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WACE Human Biology > Pathogens & Immunity > Flashcards

Pathogens & Immunity Flashcards

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1
Q

What are Infectious diseases?

A

Foreign organisms invading the body and multiplying there, some diseases can be contagious and some non contagious

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2
Q

What are Pathogens?

A

Disease causing organism such as bacteria, viruses, fungi and animal parasites

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3
Q

What are Vectors?

A

Immediate hosts pathogens i.e. mosquito or fleas

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4
Q

What is Bacteria?

A
  • Most bacteria is harmless to humans; they are non pathogenic
  • Bacteria live on skin surfaces and the alimentary canal
  • Consists of a single cell, cell shape is used to classify bacteria
  • Can be seen with a light microscope
  • Bacteria can be important in roles such as decomposition, used in industrial processes in our bodies
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5
Q

What are Viruses?

A
  • Diseases in which no bacteria cause could be found
  • Not all viruses are harmful
  • Can be seen with an Electron Microscope
  • All contain genetic material such as DNA or RNA
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6
Q

What are Fungi?

A
  • Most pathogenic fungi cause disease of the skin
  • Are useful i.e. mushrooms, yeast
    e. g. ringworm, tinea
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7
Q

What are animal parasites?

A
  • May cause little or no harm
  • Ectoparasite - Live on the surface of the body i.e. fleas or lice
  • Endoparasites - Live inside the body i.e. Malaria
    e. g. tapeworms, ticks, lice, scabies
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8
Q

What are the structures of Bacteria?

A
  • Slime Layer (around the outside of some bacteria)
  • Cell Wall
  • Cell Membrane
  • Flagella - (for movement)
  • Cytoplasm
  • Capsule
  • DNA
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9
Q

What are the 4 types of Bacteria?

A
  1. Cocci (spherical cells)
  2. Bacilli (contains flagella)
  3. Spirila (twisted cells)
  4. Vibrio (curved rods that look like a comma)
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10
Q

What are Antibiotics?

A
  • Act against bacteria
  • Drugs that are used to fight infections of micro - organisms, particularly bacteria
  • Each antibiotic is effective for only certain types of bacterial infection
  • Cannot be used to treat viral infections
  • 2 types (Bactericidal and Bacteriostatic)
  • Narrow Spectrum (effective only against specific types of bacteria)
  • Broad Spectrum (effective against a wide range of different types of bacteria)
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11
Q

What are Bactericidal Antibiotics?

A

Kill bacteria by changing structure of cell wall or cell membrane or by distracting the action of essential enzymes

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12
Q

What are Bacteriostatic Antibiotics?

A

Stop bacteria from reproducing usually by disrupting protein synthesis

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13
Q

What is Antibiotic Resistance?

A
  • The widespread use of antibiotics has created a major problem as some bacteria that antibiotics are used to kill have gradually evolved and become resistant to them
  • In the early days the problem was easily solved by changing to a different antibiotic, however some strains of bacteria are now resistant to most or all available types of antibiotics which is known as multiple drug resistance
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14
Q

What are Antivirals?

A
  • Antivirals are used specifically for treating viral infections because antibiotics are ineffective against viruses
  • Viruses enter a host cell and the viruses DNA or RNA induces the cell to produce new virus particles, these particles can then leave the cell an infect new host cells
    Killing the viruses means killing the host cell
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15
Q

How are Pathogens transmitted?

A
  1. Transmission by Contact
  2. Transmission of Body Fluids
  3. Ingestion
  4. Transmission Through Vectors
  5. Infection by Droplets
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16
Q

What is Transmission via Contact?

A

Involves the spread of the pathogen by actual physical contact, which may be direct, such as touching an infected person or indirect, touching an object that has been touched by an infected

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17
Q

What is Transmission via Body Fluids?

A

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, kissing, sexual contact then pathogens may enter the body of that person. HIV, Hepatitis B and Hepatitis C is spread in this way

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18
Q

What is Transmission via Ingestion?

A

Through congestion of food or drink contaminated with Pathogens which may result in disease. For example Cholera, Salmonella and Typhoid Fever

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19
Q

What is Transmission via Vectors?

A
  • The transfer of pathogens by other animals such as insects, ticks or mites
  • Some vectors transfer the pathogen directly; others such as house flies may spread the pathogen to food or water which is then ingested
  • Many vector born diseases are spread by a specific vector
  • e.g. malaria and dengue fever are spread by mosquitos
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20
Q

What is Transmission via Droplets?

A
  • May occur when tiny droplets of moisture, harbouring pathogenic organisms, are emitted when breathing, talking, sneezing or coughing
  • The droplets may be breathed in by others, or may settle on food or utensils to be later ingested with food
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21
Q

What are Non Specific Defences?

A 
External
- Body Defences 
- Protective Reflexes 
Internal 
- Lymphatic System 
- Fever
- Inflammatory Response
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22
Q

What are Protective Reflexes?

A
  • A reflex is an automatic response to a stimulus, reflexes protect the body from injury
  • Protective reflexes e.g. Coughing, Sneezing, Vomiting
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23
Q

What are the body’s external defences?

