Changing blood distribution

1
Changing blood distribution
2
Blood flow in humans at rest
Tissue blood flow Lungs 100 Brain 14 He
art 4 Liver and gut 27 Kidneys 20 Skeletal
muscle 21 Skin 5 Bone 9
Pulmonary Circuit Systemic Circuit
Circuits are in parallel
How might exercise change this distribution?
Blood flow to brain is typically very conserved
3
Modifying volume/path of pipes
Blood flow through capillary beds can be greatly
reduced (or bypassed altogether) Precapillary
spinchters
shunt
4
Controlling heat loss with reduced blood flow to
surface
WARM
heat flow
SKIN
Capillary bed
arterial-venal shunt CLOSED
artery
vein
Vasodilation
5
Temperature (1)

• Introduction temperature tolerance of life
• Language and concepts in thermal biology
• Definitions of heat and temperature
• Avenues of heat exchange
• Conduction (Heat exchange equation)
• Convection
• Radiation
• Evaporation

6
Animals are active within a range of 45C TB.
Chemolithotrophic bateria
100
80
Hot springs algae
60
Temperature C
Desert insects, camels, some turtles
40
Body temperature range for active animals
Birds and some mammals
Monotremes and marsupials
20
0
Inactive animals can withstand colder
Sea water freezes
7
The language of temperature biology

• Ectotherm body temperature is principally
  dependent on external sources of heat
• Endotherm body temperature is principally
  dependent on internal sources of heat
• Homeotherm animals body temperature is
  constant
• Poikilotherm animals body temperature
  fluctuates

The vast majority of animal species are
ectotherms these are the animals well talk
about for the next couple of classes
8
Thermal strategies are a continuum
Endothermy
Homeothermy
Poikilothermy
Ectothermy
9
What is heat?
10
Animal temperature
To increase temperature
Heat gain gt heat loss
To decrease temperature
Heat gain lt heat loss
To maintain constant temperature
Heat gain heat loss
Both endotherms and ectothems are concerned with
heat transfer!
11
Thermal balance
Heat exchange between animal and environment
Important to both endotherms and ectotherms!
12
Conduction
Direct transfer of heat between 2 materials in
contact (Can be solid or fluid)
13
Conduction
J/s cm2 C cm
J/s cm C
T1
T2
A
How could an animal modify conductive heat flow?
d
14
Controlling conductive heat flow
(1) Varying k (thermal conductivity)
Material Still air Fox fur Sheep wool Pigeon
feathers (ruffled) Pigeon feathers
(sleek) Fat Water Ice Aluminum
Thermal conductivity 0.024 0.036 0.063 0.065 0.16
0.17 0.59 2.20 240
Best insulators
Poorest insulators
15
Controlling conductive heat flow
(1) Varying k (thermal conductivity)
Material Still air Fox fur Sheep wool Pigeon
feathers (ruffled) Pigeon feathers
(sleek) Fat Water Ice Aluminum
Thermal conductivity 0.024 0.036 0.063 0.065 0.16
0.17 0.59 2.20 240
Air is the best insulator!
16
Controlling conductive heat flow
(1) Varying k (thermal conductivity)
Material Still air Fox fur Sheep wool Pigeon
feathers (ruffled) Pigeon feathers
(sleek) Fat Water Ice Aluminum
Thermal conductivity 0.024 0.036 0.063 0.065 0.16
0.17 0.59 2.20 240
These vary according to how much air they trap
17
Controlling conductive heat flow
(1) Varying k (thermal conductivity)
Material Still air Fox fur Sheep wool Pigeon
feathers (ruffled) Pigeon feathers
(sleek) Fat Water Ice Aluminum
Thermal conductivity 0.024 0.036 0.063 0.065 0.16
0.17 0.59 2.20 240
With feathers, k can be modified through behavior
(2.5 fold!)
18
Controlling conductive heat flow
(1) Varying k (thermal conductivity)
Material Still air Fox fur Sheep wool Pigeon
feathers (ruffled) Pigeon feathers
(sleek) Fat Water Ice Aluminum
Thermal conductivity 0.024 0.036 0.063 0.065 0.16
0.17 0.59 2.20 240
Fat (blubber) is OK But 7 times more
conductive than still air!
19
Terrestrial to Aquatic insulation
Soaking wet fur is not insulative 1) Fur works
because of AIR Aquatic animals need to 1)
trap air 2) shift to using blubber
D. W. Koon, "Is polar bear hair fiber optic?",
Appl. Opt. 37 (15), 3198-3200 (1998).
Apparently, NO! Polar bear guard hairs do not
transmit or transfer UV radiative energy
20
Controlling conductive heat flow
(2) Vary d (distance or thickness of conductive
surface)
60 - 70 cm blubber 2 cm mammal fur
Seal Cross-section 58 blubber 42 is muscle,
viscera, bone, etc.
Schmidt-Nielsen 1997
21
Convection
Transfer of heat between an object (animal) and a
moving fluid (e.g. water (liquid) or air (gas))
Two parts
(1) Conduction
Very potent avenue of heat loss!
(2) Mass transfer
WHY?
22
Convection
Boundary layer warmed air around a perfectly
still animal serves as insulation
Takes away warm layer and accelerates heat
loss (even if wind is same temp as rest of
air!!!!)
SURFACE AREA very important to convective heat
loss
23
Moving air accelerates heat loss
15C, No wind
15C, Wind (2 m/sec)
15
These Infrared Thermography images of a House
Sparrow indicate that the bird is having a harder
time maintaining high body temperature under
windy conditions
Note that the air is the same temperature in both
cases!
24
Radiation
What is it? Transfer of electromagnetic energy
between objects not in contact
What you need to know Everything not at
absolute zero emits radiation Emission of
radiation is proportional to surface temperature
The sun
Shortwave radiation comes from VERY hot objects
Longwave radiation comes from everything else
Everything else
25
Radiation
Willmer et al. 2000
26
Evaporation
1) An avenue of heat loss only!
2) Takes advantage of the heat of vaporization
of H2O 2400J/g H2O
When water evaporates, it takes kinetic energy (
heat) with it
3) Rate of evaporation depends on
a) Surface temperature
b) Difference in H2O vapor density When it is
really humid, evaporation wont work
c) Surface resistance to water
loss Different animals have different
evaporative surfaces e.g. skin, tongue, feet,
throat
27
Heat exchange exercise

