Synaptic vesicles of somatic neurons contain Multiple ChoiceStored cholineAcetylcholinePredominately sodium ionsPredominately calcium ions

To answer the question regarding the contents of synaptic vesicles in somatic neurons, let’s analyze the options provided:

1. Stored choline: While choline is a precursor for the synthesis of acetylcholine, it is not the primary substance contained within synaptic vesicles.

2. Acetylcholine: This is the primary neurotransmitter stored in the synaptic vesicles of somatic motor neurons. Acetylcholine plays a critical role in transmitting signals from neurons to muscle cells, facilitating muscle contraction.

3. Predominantly sodium ions: Sodium ions are involved in generating action potentials and neuronal signaling; however, they are not stored in synaptic vesicles.

4. Predominantly calcium ions: Calcium ions are crucial for triggering the release of neurotransmitters from synaptic vesicles upon the arrival of an action potential, but they are not stored in the vesicles.

Given this analysis, the correct answer from the options provided is Acetylcholine. This neurotransmitter is essential for communication between neurons and muscles at the neuromuscular junction.