CH 7 BODY PROTECTS SELF FROM INFECTION

Question 1

name & describe (physically) 4 types of bacteria

Answer 1

cocci - spherical cells, single, pairs, clusters, chains
bacilli - tod shaped with flagella for movement
spirilla - have twisted cells
vibrio - curved rods, often comma-shaped

Question 2

what are the physical characteristics of bacteria?

Answer 2

• slime layer (some)
• cell wall made of peptidoglycan (a combined carbohydrate-protein)
• DNA tangled, forms loops called plasmids
• flagella (some)
• cytoplasm appears granular due to ribosomes
• does not contain membrane-bound organelles
• capsule made of complex carbohydrates for protection

Question 3

describe the process of viral replication

Answer 3

E.G. HIV

1. HIV binds to the receptor site on t-lymphocyte
2. uncoated RNA from the virus enters the lymphocyte
3. the virus contains an enzyme that enables it to make a DNA copy of its RNA
4. DNA copy of HIV RNA in nucleus integrates with host cell DNA
5. new viral RNA produced
6. budding of new virus particle from lymphocyte
7. new HIV able to infect other cells

BERIPBN
bind, enter, replicate, integrate, produce, budding, new

Question 4

name the ways of transmission of pathogens

Answer 4

• CONTACT may be direct (person to person) or indirect (person to object to person)
• INGESTION through foods that are contaminated with bacterias
  e.g. salmonella
• TRANSFER OF BODY FLUIDS when fluid from one person comes into contact with the mucous membranes of another person (e.g. nose, mouth, throat, genitals, bloodstream)
  e.g. HIV
• INFECTION BY DROPLETS is the transmission of contaminated moisture across two people through coughing, sneezing, breathing, talking. may be breathed in by the 2nd person or land on food or food utensils.
  e.g. COVID-19
• AIRBORNE TRANSMISSION is when moisture in exhaled droplets evaporates, many bacteria are killed but some viruses and bacteria remain viable. particles are lighter and may remain viable for greater distances than droplets
  e.g. chickenpox
• VECTORS such as insects, ticks, or mites transfer the pathogen directly, while others such as houseflies transfer it indirectly e.g. food.
  many diseases are spread by a specific vector
  e.g. malaria is spread by mosquitos

Question 5

name 5 bacterias

Answer 5

chlamydia, gonorrhoea, leprosy, pneumonia, tuberculosis

Question 6

name 5 viruses

Answer 6

hiv/aids, chickenpox, COVID-19, influenza, ebola

Question 7

characteristics of viruses

Answer 7

• too small to be seen with an ordinary light microscope
• totally dependent on living cells for reproduction
• protein sheath surrounding a core of nucleic acid
• contains DNA or RNA but never both
• may have external lipid envelope

Question 8

use of “good bacteria”

Answer 8

• decomposition of organic material
• cycling of elements
• industrial uses - lactobacilli for yogurt production

Question 9

how do viruses infect a living cell?

Answer 9

• DNA/RNA of virus induces infected cell to manufacture more virus particles
  
  • cells become more damaged or die
• bacteriophages multiply in bacterial cells causing the death of a bacterium

Question 10

name and explain the non-specific external defences

Answer 10

SKIN (only useful if uncut/closed)
- normal bacteria occupies the skin, making it difficult for pathogens to become established
- oily secretion, “sebum” is secreted from oil glands and kills some pathogenic bacteria
- the salt and fatty acids in sweat inhibit pathogenic growth
MUCOUS membranes lining the body cavities that open to the exterior
- secrete mucous that traps particles, inhibiting entry of micro-organisms to the organs
HAIRS in nasal cavity, on nose, in ears
- nose - hair and mucous together trap 90% of particles inhaled when breathing
CILIA (tiny hair like projections that “beat”
- trachea, nasal cavity
- through “beating”, move mucous with particles to the throat to be coughed up or swallowed
ACIDS e.g. stomach juices
- kills bacteria from food and mucous swallowed
- vagina acid inhibits growth of bacteria
- acids in sweat (skin)
LYSOZYME enzyme kills bacteria
- eyes flushed out by tears containing lysozyme
- saliva, sweat, secretions of nose and tissue fluid
CERUMEN or ear wax
- protects outer ear against infection
- slightly acidic, contains lysozyme
FLUID MOVEMENT
- “flushing action” of the body keeps some areas relatively pathogen-free
- e.g. urine through urethra stops bacteria reaching kidneys
- tears, sweat, saliva

