B1 Unit 1 ~ Keeping Healthy

A healthy diet contains the right balance of different foods.  A healthy diet contains the right amount of energy.

It will provide carbohydrates for energy.

It will provide fat for energy and insulation.

It will provide protein for growth and repair.

It will provide vitamins and minerals to help our bodies function well.

It will provide fibre to ensure food moves through our digestive systems efficiently.

It will provide water, which is essential for all body processes.

If a diet is unbalanced a person is malnourished.  This can lead to being too thin or fat and to deficiency diseases.

If you use more calories than you eat you will lose weight.

If you use less calories than eat you will gain weight.

Doing exercise uses up lots of calories.

Regular exercise keeps you healthy.

It maintains a good metabolic rate.

It requires energy so uses lots of calories.

If they are not used up they are stored possibly as fat.

Respiration is a chemical reaction that allows cells to release energy from food. The metabolic rate is the speed at which such chemical reactions take place in the body and varies.

Metabolic rate is affected by the ; Proportion of muscle to fat in the body, Amount exercise and other physical activity. Pregnant women need more energy than non-pregnant women because they are building more cells. Genetcis

Other factors affect health too, including inherited factors. For example, the cholesterol level in the blood can affect health. Cholesterol is made in the liver and is needed for healthy cell membranes. However, too much cholesterol in the blood increases the risk of heart disease and diseased arteries.

Obesity is a disease where someone is carries too much body fat. Obese people have increased risk of life-threatening diseases.

In the developed world too much food and too little exercise are leading to high levels of obesity.

Some diseases linked to excess weight:

arthritis (worn joints)

diabetes (high blood sugar)

high blood pressure

heart disease.

A person is malnourished if their diet is not balanced.

This may lead to a person being too fat or too thin.  It may also lead to deficiency diseases.

Some people in the developing world suffer from health problems linked to lack of food.

Health problems connected with malnourishment include:

Reduced resistance to infection – the immune system does not work correctly.

Irregular periods in women.

A substance made by the liver. Found in the blood. The amount produced depends on diet and inherited factors. High levels increase risk of disease in the heart and blood vessels.

Cholesterol is carried around the body by 2 types of lipoprotein. Low density (LDLs) & High density (HDLs).  LDLs are ‘bad’ and can cause heart disease.  HDLs are ‘good’.

Balancing these is important to having a healthy heart. Saturated fats increase blood cholesterol levels.

Monounsaturated and polyunsaturated fats may help both to reduce blood cholesterol levels and to improve the balance between LDLs and HDLs

Pathogens

Microorganisms that cause infectious disease are called pathogens.

Bacteria

Bacteria are very small single-celled organisms.

Not all cause disease.

Pathogenic bacteria reproduce rapidly inside the body and may produce poisons (toxins) which make us feel ill.

Example: E.coli produces toxins that cause fever symptoms when we have food poisoning.

Viruses are much smaller than bacteria.

All viruses are pathogens.

Viruses produce toxins and they damage the cells in which they reproduce, leading to illness.

Viruses replicate by invading cells, reproducing inside them and bursting them.

This causes damage to tissues, leading to illness.

Example: HIV virus damages white blood cells, reducing immunity and leading to AIDS.

There are many routes through which pathogens can enter the body:

Nasal passages ,Insect bites, Mouth , Hair follicles ,Urethra, Contaminated needles ,Anus ,Scratches and cuts

Disease occurs when large numbers of pathogenic micro-organisms enter the body.

Disease Transmission

Diseases are transmitted through: 1) Unhygienic conditions 2) Direct contact with infected people 3) Inhaling droplets from coughs or sneezes.

Preventing transmission

In the 1850s, Ignaz Emmelweiss insisted that medical students washed their hands before delivering babies. This idea was not readily accepted – people were not aware of microorganisms. Nowadays, it is standard practice for people to wash hands after treating patients, to prevent disease being transmitted to other patients.

External protection from infection

• Skin is the first barrier.
•  Trachea and lungs produce mucus that traps microorganisms.
•  Blood clots seal the wound.
• The stomach secretes hydrochloric acid which kills microorganisms.

Other protection:

• Tears
• Nostril Hairs 
• Eyelashes
• Ear wax

The body has different ways of protecting itself against pathogens. White blood cells defend our internal environment from pathogens.These form part of our immune system.

There are 2 types of white blood cells:

1) Phagocytes  ~ Ingest and destroy microorganisms

2) Lymphocytes ~ Produce antibodies that destroy specific pathogens Produce antitoxins that destroy toxins released by pathogens

Some medicines, including painkillers, help to relieve the symptoms of infectious disease, but do not kill the pathogens.

Eg painkillers, hayfever drugs, asthma inhalers.

Antibiotics are substances that are used to cure bacterial infections by killing pathogenic bacteria inside the body.

 Antibiotics cannot be used to kill viral pathogens

This is because viruses live and reproduce inside cells.

It is difficult to develop drugs which kill viruses without also damaging the body’s tissues.

Penicillin is one example of an antibiotic. Other antibiotics include tetracycline and ampicillin.

Antibiotics are only useful if they attack the bacteria and not the human body.

Antibiotics have been overused. Resistant bacteria have now evolved. – how?

• Bacteria reproduce rapidly.
• In a large bacterial population, one bacterium may have a mutation that gives it resistance to antibiotics.
• This survives and reproduces.
• Soon all of the bacteria are resistant.

Some bacteria are resistant to many different types of antibiotic eg Methicillin Resistant Staphylococcus Aureus (MRSA). These bacteria can enter the body through wounds and cuts. Healthy people’s white blood cells would quickly destroy these bacteria. People who are ill in hospital are likely to have reduced immunity to bacterial disease, and become infected more easily.

Doctor’s should only prescribe antibiotics when necessary – and not for viruses. It is important that if you are prescribed antibiotics you take the whole course. A lot of people will stop taking the antibiotic when they feel better. This is wrong!

If you do this, you leave a few bacteria inside your body. These will reproduce, increasing the chance of some developing resistance.

Farmers should use less antibiotics.

They use antibiotics to prevent illness in their animals. This means that bacteria are exposed to antibiotics more often. This gives the bacteria more opportunity to become resistant to the antibiotic.

Doctor’s should only prescribe antibiotics when necessary – and not for viruses. It is important that if you are prescribed antibiotics you take the whole course. A lot of people will stop taking the antibiotic when they feel better. This is wrong!

If you do this, you leave a few bacteria inside your body. These will reproduce, increasing the chance of some developing resistance.

Farmers should use less antibiotics.

They use antibiotics to prevent illness in their animals. This means that bacteria are exposed to antibiotics more often. This gives the bacteria more opportunity to become resistant to the antibiotic.

When new medical drugs are devised, they have to be extensively tested and trialed before being used.

Drugs are tested in the laboratory to find if they are toxic.

They are then trialed on human volunteers to discover any side effects.

It can take many years before a newly discovered drug is available to be used,

People can be immunised against a disease by introducing small quantities of dead or inactive forms of the pathogen into the body (vaccination).

Vaccines stimulate the white blood cells to produce antibodies that destroy the pathogens.

This makes the person immune to future infections by the microorganism.

The body can respond by rapidly making the correct antibody, in the same way as if the person had previously had the disease.