1. 7
The Muscular System

2. Muscle Performance (7-7)
Measured in force
The maximum amount of tension produced by a muscle or muscle group
Measured in endurance
The amount of time a particular activity can be performed
Two keys to performance
Types of fibers in muscle
Physical conditioning or training
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3. Fast Fibers (7-7) The majority of muscle fibers in the body
Large in diameter
Large glycogen reserves
Few mitochondria
Rely on glycolysis
Are rapidly fatigued
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4. Slow Fibers (7-7)
About half the diameter of, and three times slower than, fast fibers
Are fatigue resistant because of three factors
Oxygen supply is greater due to more perfusion
Myoglobin stores oxygen in the fibers
Oxygen use is efficient due to large numbers of mitochondria
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5. Percentages of Muscle Types Vary (7-7)
Fast fibers appear pale and are called white muscles
Extensive vasculature and myoglobin in slow fibers cause them to appear reddish and are called red muscles
Human muscles are a mixture of fiber types and appear pink
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6. Muscle Conditioning and Performance (7-7)
Physical conditioning and training
Can increase power and endurance
Anaerobic endurance
Is increased by brief, intense workouts
Hypertrophy of muscles results
Aerobic endurance
Is increased by sustained, low levels of activity
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7. Cardiac Muscle Tissue (7-8)
Found only in heart
Cardiac muscle cells
Relatively small with usually only one central nucleus
Striated and branched
Intercalated discs, which connect cells to other cells
Communicate through gap junctions, allowing all the fibers to work together
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8. Cardiac Pacemaker Cells (7-8)
Exhibit automaticity
Make up only 1 percent of myocardium
Establish rate of contraction
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9. Cardiac Contractile Cells (7-8)
99 percent of myocardium
Contract for longer period than skeletal muscle fibers
Unique sarcolemmas make tetanus impossible
Are permeable to calcium
Rely on aerobic metabolism
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10. Smooth Muscle Tissue (7-8)
Thick filaments are scattered throughout sarcoplasm
Thin filaments are anchored to the sarcolemma
Causing contraction to be like a twisting corkscrew
Cells are bound together
Resulting in forces being transmitted throughout the tissue
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11. Smooth Muscle Tissue (7-8)
Different from other muscle types
Calcium ions from the extracellular fluid are needed to trigger a contraction mechanism that is different from other muscle tissues
Function involuntarily
Can respond to hormones or pacesetter cells
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12. Figure 7-10 Cardiac and Smooth Muscle Tissues.
muscle cell
Intercalated
discs
Cardiac muscle tissue
LM x 575
A light micrograph of cardiac muscle tissue.
Circular
muscle layer T
Longitudinal
muscle layer L
Smooth muscle tissue
LM x 100
Many visceral organs contain several layers of smooth
muscle tissue oriented in different directions. Here, a
single sectional view shows smooth muscle cells in
both longitudinal (L) and transverse (T) sections.
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13. Foldable: Muscle Types and Functions
Skeletal Muscle
Fiber size:
Function:
Nuclei:
Control:
Calcium Ion Source:
Contraction Speed:
Stamina:
Energy Source:
Cardiac Muscle
Fiber size:
Function:
Nuclei:
Control:
Calcium Ion Source:
Contraction Speed:
Stamina:
Energy Source:
Smooth Muscle
Fiber size:
Function:
Nuclei:
Control:
Calcium Ion Source:
Contraction Speed:
Stamina:
Energy Source:
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14. Smooth Muscle Tissue (7-8)
Found in the walls of most organs, in the form of sheets, bundles, or sheaths
Lacks myofibrils, sarcomeres, or striations
Smooth muscle cells
Also smaller than skeletal fibers
Spindle-shaped and have a single nucleus
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15. Table 7-2 A Comparison of Skeletal, Cardiac, and Smooth Muscle Tissues
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