Applied science (Medical physics)

applied science revision cards


ECG - Electrocardiogram

electrocardiogram is a simple method of investigating the hearts rhythem and electircal activity.

small sticky patches are attached - these are called electrodes.

the electrodes are attached to the arms, legs and chest

the electrodes are attached to a ECG recording machine and then detect the  electrical activity that makes the heart beat and relay it back to the machine which creates a trace.

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heart conditions

sinus tachycardia - sinus tachycardia is when the heart beats too fast, the normal heart rate is 60-80bpm but in sinus tachycardia the heart beat can increase to over 100bpm

a person with sinus tachycardia would have high blood pressure and a reddish complexion.

Bradycardia- Bradycardia is when the heart rate drops below 60bpm.however this condition is not uncommon in highly trained athletes.

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heart conditions

sinus arrythmia- sinus arrythmia is when the conducting system of the muscle cells in the heart has been damaged.

ventricular fibrillation- VF is when the heart has a random contraction of the muscle cells in the ventricles.

A person in VF will mostlikly collapse due to the body not being able to get enough oxygenated blood to the organs and body cells. this lack of oxygen means the cells cannot respire properly to make the energy needed. Paramedics will need to restore the hearts normal rhythem quickly, they may use a defibulator or CPR.

Difference between heart attack and VF:

A person having a heart attack will have an increased QRS wave on their ECG trace, where as a person in VF will just have a jagged and irregular ECG trace.

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EEG - Electroencephalogram

Electroencephalogram (EEG) is a method of investigating brain activity.

the system involves placing several pairs of electrodes on the patients head.

 these electrodes are discs that conduct the electrical activity detected in the brain.

 they then convey the electrical activity out through wires to a machine that amplifies the signal.

scientists attach electrodes in pairs so that the difference in voltage between the pairs can be measured.

the electrical activity in the brain corresponds to the persons state of mind.

Good contact between skin and electrode is obtained by using conductive gel.

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mind states

Alpha - these waves occur when a person is awake and relaxed

Beta- these waves occur when a person is undergoing mental activity

Delta-these waves occur in children or deep sleeping adults

Theta - these waves occur in chiledren or light sleeping adults. too many theta waves can indicate stress

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uses of EEG scans

  • Can research sleep
  • doctors can monitor anestetic
  • doctors can diagnose brain disorders like epilepsy
  • doctors can confirm brain death
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body temperature (Liquid in glass thermometer)

liquid in glass thermometers work on the simple principle that liquid when heated increases its volume.
with the liquid in glass thermometer, a liquid such as alcohol or mercury is inside a small inner tube, which is then surrounded by an outer tube.

  • the liquid in the termometer expands whe it is heated
  • it rises up the inner tube
  • the greater the increase in temperature, the more it rises
  • you can read the measurement, off the scale
  • the liquid expands a lot when heated but the glass does not expand much on heating.

the thermometet has a small bulb at the bottom which is so small it heats up very quickly.

the liquid used should remain liquid over a wide temperature range. coloured alcohol is often used as it is safet is the glass breaks

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body temperature (how to use a clinical thermomete

  • shake the thermometer to ensure the liquid is below the bend.
  • insert the thermometer into mouth, under arm or ear
  • leave for a few minutes
  • remove from mouth and read the scale
  • by rotating the thermometer the scale is magnified, making it easier to read

clinical thermometers have a bend just above the bulb at the bottom, this is to prevent the liquid from moving up the tube and distorting the results.

the clinical thermomete has a much narrower tube therefore it gives more accurate results.

there is more space for each degree so the liquid moves further up the tube for each degree. this means you can read fractions of degrees more accurately.

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thermistor thermometers

thermistor thermometers

the changes in resistance changes the current and voltage which is converted into a temperature reading.
The greater the change in temperature , the greater the change in resistance.

thermistor thermometers arent nessisarily more accurate than liquid in glass.

the factor which determines accuracy of the reading given from  a thermistor thermometer is
how much resistance changes for each degree, rise in temperature.

