Diseases and immunity (chapter 10)

What is a pathogen

Organism that causes diseases (includes bacteria and viruses)

What is the term given to organisms that harbour pathogens

Hosts

What are transmissible diseases

Pathogens that can be passed from host to host

What are the two ways pathogens can be transmitted

1. Direct contact: transfer of blood and other bodily fluids

2. Indirectly: from contaminated surfaces, foods, animals, air

Ways to prevent the spread of diseases

• Clean water supply

• Hygienic food preparation

• Good personal hygience

• Waste disposal

• Sewage treatment

How does a clean water supply control the spread of disease

contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery, and typhoid

How does a hygienic food preparation control the spread of disease

Washing hands before handling food and making sure the surfaces and utensils are clean before cooking food thoroughly at high temperatures help kill pathogens.

Covering food ensures that flies cant land on it

How does a good personal hygiene control the spread of disease

Washing hands with soap

Covering the mouth when sneezing or coughing

Washing hands after going to the toilet

How does waste disposal control the spread of disease

When rubbish is exposed, it attracts flies which may carry diseases so rubbish must be covered and disposed of in a proper manner

How does a sewage treatment control the spread of disease

To remove faeces from toilets safely.

Sewage should be treated to kill pathogens before being disposed of in the environment

What is active immunity

A defence against a pathogen by antibody production in the body

How is active immunity gained?

• After an infection by a pathogen

• By vaccination

What are antigens?

A molecule found on the surface of a cell or a pathogen that triggers an immune response

Describe an antigen

They are specific in shape.

Each pathogen have differently shaped antigens on their cell surfaces

What do lymphocytes produce

Proteins called antibodies (complimentary shape to the antigens on surface of pathogens)

What are antibodies

proteins that specifically bind to foreign antigens on pathogens

What does the binding of antibodies with antigens lead to

• Direct destruction

• Marking of pathogens for destruction by phagocytes

Explain the structure linkage between an antibody and antigen

Specific antibodies have complementary shaped which fit specific antigens

How does an antibody destroy the pathogen

They attach themselves to the antigens, causing them to clump up together, making it difficult for the pathogen to move.

Then, from that, they can either directly kill them or mark them for destruction by phagocytes

How does an antigen die from the marked destruction by phagocytes

Antibody sends a chemical signal for phagocytes to come and engulf the pathogen

How people become immune to certain diseases after only having them once?

They get long-term immunity from memory cells that were produced by lymphocytes.

The memory cells can quickly produce the original antibodies if they were to come across the same pathogen again

Process of vaccination

1. Weakened pathogens or their antigens are put into the body

2. The antigens stimulate an immune response by lymphocytes which produces antibodies

3. Memory cells are produced that give long-term immunity

Purpose of vaccination

(2 pts)

To stimulate the body’s immune response against diseases

To prevent the spread of diseases

What is Passive immunity

A short-term defence against a pathogen by antibodies acquired from another individual

Where can antibodies (acquired from another individual) be obtained

• across the placenta

• in breast milk

Effectiveness of vaccination

The effectiveness of vaccination depends on the proportionality of people vaccinated

What is herd immunity?

How does a pathogens chain of infection get broken down?

When the majority of a population is vaccinated against a pathogen.

This means that the pathogen will have fewer places to breed and therefore it is unable to pass from person to person

Why is breast feeding important for the development of passive immunity in infants

• antibodies are passed from mother to infant through breast milk

• baby's immune system is not well developed, therefore mothers antibodies can protect it against any diseases which the mom is immune to (for the first few months) until its immune system gets stronger

In which options is memory cells produced in?

Active immunity

What is cholera?

A disease caused by a bacterium which is transmitted in contaminated water.

What does cholera cause?

Diarrhoea, the loss of watery faeces from the anus.

• How does diarrhoea get triggered from cholera

• cholera bacteria attach to the wall of the small intestine

• the bacteria produces a toxin

• the toxin causes the cells lining the intestine to secrete chloride ions into the small intestine

• this causes water potential in intestine to reduce

• water potential in the cells lining the intestine is higher, therefore water moves from the cells to inside the small intestine via osmosis

• large quantities of water are lost from the body in watery faeces or diarrhoea

What does diarrhoea from cholera lead to

Dehydration and loss of ions from blood

How can diarrhoea be treated

Oral rehydration therapy