Medical Physics: Nerve Impulses, The Heart + ECG

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  • Created by: LZ95
  • Created on: 14-04-14 14:36
Name two ways in which electrical activity can be measured in the body
Using a concentric needle electrode or using surface electrodes
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Describe the function of concentric needle electrodes
They can be used to detect electrical activity in a very small area. It is invasive so there is a risk of infection.
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Describe the function of surface electrodes
They are placed on the body and a good electrical contact is made with a saline (sodium chloride) gel. It is non-invasive but cannot be used in very precise work.
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What does the right atrium and ventricle do?
Right atrium receives deoxygenated blood from the body and the right ventricle pumps deoxygenated blood to the lungs
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What does the left atrium and ventricle do?
Left atrium receives oxygenated blood from the lungs and the left ventricle pumps oxygenated blood through the aorta
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What is the pulmonary vein and the pulmonary artery?
Pulmonary vein: carries oxygenated blood; Pulmonary artery: carries deoxygenated blood
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What is the pumping action of the heart controlled by?
The sino-atrial node, located in the right atrium
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What happens when the atria contract?
Blood is forced into the ventricles through the valves
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What happens when ventricles contract?
Valves from atria close and valves to arteries open.
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What does an electrocardiogram allow doctors to do?
Look at the electrical behaviour of the heart
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What is the P wave caused by?
Depolarisation and contraction of atria
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What is the QRS wave caused by?
Depolarisation and contraction of the ventricles
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What is the T wave caused by?
Repolarisation and relaxation of the ventricles
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Where are the electrodes placed during ECG?
On the right arm, left arm, left leg and chest
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How come the right leg is not used in ECG?
It is the furthest away from the heart.
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What is an unwanted signal that is also amplified by ECG?
Mains voltage, as it operates at 50Hz
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How is this interference avoided?
All electrical leads are screened and the ECG equipment is carefully shielded.
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Why is there a high signal to noise ratio?
Random signals given off are heard as white noise which can mask small changes.
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What can ECG be used to diagnose?
Arythmia, blockage of part of the blood supply for the heart and fibrillation
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What is defibrillation?
When paddles are placed over the heart and a brief, large electric shock is given causing major contraction of the heart muscles
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Why is the frequency response even?
So that the trace is not distorted
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Other cards in this set

Card 2

Front

Describe the function of concentric needle electrodes

Back

They can be used to detect electrical activity in a very small area. It is invasive so there is a risk of infection.

Card 3

Front

Describe the function of surface electrodes

Back

Preview of the front of card 3

Card 4

Front

What does the right atrium and ventricle do?

Back

Preview of the front of card 4

Card 5

Front

What does the left atrium and ventricle do?

Back

Preview of the front of card 5
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