fibres. Artery carry blood to the body from the heart. Blood under high pressure. Veins • Thin outer wall. Thin layers of muscle and elastic fibres. Carry blood from the body back to the heart. Blood is low pressure
Heart • Requires it’s own blood supply to deliver oxygen and nutrients and to take away waste products from heart cells. • If blood vessels supplying the heart become blocked by fatty deposits it can cause a heart attack.
Heart Disease • Caused by lifestyle and/or genetic factors. Not microorganisms. • Eg: Poor diet, stress, cigarette smoking, excessive alcohol intake
Heart Disease • More common in the UK than non-industrialised countries • Regular moderate exercise reduces the risk of developing heart disease