Infection and Response

Pathogens

A microorganism that can cause disease

Types of Pathogens

• Bacteria

• Protist

• Viruses

• Fungi

Transmission

Passing of a pathogen from an infected organism to an uninfected organism.

Communicable Diseases

An infection diseases caused by a pathogen that can be spread to others

Non- Communicable diseases

• Environment

• Inherited

• Not transmitted by pathogens

Ways that pathogens can spread (transmisson)

• Through the air - Coughing and Sneezing

• Contaminated water

• Contaminated food - Food not cooked properly or infected by salmonella

• Direct contact - Athlete's foot is spread by walking barefoot on surfaces contaminated with the fungi. 

Bacteria

• Small cells that can rapidly reproduce inside your body

• They can make you feel ill by producing toxins that damage cells and tissues

Virus

• Not cells,non living can rapidly reproduce inside body

• The live inside cells and use their machinery to replicate themselves using the cells

• The cell then bursts releasing the viruses which go to infect neighbouring cells

Protists

• Eukaryotes that are single celled

• Some are parasites that live inside other organisms

• Transferred to the organism by a vector which doesn’t get the disease itself

Fungi

• Eukaryote, single and multi celled

• Hyphae(thread like strucutres) secretes enzymes to hydrolyse cell matter

• Releases spores for reproduction

Types of Viruses

• Measles

• HIV

• Tobacco Mosaic Virus

Measles

• Transmission - Air droplets (Sneeze and Cough)

• Symptom - Red Skin Rash, Fever

• Prevention - Vaccination

HIV

• Transmission - Bodily fluid exchange, Sex

• Symptom - Destroys WBCs,Increase infections and lead to AIDS

• Prevention - Antriretroviral Drugs,Protection

TMV

• Transmission - Plants. Tomatoes

• Symptom - Discoloured Leaves,Stunted Growth (no photosynthesis can take place in infected area so no sugars)

• Prevention - Destroying Infected Plants

Bacteria

• Salmonella

• Gonorrhoea

Salmonella

• Transmission - Food Poisoning,Undercooked food

• Symptom - Fever,Upset Stomatch,Diarrhoea,Vomiting

• Prevention - Vaccinate Poultry,Improve Hygiene and Cook Food properly

Gonorrhoea

• Transmission - Sexually Transmitted

• Symptom - Thick Yellow/Green Discharge,Pain to Urinate

• Prevention - Use condoms.Prevent spread,Antibiotics (gets resistant to some after a period of use though)

Ways to Prevent Spread of Disease

• Being Hygienic

• Destroying Vectors

• Isolating Infected Individuals

• Vaccination

Vector

An organism that transmits pathogens from one host to another, such as mosquitoes or ticks.

Rose Black Spot - Fungal

• Transmission - Plants,Spread in Wind and Water

• Symptom - Purple or black spots on leaves,less chlorophyll,less photosynthesis

• Prevention - Fungicides

Malaria - Protists

• Transmission - Mosquito Bites

• Symptom - Fever,Headaches,Reccuring Episodes that can be fatal

• Prevention - Prevent Mosquito Breeding,Use Mosquito Nets/Repellent, Insecticides

How human body protects us against pathogens

• Physical and Chemical Barriers

• Immune System

Barriers

• Skins

• HCL

• Mucus,CIlia (must work together)

• Tears → Lysozyme (antibacterial)

Skin Barrier

• Covers the body physically preventing pathogens from entering

• Secretes oils and antimicrobial substances that kill pathogens

• Platelets also form blood clots and seal wounds to prevent pathogens from entering

HCL Chemical Barrier

• Kills pathogens very acidic (PH-2)

Mucus + Cilia Hairs

• Mucus traps any pathogens than enter

• Cillia takes out any pathogens

• They go to the back of the throat where we can swallow it to the stomach which kills it with HCL

Three Function of WBCs

• Engulf Pathogens (Phagocytosis) - Phagocyte

• Produce Antitoxins - Lymphocyte

• Produce Antibodies - Lymphocyte

Phagocytosis Process

• The phagocyte has to track down a pathogen, and then bind to it. 

• The phagocyte's membrane will then surround the pathogen and engulf it.

• Enzymes inside the phagocyte will break down the pathogen in order to destroy it.

Antitoxins

Neutralise the bacterias toxins

Antibodies

• Proteins

• The WBC will come across a foreign antigen and create antibodies that are specific to it

• These antibodies bind to the antigen and try to kill it

• Only effective against bacteria

Antigen

Proteins present on cell membranes that are unique to an organism.

What does a vaccine contain

A small,weakened ,inactive version of the pathogen

Vaccination

Introduction of an antigen to stimulate WBCs to produce antibodies and memory cells

How does vaccination work

• Introduce weak version of pathogen

• Stimulates WBCs

• WBCs produce antibodies

• WBCs produce memory cells

• Memory cells and antibodies are stored

• 2nd infection → Quicker response with incerased concentration of antibodies

• Pathogen destroyed before it causes disease

Pros of Vaccines

• Controls Communicable Diseases

• Provides Herd Immunity

• Prevents Epidemics/Pandemics

Cons of Vaccines

• They dont always work

• Side effects

• Drug must be produce expensive and time consuming

• Unethical process to some

• Hard to vaccinate all type of people old,young,healthy,unhealthy

Tears lysozyme

Contains enzymes that break down the bacteria cell walls and kills them

Drugs

Chemicals that alter cell process

Different Types of Drugs

• Drugs that relieve pain and reduce symptoms

• Drugs that kill the disease and cure it

Painkillers

• Treat Symptoms

• Aspirin - Headache drug from willow tree that thins the blood

• Digitalis - Heart drug for foxglove plants that increases the heart rate

• Paracetamol

Antibitoics

• Penicillin from penicillium notatum (mould)

Antibiotical Resistance Ways to stop it

• Doctors only prescribing antibiotics for serious bacterial infections 

• Patients taking antibiotics for the full prescribed course 

Efficacy

How well a drug produces a desired effect

Toxicity

How harmful a drug is

Dosage

How much of a drug is required to give the desired effect

Stages Of Development

• Discovery of New Medicines

• Preclinical Testing (2 Stages)

• Clinical Trails (3 Stages)

• Peer Review and Licensing

Preclinical Testing

• Laboratory Tests (In vitro)

• Tested on cells tissues and organs

• Checks if the drug affects cells and pathogens safely

• Animal Tests (In vitro)

• Tested on live animals (like rats or mice)

• Checks toxicity,efficacy and dosage

Stage 1: Clinical Trials

• Healthy Volunteers

• Small group of healthy people

• Checks for side effects and basic safety

Stage 2:

• Small Patient Trials

• Small group of ill patients

• Tests if the drug works and monitors side effects

Stage 3:

Large scale patient trails

• Hunderd or thousands of patients

• Find the optimum dosage and checks effectiveness on a large scale

Double Blind Trial

• To avoid any bias by the patients and/or researchers

• If patients know they received the drug 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 patients

Peer Review and Licensing

• Results are peer reviewed by independent scientists

• Drug is licensed for use

• Medicines continue to be monitored for rare side effects

Pacelebo Use

• Provides comparision

• Prevents Bias (such as pschycological)