Microogranisms that cause infectious disease are called pathogens and they get inside our bodies through:
DROPLET INFECTION - cilia cells push up the pathogen with mucus. Cough, sneeze or talk
contaminate droplets of mucus/breath. E.g. cold, flu, measles, chicken pox, TB
THROUGH CONTACT - skin has oil on it for sanitation
THROUGH BREAKS IN THE SKIN - our body forms a scab
THROUGH CONTAMINATED FOOD & DRINK - hydrochloric acid in
stomach reacts to pathogen
PATHOGEN - microorganism that can infect our bodies
NATURAL BARRIER - what our body creates to fight
MICROORGANISM - small organism that can only be seen through a microscope
Bacteria and viruses may reproduce
rapidly inside the body and may
produce poisons (toxins) that makes
us feel ill. Viruses damage the cells in
which they reproduce
The immune system of the body produces specific antibodies to kill a particular pathogen.
This leads to immunity from that pathogen. In some cases, dead or inactivated pathogens
stimulate antibody production (called a vaccine). If a large proportion of the population is
immune to a pathogen, the spread of the pathogen is reduced massively.
Semmelweis recognised the importance of hand-washing in the prevention of
spreading some infectious diseases in May 1847. By insisting that doctors washed their
hands before examining patients, he greatly reduced the number of deaths from
infectious diseases in his hospital.
Handwashing removes/+kills pathogens on hands so that
you do not transfer bacteria directly/indirectly
Some medicines, including painkillers, help to relieve the symptoms of infectious disease, but do not kill the pathogen
Antibiotics, incl. penicillin, are medicines that help to cure bacterial disease by killing infectious bacteria inside the body. Antibiotics cannot be used to kill
viral pathogens, which live and reproduce inside cells. It is important that specific bacteria should be treated by specific antibiotics. The use of antibiotics has
greatly reduced deaths from infectious diseases.
Strains of bacteria, incl. MRSA, have developed resistance to antibiotics as a result
of natural selection. To prevent further resistance arising it is important to avoid
over-use of antibiotics.
Mutations of pathogens produce new strains. Antibiotics and vaccinations may no
longer be effective against a new resistant strain of the pathogen. New strain will
spread rapidly because people are not immune to it and there is no effective
People can be immunised against a disease by introducing small quantities of dead or inactive forms
of the pathogen into the body (vaccination). Vaccines stimulate the white blood cells to produce
antibodies that destroy the pathogen, artificially creating primary immune response. This makes the
person immune to future infections by the microorganism. The body can respond by rapidly making the
correct antibody, in the same way as if the person had previously had the disease.
The body has different ways of protecting itself against pathogens
White blood cells
produced in bone marrow
Two main types
sends out projections called pseudopodia (this
surrounds pathogen, digests it and gets rid of it)
PHAGOCYTOSIS - when a pathogen enters the body, white blood find the bacteria using
chemotaxis (detecting toxins bacteria releases) and sends out toxins to engulf the pathogen
STAGES: moves to site of injury --> detects pathogen using chemotaxis --> adheres to pathogen
--> sends out pseudopodia --> engulfs pathogen --> digests pathogen --> destroys pathogen
when pathogens are in body, WBCs squeeze through epithelials (blood vessel walls) to absorb
pathogens, releasing enzymes and sending out messages to bring other WBCs to affected area
Antitoxins & Antibodies
Pathogens harms bodies by attacking cells by taking over them and preventing them from taking out functions
and causing cell damage by breaking it open and killing it faster that the body can fight against it.
Bacteria releases toxins
Viruses cause cell damage
1. White blood cells secrete antitoxins and release them into blood stream. 2. Antitoxins neutralise toxins by binding to them
1895 - American started to produce antitoxins to treat dipitheria (a bacterial disease)
Antibodies are produced by white blood cells and destroy antigens on the outside of pathogens
1. Body recognises pathogens as foreign (due to differently shaped antigens from our body cells) and white blood cells come to affected area
2. WBC, specifically LYMPHOCYTES, release antibodies shaped specifically to bind to the antigens of the pathogen
Functions are: to clump together, destroy and label pathogens for destruction.
body remembers pathogens through white blood cells which become 'memory cells'
have a long longjevity
remember foreign cells so if infected again, white blood cell response is quicker
one particular memory cell remember one particular pathogen
stops us from getting viral diseases: measles, mumps, and rubella. Contain weak form of each virus
Measles = highly contagious infectious disease characterized by a high fever, a rash and generally
feeling unwell. 430 deaths from measles occur daily. Potentially fatal and childhood disease.
MMR = combined vaccine against measles, mumps and rubella. Introduced in the UK in 1988
People were worried about it because in 1998, a study published
in The Lancet raised the possibility that the jab may be linked to
autism and bowel disease
not tested so not certain
just observation, no scientific evidence
Issues with Wakefield's study
12 people - not enough tested
only included those infected (lack of a control)
Lawyers may choose cases - not random and introduces bias
Observations carried out by non-professionals (parents)
Wakefield paid and had obsession with autism (conflict of interest)