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  • Created by: Lina
  • Created on: 24-05-12 17:15


Medicines that can kill infective bacteria inside the body. They can help cure diseases caused by bacteria, such as chest or ear infections, TB, or blood poisoning.

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One of the most troublesome strains of bacteria that has developed resistance to antibiotics in MRSA. Its full name is methicillin-resistant Staphylococcus aureus. Methicillin is a very strong antibiotic only used in bad cases of infection, but this bacterium is resistant to even that. It causes many hospital-acquired infections each year and many deaths.

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Antibiotics cannot be used to kill viruses. They do not kill viruses because viruses do not carry any life processes. It is difficult to make a drug that kills viruses without also damaging your cells, as viruses have to inside your cells to reproduce.

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Ignaz Semmelweis

A Hungarian doctor Ignaz Semmelweis was the first to realise that washing hands helps prevent the spread of disease.

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Any microorganism that can cause an infectious disease is called pathogen. Some bacteria are pathogens. All viruses are pathogens.

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Some bacteria are pathogens. If they get through our gut wall or skin and into our blood or cells they can make us very ill. They reproduce rapidly inside our warm bodies and some produce toxins that make us feel ill.

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They cannot carry out any life processes. Viruses are much smaller than bacteria.

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White blood cells

There are phagocytes and lymphocites. Phagocytes engulf the pathogens. Lymphocites produce antibodies or antitoxins (proteins). Each type of antibody can destroy a particular type of bacterium or virus. This is because:

- Each type of pathogen has particular antigens with specific shape on its surface.

- Each type of antibody has a particular shape and can lock on to a particular antigen.

- The immune system makes the right sort of antibodies to lock on to the antigens of the particular pathogen that is the body.

-Once the pathogen is coated with antibodies, white blood cells (phagocytes) can ingest and kill the pathogens.

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Immunisation can make people immune to a disease, without them having the disease. 

Here's how it works:

-A small amount of dead or inactivated pathogen is introduced in the body. The dead or inactivated pathogens still have the antigens on their surface.

-Some of white blood cells recognise these antigens on the pathogens and respond by making antibodies.

-If, later on, the live pathogens get into the body, the white cells quickly make the right sort of antibodies.

-These antibodies destroy the pathogens before they make you ill.

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Mutations affect vaccines

Every year new vaccines are made for the new strains of flu, as viruses, like flu, mutate often. This causes them to change their antigens. The immune system does not recognize them without vaccination, so they can make you ill again with flu. 

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Diseases sweeping across countries- epidemic, across continents-pandemic.

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All living things need to be able to respond to changes in the environment. These changes are called stimuli. If you could not detect and respond to stimuli you would not be able to find pod or avoid danger.

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The structure of nervous system

There are 2 parts of nervous system:

The central nervous system (CNS)- the brain and spinal cord.

The peripheral nervous system- nerves taking information from sense organs into the CNS, and nerves taking information from the CNS to effectors (muscle or glands).

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Receptor cells are special cells adapted to detect stimuli. Information from the receptors passes as electrical impulses. Some responses are voluntary- they are consciously controlled by the brain.

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Reflex actions

The response is coordinated by the other part of CNS, the spinal cord. These responses are called reflex actions. 

Stimulus->receptor->sensory neurone->relay neurone->motor neurone->synapses->effector->response.

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Effectors are glands or muscles that carry out a response. 

-A muscle responds by contracting.

-A gland responds y secreting chemical substances.

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Hormones are chemicals, that:

-regulate the functions of many organs and cells

-coordinate many processes in the body

-are produced (secreted) from glands into the bloodstream

-travel in the blood to target organs.

They also regulate the blood sugar level.

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Losing and gaining water

You lose water by:

-skin in sweat

-lungs by breathing out

-kidneys in urine.

You gain water by:

-drinks containing water

-food containing water

-respiration of digested food.

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Your blood and the watery fluid in between all your cells contains ions (sodium ions, potassium ions, magnesium ions, calcium ions and hydrogen ions). They are all very important in helping your nerves to work and keeping the body fluids at the right pH.

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Your body gets rid of heat by:


-breathing our warm air

-from the warm blood flowing near the skin surface.

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Growing up

In females the sex hormones oestrogen and progesterone are made in the ovaries. These hormones are involved in the menstrual cycle.

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Hormones in the menstrual cycle

The pituitary gland in the brain produces a hormone called follicle stimulating hormone (FSH).

FSH causes:

-eggs in the ovaries to mature, one each month

-stimulates the ovaries to make oestrogen


-stimulates the pituitary gland to make luteinising hormone (LH), which causes ovulation

-prevents more FSH being secreted

-repairs the the uterus lining after menstruation.


-maintains the uterus lining

-works with oestrogen to prevent secretion of FSH.

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The menstrual cycle

Day 1-13- The egg is maturing in a folicle.

Day 14- Ovulation

Day 14-21- A yellow body forms from the empty follicle.

Day 21-28- If the egg is not fertilized, the yellow body breaks down.

Day 28-5- The egg is maturing.

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Fluid filled structure in which the ovum matures in the ovary.

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How the female sex hormones control fertility

During pregnancy both oestrogen and progesterone levels are high and they inhibit FSH production from the pituitary gland. This prevents the development and release of any more eggs.

Scientists realized that if woman took these hormones in a daily pill, the high levels in the body would prevent ovulation. Without ovulation women cannot become pregnant. These hormones are used in contraceptive pills.

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Controlling plant growth

Plants as well as animals respond to stimuli, namely changes in their environment. Plants make chemicals called plant hormones (plant growth substances) that control and coordinate

-the growth of shoots and roots


-ripening of fruits

A plant's response to stimulus called a tropism.

Plant shoots grow towards light. They are positively phototropic.

-Plant shoots tips are a growing point. They make a plant hormone called auxin and this moves down to other parts of the stem.

-When light strikes one side of the shoot up, more auxin builds up on the other side of the shoot tip.

-This causes the bend over, towards the light.

-This is useful to the plant, as it need light to make food (photosynthesis). 

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Geotropism, horticulture, weedkillers

Geotropism is the response of a plant to gravity. Roots grow downwards in response to the pull of gravity. Auxins may be involved in this response, but other chemicals that inhibit growth may also play a part.

Plant hormones can be applied to plants to either speed up or slow down their growth.

Auxins are used as selective weedkillers. They can make trees lose their leaves, without what they cannot make food

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