Chapter 24 Opener The heart circulates blood to every tissue and organ, sustaining all bodily streng

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Chapter 24 Opener The heart circulates blood to
every tissue and organ, sustaining all bodily
strength
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Figure 24.1 The human heart
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Vertebrate hearts

• Vertebrate hearts are myogenic
• Muscle cells are electrically coupled
• Birds and mammals have a pacemaker in the right
  atrium
• Special conducting muscle fibers initiate cardiac
  muscle depolarization
• Pacemaker receives autonomic input

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Figure 24.4 The conducting system and the
process of conduction in the mammalian heart
(Part 1)
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Figure 24.4 The conducting system and the
process of conduction in the mammalian heart
(Part 2)

• Depolarization spread to AV node is slow
• Depolarization from AV node to Purkinje fibers is
  rapid

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AP in contractile fibers
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Autorhythmic fibers
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The conduction system
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Figure 24.6 Electrocardiography (Part 1)
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Figure 24.6 Electrocardiography (Part 2)
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Figure 24.6 Electrocardiography (Part 3)
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Figure 24.2 The heart as a pump The dynamics of
the left side of the human heart (Part 1)
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Figure 24.2 The heart as a pump The dynamics of
the left side of the human heart (Part 2)
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Figure 24.2 The heart as a pump The dynamics of
the left side of the human heart
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Cardiac output

• Cardiac output is the volume of blood ejected
  from the left ventricle into the aorta each
  minute.
• CO (mL/min) SV (mL/beat) X HR (beat/min)
• SV EDV (blood in the ventricle during diastole)
  - ESV (blood remaining in ventricle)
• Typical stroke volume is 70mL/min, CO is
  typically 5.25 liters/min.
• Cardiac reserve is the difference between a
  persons maximum cardiac output and cardiac
  output at rest.

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Regulation of stroke volume

• Preload is the degree of stretch on the heart.
• Contractility is the force of ventricular
  contractions.
• Afterload is the pressure that must be exceeded
  to eject blood from the ventricles.
• The Frank-Starling law of the heartpreload is
  the critical factor controlling SV (stroke
  volume).

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Regulation of stroke volume
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Figure 24.7 Fluid-column effects on blood
pressure in the arterial vascular system
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Figure 24.7 Fluid-column effects on blood
pressure in the arterial vascular system (Part 1)
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Figure 24.7 Fluid-column effects on blood
pressure in the arterial vascular system (Part 1)
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Figure 24.7 Fluid-column effects on blood
pressure in the arterial vascular system (Part 2)
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Figure 24.8 Total fluid energy The true driving
force for blood flow

• Kiinetic energy accounts for a small fraction of
  total fluid energy (1-3)
• For a supine individual, potential energy is
  equal everywhere

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Figure 24.9 The physics of flow through tubes
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Pressure effects on flow rate
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Viscosity effects on flow rate
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Length effects on flow rate
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Radius effects on flow rate
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Flow rate