Chapter 7 - Protection from infection Flashcards
define pathogens
disease causing organism (viruses and bacteria)
Communicable disease
A disease passed from one person to another by infection with micro organisms. also called infectious or transmissible disease
Bacteria
single celled organisms with simple structure. Lack nucleus, DNA floats freely in cytoplasm. Effects may include producing toxins or inducing an allergic response depending on species
what are the four types of bacteria
- Cocci (spheres)
- Bacilli (rod shaped with tails)
- Spirilla (twisted)
- vibrio (comma)
Viruses
Infectious agent consisting of a protein sheath surrounding a core of nucleic acid. dependent on living cells for reproduction. Contains DNA or RNA never both
how do viruses spread in the body
infect a living cell and its DNA or RNA induces the cell to manufacture more virus particles. These particles leave host cell and infect others
Bacteriophage
virus that infects bacteria
contagious
disease passed on by direct human contact
vector
an agent (eg insect) capable of transferring pathogens
6 ways a pathogen can be transferred
- Transmission by contact: direct (touching an infected person) or indirect (touching an object touched by an infected person). EG STI’s
- Ingestion of contaminated food/drink. EG Salmonella
- transfer of body fluids. EG. HIV
- Infection by droplets (breathing, talking, sneezing, coughing). EG, COVID
- Airborne transmission. EG, measles
- Transmission by vectors (insects such as mossie). EG, malaria
two types of body defences against disease
- Specific: Directed at a particular pathogen
- Non specific: works against all pathogens
name 8 non specific external defences
- Skin: Impervious barrier, sweat prevents growth of micro organisms, large numbers of bacteria and sebum (oily secretion)
- Mucus: mucous membranes secrete mucus inhibiting entry of micro organisms
- Hairs: trap particles (nose, ear)
- Cilia: hair like projections from cells capable of beating motion that moves micro organisms towards throat to be coughed up
- Acids: Stomach juices highly acidic killing bacteria taken in with food. vagina, urine, sweat
- Lysozyme: enzyme that kills bacteria. found in tears, salvia, sweat.
- Cerumen: ear wax. protects outer ear against infection. contains lysozyme
- Movement of fluid: Flushing action of body fluids helps keep some areas relatively free of pathogens (eg, urine through urethra, tears, sweat, saliva)
what are four protective reflexes that protect against infection
- Sneezing (irritation of nasal cavity)
- coughing (irritation of respiratory tract)
- vomiting (Psychological, stretching of stomach and contraction of abdomen)
- Diarrhoea (irritation of intestines by bacteria)
name the three internal non specific defences
- Phagocytosis
- Inflammatory response
- Fever
Phagocytes
White blood cells able to engulf micro organisms and cell debris
Leucocytes
white blood cells
three types of phagocytic cells (phagocytosis)
- Monocytes and macrophages: when tissue becomes infected, monocytes leaves bloodstream and enter tissue, then differentiate into macrophages
- Neutrophils: granulated WBC, first cells to move into tissue and destroy pathogen. short life span
- Dendritic cells: Antigen presenting cell, characterised by projections from the cytoplasm. Have ability to detect, engulf and process foreign particles
Monocytes
white blood cell found in blood that migrates into damaged tissue and forms macrophages
Macrophage
phagocytic cells important in removing microbes and dying cells through phagocytosis
what is inflammation
response to damage to a tissue. Involves welling =, heat, pain and redness
three purposes of inflammation
- Reduce spread of pathogens (destroy + prevent entry)
- Remove damaged tissue and cell debris
- Begin repair of damaged tissue
Complement system
System of proteins produced by the liver that enhance the activity of antibodies and phagocytes
what are the seven steps of the inflammatory response
- Damage or chemical changes cause activation of mast cells, resulting in release of histamine and herapin into tissue fluid
- Histamine increases blood flow due to vasdilation, making walls of capillaries more permeable. Increased blood flow causes heat, redness and swelling
- Herapin prevents clotting, slowing spread of pathogen to healthy tissues due to clot of fluid
- Complement system proteins and mast cells release chemicals that attract phagocytes (particularly neutrophils) which consume micro organisms
- Pain receptors are stimulated
- Phagocytes fulled with bacteria die forming pus
- Repair of tissue takes place by mitosis
What is a fever
elevation in body temperature above 37ºC due to resetting of body’s thermostat to a higher level than normal, controlled by hypothalamus
what causes a fever
Pyrogens that are released by white blood cells during inflammatory response and act on hypothalamus
what happens in a fever
- Body’s thermostat becomes set at an abnormally high level due to infection
- Body feels cold and responds by shivering and vasoconstriction, increasing body temp
- Fever breaks (crisis points) with sweating and vasodilatation and body temp returns to normal
Benefits of a fever
Inhibits growth of bacteria and viruses, heat speeds rate of chemical reactions (increases body cell repair), inhibits viral replication
what happens if body temperature becomes too high
convulsions, brain damage and death
name a pyrogen
interleukin - 1
function of the lymphatic system
Collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system
How do lymph nodes provide non specific defence against disease
lymph entering lymph nodes contains cell debris, foreign particles and micro organisms that have penetrated the body’s external defences and may be pathogenic. Macrophages ingest and destroy these particles by phagocytosis
Immune response
a response of B and T cells triggered by foreign substances entering the body
B cells
Lymphocyte produced and matured in bone marrow that develops into either a plasma cell that produces antibodies or memory cells. involved in antibody mediated immunity
T cells
Lymphocyte produced in bone marrow and matured in the thymus that can differentiate into different kinds of cells. involved in Cell mediated immunity
what are the two parts to the immune response
- Humoral response (antibody mediated immunity): response triggered by foreign substances entering the body, involving B cells and production of antibodies
- Cell mediated response: part of immune response in which T cellls attach to antigens to destroy them
antigen
any substance capable of causing s specific immune response
