Biology B1 part 2

Biology B1 part 2

1. Infectious Disease

   • Pathogens
     • They are micro-organisms that cause disease, there are 4 different types
     • Protozoa (e.g. dysentery)
     • Viruses (e.g. Flu)
     • Bacteria (e.g. cholera)
     • Fungi (e.g. athlete's foot)
   • Malaria
     • It is caused by a protozoan, this protozoan is a parasite
     • It is carried by mosquitoes, they are vectors
       • Vectors can carry the disease without getting it themselves
     • Preventing
       • Mosquito nets
       • Fish can be introduced to eat mosquito larvae
       • Places that mosquito's go can be sprayed with insecticides
   • Immune system
     • Once inside your body, pathogens reproduce rapidly
     • White blood cells have the job of destroying them, they constantly patrol your body
     • Lines of attack
       • 1) Consuming - they engulf foreign cells and digest them
       • 2) Producing antitoxins - they counter the effects of any poisons
       • 3) Producing antibodies - each pathogen has unique molecules on the top, these are called antigens, when the white blood cells come across an antigen, they produce a specially designed antibody to kill it
         • The antibodies are then produced rapidly and flow around the body to kill the rest off
         • Some memory cells stick around so that if the person is infected again they can instantly kill it off

2. Preventing and treating

   • Antibiotics
     • They are drugs that kill off bacteria without killing body cells
     • They can't kill viruses
     • Antivirals treat viral infections, they stop viruses from reproducing
     • Some bacteria are naturally resistant to antibiotics (e.g. MRSA)
   • Immunisation
     • Risks
       • Can cause short term effects like...
         • Swelling and redness at the injection site
         • Feeling a bit under the weather
       • You can't have vaccines if you are already ill because you immune system is weak
       • People think that immunisation can cause other disorders (e.g. some people think there is a link between the MMR vaccine and autism
     • Benifits
       • Stops the disease from spreading easily
       • It stops you from getting ill
     • You can get very ill and even die from pathogens
       • To avoid this, you can be immunised
         • It involves injecting dead or inactive pathogens into the body
           • Your white blood cells produce antibodies to attack them
             • Some of these memory cells will stick around to kill off the disease if you get it
     • Active immunity is where the immune system makes it's own antibodies after being stimulated by a pathogen
     • Passive immunity is when antibodies are made by another organism, passive immunity is only temporary

3. Cancer

   • Tumors
     • Benign - the tumour grows until it runs out of room, it stays in the same place, it isn't normally dangerous
     • Malignant - the tumour grows and can spread to other parts of the body, they are very dangerous and can be fatal
     • Reduce your risk
       • Not smoking reduces your risk of getting lung cancer
       • Eating less processed meat and more fibre can reduce the risk of colon cancer
   • Drugs
     • New drugs must be tested before they are given to human
       • 1) Computer models simulate the reaction of a human to the drug, promising one's go onto the next stage
         • 2) The drugs are then tested on human tissues, again promising one's go onto the next stage
           • 3) The law states that new drugs must be tested on at least two different live mammals
             • 4) It is then tested on humans, this is called a clinical trial, in the trial, there are two groups of patients, one gets the new drug, the other get a placebo (it doesn't do anything) or the best existing treatment

4. Drugs

   • Beneficial and harmful
     • Drugs change the way our bodies work, they can be very dangerous, this is why you can only get some drugs on perscription
     • Some people get addicted to drugs and get withdrawal symptoms if they don't have it
     • Tolerance develops with some drugs, this means you get used to having it and have to have a higher dose to get the same effect
     • If someone is addicted, rehabilitation can help
   • Types
     • Depressants (e.g. alcohol, temazepam
       • They decrease the activity of the brain, causing slow reactions and poor judgement of speed and distance
     • Stimulants (e.g. nicotine, caffeine)
       • Opposite of depressants, they increase the activity of the brain, it is sometimes used to treat depression
     • Painkillers (e.g. aspirin, paracetamol)
       • They work by reducing the amount of painful stimuli at nerve endings
     • Performance enhancers (e.g. anabolic steroids
       • Sometimes taken by athletes, they help build muscle
     • Hallucinogens (e.g. LSD)
       • They distort what's seen and heard and heard by altering the pathways that the brain sends messages along
   • Illegal
     • Categorised into three categories, class A is the most dangerous
       • Class A - heroin, LSD, ecstasy, cocaine
         • Class B - cannabis, amphetamines (speed)
           • Class C - anabolic steroids and tranquillisers