Pathogens and fighting infections

Pathogens are microorganisms that cause infectious diseases.

There are two main types of pathogens: bacteria and viruses. Bacteria are very small living cells which reproduce very quickly. They make you feel bad because they damage your body cells and they produce toxins.

Viruses are a bit different. They are not living cells because they do not carry out any living processes. That's one reason why antibiotics can't kill viruses but I will talk about it some other time.

How do viruses attack body cells?
When a virus enters the cell, it releases the nuclei acid which gets to the nucleus of your cell. It uses it to replicate itself by changing the way the cell used to work. So now, the cell is ignoring its own needs and responsibilities and is focused only on producing new viruses. Eventually, the cell will burst releasing all new viruses, so they can invade other cells.

Fighting infections

 Your body helps you to fight with pathogens. It does it by:

• acid in your stomach kills some microorganisms
• tears protect eyes from microorganisms
• skin is a natural body cover
• mucus stops pathogens entering.

If you cut yourself, platelets (fragments of cells) will help to seal the wound stopping pathogens entering the body.

 White blood cells produce antibodies and pathogens have antigens. When pathogen enters the body, the white blood cell start producing specific antibodies to kill that particular pathogen. They attach to antigens.

White blood cells can also consume the pathogen and digest it or it can produce antitoxins.

Nervous System and Reflex Arc

The nervous system helps us to respond to changes in the environment.

nerve cell

central nervous system = brain + spinal cord

stimuli = changes in the environment

receptors = cells that detect stimuli

nerve impulse = electrical message that passes along a neurone

neurone = nerve cells

Five senses:

1. taste
2. smell
3. sight
4. sound
5. touch

 Reflex arc
 Reflex actions are automatic and rapid. We need them to avoid danger.

Drugs

A drug is a chemical that changes the way your body works.

Types of drugs:

• painkillers
• stimulants 
• halucinogens
• antibiotics

Medical drugs make people feel better when they are ill.
Painkillers block nerve impulses.

What is a difference between medical drugs and recreational drugs?
The difference is that medical drugs are used when a person is ill and needs his/her body to function normally and recreational drugs are drugs that are taken by people when they don't need them.

People can become addicted to a drug, which means that it is hard for them to give it up. It can damage the lungs, brain and a liver.

Sometimes drugs are not effective because the body got used to it when taking regularly.

Antibiotics
Antibiotics can't be used to kill viruses because they live in body's cells, so it would have to damage the cell to kill viral pathogens.

Penicilin
Penicilin is an antibiotic discovered by Sir Alexander Fleming in 1928. He left petri dishes with bacteria on in a sink whilst he went on a holiday. After he returned he found some mould and bacteria developing on the petri dish.

This discovery was so important because it saved many soldiers' lives during WW2. The first people who received penicillin were Ernst Chain and Howard Florey.

Drug trials
Drugs must be tested before they can be sold to see if they are safe and effective. This is checked in a series of stages:

1. in the laboratory using cells and tissues
2. in clinical trials - this involves usually three phases with healthy volunteers and patients.

Double blind trials are when one patient is given a placebo and the other one a drug. Neither the patients nor the doctors know who received placebo and who received a drug.

Problems with drugs
Some people use drugs recreationally and they can become addicted which can cause a big harm to the body. Some drugs are legal (eg. nicotine), others aren't (eg. heroine). Some people don't take drugs sensibly, they overuse them, eg. sleeping tablets.

Thalidomide
It was developed as a sleeping tablet in first place, but women found it to be effective to make them feel better during morning sickness when pregnant. Although, the drug was not tested for this use, more and more women started taking it. Many babies of those women were born with severe limb abnormalities. It was then banned.
 

  

MRSA and Semmelweis' Policy

MRSA (methicillin-resistant Staphylococcus aureus)

• one of the most troublemaking strains of bacteria
• resistant to even very strong antibiotics

To prevent MRSA, we must practicegood hygiene in hospitals and stop prescribing antibiotics for non-serious infections.