examples of antigens
Large molecules such as proteins, carbs and lipids and may include virus particles, bacterial cell, part of a bacteria, toxins, pollen grains
Two types of antigens
- Self antigens: Large molecules produced in a person’s own body do not cause an immune response
- Non self antigens: Foreign compounds that do trigger an immune response
antibodies
Y shaped specialised protein produced by plasma cells in response to a non self antigen. Belongs to group of proteins called immunoglobulins
antigen antibody complex
When an antibody combines with a particular antigen. are specific
antigen presenting cells
Phagocytic cells that detect, engulf and digest the pathogen and present the antigen to lymphocytes. include dendritic cells, macrophages and undifferentiated B cells
Antibody mediated immunity/humoral response
- Involves the production and release of antibodies into blood and lymph, providing resistance to viruses and bacteria before they enter body cells
- When an antigen presenting cell presents antigen to specific B cells, they become activated
- Antigen is also presented to helper T cells, leading to release of cytokines
- Cytokines cause helper T cells to clone themselves to release different cytokines which activate B cells
- When b cells are activated, they enlarge and divide into group of cells called clone
- Most of clone become plasma cells which secrete specific antibody capable of attaching to active site of antigen
- Remaining B cells of clone become memory cells. Spread to all body tissues to allow the response to occur more rapidly if antigen enters body again
Cytokines
Small proteins released in response to antigens, act as messengers in immune response
primary response
the response of the immune system to the first exposure to an antigen, slow and over days but leaves immune system with memory of that antigen
Secondary response
The response to a second exposure to an antigen. Faster and more intense than primary lasts longer, antigen has little effect
How do antibodies work
- Inactivate foreign enzymes/toxins by combing with them or inhibiting reactions
- Bind to surface of antigens and prevent them entering cells
- coat bacteria so they are more easily consumed by phagocytes
- Agglutination (clumping together of micro organisms or cells)
- Dissolve organisms
- make soluble substances insoluble for easy consumption by phagocytes
Cell mediated immunity
- Provides resistance to the intracellular phase of bacterial and viral infections
- important in providing resistance to fungi and parasites and rejecting foreign tissue transplants
- When an antigen presenting cell presents antigen to specific T cells, they become activated
- When T cells are activated, they enlarge and divide into group of cells called clone
- Most of clone become killer, helper or suppressor T cells
- Remaining T cells of clone become memory cells.
what are the three different types of T cells
Killer T cells, Helper t cells and suppressor T cells
What are killer T cells
T lymphocyte able to kill cells that are damaged/infected with viruses/bacteria
what are helper T cells
Role in humoral and cellular immunity. Bind to antigen on antigen presenting cells, stimulating secretion of cytokines that attract lymphocytes (intensifying response), attract macrophages to destroy antigen, intensify phagocytic activity of macrophages, promote action of killer T cells
what are suppressor T cells
After infection is dealt with, release substances that inhibit T and B cell activity, slowing down immune response
what is immunity, natural immunity and artificial immunity
- Immunity is the resistance to infection by invading micro organisms
- Natural immunity occurs without any human intervention
- Artificial immunity is giving a person a antigen, triggering an immune response or giving antibodies to an infecting antigen
what is passive immunity
Immunity produced by the introduction of antibodies from another person. Is short lived
what is active immunity
Immunity produced by the body manufacturing antibodies against a foreign antigen
example of passive natural and artificial immunity
Natural: Antibodies enter bloodstream across placenta or breast milk
Artificial: Antibodies injected into blood stream
example of active natural and artificial immunity
Natural: Ability to manufacture antibodies resulting from attack of disease
Artificial: Ability to manufacture antibodies resulting from being given an antigen from vaccination
Immunisation
Programming the immune system so that the body can respond rapidly to infecting microorganisms
Vaccination
The artificial introduction of antigens to a person so that they acquire immunity without suffering from illness
Vaccine
An antigen preparation used in artificial immunisation
What are the four types of traditional vaccines
- Live attenuated vaccines: living attenuated micro organisms are micro organisms with a decrease virulence (disease producing power) EG, polio vaccine
- Inactivated vaccines: contain dead microorganisms, shorter lasting than live attenuated. EG, whooping cough vaccine
- Toxoid vaccines: a toxin from a pathogenic organism that is altered so that it is no longer toxic. EG, tetanus
- Subunit vaccines: fragments of an organism used to produce an immune response. EG, HPV
Recombinant DNA
Synthetic DNA, made by inserting genes from one source into a DNA molecule from a different source
Herd immunity
Immunity that occurs when such a high number of people in a population are immunised, that those who are not immune are protected
antibiotics
Drugs used to fight infections of micro organisms, particularly bacteria
What are the two types of antibiotics
- Bactericidal: Drug used to treat bacterial infections by killing the bacteria
- Bacteriostatic: Job used to treat bacterial infections. Does not kill the bacteria but stops them reproducing
Broad-spectrum and narrow spectrum antibiotics
- Broad-spectrum: affects many types of bacteria
- narrow spectrum: affects only a particular type of bacteria
Multiple drug resistance
Resistance of some strains of bacteria to most of the available antibiotics. Referred to as super bugs
Total drug resistance
Resistance of some strains of bacteria to all antibiotics
Antiviral
Drug use for treatments of viral infection by Inhibiting the development of the virus
How do antibiotics work
- Preventing the synthesis of the walls of the bacterial cells, inhibiting reproduction (penicillin)
- Interfere with protein synthesis in the cells of target bacteria (steptomycin)
- Interferes with the synthesis of the cell wall, less likely that penicillin to cause an allergic reaction (Cephalosporin)
