10. Diseases & Immunity Flashcards
What is a pathogen?
A pathogen is a disease-causing organism
What are diseases caused by pathogens called and why?
Pathogens are passed on from one host to another and therefore the diseases they cause are known as transmissible diseases
In what 2 ways can pathogens be passed from one host to another?
DIRECT or INDIRECT CONTACT
What is an explanation and example of direct contact?
The pathogen is passed directly from one host to another by transfer of body fluids such as blood or semen (eg HIV, gonorrhoea, hepatitis B & C)
What is an explanation of indirect contact?
the pathogen leaves the host and is carried in some way to another, uninfected individual
What 4 methods of transmission are there?
Give an example for a disease that can spread this way
droplets in air (common cold)
food or water (cholera)
touching contaminated surfaces (athlete’s foot)
insect bites (malaria)
In what 3 ways can the body defend itself from disease?
mechanical barriers
chemical barriers
cells
Mechanical barrier definition
structures that make it difficult for pathogens to get past them and into the body
Chemical barrier definition
substances produced by the body cells that trap / kill pathogens before they can get further into the body and cause disease
Cells (as a type of defence against disease) definition
different types of white blood cell work to prevent pathogens reaching areas of the body they can replicate in
What are two examples of mechanical barriers?
skin
- hairs in the nose
How is skin a mechanical barrier?
covers almost all parts of your body to prevent infection from pathogens. If it is cut or grazed, it immediately begins to heal itself, often by forming a scab.
How are hairs in the nose a mechanical barrier?
these make it difficult for pathogens to get past them further up the nose so they are not inhaled into the lungs
What are two examples of chemical barriers?
mucus
- stomach acid
How is mucus a chemical barrier?
made in various places in the body, pathogens get trapped in the mucus and can then be removed from the body (by coughing, blowing the nose, swallowing etc)
How is stomach acid a chemical barrier?
contains hydrochloric acid which is strong enough to kill any pathogens that have been caught in mucus in the airways and then swallowed or have been consumed in food or water
What are two examples of cells as barriers?
by phagocytosis
- by producing antibodies
How is phagocytosis a cell barrier?
engulfing and digesting pathogenic cells
How is the production of antibodies a cell barrier?
which clump pathogenic cells together so they can’t move as easily (known as agglutination) and releasing chemicals that signal to other cells that they must be destroyed
What do all cells have projecting from their cell membrane and what are these called? What is unique about them?
All cells have proteins and other substances projecting from their cell membrane
These are known as antigens and are specific to that type of cell
What ability do lymphocytes have which helps them detect pathogens?
Lymphocytes have the ability to ‘read’ the antigens on the surfaces of cells and recognise any that are foreign
How do lymphocytes respond when they detect foreign cells?
They then make antibodies which are a complementary shape to the antigens on the surface of the pathogenic cell
What do antibodies do?
The antibodies attach to the antigens and cause agglutination (clumping together)
This means the pathogenic cells cannot move very easily
What do antibodies release once they attach to antigens?
At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed
What can cause a person to feel sick?
The initial response of a lymphocyte encountering a pathogen for the first time and making specific antibodies for its antigens can take a few days, during which time an individual may get sick
What will lymphocytes do when they make specific antibodies for a pathogen for the first time?
Lymphocytes that have made antibodies for a specific pathogen for the first time will then make ‘memory cells’ that retain the instructions for making those specific antibodies for that type of pathogen
Why are memory cells made?
This means that, in the case of reinfection by the same type of pathogen, antibodies can very quickly be made in greater quantities and the pathogens destroyed before they are able to multiply and cause illness
What is the overall benefit of memory cells?
people can become immune to certain diseases after only having them once
Why can a person become immune to some diseases but not some others?
It does not work with all disease-causing microorganisms as some of them mutate fairly quickly and change the antigens on their cell surfaces
Therefore, if they invade the body for a second time, the memory cells made in the first infection will not recall them as they now have slightly different antigens on their surfaces (e.g. the cold virus)
What is active immunity?
Making antibodies and developing memory cells for future response to infection is known as active immunity
What are the two ways in which an active immune response happens?
The body has become infected with a pathogen and so the lymphocytes go through the process of making antibodies specific to that pathogen
Vaccination
How fast is active immunity and how long does it last?
Active immunity is slow acting and provides long-lasting immunity
What is passive immunity?
This is when ready-made antibodies, from another source, are introduced to the body
How fast is passive immunity and how long does it last?
Passive immunity is a fast-acting, short-term defence against a pathogen by antibodies acquired from another individual,
What are two examples of passive immunity?
From mother to infant via breast milk – this is important as it helps the very young to fight off infections until they are older and stronger and their immune system is more responsive
Injected antibodies for certain diseases where the individual is already infected and a fast response is required, like rabies or tetanus
Why is passive immunity called that?
