Science B1

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  • Created on: 05-02-16 16:26

Blood pressure.

Measurement : millimetres of mercury (mmHg)

Blood pressure has two measurements:

-Systolic pressure is the maximum pressure the heart can produce.

-Diastolic pressure is the blood pressue between beats.

Factors that increase blood pressure: stress, high alcohol intake, smoking, and being over weight.

Which can lead to: blood vessels bursting, damage in the brain (a stroke), and damage to the kidneys.

Factors that decrease blood pressure: regular exercise, and eating a balanced diet.

A low blood pressure can lead to: dizziness, fainting. As the blood supple to the brain is reduced, as wel as circulation. 

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Fitness and health.

Fitness is the ability to do physical activity.

Health is being free from disease.

Measured by: your cardiovascular efficiency, strength, flexibility, stamina, agility, speed.


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Smoking can increase blood pressure in a numebr of ways :

-Carbon monoxide in cigarrete smoke causes the blood to carry less oxygen. Therefore the heart rate increases, so that the tissues receive enough oxygen.

-Nicotine in cigarrette smoke directly increases heart rate. 

Carbon monoxide decreases the oxgyen-carrying capacity of blood. It combines with haemoglobin, preventing it from combinign with oxygen, so less oxgyen is carried.

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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 saturated fat diet. which leads to build up of cholesterol in the arteries.

-high level of salt, which increases blood pressure. 

The narrowing of the arteries reduces blood flow to the heart. The plaques also make blood clots or thrombosis more likely to happen, also blocking the arteries.

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A balanced diet.

The three food groups are:

-Carbohydrates, made up of simple sugars (glucose).

-Proteins, which are made up of amino acids.

-Fats, which are made up of fatty acids and glycerol.

A balanced diet varies according t factors, for example, age, gender, level of activity, religion, vegetarian, vegan, or medical issures, or allergies.

If you eat too much fats or carbohydrates they are stored in the body. 

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

- Fats are stored inder the skin and around organ. 

- although proteins are needed fro growth and repair they cannot be stored in the body.

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Protein intake.

Protein is needed for growth and repair, therefore it i important that you eat the correct amount. 

This is Estimated Avergage Daily Requirement (EAR). And can be calcuated using this formula:

EAR in g = 0.6 x body mass in kg 

Too little protein in the diet can cause Kwashiorkor. (This is more common in developing countries).

The EAR is only an estimate, and can be affected by body mass, age, pregnancy, or breast feeding.

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

First class proteins are meats and fish, they contain all the essential amino acids that connot be made by the human body.

Second class proteins are plants, they do not contain all the essential amino acids.

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Overweight or Underweight, BMI.

Body mass index is calculated using:

BMI= Mass in kg 

         (Height in m)2

A BMI of over 30 means the person is obese. 

25-30 is overweight.

20-25 is normal.

Less than 20 is underweight.

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Maleria is caused by a protozoan called plasmodium, which feed on human red blood cells.

Plasmodium is carried by mosquitoes, which are vectors, and transmitted to humans by mosquito bites.

Plasodium 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 mosquito's life cycle has helped to stop the spread of malaria. As well as develop new treatments fro malaria.

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Changes of lifestyle and diet can reduce the risk of some cancers:

-Not smoking reduces the risk of lung cancer.

-Using suncreen reduces the risk of skin cancer.

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

Cancers are melignant tumours; the cells display uncontolled growth and may spread.

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The fight against illness 1.

-Pathogens (disease-causing organisms) produce the symptoms of an infectious disease by damaging the bodys cells or producing poisonous waste products called toxins.

-The body protects itself by producing antibodies, which lock onto antigens on the surface of the pathogens such as baterium. This kills the pathogen.

-Human white blood cells produce antibodies, resulting in active immunity. This can sow the process, but is a long lasting effect. 

- Vaccinations using antibodies from another human or animal result in passive immunity, which is a quick but short term effect.


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Treatment and trials.

Antibodies (against bacteria and fungi) and antiviral drugs are specific in their action.

An antibiotic destroys a pathogen; an antiviral drug slows down the pathogens development. 

New treatments such as vacciantions, are tested using animals, human tissue and computer models, before human trials. 

A placebo is a harmless pill. placebos are used as a comparison drug testing so the new drug can be assessed.

Blind trial: the patient does not know whether they are receiving a new drug or a placebo. 

Double blind trial: neither the patient or the doctor know which treatment is being used.

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How do eyes work?

-The main parts of the eye have special function.

-Light rays are refracted (bent) 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 image.

- The eye can focus light from distant or near objects by altering the shape of the lens. (accommodation).

- To focus on distant object the ciliary muscles relax, and the suspensory legaments 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 elasticty.

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Faults in vision.

-Red and green 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.

- Long sight: the eyeball it too short or the lens is to thin, so the image is focused behind the retina.

-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 in the front of the retina.

-Corneal surgery or a lens in glasses or contact lenses corrects long and short sight. A convex lens is used to correct long sight, a concave lens is used 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 shown by a reflex arc.

stimulus > receptor > sensory neurone > central nervous stystem > motor neurone > effector > response.

The pathway for a spinal reflex is:

receptor > sensory neurone > relay neurone > motor neurone > effector.

Neurones are adated by being long, having branched endings (dendrites) to pick up impulses and having an insulator sheath.

The gaps between neurones are called synapse. A impulse triggers the release transmitter substance, which then 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.

Types of drugs:

-Depressants (alcohol, solvents, temazepam)

-Painkillers (aspirin, paracetamol)

-Stimulants (nicotine, MDMA, caffeine)

-Performance enhancers (anabolic steroids)

-Hallucigens (LSD)

Depressants block the tansmissions of nerve impulses across synapses by binding with receptor molecules in the membrane of the receiving neurone.

