7 Steps of Neuromuscular Junction Study Guide

Question 1

1

Answer 1

1. Action potential arrives at the axon terminal

Question 2

2

Answer 2

2. Voltage-gated Ca2+ channels open; Ca2+ ions enter the motor neuron

Question 3

3

Answer 3

3. Entry of Ca2+ ions causes release of ACh into synaptic cleft via exocytosis

Question 4

4

Answer 4

4. ACh diffuses across the synaptic cleft to ACh receptors in the junctional folds

Question 4

5

Answer 4

5. ACh binding opens chemically gated ion channels

Question 4

6

Answer 4

6. Na+ enters and K+ exit muscle fiber. Net movement of Na+ in creates local change in membrane potential/end plate potential

Question 4

7

Answer 4

7. Once the membrane potential hits a threshold value (about -55mV), an unstoppable action potential propagates along the sarcolemma
   - (then ACh is degraded by acetylcholinesterase and diffuses away from the junction, stopping neural transmission to the muscle fiber)