Muscle fiber arrangement

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Muscle fiber arrangement

• Skeletal Muscle fibers arrange in bundles- called
  fascicles.
• Within a fascicle, all muscle fibers are parallel
  to each other.
• Fascicular arrangement affects a muscle power
  range of motion
• Longer fibers have greater range of motion
  cover greater distance
• Short muscles with higher cross-sectional
• area have more force

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Fascicle arrangement

• There are 5 patterns of fascicle organization.
  (Arrangement of fibers relative to axis of force
  generation)
• Parallel muscles. The fascicles run parallel to
  the long axis of the muscle.
• e.g. Stylohyoid muscle
• Fusiform or spindle-shapedmuscle tapers toward
  tendons
• e.g. Digastric muscle
• Triangular (convergent) muscles. The fascicles
  converge on a common tendon. appear fan shaped
  like pectoralis major.
• Circular muscles. The fascicles are
  concentrically arranged around an opening.
• These muscles are also called sphincters.
  When they contract the diameter of the opening
  they surround decreases. Orbicularis oculi
  muscle, Orbicularis oris of the mouth is an
  example of a circular muscle

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Pennate Fiber architecture

• Pennate means feather which the orientation of
  these fibers resemble.
• pennate fiber arrangement at an angle to the
  longitudinal axis of the muscle,
• unipennate extnesor digitorum longous
• bipennate rectus femoris
• multipennate deltoid muscle

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Coordination within Muscle group

• Prime mover or agonist contract to initiate an
  action.
• Antagonist act against the effect of the prime
  mover
• Synergist a muscle acts as a synergist when it
  prevents the unwanted action of another muscle.
• Fixators stabilize the origin of the prime mover

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Compartment muscle groups

• In the limbs, a compartment is a group of
  skeletal muscles, along with their blood vessels
  nerves, that have a common function.
• Anterior or flexor compartment
• Posterior or extensor compartment

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NERVE SUPPLY OF MUSCLES

• Muscles have both motor and sensory nerve
  endings.
• The main motor endings are large myelinated
  nerves that connect to the muscle fibers at motor
  end plates (MEP)
• Motor units A motor neuron muscle fibers it
  stimulate is called a motor unit.
• Sensory nerves of muscles
• End in receptors within the muscle or its tendon
  and provide feedback about muscle tension and
  joint position (proprioception). Some participate
  in reflexes.
• Neuromuscular junction synapse between muscle
  motor neuron

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Muscle Tone

• Muscle tone is the continuous and passive partial
  contraction of the muscles. It helps maintain
  posture keep muscle firm.
• Hypotonia decreased muscle tone (flaccid
  muscles)
• Hypertonia increased muscle tone, expressed in 2
  ways
• 1. spasticity- increased tendon reflexes.
• 2. rigidity- tendon reflexes are not affected

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Aging Skeletal Muscle

• Slow progressive loss of skeletal muscle mass
  at about 30 years of age
• Cause decline activity
• Slow muscle reflexes
• Aerobic activities