The body does not make its own antibodies or memory cells in passive immunity, hence the name
How may a disease caused by the immune system start?
Occasionally, the cells of the immune system start to attack the body’s own cells
Why is a disease caused by the immune system rare?
This is rare as lymphocytes usually recognise their own body cells by the antigens on the cell surfaces and do not respond to them
What happens in a disease caused by the immune system?
In this situation, specific body cells are targeted by lymphocytes and antibodies are made against them, destroying them
What is an example of a disease caused by the immune system
Type 1 diabetes
What happens to people with Type 1 diabetes?
People who suffer from this disease no longer make their own insulin and so are unable to regulate their blood glucose levels
What causes type 1 diabetes?
This is because their immune system is targeting and destroying the pancreatic cells which are responsible for making the insulin, eventually leading to dangerously high glucose levels in the blood
Antibiotic definition
An antibiotic is a drug that slows down or stops the growth of bacteria.
Antibody definition
An antibody is a chemical made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction.
Vaccination definition
Vaccinations give protection against specific diseases and boost the body’s defence against infection from pathogens without the need to be exposed to dangerous diseases that can lead to death
What does the level of protection from a vaccination depend on?
The level of protection in a population depends on the proportion of people vaccinated
- What do vaccinations allow to enter the body?
Vaccines allow a dead or altered form of the disease-causing pathogen, which contains specific antigens, to be introduced into the body
- Why is the pathogen weakened and what does this allow the body to do?
(vaccination)
In this weakened state, the pathogen cannot cause illness but can provoke an immune response
- How does the body respond to the vaccine?
Lymphocytes produce complementary antibodies for the antigens
The antibodies target the antigen and attach themselves to it in order to create memory cells
- What allows the vaccination be effective and helps the body fight an infection?
The memory cells remain in the blood and will quickly respond to the antigen if it is encountered again in an infection by a ‘live’ pathogen
How long is the immunity from the vaccine and why?
As memory cells have been produced, this immunity is long-lasting
What is herd immunity?
If a large enough percentage of the population is vaccinated, it provides protection for the entire population because there are very few places for the pathogen to breed – it can only do so if it enters the body of an unvaccinated person
This is known as herd immunity
What happens if the number of people vaccinated for a specific disease drops?
If the number of people vaccinated against a specific disease drops in a population, it leaves the rest of the population at risk of mass infection, as they are more likely to come across people who are infected and contagious
This increases the number of infections, as well as the number of people who could die from a specific infectious disease
Why is herd immunity important?
Herd immunity prevents epidemics and pandemics from occurring in populations
Why are many vaccinations given to children?
This is the reason that many vaccinations are given to children, as they are regularly seen by medical practitioners and can be vaccinated early to ensure the entire vaccinated population remains at a high level
What is an example of a disease which has been eradicated by vaccination?
An example of a disease which has been eradicated as a result of a successful vaccination programme is smallpox, which was officially eradicated in 1980 after a vaccination programme run by the World Health Organisation since the mid-1950s
What is the simplest way to prevent disease?
The simplest way to prevent disease is to stop pathogens from spreading
What are ways in which can stop pathogens from spreading?
hygienic food preparation
personal hygiene
waste disposal
sanitation
How does hygienic food preparation help prevent the spread of disease?
keep food cold so bacteria and fungi reproduce more slowly
prepare food hygienically to avoid contamination from pathogens by washing hands well with soap and cleaning work surfaces with products such as bleach to kill pathogens
cook food well (long enough at high temperature) to kill bacteria and fungi
cover food to prevent flies landing on it before eating
use separate chopping boards/utensils for cutting uncooked meat
wash hands after using the bathroom before handling food
How does personal hygiene help prevent the spread of disease?
washing with soap removes substances which trap pathogens as well as pathogens themselves from the skin
- use tissues to catch sneezes and coughs dispose of used tissues as soon as possible as pathogens can still be alive wash hands after using the bathroom
How does waste disposal help prevent the spread of disease?
waste food is a food source for flies that can act as vectors for transmissible diseases and so should be disposed of in a sealed container
- rubbish bins should be covered and removed to the landfill for disposal or burning regularly all rubbish should be stored before collection away from human habitation
How does sanitation help prevent the spread of disease?
homes and public places should have plumbing and drains to safely remove faeces and waste which can carry pathogens
raw sewage should be treated to remove solid waste and kill pathogens before being released into the environment
What is a pathogen?
A pathogen is a disease causing organism.
What is a transmissible disease?
A transmissible disease is a disease in which the pathogen can be passed from one host to another.
What are the two ways in which a pathogen is transmitted?
