Pathogens & Immunity Flashcards
What is a pathogen?
Diseases that are caused by foreign organisms invading the body and multiplying there
What is bacteria?
Most bacteria is harmless to humans. Huge numbers of bacteria live on our skin and alimentary canal, cell shape is used to classify bacteria. Can be seen with a light microscope. Important roles such as decomposition, industrial in our bodies
What is a virus
Small structures that do not contain any bacteria which can be too small to be seen with an ordinary light microscope but can be seen through an electron microscope. All contain DNA or RNA surrounded by a coat of protein.
List the four types of bacteria
Cocci - Spherical cells, that may occur singly, in pairs or in clusters
Bacilli - has flagella, for movement, are rod shaped
Spirila - Have twisted cells
Vibrio - Curved rods that look like a comma
Reproduction of Bacteria
There are two types; binary fusion and conjugation. Binary fusion works like mitosis it produces two genetically identical daughter cells - clones. Conjugation refers to the direct transfer of genetic material between two bacteria cells that are temporarily joined
What are antibiotics?
- ACT AGAINIST BACTERIA
- Drugs that are used to fight infections of micro - organisms, particularly bacteria.
Each antibiotic is effective for only certain types of bacterial infection and cannot be used to treat viral infections
What are the two types of bacteria?
- Bactericidal antibiotics - Kill bacteria by;
>changing structure of cell wall or membrane
>disrupting enzyme activity - Bacteriostatic - stop bacteria
>from reproducing - disrupt protein synthesis
What are antivirals?
Act on viruses. Viruses enter host cell to DNA or RNA which causes the host cell to produce more of itself which then leave the cell and destroy it, new cells are then able to infect new cells, killing the viruses means killing the host cell
List two examples of protective reflexes?
- Sneezing
Stimulus: Irritation of wall of nasal cavity
Caused by: Noxious fumes or dust particles (with micro - organisms)
Forceful expulsion of air from lungs carries mucus with foreign particles and irrupting gases out through nose and mouth - Coughing
Stimulus: Irritation of lowered respiratory tract - bronchi and bronchioles
Air is forced from lungs to remove irritant, mucus and foreign matter to throat and mouth
List the four main transmission of pathogens
- Transfer by contact
- Transfer of body fluids
- Ingestion
- Vectors
Explain transmission by contact
Involves the spread of the pathogen by actual physical contact. The contact may be direct, actually touching an infected person or indirect - touching an object that an infected person has touched.
Explain transmission by body fluids
When blood or saliva etc from an infected person comes into contact with the mucous membrane (e.g. nose, mouth throat, genitals) or the blood stream of an unaffected person such as through a needle stick or break in the skin e.g. this is how hepatitis B & C is spread
Explain transmission by ingestion
Ingestion of food or drink contaminated with pathogens may result in disease e.g. cholera
Explain transmission by vectors
Vectors containing the pathogen are transported or live in a host to transmit pathogen i.e. mosquitos, fleas, parasites
What are the body’s external barriers?
- Ear contains Cerumen - a thick wax which inhibits the growth of bacteria
- Eyes have tears which cleanses the eye and inhibits the growth of bacteria
- The vagina contains acidic secretions which also inhibit the growth of bacteria
- The nasal cavity contains hair and mucus which traps micro organisms
- The mouth cavity also contains Mucous membrane, saliva which also traps micro organisms.
- The Trachea and Bronchi contain a mucus membrane which traps micro organisms
- The skin has an impervious barrier, sebum - secreted by oil glands which Kills pathogenic bacteria
- The Stomach contains acidic juices which also kill bacteria. The Urethra acts as an external barrie by the urine flow, this prevents bacterial growth.
What is inflammation?
A response to any damage to the tissues e.g. a cut, pimple, bite
What is the purpose of an inflammatory response?
> Reduce the spread of pathogens, destroy the,prevent entry of more pathogens
Remove damaged tissue & cell debris
Begin the repair of damaged tissue
Signs of inflammatory response
> Redness
Swelling
Heat
Pain
Explain the process of an inflammatory response
- Skin broken produces a non specific inflammatory response
- Mast cells (special cells, release chemicals (histamine and heparin )
- Complement proteins are activated which attract phagocytes (macrophages and leucocytes) which swallow and digest dead cell debris and bacteria - this abnormal condition of the tissue is the cause of pain.
- Phagocytes are full of bacteria, debris and dead cells which form pus and die.
- Histamine and complement proteins which signal finished and phagocytes are no longer attracted the area, new cells are produced by mitosis and the repair of damaged tissue begins.
What is histamine and heparin?
Histamine - Increase blood flow to an area which causes blood capillaries to become leaky and permeable this increased blood flow causes redness and heat and the escape of fluid leads to swelling
Heparin - Prevents clotting in the immediate area but allows clotting around the damaged area to prevent pathogens from entering
What is the function of the lymphatic system?
To collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system, as the body’s internal defence. Lymph vessels —> lymph nodes
Explain how the lymphatic system is involved in a lymphatic response
Lymph enters to lymph nodes, bacteria is then trapped in meshwork of fibres with macrophages, phagocytes then engulf cell and destroy them with enzymes
>When infection occur -> increased lymphocytes -> lymph nodes become swollen and sore
>most important in the specific immune response to a particular pathogen
What is fever?
Elevation of body temperature, defence mechanism, non - specific
List the causes of fever?
> Infection, inflammation, cold or flu
White blood cells release pyrogens which are chemicals which act on hypothalamus to reset thermostat at a higher temperature
What are the benefits and disadvantages of fever?
Benefits:
>Increased body temperature inhibits the growth of bacteria and viruses
>Speeds up chemical reactions —-> promotes healing
Disadvantages:
>Harmful if temperature is too high
>Death if temperature is between 44.5 and 45.5 degrees celsius
What is the process of fever?
