Transcript Skeletal Muscle Problems

Skeletal Muscle
• State possible sources of fatigue
• Distinguish the different muscle fiber
types.
Origins of Localized Muscle Fatigue
SITES OF THE
SOURCES OF FATIGUE
Central
Peripheral
Afferent Psychological
Neural
Feedback
Motivation
Transmission
• AP Propagation
Muscular
Transmission
• AP Propagation
Muscular
contraction
• cross-bridge
interference
Origins of Localized Muscle Fatigue
Depletion Theory of Fatigue:
Fatigue results from the depletion
of metabolites necessary for
energy production
Glucose
ADP or
CP
ATP
Oxygen
Reaction
Enzymes
Origins of Localized Muscle Fatigue
Accumulation Theory of Fatigue:
Lactic Acid
and free H+
K+
NH3
• Decreases membrane excitability
• Decreases Ca++
affinity for Troponin
• Decreases the
release of Ca++
• Obstructs
glycolysis
• Inhibits Aerobic
Metabolism
Skeletal Muscle Fiber Types
• innervating nerve is primary determinant of fiber type
during development
• a motor unit is composed of homogenous fibers
• all human muscles contain mixture of three general
fiber types
– slow twitch (ST, oxidative, red)
– fast twitch (FTa, fast-oxidative, red)
– fast twitch (FTb, glycolytic, white)
Time Course of Contributions from Different Energy Sources
fast twitch glycolytic (white)
slow twitch oxidative (red)
Oxidative
Fiber Type Characteristics
Performance characteristics affected by:
• Ca2+-ATPase
• myosin ATPase speed
• aerobic capacity (mitochondria, myoglobin,
blood supply, fatigue resistance)
• anaerobic capacity (glycolytic enzymes)
Muscle Movements
‘Not all force results in movement.’
• Isotonic - (same force), muscle fibers create a force that moves
a load. Muscle shortens or lengthens.
• Isometric - (same distance), muscle fibers create changing
force but does not move a load. Muscle length doesn’t change.
Tendon collagen stretches out.
• concentric – develops tension while shortening
• eccentric – develops tension while lengthening
*(most muscle actions are a combination of these)