Synaptic vesicles of somatic neurons contain Multiple ChoiceAcetylcholinePredominately calcium ionsStored cholinePredominately sodium ions

The correct answer is Acetylcholine.

Explanation:

1. Synaptic Vesicles Function: Synaptic vesicles are small membrane-bound structures in neurons that store neurotransmitters, which are chemicals used for communication between neurons.

2. Role of Acetylcholine: In somatic (voluntary) neurons, the primary neurotransmitter is acetylcholine (ACh). When an action potential reaches the axon terminals, these vesicles fuse with the presynaptic membrane and release ACh into the synaptic cleft.

3. Calcium Ions: Calcium ions (Ca²⁺) play a crucial role in the release of neurotransmitters from vesicles but are not stored in synaptic vesicles; rather, they enter the neuron from the extracellular space when the action potential arrives.

4. Stored Choline and Sodium Ions: Choline is a precursor to ACh but is not stored in vesicles. Sodium ions are crucial for action potentials and other cellular processes but are not the contents of synaptic vesicles.

Thus, synaptic vesicles of somatic neurons specifically contain acetylcholine.