Final answer:
The neurotransmitter you would expect to find in the synaptic vesicle of a motor neuron that communicates with a muscle cell is Acetylcholine (ACh), which is released upon an action potential reaching the neuron's synaptic terminal and causes muscle contraction.
Step-by-step explanation:
If the receiving cell is a muscle cell, the neurotransmitter that you would expect to find in the synaptic vesicle is Acetylcholine (ACh). This neurotransmitter facilitates communication between nerves and muscles at the neuromuscular junction. When an action potential reaches the synaptic terminal of a motor neuron, it triggers the release of ACh into the synaptic cleft.
The released ACh diffuses across the cleft and binds to ACh receptors on the motor end plate of the muscle cell, which are actually ion channels for sodium (Na+). This binding opens the ion channels, allowing Na+ ions to enter the muscle cell, leading to depolarization and the initiation of an action potential that causes the muscle to contract. The entire process of neurotransmitter release, binding, and muscle cell response is dependent on the presence of calcium (Ca2+), which is essential for the synaptic vesicles to fuse with the presynaptic membrane and release their ACh content.