Please enable JavaScript.
Coggle requires JavaScript to display documents.
Infection and response (Communicable disease (Pathogens- microorganisms…
Infection and response
Communicable disease
Pathogens- microorganisms that enter body and cause disease. Can cause communicable diseases- diseases that can easily spread.
Bacteria- small cells (1/100 size of body cells). Reproduce rapidly in body. Produce toxins and damage cells and tissue.
Virus- (1/100 size of bacterium). Reproduce rapidly, live inside cells and replicate using cells machinery; cell will eventually burst, releasing new viruses.
Protists- Eukaryotes and most single-celled. They are parasites; live on or inside other organisms and cause damage. Transferred to organism by vector which doesn't get disease itself.
Fungi- single-celled, others have a body which is made up of hyphae (thread like structures). Hyphae grow and penetrate human skin and surface of plants, causing disease. Hyphae can produce spores- spread to other plants and animals.
Pathogens can spread by:
Water- drinking or bathing in dirty water- cholera.
Air- carried in air or breathed in. Airborne pathogens carried in air in droplets from coughing or sneezing- influenza virus.
Direct contact- touching contaminated surfaces including skin- athletes foot.
Viral, fungal and protist diseases
Measles- virus, spread by droplets from infected persons sneeze or cough. Symptoms: red skin rash, fever, can also lead to pneumonia, brain infection (encephalitis).
HIV- virus, spread by sexual contact or exchanging bodily fluids (blood, sharing needles). Symptoms: flu for a few weeks, then nothing for years. Can be controlled by antiretroviral drugs- stop virus replicating in body. Attacks immune cells. If immune system becomes damaged, can't cope with other infection or cancers- then known as AIDS.
Tobacco mosaic virus- affects many species of plants e.g. tomatoes. Symptoms: mosaic pattern on leaves of plants and leaves become discoloured. Means plants can't photosynthesise so affects growth.
Rose black spot- fungus, causes purple or black spots to develop on leaves of roses. Leaves turn yellow and drop off. Less photosynthesis; affects growth. Airborne or spread by water. Can be treated using fungicides and stripping plant of affected leaves. Leaves must be destroyed o affect spreading.
Malaria- Caused by protist. Mosquitoes are vectors hat pick up malarial protest when feed on infected animal. Infects other animal when feeds on others by inserting protest into blood vessels. Symptoms: repeating episodes of fever, can be fatal. Prevented by stopping mosquitoes breeding; insecticides and mosquito nets.
-
Fighting disease
Skin acts as barrier to pathogens. Secretes antimicrobial substances which kill pathogens. Hair and mucus trap particles that contain pathogen. Trachea and bronchi secrete mucus to trap pathogen. Lined with cilia (hair-like structures) which waft mucus up to back of throat where can be swallowed. Stomach; HCl- kills pathogens.
White blood cells:
1) Engulf foreign cells and digest them- phagocytosis.
2) when WBC come across foreign antigen, produce proteins called antibodies- lock onto invading cells so that they're found and destroyed by other WBC. Antibodies specific to antigen. They produce rapidly to engulf rest of pathogen. If pathogen returns, memory cells remember and produce antibodies at a faster rate to kill it- naturally immune to it.
3) Produce antitoxins to counteract toxins produced by bacteria.
-
Fighting disease- drugs
Painkillers (aspirin) relieve pain but don't actually tackle disease or kill pathogen- just reduce symptoms.
Antibiotics (Penicillin) kill bacteria without killing body cells. Different antibiotics kill different types of bacteria so important is the right one. They don't destroy viruses as they rapidly reproduce using body cells- hard to develop drug that doesn't destroy body cell. Antibiotics have greatly reduced number of deaths from communicable diseases caused by bacteria.
Bacteria can mutate causing drugs to be resistant to it. This means when you treat infection, only non-resistant strains of bacteria are killed. Individual resistant bacteria will survive and reproduce and resistant strain will increase- natural selection.
MRSA causes serious wound infections that is resistant to methicillin. So doctors must prevent overprescribing antibiotics. Must finish course to prevent some being let and increasing.
Plants produce chemicals to defend against pests and pathogens- can be used as a drug to treat human diseases or relieve symptoms.
Aspirin- painkiller to lower fever. Developed from chemical in Willow.
Digitalis- treat heart conditions. From chemical in Foxgloves.
Drugs extracted from microorganisms:
Alexander Fleming found dish of bacteria with mould and area around mould was free of bacteria- substance that killed bacteria was Penicillin.
Drugs made on a large scale in pharmaceutical industries- synthesised by chemicals in labs. But chemicals still extracted by plant.
Developing drugs
1)Pre-clinical testing on human cells and tissues in a lab. But can't use human cells and tissues to test drugs that affect whole or multiple body systems e.g. .blood pressure- must use intact circulatory system.
2) Pre-clinical testing- test drugs on live animals. For efficacy, toxicity and best dosage. Law says drugs must be tested on 2 live mammals. Not moral but ensures drug isn't dangerous for humans.
3) Clinical trial- tested on healthy human volunteers. To see harmful side effects. Low dose given and increased to maintain dosage.
Then tested on suffering illness- optimum dose found- most effective, least side effects.
Separated into 2 groups: 1 drug, 1 placebo- to see difference drug makes. They are blind- patient doesn't know. Double-blind- neither patient nor doctor know until results. Prevents bias.
Then peer-reviewed to prevent false claims and license given.