1. The action potential propagates through axon and reaches to the nerve termina
ID: 63073 • Letter: 1
Question
1. The action potential propagates through axon and reaches to the nerve terminal of motor neuron. It opens __________________ channels.
2. ________________ ions moves (into / out) of the nerve terminal, and this triggers vesicular fusion (you will learn this mechanism more in detail in Ch. 15!).
3. Neurotransmitter, ___________________, will be released from the nerve terminal, and it will bind to __________________ receptor on skeletal muscle cells (at neuromuscular junction).
4. This receptor is a ____________-gated _________________ channel. The movement of _____________ ion (into / out) of the cytosol will occur when the channel opens, and the membrane potential around the channel will be _____________________.
5. This change in the membrane potential opens neighboring ___________________ channels and ____________________ will propagate along with the plasma membrane.
6. When it reaches to ____________________, which are invagination of plasma membrane into myofibrils, it opens ____________________ channels.
7. This leads to the movement of ______________ ion (into / out) of the cytosol. In the cytosol, this ion will bind to ________________________ channels on _______________________ to release more ______________ ions to the cytosol. This wave of ______________ ions released from ________________________ throughout the myofibrils will initiate muscle contraction by the following processes.
8. ________________ ion will bind to _________________, which then causes a conformational change of _______________________, a filamentous structure associated with actin filaments. This change exposes ____________________________ of actin filaments.
9. __________________ now can bind to actin filament, and muscle contraction occurs.
10. _______________ ion will be quickly taken up by _______________________ (Ch. 12!) expressed on ______________________ membrane to terminate skeletal muscle contraction.
Explanation / Answer
1. Sodium channels
2. Calcium ions moves into
3. Acetyl choline, acetyl choline receptor
4. Ligand gated, Ion channel. Sodium ion; raised
5. Sodium channels; membrane potential
6. Synapse; calcium
7. This leads to the movement of calcium ion (into) of the cytosol. In the cytosol, this ion will bind to ion gated calcium channels on the sarcoplasmic reticulum to release more calcium ions to the cytosol. This wave of calcium ions released from the sarcoplasmic reticulum throughout the myofibrils will initiate muscle contraction by the following processes.
8. Calcium ion will bind to trophonin, which then causes a conformational change of tropomyosin, a filamentous structure associated with actin filaments. This exchange exposes myosin binding sites of actin filaments.
9. Myosin can now bind to actin filament, and muscle contraction occurs.
10. Calcium ion will be quickly taken up by calcium gates expressed on the sarcoplasmic reticulum membrane to terminate skeletal muscle contraction.
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