Question

Please place in the correct chronological order the following events that occur at the neuromuscular junction.

Action potential propagates to the terminal end (buton) of the axon
Ions (mostly Na+) diffuse into the muscle cell causing a local (or graded) potential to occur at the motor end plate
2 Ach molecules bind their receptor on the post-synaptic membrane causing a conformational change in this protein that opens a cation channel
End-plate potential depolarizes the adjacent sarcolemma to threshold and a new action potential is generated on the muscle cell membrane
AP on axonal membrane opens voltage-gated Ca channels allowing Calcium to diffuse INTO the axon.
Acetylcholine-filled secretory vesicles migrate to the pre-synaptic membrane and Ach is released into synaptic cleft by exocytosis
Ach diffuses across the synaptic cleft; most is degraded by acetylcholinesterase
a) 1, 2, 3, 4, 5, 6, 7
b) 5, 6, 2, 1, 3, 7, 4
c) 2, 6, 1, 5, 3, 7, 4
d) 1, 5, 2, 6, 3, 7, 4

Answer 1

The correct chronological order of events at the neuromuscular junction: Action potential, Calcium channels open, Ach release and diffusion, Ach binding, Ions diffuse, Ach binding and channel opening, End-plate potential and muscle cell action potential.

Step-by-step explanation:

The correct chronological order of events that occur at the neuromuscular junction is:

1. Action potential propagates to the terminal end (buton) of the axon
2. AP on axonal membrane opens voltage-gated Ca channels allowing Calcium to diffuse INTO the axon
3. Acetylcholine-filled secretory vesicles migrate to the pre-synaptic membrane and Ach is released into synaptic cleft by exocytosis
4. Ach diffuses across the synaptic cleft; most is degraded by acetylcholinesterase
5. Ions (mostly Na+) diffuse into the muscle cell causing a local (or graded) potential to occur at the motor end plate
6. 2 Ach molecules bind their receptor on the post-synaptic membrane causing a conformational change in this protein that opens a cation channel
7. End-plate potential depolarizes the adjacent sarcolemma to threshold and a new action potential is generated on the muscle cell membrane