Final answer:
High neural Ach at a neuromuscular junction is characterized by axon terminals as the presynaptic element, acetylcholine as the neurotransmitter, and acetylcholinesterase in eliminating the neurotransmitter, all crucial for synaptic transmission.
Step-by-step explanation:
Three characteristics exhibited by a high neural Ach (acetylcholine) at a neuromuscular junction (NMJ) include the presence of axon terminals of the motor neuron as the presynaptic element, the use of acetylcholine as the neurotransmitter, and the role of acetylcholinesterase in eliminating the neurotransmitter. Furthermore, the synaptic cleft is the space between the presynaptic and postsynaptic elements where acetylcholine diffuses, and the postsynaptic receptor protein is the nicotinic acetylcholine receptor located on the sarcolemma of the muscle cell. These characteristics are crucial for the proper functioning of synaptic transmission, enabling muscle contraction and various neural communications.