NEUROMUSCULAR JUNCTIONS

• WHAT IS A NEUROMUSCULAR JUNCTION?

  where a motor neurone meets a skeletal muscle fibre
• WHAT IS A MOTOR UNIT?

  where each muscle fibre is supplied by a single motor neurone (allowing for more control over exerted force)
• KEY FEATURES OF A NEUROMUSCULAR JUNCTION?

  AXON TERMINUS OF MOTOR NEURONE

  • voltage-gated Ca2+ protein channels
  • vesicles containing ACh

  MUSCLE CELL

  • receptor complimentary to ACh
  • voltage-gated Na+ protein channels
  • sarcolemma
  • T-tubule/ T-system
  • sarcoplasmic reticulum
  • sarcoplasm
  • mitochondria
  • nuclei (multinucleated)
  • myofibril
• WHAT IS MYOFIBRIL?

  an organelle
• WHAT DOES THE T-TUBULES ENSURE?

  depolarisation spreads deep into the membrane
• FEATURES OF THE MYOSIN FILAMENT?

  head

  • globular
  • contains ATPase

  tails
• FEATURES OF ACTIN FILAMENTS?

  • actin protein
  • tropomyosin
  • troponin
• WHAT HAPPENS TO EXCESS ACh?

  broken down by AChE to ensure muscle not overstimulated

  -> choline + acetyl diffuse back into neurone where they recombine to form ACh using energy from mitochondria