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BPK 432 > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Instead of warm blooded, what is a more appropriate term for mammals

A

Endothermic (from within)

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2
Q

Instead of cold blooded, what is a more appropriate term for reptiles and fish

A

Ectothermic (outside)

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3
Q

Define endotherms and give an example

A

maintain their body temps in a narrow range that is mostly dependent on the metabolic rate
e.g. humans n other mammals

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4
Q

Define ectotherms and give an example

A

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

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5
Q

Define poikilothermic? Example?

A
  • means varied + thermic;

- generally reptiles and fish that use BEHEVIOUR to REGULATE body temp

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6
Q

Define homeothermic? Example?

A
  • similar + thermic;
  • generally for mammals whose metabolism, via the autonomic nervous system and behavior, are used to regulate body core temp e.g. shivering
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7
Q

Define energy, its types, and units.

A
  • Energy: The ability to do work.
  • Types: kinetic and potential.
  • Units are Joules, calories
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8
Q

How can energy in a system or some object be quantified?

A

Measure potential energy thru mass and velocity. Will be using simple Q.

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9
Q

Define heat. How can heat in a system or in some object be quantified?

A

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
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10
Q

Define temperature. How can temp in a system or in some object be quantified?

A
  • 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
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11
Q

What is Heat Exchange? What is thermal

energy?

A

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

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12
Q

What is heat flow and is it directional?

A
  • 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
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13
Q

Difference between temp and heat?

A

HEAT vs. TEMP… HEAT IS DIRECTIONAL AND HAS MAGNITUDE

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14
Q

What are the avenues for heat exchange (5)

A

(Bi-directional)

  1. Conduction
  2. Convection
  3. Radiation
  4. Evapouration
  5. Metabolic heat generation (aka transfer)
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15
Q

What is conduction (QCD)?

A

direct contact of 2 objects gives heat transfer

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16
Q

What does conduction depend on? (3)

A
  1. depends on temp difference from body (Tb) to skin surface (Ts)
  2. area of contact
  3. conductive properties of the 2 materials
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17
Q

How does fat/muscle/fur affect conduction

A
  • 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)
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18
Q

What is the equation to calculate conduction

A

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)

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19
Q

What is thermal conductivity (k)? What is it directly related to

A

a fixed property of materials and is directly related to insulation

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20
Q

What is insulation

A

reciprocal of total heat flux per unit area per unit of temperature difference (ºC x cm^-2 x sx J^-1)

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21
Q

What is “clo”

A
  • clothing unit

- when insulation is given per m^2

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22
Q

How much is 1 clo?

A

0.16ºC x m^2 x W^-1

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23
Q

What is tissue thermal resistance (r, s x cm^-1) vs. tissue thermal conductivity?

A
  • 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
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24
Q

Eqn for thermal resistance (r)? What are the units

A

r =(ρŸ x Cp x Ÿl) / k
OR
k =(ρ x ŸCpŸx l) / r

Where: ρ x Cp = specific heat capacity of the medium, i.e. air or water;
density (ρ) = mass/vol of the layer.

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25
Q

What is specific heat capacity

A

heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree).
aka more nrg needs to be put in to inc temp = higher specific heat capacity

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26
Q

What is the relationship between resistance and thermal conductivity?

A

Reciprocal relationship

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27
Q

What is convection (QCV)?

A

Movement of a gas or liquid over or within a body resulting in heat exchange

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28
Q

What does convection depend on? (4)

A
  1. temp. difference TS to TAIR
  2. body dimensions
  3. curvature of body surface
  4. the fluid or gas:
    • thermal expansion coefficient
    • density
    • viscosity
    • velocity
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29
Q

What is the thermal expansion coefficient units?

A

change in length/ºC increase

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30
Q

Example of convection? (3)

A

wind against body; running water over body surface, human blood

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31
Q

Eqn for convection (QCV)?

A

QCV (W x m^-2 x ºC^-1)
= C x A x (TSKIN - TAIR)

Where: A = area, C = h(c) =
convection heat transfer coefficient

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32
Q

Of the factors influencing convection, what is most important?

A

Air speed or velocity

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33
Q

Convective heat exchange varies ~ as the square root of air velocity EXCEPT?

A

At very low velocities

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34
Q

Similarity btwn convective heat transfer coefficient h(c) and evapourative heat transfer coefficient h(e)? Difference?

A

Both convection and evaporation strongly dependant on air speed/velocity
- Convection also dependent on fluid velocity but not evapouration

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35
Q

What is radiation?

A

• heat transferred at the speed of light
• is emitted from all bodies
that have a temperature >
absolute zero or -273ºC

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36
Q

Wavelength of radiation depends on? (2)

A
  1. difference btwn surface temp of the emitting bodies [skin temp (TS ) and object surface (TSUR)]
  2. characteristics of the surface area of a body or object including it’s EMISSIVITY and SHININESS
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37
Q

What is I(MAX)?

