Biology

Biolgy revision for ocr gateway GCSE

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Blood pressure

Is measured in millimetres of mercury (mmHg) in either; systolic pressure - maximum pressure the heart produces or diastolic pressure- blood pressure between heart beats.

Increase in blood pressure;

is caused by; high alcohol intake, stress, smoking or being overweight

Can cause damaged kidneys and blood vessels to burst causing brain damage which is a stroke

Decrease in blood pressure;

Is caused by; regular exercise and eating a balanced diet

Can cause dizziness and fainting as the blood supply is reduced and poor circulation to areas such as fingers and toes.

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Fitness and Health

Fitnness is the ability to do physical activity 

 Health is being free from diseases such as those caused by bacteria and viruses

General fitness level can be measured by your cardiovascular efficiency

Fitness can be measured for different activities;

-strength-by the amount of weights lifted, Flexibility-by the amount of joint movement, Stamina-by the time of sustained excersie, Agility-by changing direction many times, Speed-by a sprint race.

You could be fit for a sprint race but not perform well in a marathon.

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Smoking

Smoking can increase blood pressure by;

-Carbon monoxide in cigerette smoke, it decreases the oxygen-carrying capacity of blood, it combines with haemoglobin preventing it from combining with oxygen. The heart rate increases so that the tissues recieve enough oxygen.

Nicotine in cigarette smoke directly increases heart rate.

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Diet and heart disease

Heart disease is caused by a restricted blood flow to the heart muscle, the risk of getting heart disease is increased by;

- a high level of saturated fat in the diet, which leads to a build up of cholestorol (a plaque) in arteries.

The narrowing of the arteries caused by the plaques in the coronary arteries can reduce blood flow to heart muscle, they can also make blood clots or thrombosis more likely to happen which will also block the artery.

- a high level of salt intake, which can increase blood pressure.

The blood vessel into the heart muscle is blocked NOT the blood flowing into the heart.

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A balanced diet

for good health you need to eat a balanced diet containing the correct amounts of the chemical found in food. Three of these are;

Carbohydrate-which are made up of simple sugars such as glucose,Proteins-which are made up of amino acids,Fats-which are made up of fatty acids and glycercol

A balanced diet varies according to factors such as age,gender,level activity, religion, being vegetarian or vegan, or because of medical issues such as food allergies.

If you eat too much fat and carbohydrate they are stored in the body.

- carbohydrates are stored in the liver as glycogen or converted into fats

- fats are stored under the skin and around organs as adipose tissue, although proteins are essential for growth and repair they can not be stored in the body

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Protein intake

Proteins are needed for growth and so it is important to eat the correct amount. This is called the estimated average daily requirement (EAR) the formula is;

EAR in g = 0.6 x body mass in kg   -this could be effected by factors such as body mass, age, pregnancy or breast feeding.

Too little protein in the diet can cause kwashiorkor, this is more common in developing countries due to overpopulation and lack of money to improve agriculture.

 Although proteins cannot be stored in the body, some amino acids can be converted by the body into other amino acids.

Proteins from meat and fish are called first class proteins, they contain all the essential amino acids which cannot be made by the human body; Plant proteins are called second class proteins as they do not contain all the essential amino acids.

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Overweight or underweight

To work out if a person is overweight or underweight, calculate their body mass index (BMI)

BMI = mass in kg  

       (height in m) 2      

A BMI of more than 30 means the person is obese, 25-30 is overweight, 20-25 is normal, less than 20 is underweight.

Some people may become ill as they choose to eat less than they need. This may be caused by low self-esteem, poor self-image or a desire for what they think is perfection

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Malaria

Malaria is caused by a protozoan called plasmodium, which feeds on human red blood cells.

Plasmodium is carried by mosquitoes, which are vectors (i.e not affected by the diease), and transmitted to humans by mosquito bites.

Plasmodium is a parasite and humans are its host. A parasite is an organism that feeds on another living organism causing it harm.

Knowledge of the mosquitos life cycle has helped to stop the spread of malaria ( by draining stagnant water, putting oil on the water surface and sraying insecticie). This knowledge has helped to develop new treatments for malaria.

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Cancer

Changes in lifestyle and diet can reduce the risk of some cancers;

-not smoking reduces the risk of lung cancer

- using sunscreen reduces the risk of skin cancer

Benign tumour cells, such as in warts, divide slowly and are harmless.

Cancers are maligant tumours; the cells display uncontrolled growth and may spread.