Question 11

name and explain the non-specific protective reflexes

Answer 11

SNEEZING
stimulus: irritation of walls in nasal cavity caused by noxious fumes or dust particles
- strong expulsion of air from lungs carries mucous, foreign particles, irritating gases out through nose and mouth
COUGHING
stimulus: irritation in lower respiratory tract - bronchi, bronchioles
- air drives mucous and foreign matter up trachea, through throat and mouth
VOMITING
stimulus: psychological stimuli, excessive stretching of stomach or presence of bacterial toxins
- contraction of muscles in abdomen and diaphragm expels stomach contents
DIARRHOEA
stimulus: irritation of small and large intestines by bacteria, viruses or protozoans
- irritation causes increased contractions of wall muscles in order for substance to be removed as quickly as possible
- faeces watery because it doesn’t stay in LI long enough for water to be absorbed

Question 12

name the 3 phagocytic cells

Answer 12

• monocytes and macrophages
• neutrophils
• dendritic cells

Question 13

what is a phagocyte

Answer 13

• a specialised white blood cell or ‘leucocyte’ that engulfs and digests micro-organisms and cell debris
• eliminates many pathogens before infection can occur

Question 14

talk about monocytes and macrophages

Answer 14

• monocytes leave bloodstream and enter tissue when it becomes infected or inflamed
• differentiate into macrophages
• some macrophages move through tissues looking for/destroying pathogens
• others fixed in one place, only deal with pathogens that come to them

Question 15

talk about neutrophils

Answer 15

• “granulated leucocytes” due to granules visible in cytoplasm
• lobulated nucleus
• most abundent leucocyte (55-70%)
• first cells to move to tissue to destroy pathogen during infection
• important in killing pathogens inside cells
• short life span, die after few days
• dead cells make up large portion of pus forming after na infection

Question 16

process of phagocytosis from presence of invading bacterium (5 steps)

Answer 16

1. phagocyte moves to bacterium
2. phagocyte changes shape so it completely encloses bacterium
3. lysosomes contain destructive enzymes
4. enzymes are released to destroy bacterium
5. harmless particles are released from phagocyte

Question 17

talk about dendritic cells

Answer 17

• characterised by projections from cytoplasm
• ability to detect, engulf and process foreign particles
• use info about ingested particles to assist with specific immunity

Question 18

what do words ending in “itis” indicate?

Answer 18

inflammation of specific organs or tissues

Question 19

what is inflammation and what are its 3 purposes

Answer 19

response to any damage to tissues

• reduce the spread of any pathogens, destroy them and to prevent the entry of additional pathogens
• remove damaged tissue and cell debris
• begin repair for the damaged tissue

Question 20

what are the 4 symptoms of inflammation?

Answer 20

• redness
• swelling
• heat
• pain

Question 21

what is the complement system?

Answer 21

a series of more than 20 proteins, many of which are normally inactive. when initiated, one protein activates the next, which activates the next and so on

Question 22

what are the steps of inflammation? (7 steps)

Answer 22

1. mechanical damage/local chemical changes cause mast cells to be activated by complement proteins. results in release of histamine, heparin + other chemicals into tissue fluid
2. histamine causes vasodilation (inc. blood flow), making walls of blood capillaries more permeable. more fluid moves through capillary walls into tissue. inc. bf. causes heat and redness. escape of fluid from blood causes inflammation.
3. heparin prevents clotting in immediate area of injury. clot of the fluid forms around damaged area, slowing spread of pathogens into healthy tissues
4. complement system proteins + some chemicals released by mast cells attract phagocytes, particularly neutrophils, to perform phagocytosis
5. abnormal condition in tissues stimulate pain receptors, person feels pain
6. phagocytes, filled with bacteria, debris and dead cells begin to die. dead phagocytes + tissue fluid form yellow pus
7. new cells produced by mitosis and repair of damaged tissue takes place

Question 23

what is a fever?