Due to infection the boys thermostat become set at an abnormally high temperature. The body feels cold and responds by shivering and vasoconstriction in the skin
Body temperature rises. The fever breaks with swearing and vasodilation in the skin. Body temperature falls to normal
What is a non specific defence?
Defences that protect the body by either external or internal defences. There are external defences such and protective reflexes and Internal defences and lymphatic system, inflammatory response & fever
What is a specific response?
Specifically targets the pathogen once past all non specific defences e.g. antibody mediated response and cell mediated response
What is a lymphocyte?
Involved in specific and non specific defence, produced in bone marrow and lymphoid tissues. They move around the blood, enter a tissue or lymph
What is a macrophage?
Involved in specific and non specific defence, they develop from a type of white blood cells, they are large phagocytic cells (which costume foreign substances and micro - organisms by phagocytosis). They alert immune system to the presence of foreign material
What is an antigen?
- An antigen is any substance capable of causing an immune response. Such a substance introduced to the body causes the body to produce specific antibodies
- Large molecules.
What is an antibody?
A specialised protein that is produced in response to a non self antigen
Describe B cells and T cells
B cells and T cells are types of lymphocytes. Both are produced in the bone marrow. Half mature in thymus and become T cells, half stay in bone marrow and become B cells. Both B and T cells then become incorporated in lymphoid tissue
Explain the difference between a self antigen and a non self antigen
- Self Antigen - Substances produced by a persons own body, do not trigger an immune response
- Non-self Antigen- foreign substances that do trigger an immune response
What are the types of T cells?
> Killer T cells - Migrate to the site of infection and deal with the invading antigen. They attach to the invading cells and secrete a substance that will destroy the antigen and then go in search of more antigens
> Helper T cells - Play an important role in both humoral and cell mediated immunity. They secrete a number of substances that;
- Cause lymphocytes at the infection site to become sensitised, thus intensifying the response
- Attract macrophages to the place of infection to that the macrophages can destroy the antigens by phagocytosis
- Intensify the phagocytic activity of macrophages
> Suppressed T cells - Act when the immune activity becomes excessive or the infection has been dealt with successfully. They release substances that inhibit T and B cell activity slowing down the immune response
What is immunity?
The resistance to infection by invading micro organisms
What is natural immunity?
Occurs without any human intervention
What is artificial immunity?
Results by being given an antigen or antibody
What is passive immunity?
Naturally acquired passive immunity occurs during pregnancy, in which certain antibodies are passed from the mother to infant via milk or placenta. This is a non specific immune response and provides short term immunity as no memory cells are produced. Artificially acquired passive immunity refers to antibodies being injected and is a non specific immunity. This provides short term immunity as no memory cells are produced.
What is active immunity?
Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and develops long term immunity and produces memory cells. Artificially acquired active immunity involves the antigen given via vaccine injection to the body. This is a specific immune response that allows long term immunity and produces memory cells. No symptoms are experienced by individual
What does immunisation refer to?
Programming the immune system to that the body can respond rapidly to infecting micro organisms. It can occur naturally or artificially.
What is a vaccination?
Is the artifice introduction of antigens or pathogenic organisms so that the ability to produce the appropriate antibodies is acquired without the person having to suffer the ideas. A vaccine is the antigen preparation used in artificial immunisation
List the four types of vaccines?
- Living attenuated micro- organisms
- Dead micro - organisms
- Toxoids
- Sub unit vaccines
Describe a living attenuated micro- organisms
Live micro organisms of reduced virulence (reduced ability to produce symptoms). The person does not contract the disease but makes antibodies against antigen. This immunity lasts for longer e.g. chicken pox
Describe a dead micro - organism vaccine
This immunity does not last as long e.g. Influenza,
Whooping cough
Describe a toxoid vaccine
Inactivated toxins produced by bacteria. This is made from filtrates of bacterial cultures containing toxins e.g. tetanus
Describe a sub unit vaccine
A fragment of the micro - organism is used instead of a live or dead organisms e.g. HPV, hepatitis B
What are the most common forms of vaccine delivery?
- Syringe
- Oral
- Nasal spray
- Skin patches
- Foods
What is herd immunity?
Refers to when there are a large number of immune individuals in a population, there is less chance of the disease being transmitted between them
What are the risks associated with vaccinations?
One of the main risks of vaccination is an allergic reaction. This may not occur so much from the vaccine itself but the medium in which the vaccine was cultured. It is also Impossible to isolate one virus from others within an animal tissue that is being used as a culture medium . As a result vaccines could pose a risk of cross species introduction. Manufacture is another risk associated with vaccines - Certain chemicals are used as preservatives. Individuals are concerned about vaccination as they claim that these preservatives can affect the nervous system and lead to other health issues. There are also the possibility of side effects of each vaccine.
List an ethical concern with vaccinations
> Production - A virus can only reproduce in living cells, the manufacture of viral vaccines requires host tissue. e.g. influenza virus is cultured in chicken embryos. Some people are concerned about the treatment of animals in the production of vaccines. Many viruses require human tissue because some viruses that cause disease in humans do not grow well in cells derived from other species. In addition the use of human tissue avoids the problems of cross species infection from possible unknown viruses. The source of human tissue is a concern for many people e.g. rubella is manufactured using cultured human cells. The original cells for the cultures were obtained from human foetus which raises moral questions
What is the issue with testing vaccines?
Most vaccines are produced in developed countries but are destined for use in developing countries. Most of these regions are in developing countries where education standards are low and the population may not be aware go the risk involved with trailing an experimental vaccine.
What is a phagocyte?
Phagocytes are cells that can engulf and digest micro organisms and cell debris, they are very important in defence against pathogens
