medical student was doing research in a laboratory that studiesthe neuromuscular junction. Which of the following events atthe junction are listed in correct sequential order?A. Motor neuron action potential, acetylcholine release, Na+entry at the endplateB. Ca2+ entry into the motor nerve terminal, Na+ entry at theendplate, muscle fiber action potentialC. Na+ entry at the endplate, acetylcholine release, muscle fiberaction potentialD. Motor neuron action potential, Na+ entry at the endplate,formation of an endplate potentialE. Ca2+ entry into the motor nerve terminal, acetylcholinerelease, Na+ entry at the endplate
Question
medical student was doing research in a laboratory that studiesthe neuromuscular junction. Which of the following events atthe junction are listed in correct sequential order?A. Motor neuron action potential, acetylcholine release, Na+entry at the endplateB. Ca2+ entry into the motor nerve terminal, Na+ entry at theendplate, muscle fiber action potentialC. Na+ entry at the endplate, acetylcholine release, muscle fiberaction potentialD. Motor neuron action potential, Na+ entry at the endplate,formation of an endplate potentialE. Ca2+ entry into the motor nerve terminal, acetylcholinerelease, Na+ entry at the endplate
Solution
To determine the correct sequential order of events at the neuromuscular junction, let's break down the process step by step:
- Motor neuron action potential: An action potential travels down the motor neuron to the nerve terminal.
- Ca2+ entry into the motor nerve terminal: The action potential causes voltage-gated calcium channels to open, allowing Ca2+ to enter the nerve terminal.
- Acetylcholine release: The influx of Ca2+ triggers the synaptic vesicles to release acetylcholine (ACh) into the synaptic cleft.
- Na+ entry at the endplate: Acetylcholine binds to receptors on the muscle endplate, causing Na+ channels to open and Na+ to enter the muscle cell.
- Muscle fiber action potential: The influx of Na+ generates an endplate potential, which, if strong enough, will trigger an action potential in the muscle fiber.
Now, let's match these steps to the options provided:
A. Motor neuron action potential, acetylcholine release, Na+ entry at the endplate
- This option skips the Ca2+ entry into the motor nerve terminal, so it is incorrect.
B. Ca2+ entry into the motor nerve terminal, Na+ entry at the endplate, muscle fiber action potential
- This option skips the motor neuron action potential and acetylcholine release, so it is incorrect.
C. Na+ entry at the endplate, acetylcholine release, muscle fiber action potential
- This option has the events out of order, so it is incorrect.
D. Motor neuron action potential, Na+ entry at the endplate, formation of an endplate potential
- This option skips the Ca2+ entry into the motor nerve terminal and acetylcholine release, so it is incorrect.
E. Ca2+ entry into the motor nerve terminal, acetylcholine release, Na+ entry at the endplate
- This option correctly follows the sequence of events after the motor neuron action potential.
Therefore, the correct answer is:
E. Ca2+ entry into the motor nerve terminal, acetylcholine release, Na+ entry at the endplate
Similar Questions
Put the steps involved in muscle contraction in the correct chronological order after an action potential arrives at the motor neuron axon terminal:
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