Answer 23

• infection accompanied by the elevation of the body’s set point of internal body temperature, over 37ºC
• body’s temp still fluctuates in response to hot and cold
• set point change is due to hypothalamus

Question 24

what causes a fever?

Answer 24

• pyrogens released in white blood cells during inflammatory response act on hypothalamus
• a pyrogen, interleukin-1 is predominantly produced by activated macrophages, and by other cells such as dendritic and epithelial cells

Question 25

how does body temperature rise during a fever?

Answer 25

• thermo receptors detect body temp, hypothalamus recognises that it is lower than the new, higher set point.
• so, vasoconstriction in the skin and shivering occur, conserving and increasing heat

Question 26

explain the crisis point in a fever

Answer 26

• fever breaks and falls rapidly
• set point set back to normal
• person feels hot and appears flushed, as vasodilation and sweating occur

Question 27

how can fevers be beneficial?

Answer 27

high body temp believed to inhibit growth of some bacteria and viruses. heat speeds the rate of chemical reactions, which may help body cells repair themselves more quickly during disease.

Question 28

how can fevers be dangerous?

Answer 28

may inhibit viral replication by allowing interferons to operate more quickly. however, if body temp goes too high (due to positive feedback loop), can cause convulsions and brain damage. death will occur at 44.4-45.5ºC

Question 29

what does the lymphatic system consist of?

Answer 29

• network of lymph capillaries joined at larger lymph vessels
• lymph nodes, located along length of some lymph vessels

Question 30

what are the functions of the lymphatic system?

Answer 30

• collect some fluid that escapes b capillaries and return it to circulatory system
• internal defence against pathogenic organisms

Question 31

role of lymphatic system in infection etc

Answer 31

• each contains masses of lymphoid tissue, the cells of which are criss-crossed by a network of fibres
• lymph entering lymph nodes contains cell debris, foreign particles & micro-organisms that have penetrated body’s external defences
• some micro-organisms may be pathogenic and if not destroyed could cause disease
• larger particles, e.g. bacteria are trapped in meshwork of fibres as lymph flows through spaces in nodes. macrophages ingest and destroy these particles via phagocytosis
• during infection, lymph nodes become swollen and sore

Question 32

define non-specific defence

Answer 32

defence of the body against all pathogens

Question 33

define specific defence

Answer 33

defence of body against specific pathogens

Question 34

what is an immune response?

Answer 34

• homeostatic mechanism
• helps deal with invasion of foreign substances + micro-organisms
• helps restore internal environment to normal condition
• response involving the reaction of B-cells and T-cells

Question 35

life cycle of b and t cells, up to lymphoid tissue

Answer 35

• both start in bone marrow
• T-cells are cells that have gone to mature in the thymus
• B-cells mature in the bone marrow
• once matured, both become part of the lymphoid tissues
• lymphoid tissues mostly in lymph nodes, also in spleed, thymus, tonsils

Question 36

what are the two parts to the immune response?

Answer 36

• humoral response / antibody-mediated immunity involving production of antibodies by b cells
• cell-mediated response due to t cells and involves formation of special lymphocytes that destroy invading agents

Question 37

what is triggered by antigens?

Answer 37

specific immune response;

• humoral / anitbody-mediated immunity
• cell mediated immunity

Question 38

list molecules that antigens may occur as

Answer 38

• proteins
• carbohydrates
• lipids
• nucleic acids
• V particles
• whole MOs such as a bacteria cell
• part of a bacterium, such as a flagella, cell wall or capsule
• toxins
• molecules on cells e.g. blood cells
• pollen grains
• egg whites

Question 39

name for large molecules produced by the body that DO NOT cause an immune response

Answer 39

self antigens

- immune system is programmed before birth to distinguish between self and non-self

Question 40

name for large molecules produced by the body that DO cause an immune response

Answer 40

non-self antigens

Question 41

what is an antibody?