• Groups of THREE or FOUR
• Youll be shown
• Seven slides of animal behavior (sometimes
  behavior morphology)
• Youll have 30 seconds to identify the following
• Which avenues of heat gain or loss are affected
  by the behaviors?
• If conduction, through which term in the heat
  exchange equation?
• Whether the behaviors
• MINIMIZE OR MAXIMIZE /
• HEAT GAIN OR HEAT LOSS

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Discussion
36
Radiation Basking
Orienting body to intercept the maximal solar
radiation
MAXIMIZES RADIATIVE HEAT GAIN
Animals are cold
37
Evaporation panting gular flutter and spraying
Does not waste body water!
Uses body water!!
MAXIMIZES HEAT LOSS
Animals are too hot
38
Conduction ptiloerection (fluffing feathers)
Modifies d or k (insulation)
MINIMIZING HEAT LOSS
Birds are warm Air is cold
39
Conduction Stilting in desert beetles
Affects Area of contact between insect and ground
MINIMIZES CONDUCTIVE HEAT GAIN
Ground is HOT!!
40
Radiation and convection Obelisk posture
Intercepts least amount of radiation
MINIMIZES HEAT GAIN
Exposes body to convection
MAXIMIZES HEAT LOSS
Dragonfly is HOT!
41
B
A
42
B
A
Allens Rule Animals at high latitudes have
extremities with reduced surface area relative to
tropical relatives
43
Summing it all up
Heat storage temperature increase or decrease
of animal
44
Clarifying reading

• Schmidt-Nielsen
• This class page 242-254 (beginning of chapter 7)
• Next class 218 238 (chapter 6)