Six events lead to the contraction of a skeletal muscle fibre…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Six events lead to the contraction of a skeletal muscle fibre. They are listed here in a mixed order.
- Calcium ions bind to troponin.
- An action potential is made in the sarcolemma.
- A neural signal reaches the neuromuscular junction.
- Calcium ions are released from the sarcoplasmic reticulum.
- Acetylcholine is released.
- The active sites on the actin are uncovered.
Write the letters in the right order.
Need a reminder? The key ideaShow
The signal goes from the central nervous system along a motor neuron to the neuromuscular junction. Acetylcholine makes an action potential in the sarcolemma, which spreads through the fibre and releases Ca from the sarcoplasmic reticulum. The calcium binds to troponin and unmasks the sites on the actin. A motor unit is a motor neuron with all the fibres that it supplies.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Six events.
Plan. Follow the signal from the nerve to the thin filament.
Step 1. The neural signal reaches the junction: (c).
Step 2. The neuron releases acetylcholine: (e).
Step 3. An action potential is made in the sarcolemma: (b).
Step 4. Calcium ions come out of the sarcoplasmic reticulum: (d).
Step 5. They bind to troponin: (a).
Step 6. The sites on the actin are uncovered: (f).
Answer: (c), (e), (b), (d), (a), (f).
Check. The order goes from the nerve, across the junction, along the membrane, to the store of calcium, and then to the thin filament.
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