Answer 41

• y shaped specialised protein produced by plasma cells in response to non-self antigen
• belong to group of proteins called immunoglobulins

Question 42

what is meant by the term “antigen-antibody complex”

Answer 42

antigen molecules have specific active sites with a particular shape while the antibody has the complementary shape
allows both molecules to lock together like lock and key
each antibody can combine with only ONE particular antigen

Question 43

what does/can an antigen presenting cell do?

Answer 43

• undifferentiated b-cells, dendritic cells, macrophages
• detect presence of non self antigen
• engulf the pathogen
• digest the pathogen, producing small fragments that move to the surface of the cell
• present the antigen to lymphocytes

Question 44

describe the process of antibody-mediated immunity (7 points)

Answer 44

1. A-P cells recognise, engulf and digest Ps, displaying the antigen on their surface
2. A-P cells reach lymphoid tissue and present antigen to lymphocytes
3. helper T-cells stimulated by A-P cells, releasing cytokines
4. specific b-lymphocytes are stimulated to undergo rapid cell division
5. most new b-cells develop into plasma cells, which produce antibodies and release them into blood and lymph
6. antibodies combine with the specific antigen and inactivate or destroy it
7. some of the new b-cells form memory cells

Question 45

describe the process of cell-mediated immunity (7 points)

Answer 45

1. A-P cells recognise, engulf and digest Ps, displaying the antigen on their surface
2. A-P cells reach lymphoid tissue and present antigen to lymphocytes
3. helper T-cells stimulated by A-P cells, releasing cytokines
4. specific t-lymphocytes are stimulated to undergo rapid cell division
5. most new t-cells develop into killer t-cells or helper t-cells, which migrate to the site of the infection
6. killer t-cells destroy the antigen while helper t-cells promote phagocytosis by macrophages
7. some sensitised t-cells form memory cells.

Question 46

what do suppressor t-cells do?

Answer 46

act when the immune activity becomes excessive or infection has been dealt with successfully. release of suppressors inhibit b and t cell activity, slowing down immune response

Question 47

what are the functions of antibodies?

Answer 47

• inactivate foreign enzymes or toxins by combining with them or inhibiting their reaction with other cells or compounds
• bind to the surface of viruses and prevent them entering the cells
• coat bacteria so that they are more easily consumed by phagocytes
• cause particles such as bacteria, viruses or foreign blood cells to clump together (agglutination)
• dissolve organisms
• react with soluble substances to make them insoluble and thus more easily consumed by phagocytes

Question 48

explain the types of immunity (natural passive, artificial passive, natural active, artificial active)

Answer 48

Natural-Passive: antibodies enter the bloodstream across the placenta or in breast milk
Artificial-Passive: antibodies are injected into the bloodstream
Natural-Active: ability to manufacture antibodies results from an attack of a disease
Artificial-Active: ability to manufacture antibodies results from being given an antigen by vaccination

Question 49

differentiate between immunisation and vaccination

Answer 49

immunisation: programming the immune system so that the body can respond rapidly to infecting MOs.
Vaccination: artificial introduction of antigens of pathogenic organisms so that the ability to produce the appropriate antibodies is acquired without the person having to suffer disease.
a vaccination is a type of immunisation

Question 50

types of vaccines

Answer 50

LIVE ATTENUATED - MOs of reduced ability to produce disease symptoms. person does not contract disease but manufactures the antibodies.
e.g. vaccines for polio, tuberculosis, rubella, measles, mumps, yellow fever
INACTIVATED - containing dead MOs. shorter lasting immunity.
e.g. cholera, typhoid, whooping cough
TOXOID - in cases where Bs produce their effect in humans by liberating toxins, not necessary to use B for immunisation. toxins inactivated, do not make person ill when injected. inactivated toxins = toxoids
e.g. diphtheria, tetanus
SUB-UNIT - fragment of MO used to provoke immune response
e.g. HPV, hepatitis B

Question 51

what is recombinant DNA

Answer 51

synthetic DNA; made by inserting genes from one source into a DNA molecule from a different source

Question 52

methods of vaccination

Answer 52

• syringe injection
• sweet syrup or sugar lump (by mouth, e.g. polio)
• under research: fine spray, skin patches, ingestion in food

Question 53

why should vaccination be postponed until 2 months after birth?