A

Predominant wavelength of radiation from a body

38
Q

How is I(MAX and T(SUR) related?

A

I(MAX) is inversely proportional to T(SUR) (Wien’s Law)

39
Q

What is reflectance

A
  • ratio of the INTENSITY of REFLECTED to INCIDENT radiation on a surface
  • bidirectional
40
Q

What is emissivity (ε) of a body?

A

ability of body to emit energy by radiation.

  • is a DIMENSIONLESS constant for any material = ratio of nrg emitted by that body to that emitted by a black body at the same temp; is unidirectional.
  • is related to the familiar concepts of COLOR and SHININESS of the surface
  • biological materials have ε in medium to long IR radiation with values btwn 0.90 and 0.99
41
Q

What is a “perfect” black body? How does this compare to a mirror?

A

an ideal emitter and; gives off ≥ energy than any other body and has ε=1 vs. mirror or perfect reflector has an ε = 0.

42
Q

What is Evaporation (QE)

A

is heat loss due to the evaporation of

sweat/H2O from surface of the human body

43
Q

What is the most effective heat loss from the human body

A

QE (Evaporation)

44
Q

What factors do Evaporation (QE) depend on

A 
- same factors
as for convection 
1. temp. difference TS to TAIR
2. body dimensions
3. curvature of body surface
4. the fluid or gas:
• thermal expansion coefficient
• density
• viscosity
• velocity 
plus some additional:
1. surface temp
2. H2O vapor density
between surface and
surrounding air
3. resistance to H20 loss by
the surface
45
Q

What is the latent heat of evaporation

A
  • gas to liquid phase
  • latent heat of evaporation
    is 2400-2500 J/g H20
46
Q

What is the eqn for evapouration

A

QE (W xŸ m^-2 xŸ kPa) = C xŸ A Ÿ x (PSKIN-PAMB)
Where: A = area, C = he = evaporation heat transfer coefficient, PSKIN
skin water vapour pressure, PAMB = ambient water vapour pressure

47
Q

What happens to eqn for evapouration when skin surface is completely wet

A

If skin surface is completely wet, skin water vapour pressure = saturation water vapour pressure for that skin temp. Then QE is maximum (QEMAX) for those environmental conditions.

QEMAX (W xŸ m-2 xŸ kPa) = C xŸ A Ÿx (PSKIN,SAT - PAMB)
Where: PSKIN, SAT = Saturation water vapour pressure

48
Q

What happens to eqn for evapouration when skin surface is not completely wet

A

If skin surface not is completely wet, a skin wettedness coefficient (w) is used = ratio of QE/ QEMAX, with 0 ≤ w ≤ 1

QE (W Ÿx m^-2 xŸ kPa) = C xŸ A xŸ wQE x (PSKIN, SAT - PAMB)

49
Q

Wettedness depends on hydration ____ and fraction of _____ that is wet

A

Wettedness depends on hydration EPIDERMIS and fraction of SKIN that is wet

50
Q

What is Relative Humidity (RH):

A

For a certain air temp there is a given capacity for H2O vapor

51
Q

Rqn for RH

A

actual water vapor / water vapor capacity for given temp

52
Q

DEC air temp = ____ air vapor capacity

A

DEC air temp = DEC air vapor capacity

53
Q

INC air temp = ____ air vapor capacity

A

INC air temp = INC air vapor capacity

54
Q

RH is ______ related to evaporation from the skin. e.g. in a cold environment, Pa will be ____ enough that sweat can easily evaporate from the skin even if ____ = 100

A

RH is INDIRECTLY related to evaporation from the skin. e.g. in a cold environment, Pa will be LOW enough that sweat can easily evaporate from the skin even if RH = 100

55
Q

How is wet bulb temp diff from dry bulb temp

A

WBT = DBT when air is saturated w/water

56
Q

What is dew point temp (DPT)

A

is the DBT at which a moist air sample at the same pressure would reach water vapor saturation

57
Q

What is metabolic heat production (QM)? What is the heat produced proportional to

A
  • when a fuel is oxidized or burned up, heat is
    liberated from the body
  • the amt of heat liberated is proportional to type of fuel oxidized and rate of metabolism
58
Q

For metabolic heat production (Qm), how does the heat produced vary with whats oxidized?

A
  • heat produced varies with proportions of fat/CHO oxidized (INC fat oxidized = INC heat produced)
59
Q

For metabolic heat production (Qm), how can it be estimated?

A
  • estimated by direct and indirect calorimetry

- efficiency of energy transfer

60
Q

What is the Rate of Heat Exchange (S)

A

this is the net of the different rates of heat exchange via the different avenues

61
Q

Eqn for Rate of Heat Exchange (S)

A

S = +QM +/- QCD(Tb-Ts) Qconv(Ts-Ta) +/- Qrad(Ts-Tsur) -QE(PSKIN-PAMB)

Where:
Qx x ΔT= rate of heat exchange, where x = avenue of heat exchange
and ΔT = difference in temperature
- Qx= heat transfer coefficient for that avenue of heat exchange
- Tb = temperature of body contacting the skin
- Ts = skin temperature
- Ta = air temperature
- Tsur = temperature of an object emitting radiation
- P = Pressure

62
Q

What is the 1st line of defence to a change in ambient temp.

