NEUROMUSCULAR JUNCTION I

1.    Skeletal muscle:
     -     consists of a bundle of long fibres
     -      running the length of the muscle.
2.   Muscle fibre”
     -      long cylindrical cell
     -      with many nuclei
     -      each consists of smaller myofibrils
     -     arranged longitudinally.

3.   Content of muscle fibre:
     -     cytoplasm (sarcoplasm)
     -     mitochondria,
     -     endoplasmic reticulum (sarcoplasmic reticulum),
     -     plasma membrane (sarcolemma).

4.   Sarcolemma:
     -     folded inwards
     -     at intervals
     -     to form T tubules.
5.    T tubules - very closely associated with the sarcoplasmic reticulum.
6.   Myofibril = composed of thick + thin filaments.
     -     Thick filaments = composed of protein myosin.
     -     Thin filaments = composed of protein actin.
     -     organised into repeating units (sarcomeres).












7.   Sarcomeres:
     -     basic units of muscle contraction.
     -     shortening à causes whole muscle fibre to shorten.
     -     joined at their ends by 2 lines (Z lines).












8.   Arrangement of thick (myosin) + thin (actin) filaments:
     -     form sarcomere à hence the whole muscle contracts.
     -      form alternating light + dark bands in a skeletal muscle
     -     form striations pattern.
     -     banded pattern = Z lines, A band, I band + H zones.












9.   During muscle contraction:
     -     changes in banding pattern
     -     due to sliding motion
     -     between thick + thin filaments.