Answer 53

• child’s blood contains antibodies from mother via placenta or breast milk
• if given vaccine, antibodies from mother will eliminate antigens in vaccine, which will occur before the infant’s immune system can mount an immune response.
• a few months are needed for child’s immune system to become activated and therefore prevent child from getting diseases they are being vaccinated against

Question 54

why is it usually necessary for infants to receive more than one injection of a vaccine?

Answer 54

• antibody levels from primary response need to stimulate a secondary response
• 2nd “booster” vaccination is required to trigger secondary response
• memory cells react quickly to second exposure, resulting in higher, longer lasting levels of antibodies in addition to more memory cells
• if booster given too soon: antibodies present in blood will eliminate material in vaccine before more b-cells can be activated
• period of time required to allow antibodies in blood to be eliminated, usually 2 months, before booster shot

Question 55

what is meant by the term ‘herd immunity’?

Answer 55

• vaccination program not only reduces chance of disease in most susceptible individuals, but also increases immunity of the population
• high proportion of individuals being immunised
• large number of immunised individuals = less chance of disease being transmitted between them
• higher contagiousness of a disease requires higher percentage of herd immunity

Question 56

why are some people unable to be vaccinated?

Answer 56

ALLERGIC

• may occur not from vaccine but from medium
• e.g. influenza + fertilised eggs (egg protein)
• e.g. hepatitis B + yeast

PRESERVATIVES

• e.g. thiomersal, formaldehyde, phenol, aluminium phosphate, alum, acetone
• may affect nervous system leading to other health issues

Question 57

what ethical concerns do people have with vaccinations?

Answer 57

• use of animals to produce vaccines (host tissue required)
• use of human tissue to produce vaccines (some human vaccines need human hosts - human foetus)
• informed consent (not fully aware of risks)
• testing on animals

Question 58

what are the reasons (other than ethical concerns) that people are reluctant to be vaccinated?

Answer 58

• promoting sexual activity in teenagers
• (lack of) availability
• religious beliefs (healing through prayer)
• cost
• commercialisation (interests of commercial vaccine production may affect its use)

Question 59

what are antibiotics and what can and cant they fight?

Answer 59

• drugs used to fight infections of MOs
• each is specific to a bacteria
• cannot fight viral infection

Question 60

what are the common antibiotics that have been produced?

Answer 60

• 1st - penicillin works by preventing synthesis of walls of bacteria cells, inhibiting reproduction of bacteria. 10% people allergic.
• streptomycin, erythromycin, tetracycline, vancomycin, cephalosporin

Question 61

what are the types of antibiotics?

Answer 61

• bactericidal kill bacteria by changing structure of cell wall or membrane, or by disrupting action of essential enzymes
• bacteriostatic stop bacteria from reproducing, usually by disrupting protein synthesis
• the above types could be broad-spectrum (wide-range of bacteria) or narrow-spectrum (specific types of bacteria)

Question 62

what is meant by ‘resistance’, ‘multiple drug resistance’ and ‘total drug resistance’ in terms of antibiotics?

Answer 62

R: widespread use of antibiotics has caused some bacteria to gradually evolve and become resistant to them.
MDR: some strains of bacteria now resistant to multiple drugs. known as ‘super bugs’
TDR: totally resistant strains of bacteria (all drugs)

Question 63

what are antiviral drugs?

Answer 63

• drugs used specifically for treating viral infection
• the way in which viral cells replicate make it difficult to find drugs to treat the infection
• any drug interfering with viral replication is likely to be toxic to the host
• antivirals inhibit development of the virus
  e. g. Relenza for influenza