Human defence system

Describe the process on how a white blood cell/ phagocytosis ingests a bacteria

* White blood cell moves towards the bacterium/pathogen
* White blood cell engulfs the pathogen
* white blood cell digests the bacteria/pathogen using enzymes

Non specific defense systems of the human body against pathogens

* Skin
* nose
* trachea and bronchi
* stomach

Responses of a white blood cell to infection caused by pathogens

* White blood cells / **lymphocytes produce (specific) antibodies against a pathogen;**

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* Another type of white blood cell produces antitoxins (against toxins produced by the pathogen);

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* White blood cells / **phagocytes engulf pathogens** / carry out phagocytosis to remove / destroy the pathogen;

Why does the amount of white blood cells reduce but is still slightly higher than pre infection level?

* Memory cells remain in the blood
* produce antibodies upon reinfection with the same pathogen
* helps to prvide long-term immunity

What are communicable disease?

* A disease caused by a **Pathogen**
* That can be spread between organisms/is contagious

Why can viruses not be trated by antibiotics?

Antibiotics only kill bacteria

viruses exist inside host cells

Where is the drug penicillin extracted from?

Pencillium mould

Where does heart drug digitalis originate from?

Foxgloves

Where does aspirin originate from?

willow

What is clinical trial and describe its stages

Very low dosage of the drug are given at the start of the clinical trial

if the drug is found to be safe, furthur clinical trials are carried out to find the optimum dose for the drug.

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What is preclinical trial?

They are testings done on a laboratory using cells, tisussues and live animals. They test for toxicity, dosage and efficacy.

Describe and explain on why double blind trial is useful.

* A placebo is used in a double-blind trial
* It is a treatment made to look like the new drug but does not contain the new drug
* It can be used to test the efficacy of the new drug

How do vaccines work?

Vaccines work by

* Injecting dead/inactive forms of a pathogen/antigen
* white blood cells/ lymphocytes
* produce antibodies
* **in future if reinfected antibody production is faster.**

Explain why drugs must be tested extensively before they can be prescribed routinely to patients

* Drugs must be tested to check efficacy as they may behave differently in the human body
* they need to be checked for toxicity so that they are not harmful or poisonous
* To achieve the correct dosage to achieve the desired effect
* to determine whether they interact with other drugs, positively or negatively

How does antibiotic resistance occur?

* mutation occurs giving resistance to antibiotics
* Non-resistance bacteria are more likely to be killed
* resistant bacteria are not able to be treated
* these bacteria multiply

Describe how the skin acts as a non specific defence against pathogens.

dead outer layer

Skin acts as a barrier

sebum on the surface of the skin which repels pathogens

scabs form over cuts or scbs form a barrier

platelets are involved in forming clots

How does the human body defend iteself against pthogens insdie the body?

• Phagocytes inside the body destroys the pathogen

• White blood cells encounter the pathogen/antigens on the pathogen

• Phagcytes engulf pathogens

• White blood cells produces antitoxins which neutrilises toxins

• White blood cells produces antibodies which help destroy pathoge

• memory cells are formed which gives a rapid response id pathogen reenters.

Why would having differently shaped antigens cause the vaccines to be less effective against the virus?

* Antibodies are specific to a particular antigen
* If the antigen shape changes, antibodies cannot bind to antigens against a virus
* Less antibody binding means less virus killed by white cells

Copare the mechanisms of actions of painkillers and antibiotics

Antibiotics kill bacteria/ treat the cause of the infection

painkillers reduce the symptoms/ the pain of the infection

Describe all the stages of testing a new drug before it can be prescribed to a patient

* The drug enters **pre-clinical trial**s for toxicity, dosage and efficacy on cells / tissues / live animals
* **Low doses of the drug** enter clinical trials, first tested on healthy volunteers (is it safe / are there side effects?) and then on patients at very low doses
* Optimum dosage testing / tests for efficacy trials follow
* **Double-blind trial** - doctors/scientists/patients do not know who receives the drug and who receives a **placebo**
* **Random allocation of patients to a group**
* Data collected is **subject to peer-review** to check validity / that no false claims are made

How are new drugs found?

* Scientists/chemists synthesise new drugs in the lab; 
* Chemicals extracted from plants are used as a starting point;