Unformatted text preview: ls innervated by the same motoneuron are
all of the same fiber type, thus
– share properties such as contraction velocity, max.
42 KNES 462 ©FK ‘08 KNES 462 white muscle generate higher force than red muscles The Motor Unit IV sir charles sharington--termed the motor unit
MU1 wikipedia him CNS (spinal cord) MU2 43 largest motor units have largest bodies and thickets axons
makes sense man KNES 462 ©FK ‘08 The Motor Unit: Types
• Three types of Motor Units:
– slow fatigable (Type 1, red) : slower, resistant to
fatigue. Generate ~ 1-10% of force of ff. Located more
deeply in the muscle, highly dependent on metabolic
support. Smallest motor units consist of Type 1.
– fast fatigable (Type 2, pale): fast, fatigue rapidly when
stimulated repeatedly. Largest force created during
twitch / tetanic contraction. Closer to the surface,
dependent on glycolysis.
– fast fatigue-resistant: intermediate between ff and sf. 44 KNES 462 ©FK ‘08 The Motor Unit: Force graphs white-early peak
int--well it is intermediate
red--- no peak 46 KNES 462 ©FK ‘08 KNES 462 The Motor Unit: Properties
• Close match between neuronal and muscle fiber
– ff fibers innervated by larger diameter axons,
– sf fibers innervated by smaller diameter axons, with
low frequency firing rates. contraction speed of the...
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- Winter '13
- gastrocnemius muscle, Motor unit, Motor Unit II, Motor Unit III, Motor Unit IV