By direct contact, including through blood and other body fluids.
Indirectly, including from contaminated surfaces, animals and air.
What are 5 body defenses?
Skin.
Hairs in the nose.
Mucus.
Stomach acid.
White blood cells.
What are the 5 important factors in controlling the spread of disease?
A clean water supply.
Hygenic food preparation.
Good personal hygiene.
Waste disposal.
Sewage treatment.
What is active immunity?
Active immunity as defence against a pathogen by antibody production in the body.
Fill in the missing spaces:
Each pathogen has its own ______, which have ______ _____.
Each pathogen has its own antigens, which have specific shapes.
What are antibodies?
Antibodies are proteins that bind to antigens leading to the direct destruction of pathogens or marking of pathogens for destruction by phagocytes.
Fill in the missing spaces:
Specific antibodies have ________ ______ which fit specific _______.
Specific antibodies have complementary shapes which fit specific antigens.
How is active immunity gained?
Active immunity is gained after an infection by a pathogen or by vaccination.
What are the three processes of vaccination?
Weaked pathogen or their antigens are put into the body.
The antigens stimulate an immune response by lymphocytes which produce antibodies.
Memory cells are produced that give long-term immunity.
What is passive immunity?
Passive immunity is a short-term defense against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk.
Are memory cells produced in passive immunity?
Memory cells are not produced in passive immunity.
Are memory cells produced in passive immunity?
Memory cells are not produced in passive immunity.
What is cholera?
Cholera is a disease caused by a bacterium which is transmitted in contaminated water.
What does cholera bacterium produces and what is the effect of this?
Cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine causing osmotic movement of water into the gut, causing diarrhoea, dehyradration and loss of ions from the blood.
Explain the role of vaccination in controlling the spread of diseases.
If a large enough percentage of the population is vaccinated, it provides protection for the entire population because there are very few places for the pathogen to breed - this is known as herd immunity.
Explain the importance of breast-feeding for the development of passive immunity in infants.
Antibodies pass from mother to infant via breast milk - this is important as it helps the very young to fight off infections until they are older and stronger and their immune system is more responsive.
Blood
made of cell fragments suspended in a yellow liquid called plasma, which consists of many
nutrients, wastes, blood proteins, and hormones dissolved in water
The red color of the blood is due to the
presence of hemoglobin in RBCs
There are three main types of cells in blood:
1) red blood cells
2) white blood cells
3) platelets
Red blood cells :
have no nucleus and have cytoplasm that is full of hemoglobin - traps oxygen for transport around the body
White blood cells
contain nuclei and responsible for disease prevention
Platelets :
tiny cell fragments that cause blood to clot. Transport ions, nutrients (glucose and
amino acids), CO 2, and hormones
The main function of RBCs is the
transport of oxygen.
Hemoglobin is made
of iron
Hemoglobin combines with oxygen to make
oxyhemoglobin
red blood cells structure and adaptations
contains hemoglobin: hemoglobin transports oxygen from the lungs to all parts of the body.
no nucleus: carry more hemoglobin which leads to increased transport of oxygen
circular biconcave shape: increased surface area to volume ratio of the cell. hence increasing the transport of oxygen
There are two types of
WBCs:
● Phagocytes
● Lymphocytes
Phagocytes
These WBCs ingest
pathogens such as bacteria.
They surround the pathogen
and take them into food
vacuoles. This process is
known as phagocytosis.
Lymphocytes
Each lymphocyte is specifically made for a certain pathogen. Lymphocytes produce antibodies that have
unique cell surface receptors. The receptors only bind to a certain antigen (antigens are small extensions
of the pathogen)
Antibodies have three ways of attacking a pathogen:
● They make them stick together - makes them immobile (agglutinate)
● They dissolve their cell membranes - water enters the cell and they burst
● Antitoxins (a type of antibody) neutralize pathogenic toxins.
Blood clotting
When a blood vessel is damaged, platelets release substances that change the soluble substance in the
blood called fibrinogen into insoluble fibrin. Fibrin is a thread-like substance that forms a mesh over the damaged area. RBCs get trapped in the mesh, forming a clot. The clot hardens forming a scab that falls
off over time. This process prevents excessive blood loss and pathogens entering the body
Pathogen –
a disease-causing organism
Transmissible disease-
disease in which the pathogen can be passed from one host to another
Active immunity-
defense against a pathogen by antibody production in the body
Passive immunity
short term defense against a pathogen by antibodies acquired from another individual (mother to infant)
These diseases may be transmitted directly through
blood or other body fluids , or indirectly through
contaminated food and drink, animals, and the air
mechanical barriers
skin
hair in the nose
chemical barriers
stomach HCL
mucus in the trachea
cell’s defense to disease
Phagocytosis
Antibody production by lymphocytes
The body’s defenses can be enhanced by
vaccinations
immune response
The activation of lymphocytes
Lymphocytes produce antibodies that have
unique cell surface
receptors. The receptors only bind to a certain antigen
antigens
small extensions of the pathogen
Antibodies have three ways of attacking a pathogen:
● They make them stick together (agglutinate) - makes
them immobile
● Prevent flagella from moving - also makes them
immobile
● They dissolve their cell membranes - water enters the
cell and they burst
● Antitoxins (a type of antibody) neutralize pathogenic
toxins.
