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Bell Ringer!!!!
• Identify the fuel source, number of ATP
produced, whether oxygen is used, and
duration of energy given for each of the
following pathways of ATP production
• Direct phosphorylation
• Anaerobic (glycolytic) pathway
• Aerobic pathway
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Muscle Fiber Type
Classified according to two characteristics:
1. Speed of contraction: slow fibers or fast
fibers
•
Determined by the speed of which
the enzyme ATPase breaks ATP down
to ADP + P
2. Metabolic pathways for making ATP:
• Oxidative fibers—use aerobic pathways
• Glycolytic fibers—use anaerobic glycolysis
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Muscle Fiber Type
Three types:
• Slow oxidative fibers
• Fast oxidative fibers
• Fast glycolytic fibers
So…what’s the difference between a chicken and a duck?
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Slow Oxidative Fibers
(*dark meat*)
• Contract slowly
• Depend on oxygen delivery and aerobic
pathways
• Many mitochondria
• Fatigue resistant High endurance
• Rich capillary supply (to deliver more O2)
• Red in color (good supply of myoglobin)
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Fast Glycolytic Fibers
(*white meat*)
• Contract rapidly
• Anaerobic
• Depends on glycogen reserves for fuel
• Powerful contractions but tires quickly
(fatigable)
• Appears white, little myoglobin and low
capillary density
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Fast Oxidative
• Intermediate between other two types
• Least common of all fiber types
• Contract quickly
• Oxygen dependent
• Many mitochondria
• Good supply of myoglobin and capillaries
• Pink in color
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Effects of Exercise
Aerobic (endurance) exercise:
• Leads to increased:
• Muscle capillaries
• Number of mitochondria
• Myoglobin synthesis
• Results in greater endurance, strength, and
resistance to fatigue
• May convert fast glycolytic fibers into fast
oxidative fibers
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Effects of Resistance Exercise
Resistance exercise (typically anaerobic) results in:
• Muscle
hypertrophy (due to increase in fiber size)
• Increased mitochondria, myofilaments, glycogen stores,
and connective tissue
• May convert fast glycolytic fibers into fast oxidative
fibers
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The Overload Principle
• Forcing a muscle to work hard promotes
increased muscle strength and endurance
• Muscles adapt to increased demands
• Muscles must be overloaded to produce
further gains
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Table 9.2
FO
SO
FG
Note: Don’t memorize table 9.2! Use it as a reference . Start with
what you know and see how the characteristics support the chart.
Let’s practice!
Critical Thinking: You call several friends to help you move.
Would you prefer to have your friends with more slow oxidative
muscle fibers or those with more fast glycolytic fibers as helpers?
Why?
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Figure 9.24
So let’s talk turkey…err…chicken
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Smooth Muscle
• Found in walls of most hollow organs
(except heart)
• Usually in two layers (longitudinal and
circular)
• Involuntary, controlled by the autonomic
nervous system
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Longitudinal layer
of smooth muscle
(shows smooth
muscle fibers in
cross section)
Small
intestine
(a)
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Mucosa
(b) Cross section of the
intestine showing the
smooth muscle layers
(one circular and the
other longitudinal)
running at right
angles to each other.
Circular layer of
smooth muscle
(shows longitudinal
views of smooth
muscle fibers)
Figure 9.26
Contraction of Smooth Muscle
• Slow, synchronized contractions
• Can be controlled by nerves, hormones, or
local chemical changes
• Rate and intensity of contraction may be
modified by neural and chemical stimuli
***We will go into further detail when we
discuss each body system individually
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Developmental Aspects
• Muscular development reflects
neuromuscular coordination
• Development occurs head to toe
(cephalocaudal), and proximal to distal
• Peak natural neural control occurs by midadolescence
• Athletics and training can improve
neuromuscular control
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Developmental Aspects
• Female skeletal muscle makes up 36% of
body mass
• Male skeletal muscle makes up 42% of body
mass, primarily due to testosterone
• Body strength per unit muscle mass is the
same in both sexes
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Developmental Aspects
• With age, connective tissue increases and
muscle fibers decrease
• By age 30, loss of muscle mass (sarcopenia)
begins
• Regular exercise reverses sarcopenia
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Muscular Dystrophy
• Group of inherited muscle-destroying
diseases
• Muscles enlarge due to fat and connective
tissue deposits
• Muscle fibers atrophy
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Muscular Dystrophy
Duchenne muscular dystrophy (DMD):
• Most common and severe type
• Inherited, sex-linked, carried by females and
expressed in males (1/3500) as lack of dystrophin
• Diagnosed between 2-7 years of age. 1st sign,
victims become clumsy and fall frequently; usually
die of respiratory failure in their 20s
• No cure, but viral gene therapy or infusion of stem
cells with correct dystrophin genes show promise
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