B6 - Diseases

Question 1

What are the ways in which the body stops microbes getting in?

Answer 1

Skin
Digestive system
Respiratory system
Reproductive system

Question 2

How does skin prevent entry of microbes and how may they overcome this?

Answer 2

Acts as a physical barrier to prevent microbes entering BUT cuts in the skin allow microbes in.

Washing reduces numbers of microbes on skin BUT insect bites penetrate the skin.

Blood clots at a cut to form a scab and seal the skin BUT infected needles carry microbes through the skin.

Question 3

How does the digestive system prevent entry of microbes and how may they overcome this?

Answer 3

Acid in the stomach kills bacteria BUT eating undercooked food or drinking infected water containing large numbers of microbes.

Question 4

How does the respiratory system prevent entry of microbes and how may they overcome this?

Answer 4

Cells lining the airways produce a sticky mucus which traps microorganisms.
Fine hair-like cilia move the mucus with trapped microbes
up to the throat for swallowing.

BUT

Some airborne microbes such as cold viruses can get past the cilia.
Smoking stops the cilia working.

Question 5

How does the reproductive system prevent entry of microbes and how may they overcome this?

Answer 5

Acidic urine kills many microbes BUT Some microbes are resistant to acid.
Microbes are passed from one person to another by sexual contact.

Question 6

How can microbes get past a hosts defences?

Answer 6

Contaminated food
Contaminated water
Airborne transmission
Contact

Question 7

How can microbes get to a host through contaminated food?

Answer 7

Many bacteria such as Salmonella and E. coli are common on unwashed vegetables and meat. If the food is not washed or cooked correctly, the bacteria will grow and reproduce. They will then be ingested along with the food. High levels of the bacteria will lead to food poisoning.

Question 8

How can microbes get to a host through contaminated water?

Answer 8

Cholera is a disease caused by drinking water contaminated with sewage. This water contains the bacterium Vibrio cholerae, which causes the disease.

Question 9

How can microbes get to a host through contact?

Answer 9

Many microbes are spread or transmitted by direct contact with an infected person. The microbe can also be transferred by touching a surface that an infected person has touched. One common example of this is athlete’s foot, which is caused by a fungus called Trichophyton.

Question 10

How can microbes get to a host through airborne transmission?

Answer 10

Viruses like the influenza virus are spread in small water droplets in the air. When someone sneezes, the droplets are red out into the air for someone else to breathe in.

Question 11

How can natural disasters spread disease?

Answer 11

Cholera and food poisoning may spread easily because:
• sewage pipes may be broken, causing sewage to leak out
• water supply systems may be damaged, cutting off the supply of clean fresh water
• electricity may be cut off, so food cannot be refrigerated
• many people may lose their homes and live crowded together in camps, where disease can spread
• the health service may become over-stretched, and lacking in supplies

Question 12

What pathogen causes cholera and how is it transmitted? Symptoms?

Answer 12

Caused by a Vibrio bacterium transmitted in contaminated drinking water.
The symptoms of the disease are severe diarrhoea and vomiting which lead to dehydration.
Cholera is often fatal and develops particularly quickly in children.

Question 13

What pathogen causes food poisoning and how is it transmitted? Symptoms?

Answer 13

Bacteria are ingested in contaminated food. The symptoms include stomach pains, diarrhoea, and vomiting. It can be so severe that it can be fatal in children and elderly people.

Question 14

What pathogen causes influenza and how is it transmitted? Symptoms?

Answer 14

Virus. The in uenza virus is usually breathed in. Flu is one of the most common diseases.
The symptoms include headaches, a running nose, coughs, and sneezes. The disease can occasionally be fatal in weak and elderly people.

Question 15

What pathogen causes chickenpox and how is it transmitted? Symptoms?

Answer 15

Virus. This disease spreads by direct contact, or by breathing in viruses transmitted by an infected person coughing.
Symptoms include a rash on the skin that becomes very itchy. Headaches and fevers are also common. Chickenpox is not usually fatal.

Question 16

What pathogen causes athletes foot and how is it transmitted? Symptoms?

Answer 16

The fungus infects the skin between the toes because it is often moist here. The symptoms include cracked aking skin. It can be painful and in severe cases may bleed.

Question 17

How do infectious diseases develop?

Answer 17

• a microbe enters the body , usually through the mouth, nose or breaks in the skin
• once inside, it begins to use the body to supply all the conditions it needs for growth such as food, warmth and moisture. The pathogen now begins to reproduce rapidly, producing large numbers. This is the incubation period.
• as they grow and reproduce the pathogens produce many waste products which are often toxic
• high levels of toxin make the body begin to feel unwell. Doctors can use the symptoms to diagnose the disease. Symptoms can include fevers, rashes, sores, headaches and diarrhoea