Muscle

Muscle


  Antique apparatus for recording successive muscular contractions

Biceps: when the muscle shortens, points (a) insertion and (b) origin are brought closer together and the arm is bent, or flexed at the elbow.

  Antique apparatus for recording successive muscular contractions

Sliding Filaments

Myofibrils comprised of actin and myosin myofilaments

Muscle Length-tension Relationship

 

Muscle Fatigue & Blood Supply

 
Greatest tension is developed at point B (slightly stretched) with less tension developed at points A (contracted) and C (stretched).  
Muscle Fatigue (a) muscle with intact circulation (b) isolate muscle. Note sustained muscular contraction may occlude the local vasculature momentarily impeding blood flow to the activated muscle. Also see Pump and Burn.

Fast-Twitch versus Slow Twitch Fibers

Slow-twitch fibers (Type I)

    • More resistant to fatigue
    • Associated primarily with long-duration, aerobic-type activities

Fast-twitch fibers (Type IIa)

    • Capable of producing quick, forceful contractions
    • Moderately resistant to fatigue

Fast-twitch fibers (Type IIb)

    • Capable of producing quick, forceful contractions
    • Associated primary with short term, high intensity activities

The ratio of both types of muscle fiber varies in each individual and each muscle.

    • Ratio is thought to be genetically determined.
    • Both types of fibers can improve their metabolic capabilities through specific strength and endurance training.
    • Sprinters and weight lifters have a large percentage of fast-twitch fibers.
    • Marathon runners generally have a higher percentage of slow twitch fibers.
    • Muscles that primarily maintain posture against gravity require more endurance and generally have a higher percentage of slow-twitch fibers.
    • Muscles that produce powerful, rapid, explosive strength movements tend to have a greater percentage of fast-twitch fibers.
An artery branching into capillaries between three muscle fibers Record of successive conctractions of elbow flexor muscles
   
One end of muscle fiber showing attachment of tendon to sarcolemma Part of a muscle fiber specially prepared to bring out the numerous nuclei

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