CAT Scans and Electricity

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What do CAT scans produce?
They produce an image of a two dimensional slice of the body
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How does a CAT machine work?
An x-ray beam rotates around the body and is picked up by thousands of detectors and a computer works out how many of the x-rays are absorbed and produces a high quality image
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How can CAT scans produce three dimensional images?
By 'stacking' the individual slice images.
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What do CAT scans do?
They help to look for tumours and cancer.
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What is resting potential?
The potential difference across the cell membrane of a muscle cell at rest
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How can the difference be measured?
By using tiny electrodes
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What happens when a cell is stimulated by an electrical signal?
It's resting potential changes from -70 millivolts to 40 millivolts
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What is this increase known as? What does it do?
The action potential. It passes down the length of the cell and makes the cell contract.
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What does an electrocardiograph do? (ECG)
They measure the action potentials of the heart.
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What happens when the heart beats?
Action potentials pass through the atria making them contract, and a fraction of a second later the same happens in the ventricles.
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What happens when the action potential has passed?
The muscles relax.
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What do the potentials produce?
They produce weak electrical signals on the skin.
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How does an ECG record the heart's action potentials?
By using electrodes which are placed on the chest, arms and legs.
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How are the results displayed?
They're displayed on a screen or are printed as a graph called an electrocardiogram (ECG)
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What is the heart's natural pacemaker?
A group of cells in the wall of the right atrium that produce electrical signals that pulse about 70 times a minute.
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What do these signals do?
They spread to the atria/ventricles and make them contract by action potential. This directly controls heart rate.
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What problems can there be with a natural pacemaker?
It can be too slow, or pulse irregularly.
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How are artificial pacemakers made?
They use small electrical impulses to stimulate the heart to beat.
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How are the impulses sent to the heart?
Through thin wire electrodes that are attached to the heart.
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How are artificial pacemakers powered?
They use batteries so need replacing, but modern pacemakers can be programmed externally so surgery is not needed for a settings change.
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What can some modern pacemakers also do?
They can monitor breathing and temperature and use these to adjust your heart rate.
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Other cards in this set

Card 2

Front

How does a CAT machine work?

Back

An x-ray beam rotates around the body and is picked up by thousands of detectors and a computer works out how many of the x-rays are absorbed and produces a high quality image

Card 3

Front

How can CAT scans produce three dimensional images?

Back

Preview of the front of card 3

Card 4

Front

What do CAT scans do?

Back

Preview of the front of card 4

Card 5

Front

What is resting potential?

Back

Preview of the front of card 5
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