Topic 2 - Xrays And ECGs

Question 1

What happens to the electrons after they’ve escaped (produce x rays)

Answer 1

They accelerate towards the anode by a voltage between the anode and cathode
Electron beams can be used to produce x rays when the electrons collide with a metal target some of their kinetic energy is converted into x rays

Question 2

Why does the production of x rays happen in a glass tube covered by a lead casing

Answer 2

It happens in a glass tube so that it is in a vacuum so that the electrons don’t collide with any other particles which would change their direction and decrease their energy
The lead casing is to make sure that the x rays are only aimed at the specific target

Question 3

Why are x rays dangerous to us

Answer 3

High frequency high energy
Ionise molecules in living cells
Leaving cells as positively charged ions
Cause tissue damage or cancer

Question 4

What is the inverse square relationship

Answer 4

If you move twice as far from the source the same radiation is being spread over four times the area

1. 1
   – Or —-
   2 squared. 4

Question 5

What are X-rays absorbed by

Answer 5

Thicker materials like lead and concrete

Question 6

What is X-ray fluoroscopy

Answer 6

Moving images of the inside of a patient

Question 7

Describe the process of fluoroscopy

Answer 7

Patient is placed between an x Ray source and a fluorescent screen
Different amount of X-rays are absorbed as they pass through the patients body
The X-rays then hit a fluorescent screen which absorbs then and gives off light to show a live image on the screen
The higher the intensity of the x rays the brighter the screen
Images are recorded

Question 8

What can fluoroscopy be used to check

Answer 8

Blood flow

Gastrointestinal tract

Question 9

What does a CAT scan work

Answer 9

X Ray beam rotates around the body and is picked up by thousands of detectors
Works out how many x rays are absorbed and produces a very high quality image
Can be used to make 2D or 3D images

Question 10

What can CAT scans be used to look for

Answer 10

Tumours and cancers

Question 11

Advantages of x rays

Answer 11

Better diagnosis
Hospitals try to limit the exposure
It’s a non invasive procedure

Question 12

What is resting potential

Answer 12

The potential difference across the cell membrane of a muscle cell at rest

Question 13

What is the average resting potential

Answer 13

-70mV

Question 14

What is action potential

Answer 14

When a muscle cell is stimulated by an electrical signal the potential difference changes

Question 15

What is the average action potential

Answer 15

40mV

Question 16

What happens in the process of the heart beating

Answer 16

An action potential passed through the atria making them contract
Another action potential passes through the ventricles making them contract too
The muscles then relaxess

Question 17

What does an ECG do

Answer 17

Records the action potentials of the heart usin electrodes stuck into the chest arm and legs

Question 18

What does The blip P mean on an ECG

Answer 18

Shows the contraction of the atria

Question 19

What does the QRS blip show

Answer 19

The contraction of the ventricles but also the relaxation of the atria

Question 20

What does the T blip show

Answer 20

The relaxation of the ventricles

Question 21

What is a pacemaker

Answer 21

A device used to regulate heart beat

Question 22

Where is the hearts natural pace maker

Answer 22

A group of cells in the wall of the right atrium

Question 23

How does an artificial pace maker work and how is it fitted

Answer 23

Sends small electrical impulses via electrodes to stimulate the heart to beat
Minor surgery and only a small incision
They are powered by batteries which need to be changed however modern ones you can programme them externally

Question 24

What type of light is used in a pulse oximeter

Answer 24

Red and infrared light

Question 25

What does a pulse oximeter measure

Answer 25

The amount of oxygen in a patients blood

Question 26

Where is a pulse oximeter placed

Answer 26

On a thin part of the body earlobe or finger

Question 27

How does a pulse oximeter work

Answer 27

As the light passes through the finger some is absorbed, the detector measures how much is absorbed
The amount of light absorption depends on the colour of the blood

Question 28

What is th colour of the blood affected by

Answer 28

Whether it’s oxyhemoglobin or reduced haemoglobin

Question 29

What is thermionic emissions

Answer 29

A firmament acts as a cathode. The filament is heated which gives more energy to its electrons. Once they have enough energy they escape