A
  1. Skin - sebum is produced by oil glands which contain substances that kill some pathogenic bacteria
  2. Ear - cerumen containing lysozyme which inhibits bacterial growth
  3. Eyes - tears containing lysozyme cleanse the eyes and inhibits bacterial growth
  4. Nasal Cavity - contains hairs, cilia, mucous which trap micro-organisms
  5. Mouth Cavity - mucus membranes and saliva traps micro-organisms
  6. Urethra - urine flow prevents bacterial growth
  7. Stomach - acidic juices within the stomach oil micro-organisms
  8. Vagina - acidic secretions, iInhibits bacterial growth
  9. Trachea & Bronci - mucus layer and beating cilia trap micro-organisms
24
Q

What is the Inflammatory Response?

A
  • An internal non specific response to pathogens
  • Inflammation is a response to any damage to the tissues
    e. g. a cut, pimple, mosquito bite
25
Q

What are the purposes of an Inflammatory Response?

A
  • Reduce the spread of pathogens, to destroy them and to prevent entry of more pathogens
  • Remove the damaged tissue and cell debris
  • Begin the repair of damaged tissue
26
Q

What are the signs of an Inflammatory Response?

A
  • Redness
  • Swelling
  • Heat
  • Pain
27
Q

What are the steps in an Inflammatory Response?

A
  1. Skin is broken and a non specific inflammatory response begins
  2. Mast cells (specialised cells) release chemicals histamine and heparin
  3. Complement Proteins are activated which attract phagocytes (macrophages and leucocytes) which swallow and digest dead cell debris and bacteria by phagocytosis, which causes pain
  4. The Phagocytes, filled with bacteria, debris and dead cells begin to die and the dead phagocytes and tissue fluid form a yellow liquid called pus
  5. Histamine and Complement proteins which signal finished and phagocytes are no longer attracted to the area, new cells are produced by mitosis and the repair of damaged tissues begins
28
Q

What is Fever?

A
  • An internal non specific response to pathogens
  • Fever is an elevation of body temperature and defence mechanism to protect the body
  • It is the change in a body’s temperature is due to the resetting of the body’s thermostat, controlled by the hypothalamus to a higher level
29
Q

What are the benefits of Fever?

A
  • Fever is beneficial up to a point as high body temperature is believed to inhibit the growth of some bacteria and viruses
  • Heat speeds up the rate of chemical reactions which may promote healing more quickly during a disease
30
Q

What are the disadvantages of Fever?

A
  • Harmful if temperature is too high

- Death if temperature is between 44.4 and 45.5 degrees celsius

31
Q

What is the process of Fever?

A
  1. Due to infection the body’s thermostat become set at an abnormally high temperature
  2. The body feels cold and responds by shivering and vasoconstriction in the skin
    Body temperature rises
  3. The fever breaks with sweating and vasodilation in the skin
  4. Body temperature falls to normal
32
Q

What is the main function of the Lymphatic System?

A

To collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system, in addition the main function is its role in the body’s internal defence against pathogenic organisms

33
Q

What is the Process of Lymphatic System Defence?

A
  • Larger particles such as bacteria are trapped in the criss cross meshwork of fibres as the lymph flows through the spaces in the nodes
  • Macrophages ingest the particles by phagocytosis
34
Q

What are Lymphocytes?

A
  • A type of White Blood Cell
  • Involved in specific and non defences
  • These are produced in the bone marrow and lymphoid tissue and move around the blood and enter a tissue or lymph
  • Contain B-cells and T-cells
35
Q

What are Macrophages?

A
  • A type of White Blood Cell
  • Involved in specific and non specific defences
  • Are large phagocytic cells which consume foreign substances and micro organisms by phagocytosis
  • They alert the immune system to the presence of foreign materials
36
Q

What are Specific Defences?

A
  • Are those directed towards a particular pathogen

- Specific defences are part of our immune system

37
Q

What is the Immune System?

A
  • Composed of different types of cells that occur in most of the organs in the body
  • These cells protect against foreign organisms, a range of chemicals as well cancerous and other abnormal cells
  • Some of these cells are non specific such as phagocytes which are able to engulf and digest micro-organism and cell debris
  • Others such as B-cells and T-cells only provide protection against a specific micro-organisms or disease causing substance
38
Q

What is an Immune Response?

A
  • A homeostatic mechanism
  • When micro-organism or foreign substances enter the body, the immune response helps to deal with the invasion and restore the internal environment to its normal condition
  • Two parts: Antibody Mediated Immunity (B-cells and T-cells) and Cell Mediated Immunity
39
Q

Where are B-cells and T-cells produced?

A
  • Both of these cells are produced by the bone marrow and both end up in the lymphoid tissue, but they mature by following two different routes between bone and lymphoid tissue
  • T-cells mature in the Thymus before being incorporated into the Lymphoid tissues
  • B-cells mature in the Bone Marrow and then also become part of the lymphoid tissue
40
Q

What are B-cells?