● Marking their positions for phagocytes to destroy
how does one possess active immunity
gained after an infection from a
pathogen or after a vaccination.
phagocytosis
phagocytes ingest pathogens such as bacteria.They surround the pathogen and take them into food vacuoles
Vaccination
● The patient is given a dose of dead or inactive pathogen , which contain antigens
● Antigens trigger an immune response , causing lymphocytes to produce antibodies
● Weak pathogen is easily defeated
● Memory cells remain in the body, so the next time a pathogen attacks, the body is prepared
● The vaccinated individual now has active immunity
● Vaccination reduces the number of people that can catch a disease and spread it to others.
If protection is required in a hurry,
antibodies can be given through an
injection.
In passive immunity, memory cells are not
created as lymphocytes are not triggered
When an infant is growing in a mother’s womb, antibodies pass
through the placenta into the baby’s
body. The immunity is only short term though as the baby’s body soon treats the antibodies as foreign
and kills them
Malfunction of the immune system
Sometimes, the immune system treats our antigens as foreign and prompts an immune response. As a
result, healthy tissues are destroyed. This can cause a variety of diseases known as autoimmune
diseases. Eg: rheumatoid arthritis, multiple sclerosis, and Type 1 diabetes.
Type 1 Diabetes
This occurs when the immune system attacks and destroys pancreatic cells that make insulin. Insulin is
responsible for controlling the glucose concentration in the blood. When food is consumed, insulin
stimulates the absorption of food and instructs the liver to store glucose as glycogen.
The symptoms of Type 1 Diabetes are:
● Weight loss - cells use protein and fat instead of glucose as sources of energy
● Thirst - due to increased concentration of glucose in the blood (decreased water potential)
● Tiredness - due to lack of glycogen that can be converted to glucose
Disease prevention
● Personal hygiene
● Hygienic food preparation
● Proper waste disposal
● Sewage treatment
Pathogen
disease-causing organism
Transmissible disease
a disease in which the pathogen can be passed from one
host to another.
A pathogen is transmitted
by direct contact, through blood and other body fluids.
by indirectly contact, from contaminated surfaces, food, animals and air.
Body’s defense system includes
skin, hairs in the nose, mucus, stomach acid and
white blood cells.
To prevent spreading of diseases use
a clean water supply - water from dirty rivers or lakes can contain many different
pathogens.
hygienic food preparation - bacteria can grow on the food too, houseflies have
harmful bacteria on their feet and they can land on the food to contaminate it.
good personal hygiene - we should clean our body regularly because oil, dirt and
sweat can build up on the skin and this will provide breeding ground for harmful
bacteria.
waste disposal - harmful bacteria can grow on organic waste so it must be
disposed as soon as possible.
sewage treatment - treating the water before drinking removes dirt and
microorganisms from it
Active immunity
defence against a pathogen by antibody production in the body.
Antibodies
are proteins that bind to antigens leading to direct destruction of
pathogens or marking of pathogens for destruction by phagocytes.
Specific antibodies have
complementary shapes which fit specific antigens
Active immunity is gained after
an infection by a pathogen or by vaccination
Process of vaccination
weakened pathogens or their antigens are injected into the body
the antigens stimulate an immune response by lymphocytes which produce
antibodies
memory cells are produced that give long-term immunity.
Vaccination provide active immunity to
individuals and prevents pathogens from
breeding in them. If 90% of the people are vaccinated to a disease, the pathogen will
have very few places to live and grow therefore the spread of disease will decrease.
Non-vaccinated individuals will also get protection as a result of herd immunity
Passive immunity
short-term defence against a pathogen by antibodies acquired
from another individual, e.g. across the placenta and in breast milk.
A young baby’s immune system is not well developed, and so the mother’s
antibodies can protect it against any diseases to which she is immune, for the first
few months of its life.
Memory cells are not produced in
passive immunity.
Cholera
disease caused by a bacterium which is transmitted in contaminated
water.
The cholera bacterium produces a toxin that causes secretion of chloride ions into
the small intestine, causing osmotic movement of water into the gut, causing
diarrhoea, dehydration and loss of ions from the blood.
