Medical Physics

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 Author: Kirstys06 ID: 150879 Filename: Medical Physics Updated: 2012-04-29 11:26:23 Tags: physics GCSE Folders: Description: edexcel Show Answers:

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1. How do endoscopes work?
They work using bundles of optical fibres, they carry light to the area of interest and allow you to see an image.
2. Desrcribe pulse oximetery
Pulse oximetres are made up of 2 beams of red light, one infrared and one just red. Using your finger you can tell whether there is more oxigenated haemoglobin in your blood or more deoxygenated, you can do this by looking at the absorption of each light.
3. If more red light is absorbed than infrared, which is there more of oxigenated or deoxygenated?
• deoxygenated, y axis is absorption.
4. Define "power"
Power is energy transferred per second, its worked out by work done/time taken.
5. A toy rocket with a mass of 2.5kg, accelerating at 20m/s2 travels 40m in 2 seconds, calculate the power of the rocket motor...
• WD = F x S work done = force x time
• F = m x a force = mass x acceleration
• W = F x s = (m x a )= (2.5 x 20) x 40 = 2000J
• Power = work/time
• power = 2000/2 = 1000W
6. What does metabolic rate mean?
The rate your body uses energy.
7. What does BMR stand for?
Basal metablic rate
8. What is basal metabolic rate?
The rate of energy you burn at rest.
9. Name the 5 factors that affect BMR...
• Age
• Body fat percentage
• Body surface area
• Diet
• External temperature
10. Explain how muscle cells can generate potential differences..
Between the insides of the muscle and the outside, theres a potential difference (voltage). The potential difference across the cell membrane of a muscle at rest is called resting potential. They can be measured by using a machine called electromyography.
11. Name the 4 sections of this heart
• A- right atrium
• B- right ventricle
• C- left atrium
• D- left ventricle
• Notice the lefts and rights seem the wrong way around, the reason for this is we lable diagrams as if it was on our body so think like you're labelling your own heart!
12. Explain the different parts of this ECG (electrocardiograph)
• The blip at P shows the contraction of the atria
• The QRS shows the contraction of the ventricle, its a strange shape as at the same time the atrias relaxing.
• T shows the relaxing of the ventricles.
13. How can you work out heart rate (beats per minute) using and ECG?
On the graph measure the time between each peak, use frequency = 1/time period... so if your gap was 0.8 you would do 1/0.8 = 1.25 and to find beats per minute you times it by 60, so the examples heart rate in 75 beats per minute.

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