Tag Archives: Physical therapy

Something about Shoulder replacement surgery

The human shoulder joint

Image via Wikipedia

Joint replacement involves surgery to replace the ends of bones in a damaged joint. This surgery creates new joint surfaces.

In shoulder replacement surgery, doctors replace the ends of the damaged upper arm bone (humerus) and usually the shoulder bone (scapula) or cap them with artificial surfaces lined with plastic or metal and plastic. Shoulder joint components may be held in place with cement, or they may be made with material that allows new bone to grow into the joint component over time to hold it in place without cement.


Muscles Are Organized Into Motor Units

  • When a single nerve enters a muscle it splits and makes neuromuscular junctions (NMJs) with several muscle cells
  • A nerve and the muscle cells it makes NMJs with is called a motor unit
  • When the nerve fires the whole motor unit is stimulated and the muscle cells contract together
  • Muscles with large motor units have coarse movements
  • Muscles with small motor units give fine, graded movements
  • This is a small motor unit with only 3 muscle fibersTwo Basic Types of Contraction Are Isotonic and Isometric