Discoving the muscle

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Discoving the muscle

  1. 1. + Understanding the muscle Pairings, microscopic structure and function
  2. 2. + Understanding the muscle  Muscles never work on their own, and always work in teams.  A muscle belly will have tendons at either end to attach them to bone  A muscle is always attached to 2 or more bones (by tendons) to allow a stable and strong surface to pull against. These connections are called the origin and insertion.
  3. 3. + Muscle connections to bones Origin  Is the place where the muscle is attached to the most stable surface – which is usually a flat bone such as the scapula or pelvic girdle.  This provides the muscle with a strong surface to pull against Insertion  Is at the other end of the muscle at attached to the bone where the movement occurs.
  4. 4. + Origin and insertion example  Bicep  Its origin is at the scapula and insertion is the radius  So when the bicep shortens, the lower arm (including the radius) will move towards its origin
  5. 5. + Reciprocal inhibition  When muscles on one side of a bone or joint relax to accommodate contraction on the other side of the bone or joint  Biceps and triceps  Quads and Hamstrings  Gastrocnemius and tibialis anterior
  6. 6. + Agonist – Antagonist relationship  Muscles always work in pairs  The agonist is the muscle primarily responsible for producing a movement  The antagonist is the muscle which relaxes while the movement takes place to prevent injury  When a muscle contracts, it is critical for the muscle which performs the opposite movement to relax to prevent an injury occurring (muscle tear)
  7. 7. + Stabilisers  Provide stability to the origin so maximal contraction force can be applied.  EXAMPLE: During elbow flexion the trapezius contracts to stabilise the scapula and provide a strong, rigid base for the bicep to pull on.
  8. 8. + Inside the Muscle Belly Microscopic structure of a muscle
  9. 9. + The structures  The muscle belly consists of thousands of muscle fibres known as fascicles which run side by side along the length of the muscle  Each of these fibres is encased in and surrounded by connective tissue known as perimysium, which assists in keeping the fascicles together.
  10. 10. + Muscle Fibres  Each fascicle is made up of several muscle fibres, which are made up of even smaller fibres called myofibrils, which are similar to the many wires within a telephone cable. These have many units, known as sarcomeres, which are arranged end to end for their entire length of the myofibril
  11. 11. + The Sarcomere  Is a contractile unit, and each end is designated by a line called a Zline.  Each sarcomere consists of two proteins myofilaments called actin and myosin.  Actin is a thin filament which is attached to the Z-line  Myosin is a thick filament which is situated between each of the actin filaments
  12. 12. The Lines and Zones of a Sarcomere +
  13. 13. + The Lines and Zones of a Sarcomere  The Z-line: Marks the two ends of a sarcomere  The I-band: Where only actin is found  The A-band: Where both actin and myosin are found and equates to the length of the myosin filaments  The H-zone: Where only myosin is found and is the gap between the ends of the actin
  14. 14. + A muscle contraction  The myosin filaments have cross bridges (oar-like structures) that are attracted to the actin filaments  At rest, there is little contact between the actin and the myosin  However, when the sarcomere contracts, the cross bridges attach to the actin filaments and pull them into the centre of the sarcomere in a ‘rowing’ action    The cross bridges continue to detach and reattach themselves from the actin filaments, shortening the sarcomere.  Every sarcomere along the muscle fibre shortens, leading the whole muscle to contract.    The muscle will relax when the actin and myosin filaments lose contact with each other that is, when the cross bridges detach from the actin.
  15. 15. + Muscle Tone  Not all the myosin filaments detatch themselves from the acti. Some may stay in contact, so the muscle is never completely relaxed.  If this is the case, the muscle is said to have ‘tone’  The advantage of muscle tone is that the actin and myosin filaments are always ready to contract

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