Biology

Unit One

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  • Created by: lizzie
  • Created on: 10-05-10 17:59

IVF

A woman is injected with a fertility drug (FSH). This causes eggs to mature in her ovaries. The eggs are then removed using a syringe and placed in a petri dish where they are mixed with sperm cells. A microscope is used to see which ones have fertilised. the fertilised eggs are then placed into a woman's uterus. the final stage is to inject the woman with drugs to make her realise she is pregnant.

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Normal Nervous Pathway

stimulus --> receptor --> sensory neurone --> CNS --> motor neurone --> effector

Normal reflex actions such as seeing a football and choosing to run towards it take a lot of time. this is because messages travel up to the brain and back. it is useful if we want to chose whether to do something or not.

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Reflex actions

stimulus --> receptor --> sensory neurone --> relay neurone --> effector

In dangerous situations, reflex actions are used because they don't pass through the brain, so are quicker and can protect us from danger.

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Controlling temperature

Enzymes work best at 37 degrees, the temperature around us is rarely at 37 degrees so, we sweat when we are too hot and shiver when we are too cold.

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Controlling blood sugar levels

Cells need a constant supply of energy, we can't eat 24 hours a day so, when we eat out blood sugar level rises, the pancreas releases insulin which is used to channel excess glucose into body cells where it is stored until needed.

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Controlling salt(ion) levels

Ions such as sodium and potassium are very important in making nerves work properly. Ions are lost via the skin when we sweat and via the kidneys in urine. our kindeys can increase or decrease the ions escaping via urine when levels are too high/low/

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Controlling water levels

our cells need water inside them so that they can perform chemical reactions, water is lost when we breathe, sweat and in out urine. our kidneys can increase/decrease the amount released via urine.

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3 hormones in menstruation

FSH is made in the pituitary glands, causes eggs to produce in the ovaries and stimulates the production of Oestrogen.

Oestrogen is made in the ovaries, cause the production of LH and inhibits further production of FSH.

LH is made in the pituitary gland, cause the mature egg to be released via the fallopian tube.

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Matabolism

The rate that chemical reactions in the cells of our bodies are carried out. it varies with the amount of exercise you do and the proportion of muscle to fat in your body. it may be affected by inherited factors.

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Developed world

Too much food and too little exercise, leading to high levels of obestiry and diseases linking to weight:

arthritis - ends of bones become rough and rub against eachother painfully

diabetes - body loses the ability to control blood sugar levels

High blood pressure - blood is pumped through arteries at high pressures damaging them

heart disease - when arteries leading to the heart become blocked with fatty plaques.

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Cholesterol

  1. Low-density lipoproteins - LDLs - carry cholesterol from the liver to the cells
  2. High-density lipoproteins - HDLs - carry excess cholesterol back to the liver.

LDLs are often called 'bad' cholesterol because they lead to fat building up on artery walls, which causes heart disease. HDLs are often called ‘good’ cholesterol because they help to stop fat building up in the arteries.

saturated fats raise cholesterol levels

mono and poly unsaturated fats help lower cholesterol levels and improve the levels between HDLs and LDLs

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Drugs/addiction

Alters the chemical processes happening inside our body. some are very addicted which means people get hooked on them and want more and more to satisfy their desire (caffeine, nicotine)

once a person is addicted to a drug it becomes very difficult for them to stop taking the drug so many suffer from withdrawal symptoms eg. headaches, muscle pains, sweating, lack of sleep.

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Statins

Lower the level of cholesterol made by the liver. usefel in people who have high levels because of their genes or people who eat a lot of saturated fats.

Benefits - incredibly effective, can be used in people with high risk of having high cholesterol because of their genes (not their fault)

drawbacks - expensive, why should people who live unhealthily have lots of money spent on the by the NHS

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medicines and recreational drugs

Drugs taken to relieve illness or disease are calld medicines e.g. Statins, asprin

Drugs that are taken from pleasure are called recreational drugs e.g. alcohol, cocaine

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Alcohol

slows down the speed at which messages travel around the nervous system, so can cause people to relax. however, too much can cause the body to relax too much and may lead to lack of self control, unconsciousness and a coma.

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Thalidomide

developed as a sleeping pill

effective in relieving morning sickness

babies born with deformities

now used to treat leprosy

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Micro organisms

tiny living organisms, some are useful and some cause infectious disease.

Viruses, form of pathogen - small and able to effect body cells

dead so need machinery inside our cells to make copies

take over body cells and cause lots of damage

rarely damage our bodies by producing toxins

Bacteria, form of pathogen - larger then viruses not able to infect body cells

living cells can divide without help from our cells

dont take over body cells

cause damage by producing toxins that make us feel ill

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White blood cells

ingest pathogens

produce antibodies which destroy bacteria or viruses

produce anti toxins which counteract toxins produced by pathogens

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painkillers and antibiotics

painkillers help relieve symptoms of infectious disease but do not kill the pathogens. Antibiotics including penicillin cure disease by killing bacteria inside the body, they can be used to kill viral pathogens however, it is difficult to kill viruses without damaging body tissue because they live inside cells.

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Mutating Pathogens

most cause no change, some cause bad changes, a few cause good changes.

if a mutation took place that made the cell wall of a bacterium thicker, the bacteria would be better suited to withstand antibiotics which often work by destroying cell walls. while it lives on to reproduce, the weaker bacteria will be killed off. the next generation will be clones of the strong bacterium so will all have increased resistance to antibiotics. also, by killing off the weaker ones, helps the strongest because they no longer have to compete for water etc.

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Vaccination

injecting dead or inactive pathogens into the body. cause the body to stimulate white blood cells to produce anti bodies to destroy the pathogens. this makes the person immune in the future because they can respond by rapidly making the correct anti body.

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