The following are events in the transmission of a signal at a chemical synapse.

Neurotransmitter binds with receptors associated with the postsynaptic membrane.
Calcium ions rush into neuron's cytoplasm.
An action potential depolarizes the membrane of the presynaptic axon terminal.
The ligand-gated ion channels open.
The synaptic vesicles release neurotransmitter into the synaptic cleft.

Which sequence of events is correct?

Question

The following are events in the transmission of a signal at a chemical synapse.

Neurotransmitter binds with receptors associated with the postsynaptic membrane.
Calcium ions rush into neuron's cytoplasm.
An action potential depolarizes the membrane of the presynaptic axon terminal.
The ligand-gated ion channels open.
The synaptic vesicles release neurotransmitter into the synaptic cleft.

Which sequence of events is correct?

BlackTom AI · Accepted Answer

To determine the correct sequence, I’ll map each event to its place in the classic chemical synapse transmission sequence and then compare the options.
Option A: 2 → 3 → 5 → 4 → 1
This suggests calcium influx occurs before the action potential depolarizes the presynaptic membrane. Biophysically, calcium entry is triggered by depolarization via voltage-gated calcium channels, so this ordering is incorrect.
Option B: 4 → 3 → 1 → 2 → 5
Here, ligand-gated channels opening is placed before the action potential and before vesicle release. In reality, postsynaptic receptor activation (ligand-gated channels opening) depends on neurotransmitter release, which requires vesicle fusion after Ca2+ influx; so this sequence misplaces the trigger for postsynaptic effects.
Option C: 3 → 2 → 5 → 1 → 4
This sequence starts with the presynaptic membrane depolarization (action potential, 3), followed by Ca2+ influx (2), then vesicle fusion and neurotransmitter release (5), then neurotransmitter binding to postsynaptic receptors (1), and finally ligand-gated channels opening (4). This aligns with the established order: depolarization → Ca2+ entry → vesicle exocytosis → transmitter-receptor binding → postsynaptic channel opening.
Option D: 1 → 2 → 3 → 4 → 5
This places neurotransmitter binding to receptors before depolarization and Ca2+ entry, and even before vesicle release, which cannot occur without the presynaptic action potential and Ca2+ influx. It contradictions the causal sequence of synaptic transmission.
In summary, the only option that preserves the causal dependencies—depolarization triggering Ca2+ influx, which triggers vesicle release, which leads to transmitter binding and subsequent receptor channel opening—is 3 → 2 → 5 → 1 → 4. Thus, option C is the correct sequence. The other options fail because they invert or misplace key causal steps such as Ca2+ entry, vesicle fusion, or transmitter-receptor interaction relative to the triggering action potential and vesicle release.

Bio 93 Section CDE 2025 Final Exam Practice, Part 1

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Bio 93 Section CDE 2025 Final Exam Practice, Part 1

查看解析

登录即可查看完整答案

类似问题

Which of the following explains why one-way synaptic transmission occurs?

Question at position 3 Select all the ways a neurotransmitter can exit the space between neurons.DiffusionReuptake/recyclingAxon travelEnzymes will digest the neurotransmitter.Immune cells will attack.

At a synapse between two neurons, the dendrites release the neurotransmitters.

Consider a neuron-neuron synapse. Match the description with the presynaptic or postsynaptic neuron. 1: Action potential travels away from the synapse via this neuron. ____ 2: First in the chain of neurons. ____ 3: Second in the chain of neurons. ____ 4: Releases neurotransmitter. ____

The theory of quantal mechanism of neurotransmission was based on electrophysiology providing evidence for quantal activity in synaptic transmission combined with electron microscopy revealing vesicles near terminal boutons.

Which of the following is the correct sequence of events that occur during synaptic transmission?

What accounts for the longest delay in neuronal signalling?

What accounts for the longest delay in neuronal signalling?

更多留学生实用工具

希望你的学习变得更简单

Consider a neuron-neuron synapse. Match the description with the presynaptic or postsynaptic neuron. 1: Action potential travels away from the synapse via this neuron. 2: First in the chain of neurons. 3: Second in the chain of neurons. 4: Releases neurotransmitter.