Semmelweis and washing hands
Semmelweis stated that all doctors should wash their hands after each contact with patient, so pathogens don't spread out to other patients.  

 

An exam question taken from  http://www.aqa.org.uk/subjects/science/gcse/science-a-4405/past-papers-and-mark-schemes

 

Vaccinations

How vaccines work?

1. A vaccination is a dead or inactive pathogen.
2. Vaccination is injected.
3. The pathogen is detected and white blood cells start producing specific antibodies to kill that particular pathogen.
4. White blood cells remember the pathogen.
5. When live pathogen enters the body, white blood cells recognise the pathogen and produce antibodies.
6. The pathogen is removed before it can develop any symptoms.

MMR vaccine
MMR vaccine is injected to children to protect them against measles,mumps and rubella.

Advantages

• Epidemics can be prevented as there are fewer number of people who can pass the disease on.
• By having vaccinations, we can control diseases.

Disadvantages

• Some people can react badly to the vaccination.
• Vaccines don't always work.

 

Balanced diet

Your diet must provide you with sufficient energy for good health.

To be healthy you need a right balance of different foods as they have got a different effect on your body.

You need:

• carbohydrates to release energy
• fat to release energy and keep warm
• protein for cell replacement, cell repair and growth
• vitamins and minerals so your body is functioning well and is healthy (e.g. keeps your skin look healthy)
• fibre to make sure everything is going alright in your digestive system.

Your metabolism is the energy needed for chemical reactions in your body to take place. The speed at which they happen is your metabolic rate.

Different people have different metabolic rates but there are ways to boost your metabolic rate. For example, exercising.

When you exercise you need more energy so all reactions must happen faster so your metabolic rate goes up. Exercise also builds muscle and muscle need more energy so therefore metabolic rate must be higher.

If your diet is out of balanced (like... really badly), you are MALNOURISHED. But there is a significant difference between MALNOURISHMENT and STARVATION. When you starve it means you don't get enough food of any sort.

As you all probably know, eating too much can lead to obesity. But there are even more health problems when eating too much:

• type 2 diabetes
• high blood pressure
• arthritis
• heart disease
• and sometimes you risk some types of cancer.

So... what causes obesity?
The first would be unbalanced diet (common sense really because this post is about diet), lack of exercise and sometimes inherited factors.
If you're eating too much carbohydrates and fat it is likely for you to become obese.

But don't put your forks and knives down yet. Eating too little can cause some problems as well. Probably most known is anorexia but it's not all about diet; it's in your mind.

Eating too little can cause:

• poor resistance (having a cold all year round... brrr...)
• small growth in children
• irregular periods in women

If you inherit an underactive thyroid gland it can lower your metabolic rate.
Other inherited factors can affect your cholesterol.

What is actually cholesterol? It is a fatty substance and it is essential for your good health.
BUT... if your cholesterol level is too high it can increase the chance of developing a heart disease. How? The cholesterol can block the arteries, so blood with oxygen can't reach the heart and if the muscle can't work, you get the heart attack because your heart can't beat properly.

Saturated fats = raised cholesterol level
Unsaturated fats = lower cholesterol level
HDL (high density lipoprotein) is a good cholesterol.

LDL (low density lipoprotein) is a bad cholesterol.

Generating Electricity

The way electricity is generated is by burning fuels to heat water. This creates the steam which spins the turbine (1). The turbine is connected to the generator, so when it spins, it turns the generator (2). The generator produces electricity which goes to the transformer where its voltage is increased before it travels down the power lines (3).

I know this diagram isn't the best in the world, but if you make something by yourself, you learn more.

Energy Transfers
Furnace: chemical energy into heat energy
Turbine: heat energy into kinetic energy
Generator: kinetic energy into electrical energy

Transformers
The step up transformers are used because they increase the voltage (not the current) before it travels down the line, so they reduce the heat loss and increase the efficiency. Then, it gets stepped down on the other end of the line.
If the current was increased even more heat energy would be lost.