Download The Cardiovascular System: Cardiac Function

PRINCIPLES OF
HUMAN PHYSIOLOGY
13
THIRD EDITION
Cindy L. Stanfield | William J. Germann
The Cardiovascular
System:
Cardiac Function
Part A
PowerPoint® Lecture Slides prepared by W.H. Preston, College of the Sequoias
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Anatomy of the Heart
• Four Chambers
•
Two atria
•
Two ventricles
• Valves
•
Atrioventricular
•
Semilunar
• Interventricular
septum
• Base
• Apex
Figure 13.1
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Path of Blood Flow
• Cardiovascular system = closed system
• Flow through systemic and pulmonary circuits is in
series
• Left ventricle  aorta  systemic circuit 
vena cavae  right atrium  right ventricle 
pulmonary artery  pulmonary circuit 
pulmonary veins  left atrium  left ventricle
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Path of Blood Flow
Figure 13.2
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Heart Location
Figure 13.5
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Ventricular Muscle
Figure 13.6
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Properties of Cardiac Muscle
• Cells are smaller than cells of skeletal muscle
• Cells demonstrate branching
• Striations are evident
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Properties of Cardiac Muscle
• Intercalated disks
•
Gap junctions
• Cause heart to contract as a unit
•
Desmosomes
• Resist stress
• Atria and ventricles
•
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Properties of Cardiac Muscle
• Aerobic muscle
• No cell division after infancy—growth
by hypertrophy
• 99% contractile cells (for pumping)
• 1% autorhythmic cells (set pace)
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Function of Cardiac Muscle
• Rhythmic contraction and relaxation generates
heart pumping action
• Contraction pushes blood out of heart into
vasculature
• Relaxation allows heart to fill with blood
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Heartbeat
• Wave of contraction through cardiac muscle
• Atria contract as a unit
• Ventricles contract as a unit
• Atrial contraction precedes ventricle contraction
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Valves and Unidirectional Blood Flow
• Pressure within chambers of heart vary with
heartbeat cycle
• Pressure difference drives blood flow
•
High pressure to low pressure
• Normal direction of flow
•
Atria to ventricles
•
Ventricles to arteries
• Valves prevent backward flow of blood
• All valves open passively based on pressure
gradient
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Atrioventricular Valve Action
Figure 13.7
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Semilunar Valve Action
Figure 13.8
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Autorhythmic Cells
Location
SA Node
AV Node
Bundle of His
Purkinje Fibers
Firing Rate at Rest
70-80 APs/min*
40-60 APs/min
20-40 APs/min
20-40 APs/min
• Cardiac cells are linked by gap junctions
• Fastest depolarizing cells control other cells
• Fastest cells = pacemaker = set rate for rest of
heart
* action potentials per minute
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.
Cardiac Electrical Connections
Figure 13.9
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Conduction System of Heart
Figure 13.10
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Pathway of Depolarization
Figure 13.11
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Electrical Activity: Pacemaker Cell
Figure 13.12
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Electrical Activity: Pacemaker Cell
Table 13.1
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Electrical Activity: Contractile Cell
Figure 13.13
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Electrical Activity: Contractile Cell
Table 13.2
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© 2008 Pearson Education, Inc., publishing as Benjamin Cummings.