Lecture 2 Flashcards
Instead of warm blooded, what is a more appropriate term for mammals
Endothermic (from within)
Instead of cold blooded, what is a more appropriate term for reptiles and fish
Ectothermic (outside)
Define endotherms and give an example
maintain their body temps in a narrow range that is mostly dependent on the metabolic rate
e.g. humans n other mammals
Define ectotherms and give an example
have body temps that depend on external heat sources, usually the sun, allowing a wider range of body temperatures; mostly
behavioral temp regulation
e.g. alligator lying in the sun
Define poikilothermic? Example?
- means varied + thermic;
- generally reptiles and fish that use BEHEVIOUR to REGULATE body temp
Define homeothermic? Example?
- similar + thermic;
- generally for mammals whose metabolism, via the autonomic nervous system and behavior, are used to regulate body core temp e.g. shivering
Define energy, its types, and units.
- Energy: The ability to do work.
- Types: kinetic and potential.
- Units are Joules, calories
How can energy in a system or some object be quantified?
Measure potential energy thru mass and velocity. Will be using simple Q.
Define heat. How can heat in a system or in some object be quantified?
Energy transferred from one system to another as a result of thermal interactions
- Quantified as the net amount and direction of transfer (units in Joules/time or Watt).
- Flow from hot to cold
Define temperature. How can temp in a system or in some object be quantified?
- Degree or intensity of heat in environment or object.
- Units: Celsius, Farenheit, Kelvin.
- Measured: thermal expansion coefficient. As mercury goes up or down, water/substance expands and contracts and its thermal expansion coefficient is proportional to temperature.
- Temperature has MAGNITUDE but NO DIRECTION
What is Heat Exchange? What is thermal
energy?
Heat exchange: Transfer of nrg from two physical systems, specifically thermal nrg (kinetic nrg of molecules which can be inc with heat).
- Thermal nrg: example of kinetic nrg, due to motion of particles
What is heat flow and is it directional?
- Heat flow: movement of thermal nrg between two objects, directional where by moves from hotter object to cooler object.
- Heat flow has magnitude n direction, heat exchange is a to descriptor (convection, conduction, radiation)
- Flow can be thought of as mass of energy transferred over timed. Heat exchange is used to describe process
Difference between temp and heat?
HEAT vs. TEMP… HEAT IS DIRECTIONAL AND HAS MAGNITUDE
What are the avenues for heat exchange (5)
(Bi-directional)
- Conduction
- Convection
- Radiation
- Evapouration
- Metabolic heat generation (aka transfer)
What is conduction (QCD)?
direct contact of 2 objects gives heat transfer
What does conduction depend on? (3)
- depends on temp difference from body (Tb) to skin surface (Ts)
- area of contact
- conductive properties of the 2 materials
How does fat/muscle/fur affect conduction
- conduction varies w/fat n skeletal muscle insulation in humans n fat/fur in animals
- fat is a much poorer insulator than a few cm of fur like in a down jacket.
- insulation of fur and clothes is mainly due to trapping of air (best insulator)
What is the equation to calculate conduction
Two possible eqns:
QCD (W x ºC^-1 x cm-1 ) = kA(T2-T1)/d
Where:
A = area of contact
d = distance btwn 2 temps T1 & T2
k = thermal conductivity (units of J x s^-1 x ºC^-1 x cm^-1)
But since d and A hard to measure, use:
QCD (W x ºC^-1) = C x ΔT(2-1)
Where:
ΔT2-1 = thermal gradient
C = thermal conductance heat transfer
coefficient (W x ºC^-1)
What is thermal conductivity (k)? What is it directly related to
a fixed property of materials and is directly related to insulation
What is insulation
reciprocal of total heat flux per unit area per unit of temperature difference (ºC x cm^-2 x sx J^-1)
What is “clo”
- clothing unit
- when insulation is given per m^2
How much is 1 clo?
0.16ºC x m^2 x W^-1
What is tissue thermal resistance (r, s x cm^-1) vs. tissue thermal conductivity?
- In bio or physiology, a tissue layer can be expressed as RESISTANCE
- Takes into account thermal CONDUCTIVITY (k) and adds the THICKNESS (l) of the layer
Eqn for thermal resistance (r)? What are the units
r =(ρ x Cp x l) / k
OR
k =(ρ x Cpx l) / r
Where: ρ x Cp = specific heat capacity of the medium, i.e. air or water;
density (ρ) = mass/vol of the layer.