A

Provide Antibody mediated immunity, produced in the bone marrow, these circulate the body and attack invading agents

41
Q

What are T-cells?

A

T Cells - Provide Cell Mediated immunity, produced in the bone marrow and mature in the Thymus

42
Q

What are Antigens?

A
  • Any substance capable of causing a specific immune response, such a substance, introduced to the body, causes the body to produce specific antibodies
  • Antigens are large molecules and could be a virus particle or whole micro-organism such as a bacterial cell or part of a bacterium, toxins produced by bacteria are also antigens
  • Two types: self antigens and non self antigens
43
Q

What are Non Self Antigens?

A

Foreign substances that do trigger an immune response

44
Q

What are Self Antigens?

A

Substances produced by a persons own body, these do not trigger an immune response

45
Q

What are Antibodies?

A
  • A specialised protein that is produced in response to a non self antigen (foreign substances)
  • Antibodies belong to a group of proteins known as immunoglobulins
  • The antibody produced in response to an antigen can combine with that antigen to form an antigen-antibody complex (lock and key)
  • Each antigen can combine with only one particular antigen
46
Q

What is Anti Body Mediated Immunity?

A
  • Also known as the Humoral Response
  • Occurs after the pathogen has entered the body and the external defence mechanisms have not worked
  • Involves the production and release of antibodies into the blood and lymph
  • Provides resistance to viruses, bacteria and bacterial tons before these micro-organisms or substances enter the body’s cells
  • Lymphoid tissue contains thousands of types of B cells and each type if capable of responding to a specific antigen
  • When an antigen activates B cells they enlarge and divide into groups of cells called a clone
  • Most of the clone become plasma cells, which secrete the specific antibody capable of attaching to the active site of the antigen
  • The B cells of the clone that did not differentiate into plasma cells remain as memory cells which spread to all body tissues to allow the response to occur more rapidly should the antigen enter the body again
47
Q

How an Antibody Kill Pathogens?

A
  1. Can combine with foreign enzymes or bacterial toxins or inactivate them by inhibiting reaction with other cells or compounds
  2. Bind to the surface of viruses to prevent the viruses from entering cells
  3. Coat bacteria so that the bacteria are more easily consumed by phagocytes
  4. Agglutination, where particles such as bacteria, viruses and foreign cells clump together
  5. Dissolve organisms
  6. React with soluble substances to make them insoluble and thus more easily to be consumed by phagocytes
48
Q

What is Cell Mediated Immunity?

A
  • Provides resistance to the intracellular phase of bacterial and viral infections
  • Also involved in the rejection of transplants of foreign tissues and has the ability to fight some cancer cells
  • The T-Lymphocytes are responsible for cellar immunity they occur in the lymphoid tissue and there are thousands of types however each T cell responds to only one particular antigen
  • When a foreign antigen such as a virus or a bacterium enters the body, the particular type of T cell that are specifically programmed for that antigen becomes activated or sensitised after a B cell or macrophage encoders the foreign antigens and travels to the nearest lymph node and presented it to the T cells
  • The sensitised T cells enlarge and divide, each giving rise to a clone, a group of identical T cells
  • Some cells of the clone remain in the Lymphoid tissue as memory cells and those which do not become memory cells develop further producing three types of T cells: killer, helper and suppressor T-cells
49
Q

What are the types of T-cells?

A

> 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
Helper T Cells - Secrete a number of substances that:
cause lymphocytes at the infection site to become sensitised, attract macrophages to the place of infection, Intensify the phagocytic activity of macrophages
Suppressor T Cells - When the immune activity becomes excessive or the infection has been dealt with successfully, the release substances that inhibit T and B cells activity, slowing down the immune response

50
Q

What is Immunity?

A
  • Immunity is the resistance to infection by invading micro organisms
  • The ability to respond rapidly may be natural or artificial
51
Q

What are the types of Immunity?

A
  1. Natural Immunity - occurs without any human invention
  2. Artificial Immunity - results from giving people an antibody or antigen
    - Can be passive or active
52
Q

What is Passive Immunity?

A
  • Passive immunity is when a person is given antibodies produced by someone else, short lived and only lasts until antibodies are broken down and excreted
  • The individuals body plays no part in the production of antibodies
  • Can be natural or artificial
    1. Natural: such as when antibodies from the mother pass across the placenta to a developing foetus or when the mothers antibodies are passed to the baby via breastfeeding
    2. Artificially: such as when person is injected with antibodies to combat a particular infection, immunity is established immediately
53
Q

What is Active Immunity?

A
  • Active immunity results when the body is exposed to a foreign antigen and manufactures antibodies in response to that Antigen
  • This type of immunity is long lasting, often for life as it involves memory cells
    1. Natural - Results from an actual attack of the disease
    2. Artificial - Injection or vaccination of the antigen
54
Q

What is the role of Histamine?

A

Histamine is involved in the Inflammatory response in which it increases 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

55
Q

What is the role of Heparin?

A

Heparin is involved with the Inflammatory response in which it prevents clotting in the immediate are abut allows clotting around the damaged area to prevent pathogens from entering

WACE Human Biology (15 decks)

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