Topic 2 - Xrays And ECGs Flashcards
What happens to the electrons after they’ve escaped (produce x rays)
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
Why does the production of x rays happen in a glass tube covered by a lead casing
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
Why are x rays dangerous to us
High frequency high energy
Ionise molecules in living cells
Leaving cells as positively charged ions
Cause tissue damage or cancer
What is the inverse square relationship
If you move twice as far from the source the same radiation is being spread over four times the area
- 1
– Or —-
2 squared. 4
What are X-rays absorbed by
Thicker materials like lead and concrete
What is X-ray fluoroscopy
Moving images of the inside of a patient
Describe the process of fluoroscopy
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
What can fluoroscopy be used to check
Blood flow
Gastrointestinal tract
What does a CAT scan work
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
What can CAT scans be used to look for
Tumours and cancers
Advantages of x rays
Better diagnosis
Hospitals try to limit the exposure
It’s a non invasive procedure
What is resting potential
The potential difference across the cell membrane of a muscle cell at rest
What is the average resting potential
-70mV
What is action potential
When a muscle cell is stimulated by an electrical signal the potential difference changes
What is the average action potential
40mV
What happens in the process of the heart beating
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
What does an ECG do
Records the action potentials of the heart usin electrodes stuck into the chest arm and legs
What does The blip P mean on an ECG
Shows the contraction of the atria
What does the QRS blip show
The contraction of the ventricles but also the relaxation of the atria
What does the T blip show
The relaxation of the ventricles
What is a pacemaker
A device used to regulate heart beat
Where is the hearts natural pace maker
A group of cells in the wall of the right atrium
How does an artificial pace maker work and how is it fitted
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
What type of light is used in a pulse oximeter
Red and infrared light
What does a pulse oximeter measure
The amount of oxygen in a patients blood
Where is a pulse oximeter placed
On a thin part of the body earlobe or finger
How does a pulse oximeter work
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
What is th colour of the blood affected by
Whether it’s oxyhemoglobin or reduced haemoglobin
What is thermionic emissions
A firmament acts as a cathode. The filament is heated which gives more energy to its electrons. Once they have enough energy they escape
