Chapter 6- Defence Against Infectious Diseases Flashcards
What are microbes that cause disease called?
Pathogens
How does skin act as a primary defence against pathogens?
- 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
How does much mucous membranes act as a barrier
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
How are cuts in skin sealed?
By blood clotting- blood emerging from a cut changes from being a liquid to a semi-solid gel- clots also prevent entry of pathogens
Where are clotting factors released from?
Platelets
The cascade results that occur after the clotting factor quickly results in the production of what?
An enzyme called thrombin- conveys fibrinogen to fibrin - this forms a mesh in cuts that traps more platelets
What is the cause of blood clot formation in coronary arteries?
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
what is the consequences of blot clot in the coronary arteries?
Heart becomes deprived of oxygen and nutrients- then unable to provide sufficient amounts of ATP- contractions become irregular and uncoordinated - proves to be fatal
What is the 2nd line of defence against the disease?
White blood cells
What do white blood cells do?
Engulf pathogens by endocytosis and digest them
What does production of antibodies by lymphocytes in response to particular pathogens result in?
Specific immunity
What is the specific immune response?
Is the production of antibodies in response to a particular pathogen- antibodies bond to an antigen on that pathogen
Why do infections occur in a sense?
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
Why do some lymphocytes produced during an infection become memory cells?
These cels remain inactive unless the same pathogen infects the body again - immunity 💃🏻
Explain the effects of HIV on the immune system
- 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
How is HIV spread?
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)
what do antibiotics do?
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
What processes are targeted by antibiotics?
DNA replication, transcription, translation, ribosome function and cell wall formation
How did Florey and chain experiment to test penicillin?
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
Why cants viral diseases be treated using antibiotics?
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
Some strains of bacteria have evolved with genes to what?
Resistance to antibiotics and some strains have multiple resistance
Example of a bacteria that has become antibiotic resistant?
MRSA- infects blood or surgical wounds
5 ways of preventing antibiotic resistance?
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
What do the skin and the mucous membrane form?
A primary defence against pathogens that cause infectious disease
