Which of the following best describes the role of calcium (\(\mathrm{Ca^{2+}}\)) in synaptic activity?

• A. It directly binds to neurotransmitters to activate postsynaptic receptors.
• B. It triggers the fusion of synaptic vesicles with the presynaptic membrane, leading to neurotransmitter release.
• C. It degrades neurotransmitters in the synaptic cleft.
• D. It inhibits the generation of action potentials in the presynaptic neuron.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the context of the problem. The question is about the role of calcium ions (\(\mathrm{Ca^{2+}}\)) in synaptic activity, which is a key process in neuronal communication.
2. Step 2: Recall the process of synaptic transmission. When an action potential reaches the presynaptic terminal, voltage-gated calcium channels open, allowing \(\mathrm{Ca^{2+}}\) to enter the presynaptic neuron.
3. Step 3: Recognize the role of \(\mathrm{Ca^{2+}}\) in triggering synaptic vesicle fusion. The influx of \(\mathrm{Ca^{2+}}\) binds to specific proteins (e.g., synaptotagmin) on the synaptic vesicles, which facilitates their fusion with the presynaptic membrane.
4. Step 4: Understand the result of vesicle fusion. This fusion releases neurotransmitters into the synaptic cleft, where they can bind to receptors on the postsynaptic membrane to propagate the signal.
5. Step 5: Eliminate incorrect options. \(\mathrm{Ca^{2+}}\) does not directly bind to neurotransmitters, degrade them, or inhibit action potentials. Its primary role is to trigger vesicle fusion and neurotransmitter release.