P3.2 X-rays And ECGs

Question 1

How does an x-ray machine produce x-rays?

Answer 1

A cathode is heated until they are released through thermionic emission. The electrons accelerate towards the anode by a potential difference between the cathode and anode. When they collide with the spinning anode, some of the kinetic energy are released as x-rays.

Question 2

How can you calculate the KE of each electron?

Answer 2

Kinetic Energy= electronic charge * accelerating potential difference
KE= e*v

Question 3

How can you calculate the size of the current produced?

Answer 3

Current= Number of particles per second * charge on each particle
I= N*q

Question 4

What is the danger of x-rays?

Answer 4

They can remove electrons from molecules in living cells-leaving them as ions. This means cells can be destroyed, leading to cancer.

Question 5

What is the inverse square law relating to intensity of radiation?

Answer 5

The inverse square law states that if you move twice as far from the radiation source as you preciously were, then the radiation will be 2 squared times less intense.

Question 6

How does the thickness of a material affect the amount of x-rays it absorbs?

Answer 6

The denser or thicker a material is the more x-rays it absorbs.

Question 7

What materials can be used to reduce peoples exposure to x-rays?

Answer 7

Lead or Concrete

Question 8

How does a fluoroscope work?

Answer 8

X-rays are fired through a patient onto a fluorescent plate. Where less is received there will be a contrast, which lets to doctor view a moving image of the patients body.

Question 9

What is a CAT scan (Computerised axel tomography)?

Answer 9

An x-rays rotates around the body and is picked up by thousands of detectors. A computer works out how many x-rays are absorbed and creates a slice of a patients body.

Question 10

What are the benefits of x-rays?

Answer 10

1. They are the clearest and more accurate form of diagnosis.
2. Its better to use x-rays than to risk using the wrong treatment.
3. Its non-invasive.

Question 11

What are the drawbacks of using x-rays?

Answer 11

They are ionising

They can cause cancer

Question 12

What is the resting potential?

Answer 12

The potential difference across the cell membrane of a muscle cell.

Question 13

What is an action potential?

Answer 13

The increase in potential difference when an electrical impulse travels along the muscle cell.

Question 14

What is an ECG?

Answer 14

An ECG (electrocardiogram) measures the action potentials across the heart.

Question 15

How do you work out heart rate?

Answer 15

Frequency = 1/ time period (s)

Question 16

What are the 3 main stages of a heartbeat (often referred to as P, QRS and T)?

Answer 16

P- The atria contracting
QRS- The ventricles contracting
T- The ventricles relaxing.

Question 17

How is the ECG recorded?

Answer 17

Using electrodes on the body which pick up the action potentials travelling along the skin.

Question 18

What is a pacemaker?

Answer 18

A device that is fitted to the heart to produce action potentials to make the heart beat if your body is no longer able to do it.

Question 19

What is a pulse oximeter?

Answer 19

A device that is used to quickly measure your pulse and blood oxygen saturation levels.

Question 20

How does a pulse oximeter work?

Answer 20

It has emitters of IR and red light in the top and a detector on the bottom. If lots of IR and little red light is detected, you blood oxygen saturation is low as oxygenated blood absorbs IR but nor red light. If little IR and lots of red light is detected, your blood saturation is high.