  • you measure body temperatures in the mouth or under the arm rather than the skin because; it is closer to the core body temperature
  • the skin gets cooled by the air surrounding it.
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advantages of thermistor thermometers over clinini

  • a clinical thermometer can be difficult to read due to the thread and liquid being so small.
  • there is a slight risk with the liquid in glass thermometer, the patient may bite down on it and end up with the liquid and broken glass in the mouth.
  • no human error with the thermistor thermometer as you get a digital reading.
  • thermistors can be set up to monitor the temperature continuously.
  • thermistors can be connected to an alarm that sounds if the temperature gets too high or too low.
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key temperatures

Normal:- 36.8  but anywhere within the range of-  36.5 - 37.2 degrees celcius

death from being too hot:- 43 degrees celcius and over

death from being too cold (hypOthermia):- below 25 degrees celcius

heat stroke (hypErthermia):- above 38 degrees in the absence of infection

fever:- above 37.2 degrees celcius

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HypErthermia and its symptoms

hyperthermia is a condition that sets in at body temperature 38 degrees celcius and in the absence of infection.

its symptoms can include:

Abdominal cramps

Muscle cramps





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hypothermia is when the body's temperature drops below 32 degrees celcius.

symptoms can incude:

clumsiness and lack of coordination

slurred speech

shallow dreathing

loss of consiousness

pale skin and lack of blood flow to the extremities

Shiny foil blankets are wrapped around the patient with hypothermia because they are shiny and silvery they reflect the infrared heat they are loosing, back into the patient.

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Blood Pressure

Blood pressure is a measurement of the force blood exerts as it travels through a blood vessel. it is measured using a sphygmanometer (sphyg-mo-mano-meter)

there are two readings taken for blood pressure:

systolic pressure - is the maximum pressure the heart produces when it contracts

dyastolic pressure - is the blood pressure between the heart beats, when the heart relaxes.

mmHg is the units  blood pressure is measured in. normal blood pressure is around 120/80mmHg

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How to measure blood pressure.

  • wrap the cuff around the upper arm, level with the heart
  • inflate the cuff by squeezing the hand pump
  • while inflating, listen to the blood flow in the patients arm using a stethascope
  • raise the pressure to 200mmHg, this will flatten the branchial artery and stop the blood flow.
  • keep the stethoscope over the brachial artery and release the air in cuff using the valve.
  • when the artery makes a tapping sound this means the blood is just starting to flow again - this is the systolic pressure (record this reading).
  • continue to lower the pressure in the cuff untill the point the tapping sound stops.
  • at this point the blood will be flowing freely, you will have the dyastolic pressure (record this)

the cuff is placed around the upper arm to be level with the heart, if we placed it in the ankle then it would be greater.

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Key Blood Pressure Values

High blood pressure - 160/100 mmHg

Low blood pressure - 90/60 mmHg

Healthy blood pressure for a young adult female- 123/80 mmHg

Healthy blood pressure for a young adult male- 125/80 mmHg

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electrical blood pressure monitors

Advantages of having personal patient electronic blood pressure monitors for at home use:

  • they will be more convenient for the patient, they will not have to travel to a medical centre
  • it will save costs of medical professional monitoring blood pressure
  • the patient can alert the medical staff if the reading shows there is a problem.

People may become stressed at the thought of going to the medical centre for a doctors appointment, this will naturally increase blood pressure.

Blood pressure can be measured by using an arterial line. this is a fine catheter inserted into the artery. it is usually used when a patient is in intensive care or under anaesthetic to monitor blood pressure.

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blood pressure advantages and disadvantages of usi

the advantages of this INVASIVE method are;

  • blood pressure can be monitored constantly
  • it is more accurate
  • doctors can use the same line to take a blood sample for further tests.

the disadvantages of this INVASIVE method are;

  • bleeding can occur if the artrial line comes out
  • the patient could get infections from the inserted line

INVASIVE means; the body is cut or penetrated to have something inserted into it. so a arterial line is invasive but a sphygomomanometer is NON-INVASIVE

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Very good :) thank you

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