Muscular System, Skeletal Muscle
The junction between the terminal of a motor neuron and a muscle fiber is called the neuromuscular junction. It is simply one kind of synapse. (The neuromuscular junction is also called the myoneural junction.)
Osmosis is the diffusion of water down its concentration gradient. Normally one thinks of water as the solvent, and focuses on the concentration of the solutes, but water itself has a concentration in any solution.