Biology 2672a: Comparative Animal Physiology

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Biology 2672a Comparative Animal Physiology

• Circulation

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Why have a circulatory system?

• Diffusion sucks!
• Moves oxygen and nutrients to cells
• Removes CO2 and waste products from cells

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How do I know its a circulatory system?

• Pump
• Fluid
• Vessels or spaces

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Primitive circulatory systems
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Open systems have all the characteristics of a
circulatory system
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The vessels in open systems can be quite
elaborate
Fig 24.24
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Open Circulatory Systems

• Low pressure
• Relatively inefficient
• Cant keep interstitial fluids and blood separate
• Dont allow impressive athletic feats

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But what about insects?

• Insect flight muscle has the highest work output
  in living organisms
• Oxygen delivery (via the tracheal system) is
  decoupled from the fluid circulatory system

Box 23.3
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Closed Circulatory System
From Heart
To Heart
Fig 24.11
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Flow Rate through a system
Q ?P
Flow rate
Difference in pressure between the entry and exit
to the system
R
Resistance in the system
P1
P2
?PP1-P2
Equation 24.3
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Flow Rate
Q ?P
R

• Flow rate can be determined by
• Pressure at the start of the system
• Pressure loss in the system
• Resistance in the system
• Pressure is proportional to both flow rate and
  resistance

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Resistance in a system
length
resistance
R 8 L ?
viscosity
p r4
radius
L
r
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Resistance
R 8 L ?
p r4

• Longer systems have more resistance
• More viscosity higher resistance
• Resistance is proportional to the 4th power of
  the radius of the tube
• A small change in tube diameter a huge change
  in resistance

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A teleost heart
Fig. 24.14b
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Fish circulatory system
Fig. 24.14a
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What does this mean physiologically?
3 kPa
5 kPa
Counter this with relatively large variation in
heart size and performance
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Heart oxygen demand may be a limiting factor in
teleosts
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High performance fish hearts

• Deoxygenated blood perfusing spongy myocardium is
  a limiting factor for fish
• Salmonids, Tuna, Sharks have a hybrid heart.

Fig. 24.3c
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(Most) Fishes Breathing Air
Plecostomus - Gut
Electric Eel - Mouth
Bowfin Swim bladder
Fig. 23.15
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(Most) Fishes breathing air

• No change to heart design
• Air breathing organs usually in parallel with
  body tissues
• Direct mixing of oxygenated and deoxygenated
  blood
• Ensures adequate O2 for the heart(?)

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Frog heart
Moyes Schulte Fig. 9.15b
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Frog circulation
Selective distribution of oxygenated and
deoxygenated blood
Moyes Schulte Fig. 9.11c
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Cephalopod Molluscs

• Radiated 200 Mya
• Have a closed, divided circulatory system

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Fig. 24.20a
Oxygenated blood in heart
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Oxygen delivery to octopus heart muscle
Fig. 23.3d
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Octopus circulation

• Two branchial hearts, one systemic
• Gills are in series with the tissues
• Allows oxygenated blood to be pumped at higher
  rate through systemic tissues.

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Circulation in mammals and birds
Fig. 24.10a
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An untwisted mammalian circulatory system
Fig. 24.10b
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End of material for mid-term exam
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Reading for Thursday

• Regulation of Circulation
• Pp 611-641 (continued)