Stimulants cause more neurotransmitter substaces to cross synapses.

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The fight against illness 2.

Each pathogen has its own antigens, so a specific antibody is needed for each pathogen. 

The process of immunisation is also called 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 or T-lymphocyte cell) remain in the body, providing long- lasting immunity to that disease. 

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

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Effects of smoking.

-Cigarette smoke contains many chemicals that stop cilia moving.

-Cilia is found in the epithelial lining of the trachea, bronchi and bronchioles.

- A 'smokers cough' is caused by:

-Dust and particulates in cigarette smoke collecting and irritating the epithelial lining.

-Mucus not being moved by the cilia.

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Effects of alcohol.

Measurement: Units.

Drinking alcohol increases the time taken to react and increses risk of accidents.

The liver is damaged when it breaks down toxic chemicals (alcohol).

This is called cirrhosis.

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Homeostasis: Keeping a constant internal environment.

-Homeostasis involves balancing bodily inputs and outputs.

-Automatic control systems keep the levels of temperature, water and carbon monoxide steady.

Making sure all the cells can work at their optimum level.

Negative feedback controls are used in homeostasis. 

-Negative feedback systems act to cancel out change such as a decreasing temperature level.

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Temperature control 1.

-The body temperature of 37 degrees is linked to the optimum temperature for many enzymes.

A higher temperature can cause:

-Heat stroke (skin becomes cold and clammy and pulse is rapid and weak).

-Dehydration (loss of too much water).

To avoid overheating, sweating increases heat transfer from the body to the environment.

The evaportation of sweat requires body heat to change the liquid sweat into water vapour.

A very low temperature can cause hypothermia (slow pulse rate, violent shivering).

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Temperature control 1.

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Temperature control 2.

-Blood temperature is monitored by the hypothalamus gland in the brain. 

-Reaction to temperature extremes are controlled by the nervous and hormonal systems, which trigger vasoconstruction or vasodilation.

-Vasoconstruction is the constriction (narrowing) of small blood vessels in the skin. This causes less blood flow and less heat transfer.

-Vasodilation is the dilation (widening) of small blood vessels in the skin. This causes more blood flow near the skin surface resulting in more heat transfer.

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Control of blood sugar levels.

-A hormone called insulin controls blood sugar levels.

-Hormone action is slower than nervous reactions as the hormones travel in the blood.

-Type 1 diabetes is caused by the pancreas not producing any insulin, so is treated by doses of insulin.

-Types 2 diabetes is caused by either the body producing too little insulin or the body not reaction to it, therefore can be controlled by diet.

Insulin converts excess glucose in the blood into glycogen, which is stored in the liver. The regulates the blood sugar level.

-The insulin dosage in type 1 diabetes needs to vary according to the persons diet and activity.

-Strenuous exercise needs more glucose to be present in the blood, therefore a lower insulin dosage is required.

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Plant responses.

Phototropism is a plants growth response to light. 

Geotropism is a plants growth response to gravity.

Parts of the plant respond in different ways:

-Shoots are positively phototrophic (they grow towards light) and negatively geotrphic (they grow away from the pull of gravity).

-Roots are negatively phototrophic (they grow away from the light) and positively geotrophic (they grow towards the pull of gravity).

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Plant hormones (auxins).

-Auxins are a group of plant hormones.

-They move through the plant in solution.

-Auxins are involved in geotropism and phototropism.

-Auxins are made in the root and shoot tip.

-Different amounts of auxin is found in different parts of the shoot when the tip is exposed to light.

-More auxin is found in the shaded part of the shoot.

-A higher amount of auxin will increase the length of cells.

-Therefore the increase in the cell length on the shady side of the shoot can cause curvature of the shoot towards light.

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Commercial uses of plant hormones.

Plant hormones have many commercial uses:

-As selective weedkillers, which kill specific weeds and increase crop yield.

-As rooting powder to increase root growth of cuttings.

-To decay or accelerate fruit ripening to meet market demands.

-To control dormancy in seeds.

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Inherited characteristics

Some human characteristics, such as facial features, can be inherited. They can be dominant or recessive.

Alleles are different versions of the same gene.

There is a debate over how much nature (genetic or environmental factors) affect intelligence, sporting ability and health.

Dominant and recessive characteristics depend on dominant and resessive alleles.

Dominant alleles are expressed when present but ressesive alleles are expressed only in the absense of the dominant allele.

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Most body cells have the same number of chromosomes. The number depends on the species of organism.

Human cells have 23 pairs.

-Sex chromosomes determine sex in mammals.

-Females have identical sex chromosomes called **.

-Males have different sex chomosomes called XY.

-A sperm will carry either an X or a Y chromosome.

-All eggs will carry an X.

There is a random chance of which sperm fertilisers an egg. There is therefore an equal chance of the offspring being male or female.

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Genetic variation.

Genetic variation is caused by:

-Mutations, which are random changes in genes or chomosomes.

-Rearrangement of genes during the formation of gametes.

-Fertilisation, which results in a zygote with alleles from the father and mother.

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A monohybrid cross.

-A monohybrid cross involves only one pair of characteristics controlled by a single gene.

-One allele being dominant and one recessive.

-Homozygous means having identical alleles.

-Heterozygous means having different alleles.

-A persons genotype is their gentic make up. 

-Their phenotype is which alleles are expressed.

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Inherited disorders.

Inherited disorders are caused by faulty genes. 

Many personal and ethical issues are raised:

-In deciding to have a gentic test (a positive result could alter lifestyle, career, insurance).

-By knowing the risks of passing on an inherited disorder (whether to marry/have kids).

Inherited disorders are caused by faulty alleles, most of which are recessive.

It is possible to predict the probability of inheriting such disorders by interpreting genetic diagrams.

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