The neuromuscular junction and the sliding filament model

Overview

How an impulse crosses to the sarcolemma, the calcium ions that expose the binding sites, cross-bridge formation and the power stroke, and the ATP and creatine phosphate that supply it.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a neuromuscular junction?

   Model answer

   The synapse between a motor neurone and a muscle fibre.

2. 2

   What happens when an action potential arrives at the motor neurone terminal at a neuromuscular junction?

   Model answer

   Calcium ions enter the terminal.

3. 3

   What causes vesicles to release acetylcholine at the neuromuscular junction?

   Model answer

   Calcium ions entering the motor neurone terminal cause vesicles to fuse with the membrane and release acetylcholine.

4. 4

   What happens when acetylcholine binds to receptors on the sarcolemma?

   Model answer

   Sodium ions enter the muscle fibre, causing depolarisation.

5. 5

   How does the action potential spread through the muscle fibre after depolarisation of the sarcolemma?

   Model answer

   The action potential spreads along the sarcolemma and into the T-tubules.

6. 6

   Explain the sliding filament model of muscle contraction.

   Model answer

   Actin filaments slide over myosin filaments, shortening the sarcomere without the filaments themselves changing length.

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