MUSCLE CONTRACTION-MECHANICS-BIOMECHANICS NOTES
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