A

Behavioral Responses

63
Q

Example of Behavioral Responses to Changes in Body Temperatures

A
  • In hot/cool climates we choose appropriate clothing, activities, and locations to minimize the changes in our body temp
    e. g. in deserts we look for shade, drink water, wear shorts and sandals
    e. g. in winter we stay inside, are more active to generate heat, wear warm insulated clothing
64
Q

What is Hyperthermia

A

inc of core temp by ~1ºC above resting normothermic levels

65
Q

What is hypothermia

A

dec in core temp by ~1ºC below resting normothermic levels

66
Q

What is vasodilation

A

Inc in caliber of a blood vessel

67
Q

What is vasoconstriction

A

an actively mediated dec in peripheral BF by various mxn(s)

68
Q

What is vasomotion

A

changes in caliber of vessels by vasoconstriction or vasodilation actions

69
Q

What are arteriovenous anastomoses (AVAs)

A

Direct arterial to venous conduit in a capillary bed that connects arterioles and venules; allows bypassing of capillary beds; useful for heat conservation in cold climates

70
Q

What are the diameter of capillaries vs. AVAs

A

Capillaries = 5-10µ, AVA 20-70µ

71
Q

What are eccrine sweat glands

A

produce sweat that is employed in body cooling after increases in body temp

72
Q

What are apocrine sweat glands

A

produce sweat often after an emotional event

73
Q

What is a set point

A

– point of core temps about which core temp is regulated

74
Q

What is null zone

A

a zone of core temp with no sweating or shivering and just vasomotion

75
Q

What is core temp? How can it be measured

A

– temp of the bodys core, usually measured in the esophagus, GI tract, rectum or on the tympanic membrane

76
Q

What is skin temp

A

– temp on the surface of the body, usually measured w/a thermocouple or thermistor taped to the skin surface at multiple sites

77
Q

What is the periphery

A

– describes the peripheral tissues; there are

no definite boundaries for the periphery; and its size inc or dec depending on the peripheral vessels states

78
Q

What is the core

A

– describes the central tissues, there are no definite boundaries for the core and its size inc or dec depending on the peripheral vessels states

79
Q

What is the Hypothalamus

A

centre for temp regulation

80
Q

What are cold sensitive neurons

A

dec’s in their temps cause inc firing rates

81
Q

What are Warm sensitive neurons

A

inc in their temps cause inc firing rates

82
Q

Discuss the control of room temp when there is a disturbance (include what is the receptor, control centre, effector)

A

E.g. if room temp rises, the thermometer (RECEPTOR) located inside the thermostat (CONTROL CENTER) sends this info to the thermostat which sends the command of the AC (EFFECTOR) to turn on. A thermostat stabilizes room temp by turning on AC (or heater) as needed to keep room temp near desired set point. When room temp rises, thermostat turns on AC, and room temp returns to normal lvls. With this regulatory system room temp oscillates around set point

83
Q

Describe the POAH (its neurons inc in firing due to? how is the output inhibited?)

A
  • has neurons that inc in firing with increased temp = stimulates heat loss
  • this output is inhibited by cold input from skin
84
Q

Describe the DMPH (its neurons inc in firing due to? how is the output inhibited?)

A

has neurons that increase in firing with dec temp

- this output is inhibited by warm input from skin

85
Q

As core temp drops, metabolic rate ____

A

As core temp drops, metabolic rate INC

86
Q

Who identified a null zone of core temp with no sweating or shivering responses

A

Mekjavic

87
Q

What are responses to cold environment

A
  • shivering (inc metabolic rate) and vasoconstriction
  • sympathetic response to catecholamines via ß1 and
    ß2 receptors; also thyroxine over long term increases metabolic rate
  • Non-shivering thermogenesis
88
Q

What is involved in non shivering thermogenesis and what receptor? Researcher who discovered this

A
  • brown adipose and other tissues via ß3 receptors
  • uncoupling proteins UCP1, UCP2 and UCP3
  • J. Himms-Hagen /Mary-Ellen Harper in Ottawa
89
Q

In regulation of Regulation of Body Heat Content, what does the time constant (tau) represent

A

– represents the time it takes a system’s step response to reach 1-1/e that is approximately 63.2% of its final asymptotic value

90
Q

Describe indirect calorimetry

A

Computer interfaces with:

  • A flow-measuring device that records air volume breathed
  • O2 and CO2 analyzers that measure the composition of the expired gas mixture
  • Mouth piece/nose clip or hood

BPK 432 (17 decks)

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