Operation of the Neuromuscular Junction

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1. What feature of intercalated disks in the cardiac muscle allows the action potential to pass easily between cardiac muscle fibres

  • Gaps junctions which allows free diffusion of ions
  • The part of the atrioventricular node that carry electrical impulses
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2. Examples of this type of muscle include peristalsis in the walls of the intestine and contraction of muscle to narrow arteries

  • Involuntary (smooth) muscle
  • Actin and myosin
  • Cardiac

3. Step 4 (Operation of the Neuromuscular Junction)

  • Ca2+ binds to proteins in the muscle, which leads to contraction. Acetylcholine is recycled by acetylcholineesterase so that contraction only occurs when impulsed arrive continuously
  • T tubules channel the action potential into the cell, towards the sarcoplasmic reticulum, this organelle releases stored Ca2+ ions into cell cytoplasm in response to depolarisation
  • The post synaptic membrane depolarises, if the threshold potential is reached an action potential is generated, this travels along the muscle cell membrane and into special structures called T tubules
  • ATP arriving at motor neurone causes calcium channels to open, Ca2+ ions flood into the cell

4. Slow twitch muscle fibres in skeletal muscle are used during endurance activities because they contract slowly and can work for long periods of time, they have a large number of

  • Mitochondria, a high concentration of myoglobin (basically haemoglobin) and an excellent blood supply (so sometimes called red fibres)
  • Sarcomeres and mesosomes

5. The location of this muscle is in the walls of the intestine, when it contracts this is known as peristalsis

  • Involuntary (smooth) muscle
  • Cardiac
  • Voluntary


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