External Defences
What are the protective reflexes?
Sneezing, Coughing, Vomiting, Diarrhoea
Non-specific Defences
Sneezing
the forceful expulsion of air from lungs.
- stimulated by irritation of nasal cavity such as fumes + dust particles + foreign substances + pathogens
Non-specific Defences
Coughing
irritation of lower respiratory tract (the bronchi and bronchioles)
- air is forced from lungs which induces sneezing
Non-specific Defences
Vomiting
abdomen and diaphragm contract to expel stomach contents (with toxins from bacteria)
- induced psychologically, stretching of stomach
Non-specific Defences
Diarrhoea
irritation of small/large intestines by bacteria, virus or protozoans.
- increases contractions of intestinal muscles so irritant is removed quickly
- no time for absorption to happen
Response to Infecion: Prevention
What are the two types of antibiotics?
bactericidal: change structure of cell wall/membrane or disrupt the enzymes
bacteriostatic: stop bacteria from reproducing by [disrupting protein synthesis]
Response to Infecion: Prevention
How can we prevent antibiotic resistance in bacteria?
Antibiotics are resistant from improper and widespread use.
- prevent misuse
- develop a new class of antibiotics
- genetically engineer bacteria to disable the resistance
Non-specific Defences
Can you explain the process of phagocytosis?
- The** phagocyte** moves into the invading bacterium
- Phagocyte changes shape so it completely encloses bacterium
- Lysosomes contain destructive enzymes
- Enzymes are released and destroy the bacterium
- Harmless particles are released from phagocyte
IELEH (invade, enclose, lysosome, enzyme, harmless)
How do antivirals prevent the reproduction of viruses
Aimed at identifying viral proteins that can be disabled after genetic sequences of virus.
Pathogens
Differences between bacteria and viruses
Bacteria:
* unicellular, prokaryotic organisms that use binary fission to replicate
* reproduce without a host cell
* very small, bigger than virus
* not all bacteria are pathogenic
* contains DNA
* made up of a slime layer/coat
Virus:
* non-living organisms that need a host to replicate
* they are not cells but **genetic material **surrounded by a capsid.
* very small, even smaller than bacteria
* all viruses are pathogenic
* can have DNA or RNA
* has a coat or an envelop
Non-specific Defences
Can you describe the process of inflammation?
- Mast cells: stimulated by mechanical damage or local chemical changes, which releases heparin and histamine.
- The chemicals that mast cell’s produce attract phagocytes which attack invading pathogens + foreign objects and eats remaining debris of infection
- Stimulates nociceptors in the area
- Dead phagocytes with debris or bacteris form pus
- New cells made by mitosis + damaged tissue is repaired.
MANDN acronym
Non-specific Defences
Can you explain the process of fever?
- Due to infection, the body’s thermostat is set at an abnormaly high rate (38.5> is considered a fever)
- The body responds through shivering and vasoconstriction.
- The body temperature continues to rise
- Crisis point is reached and the fever breaks with sweating and vasodilation on skin.
- Body falls to its normal temp.
Crisis point is when the thermostat resets and resets back to normal
Non-specific Defences
What is the lymphatic system?
- A network of lymph capillaries joined to larger lymph vessels
- lymph node, located at some lymph vessels.
Non-specific Defences
What is the function of the lymphatic system
- Collect fluid from escaping blood capillaries + return to circulatory system
- Internal defence of micro-organisms
a. lymph nodes contain network of lymph vessels containing macrophages and kill micro-organisms quickly
b. lymphocyte formulation increases when infection occurs · swollen + sore lymph nodes.
Immune Response
What does antibody-mediated immune response involve?
It involves B-cells and eliminate extracellular antigens.
This is also called humoral.
Immune Response
What does cell-mediated immune response involve?
It involves T-cells and eliminates intracellular antigens
This is also called cellular.
Immune Response
What does a humoral immune response work against?
- Works against bacteria, toxins and viruses before they enter the body’s cells.
- Also works against the eryhtrocytes of different blood groups
Note: think of “Bacteria, virus and blood group entering? Funny!”
Immune Response
Explain the process of humoral immune response.
- Foreign antigens reaches the lymphoid tissue
- Certain B-cells stimulate to undergo rapid cell division
- Most new B-cells become plasma cells to produce + release antibodies.
- Antibodies combine with antigent to incactivate/ destroy
- Some new B-cells form memory cells
What does cellular immune response work against?
- Work against cells infected by viruses, bacteria, fungi and parasites.
- Also, cancer cells, transplanted tissues and organs.
Can you explain the process of cellular immune response
- Foreign antigens reaches lymphoid tissue
- Certain T-cells stimulate to undergo** rapid cell division**
- Most new T-cells become killer T-cells or helper T-cells which migrate to site of infection
- Killer T-cells destroy antigen, helper T-cell promote phagocytosis
- Some sensitised T-cells form memory cells.
T-cells ARE CELLULAR
What is the role of histamine?
increases blood flow by** vasodilation** + makes blood vessel walls more permeable to allow more fluid to move into tissues.
What is the role of heparin?
prevents clotting in immediate area so clots form around damage instead, preventing the spread of pathogens.
The difference between enveloped and non-enveloped viruses?
- Enveloped viruses have an extra layer of protein molecules that surround the DNA/RNA
- Non-enveloped viruses do not have this lipid layer.
What is the advantage of an enveloped virus.
- The lipid layer they use is a replica of the host cell.
- Harder for the body to detect it as a threat
- Escape lysis with envelope
