28 Questions
What is heat in medicine?
The total energy of molecular motion in a substance
What is temperature?
The average kinetic energy of molecules in a substance
What is the unit of temperature on the absolute scale?
oK
What is the normal body temperature in Celsius?
37oC
How does heat travel?
By four methods: conduction, convection, evaporation, and radiation
What is the purpose of an opaque white backing in a thermometer?
To increase the visibility of the capillary
What is a thermistor?
A special resistor that changes its resistance rapidly with temperature
What is the advantage of using a thermistor in medicine?
It is more sensitive to temperature changes
What is the relationship between the temperature scales?
oK = 273.15oC
What is the expansion of the liquid in a thermometer?
1 cm³ of mercury increases in volume by 1.8% when going from 0 to 100°C
What is the primary purpose of using a thermocouple in medical physics?
To measure the temperature of individual cells
What is the Stefan-Boltzmann law used for in medical physics?
To calculate the radiation power from the body
What is the effect of heat therapy on damaged tissue?
It increases the metabolism and increases blood flow
What is the range of wavelengths for radiant (IR) heat in medical physics?
800-40000 nm
What is the method of short-wave diathermy that uses an oscillating electric field?
Capacitance method
What is the purpose of keeping one junction of a thermocouple at a reference temperature?
To measure the temperature difference
What is the unit of the Stefan-Boltzmann constant?
W/cm^2K^4
What is the effect of heat therapy on the capillary system?
It increases the blood flow and dilates the capillaries
What is the method of heat transfer used in hot baths and hot packs?
Conductive method
What is the temperature range of the core of the body?
Within ±1°F (±0.6°C) of normal body temperature
What is the frequency of microwave diathermy usually used in physical therapy?
2450 MHz
What is the purpose of ultrasonic waves in physical therapy?
Heating body tissue
What is the advantage of ultrasonic heating in bones?
Bones absorb ultrasound energy more effectively than soft tissue
What is the name of the science and technology of producing and using very low temperatures?
Cryogenics
What is the purpose of the Dewar container?
To store and transport liquids at very low temperatures
What is the temperature of liquid nitrogen?
-196°C
What is the name of the method used to freeze blood at cryogenic temperatures?
Blood-sand method
What is the advantage of using cryogenic temperatures for preserving blood and tissues?
It allows for long-term preservation
Study Notes
Topic: Heat and Cold in Medicine
- Heat is the total energy of molecular motion in a substance.
- Temperature is a measure of the kinetic energy of molecules, and it is related to the temperature of a substance.
Temperature Scales
- Fahrenheit (oF) scale: water freezes at 32oF and boils at 212oF, normal body temperature is about 98.6oF.
- Celsius (oC) scale: water freezes at 0oC and boils at 100oC, normal body temperature is about 37oC.
- Kelvin (oK) scale: absolute temperature scale, water freezes at 273.15oK and boils at 373.15oK, normal body temperature is about 310oK.
Heat Transfer
- Four methods of heat transfer: conduction, convection, evaporation, and radiation.
- Heat energy will always move from higher to lower temperatures.
Temperature Measurement
- Thermometer: a device that measures temperature, examples include mercury thermometer and thermistor.
- Mercury thermometer: contains mercury or alcohol that expands more than the glass, producing an increase in the level of the liquid.
- Thermistor: a special resistor that changes its resistance rapidly with temperature, used in medicine because of its sensitivity.
Core Temperature and Skin Temperature
- Core temperature remains almost constant, within ±1oF (±0.6oC), while skin temperature rises and falls with the surrounding temperature.
- The Stefan-Boltzmann law is useful for calculating the total radiated power per surface area.
Heat Therapy
- Heat therapy has primary therapeutic effects: increase in metabolism, relaxation of the capillary system, and increase in blood flow.
- Physical methods of producing heat in the body: conduction, radiation, and short-wave diathermy.
- Short-wave diathermy: uses electromagnetic energy to heat the body, two methods are used: capacitance and inductance methods.
Cold in Medicine
- Cryogenic: the science and technology of producing and using very low temperatures.
- Cryobiology: the study of low temperature effects in biology and medicine.
- Dewar container: an insulated container developed by James Dewar in 1892, used to minimize conductive, convective, and radiative heat losses.
- Cryogenic methods are used in medicine for long-term preservation of blood, sperm, and tissues at very low temperatures.
This quiz covers the basics of heat and temperature, including temperature scales and their applications in medicine. Learn about the differences between Fahrenheit, Celsius, and Kelvin scales and how they are used to measure body temperature.
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