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The fight against illness

Pathogens (disease-causing organisms) produce the symptoms of an infectious disease damaging the body's cells or producing poisonous waste products called toxins. - The body protects itself by using antibodies, which lock onto antigens on the surface of pathogens such as bacterium. This kills the pathogen. Each pathogen has its own antigens so a specific antibody is needed for each pathogen.

 Human white blood cells produce antibodies,  resulting in active immunity. This can be a slow process but has a long lasting effect where as vaccinations using antibodies from another human or animal result in passive immunity which has a quick but short term effect.

The process of immunisation is also a vaccination; -it starts with injecting a harmless pathogen carrying antigens, the antigens trigger a response by white blood cells, producing the correct antibodies, Memory cells( a type of T-lymphocyte cell) remain in the body, providing long lasting immunity to that disease.

Immunisation carries a small risk to the individual, but it avoids the potentially lethal effect of the pathogen, as well as decreasing the risk of spreading the disease.

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Treatments and Trials

Antibiotics (against bacteria and fungi) and antiviral drugs (against viruses) are specific to their action. - An antibiotic destroys a pathogen; an antiviral drug slows down the pathogens development.

New treatments such as vaccinations, are tested using animals, human tissue and computer models before human trials. Some people object to causing suffering to animals in such tests,

A placebo is a harmless pill. Placebos are used as a comparison in drug testing so the effect of a new drug can be assessed. In a blind trial, the patient does not know whether they are recieving a new drug or a placebo, in a double-blind trial neither the patient nor the doctor know which treatment is being used. These types of trials avoid a 'feel-good factor' and a biased opinion.

Excessive use of antibiotics has resulted in resistant forms of bacteria being more common than non-resistant forms. for example, resistant MRSA has thrived, causing serious illness.

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How do eyes work

The main parts of the eye have special functions,

Light rays are refracted by the cornea and lens

The retina contains light receptors, some are sensitive to different colours

Binocular vision helps to judge distance by comparing the images from each eye, the more different they are, the nearer the object.

The eye can focus light from distant or near objects by altering the shape of the lens. This is called accommodation.

To focus on distant objects, the ciliary muscles relax and the suspensory ligaments tighten, so the lens has a less rounded shape.

To focus on near objects, the ciliary muscles contract and the suspensory ligaments slacken, so the lens regains a more rounded shape due to its elasticity,

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Faults in vision

Red-green colour blindness is caused by a lack of specialised cells in the retina.

Long and short sight are caused by the eyeball or lens being the wrong shape, in long sight, the eyeball is too short or the lens is too thin so the image is focused behind the retina.

 In short sight the eyeball is too long or the lens is too rounded so the lens refracts light too much, so the image would be focused infront of the retina.

Corneal surgery or a lens in glasses or contact lenses corrects long or short sight. A convex lens is used to correct longsight, a concave lens to correct short sight.

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Nerve cells

Nerve cells are called neurones, nerve impulses pass along the axon.

What happens in a reflex action is show by a refelex arc the links in a reflec arc are;

stimulus-receptor-sensory neaurone-central nervous system-motor neurone- response

The pathway for a spinal reflex is;

receptor-sensory neurone-relay neaurone-motor neurone-reflector

Neurones are adapted by being long, having branched endings(dendrites) to pick up impulses and having unsulator sheath. The gap between neurones is called a synapse. The arrival of an impulse triggers the release of a transmitter substance, which diffuses across the synapse. The transmitter substance binds with receptor molecules in the membrane of the next neurone causing the impulse to continue.

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Types of drugs

Drugs have a legal classification. Class A drugs are the most dangerous and have the heaviest penalties. Class C drugs are the least dangerous, with the lightest penalties.

Depressents (alcohol,solvents,temazepam)

Painkillers (aspirin,paracetamol)

Stimulants ( nicotine, ecstasy, caffeine)

Performance enhancers ( anabolic steroids)

Hallucinogens ( LSD)

Depressants block the transmission of nerve impulses across synapses by binding with receptor molecules in the membrane of the recieving neurone. Stimulants cause more neurotransmitter substances to cross synapses.

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Effects of smokingand alcohol

Cigarette smoke contains many chemicals that stop cilia moving.

Cilia(tiny hairs) are found in the epithelial lining of the trachea, bronchi and bronchioles.

A 'smokers cough' is a result of;

dust and particulates in cigarette smoke collecting and irritating the epithelial lining

mucus not being moved by the cilia

The alcohol content of alcoholic drinks is measure in units of alcohol.

Drinking alcohol increases reaction times and increases the risk of accidents.

The liver is damaged when it breaks down toxic chemicals such as alcohol. This is called cirrhosis of the liver.

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