Chapter 6- Defence Against Infectious Diseases

Question 1

What are microbes that cause disease called?

Answer 1

Pathogens

Question 2

How does skin act as a primary defence against pathogens?

Answer 2

• outer layer is tough and provides a physical barrier against entry of pathogens
• sebaceous glands are associated with hair follicles and they secrete a chemical called sebum which maintains skin moisture and slightly lower skin pH- inhibits the growth of bacteria and fungi

Question 3

How does much mucous membranes act as a barrier

Answer 3

Thinner and softer type of skin that is found in areas such as the nasal passage- areas of skin secrete a sticky solution of glycoproteins- mucus acts as a physical barrier - pathogens gets trapped in it

Question 4

How are cuts in skin sealed?

Answer 4

By blood clotting- blood emerging from a cut changes from being a liquid to a semi-solid gel- clots also prevent entry of pathogens

Question 5

Where are clotting factors released from?

Answer 5

Platelets

Question 6

The cascade results that occur after the clotting factor quickly results in the production of what?

Answer 6

An enzyme called thrombin- conveys fibrinogen to fibrin - this forms a mesh in cuts that traps more platelets

Question 7

What is the cause of blood clot formation in coronary arteries?

Answer 7

These are the arteries that branch off from the aorta to the semilunar valve- they carry blood to the wall of the heart - atherosclerosis causes occlusion in these arteries- they tend to become damaged and roughened

1) smoking
2) high blood pressure
3) diabetes
4) obesity

Question 8

what is the consequences of blot clot in the coronary arteries?

Answer 8

Heart becomes deprived of oxygen and nutrients- then unable to provide sufficient amounts of ATP- contractions become irregular and uncoordinated - proves to be fatal

Question 9

What is the 2nd line of defence against the disease?

Answer 9

White blood cells

Question 10

What do white blood cells do?

Answer 10

Engulf pathogens by endocytosis and digest them

Question 11

What does production of antibodies by lymphocytes in response to particular pathogens result in?

Answer 11

Specific immunity

Question 12

What is the specific immune response?

Answer 12

Is the production of antibodies in response to a particular pathogen- antibodies bond to an antigen on that pathogen

Question 13

Why do infections occur in a sense?

Answer 13

There are few lymphocytes initially to produce enough antibodies to control a pathogen that has not previously infected the body- however antigens on the pathogens stimulate cell division so then if that infection comes along again there are already pathogens ready

Question 14

Why do some lymphocytes produced during an infection become memory cells?

Answer 14

These cels remain inactive unless the same pathogen infects the body again - immunity 💃🏻

Question 15

Explain the effects of HIV on the immune system

Answer 15

• production of antibodies is helped by helper T cells
• HIV invades and destroyed these cells- consequences is a loss of antibodies
• in early stages immune system makes antibodies against HIV which makes them HIV positive
• antibodies eventually become so ineffective that an infection that could easily be fought of by a healthy individual would have a drastic effect
• HIV develops into AIDS- a collection of several diseases in the body is called a syndrome- if caused by HIV the person is said to have AIDS

Question 16

How is HIV spread?

Answer 16

1) sexual intercourse, during which abrasions to the mucous membranes of the penis and vagina can cause minor bleeding
2) transfusion of infected blood
3) sharing needles (drug use)

Question 17

what do antibiotics do?

Answer 17

Block processes that occur in prokaryotic cells but not in eukaryotic cells - therefore can be used to kill bacteria inside the body without causing harm to human cells

Question 18

What processes are targeted by antibiotics?

Answer 18

DNA replication, transcription, translation, ribosome function and cell wall formation

Question 19

How did Florey and chain experiment to test penicillin?

Answer 19

1) tested it on bacteria- and it killed it
2) tested it on mice- eight were infected with bacteria that cause death from pneumonia - 4 were given penicillin- 4 that didn’t died within 24 hours- 4 that got injection were healthy
3) made more penicillin for human use- chose a policeman who had a life threatening bacterial infection caused by a scratch- given it for 4 days- worked, but supplies ran out and he suffered relapse and died
4) more penicillin was created 5 patients tested - 1 died
5) pharmaceutical companies in the USA began to produce it in much larger quantities allowing more testing- confirmed it was highly effective

Question 20

Why cants viral diseases be treated using antibiotics?

Answer 20

Because they lack a metabolism- they are non living organisms and can only reproduce when they are inside living cells - rely on host cell so if antiobiltics were used the host cel would be damaged too

Question 21

Some strains of bacteria have evolved with genes to what?

Answer 21

Resistance to antibiotics and some strains have multiple resistance

Question 22

Example of a bacteria that has become antibiotic resistant?

Answer 22

MRSA- infects blood or surgical wounds

Question 23

5 ways of preventing antibiotic resistance?

Answer 23

1) doctors prescribing antibiotics only for serious bacterial infections
2) patients completing courses of antibiotics to eliminate infection is completely
3) hospital staff maintaining high standards of hygiene to prevent cross infection
4) farmers not using antibiotics in animal feeds to stimulate growth
5) pharmaceutical companies developing new types of antibiotics… No new types have been introduced since 1980s

Question 24

What do the skin and the mucous membrane form?

Answer 24

A primary defence against pathogens that cause infectious disease