which components of cells are physically connected by a gap junction
Gap junction Gap junctions are a specialized intercellular connection between a multitude of animal cell-types.[1][2][3] They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.[4][5]
Neuromuscular junction The neuromuscular junction is where a neuron activates a muscle to contract. Upon the arrival of an action potential at the presynaptic neuron terminal, voltage-dependent calcium channels open and Ca2+ ions flow from the extracellular fluid into the presynaptic neuron's cytosol. This influx of Ca2+ causes neurotransmitter-containing vesicles to dock and fuse to the presynaptic neuron's cell membrane through SNARE proteins. Fusion of the vesicular membrane with the presynaptic cell membrane results in the emptying of the vesicle's contents (acetylcholine) into the synaptic cleft, a process known as exocytosis. Acetylcholine diffuses into the synaptic cleft and can bind to the nicotinic acetylcholine receptors on the motor endplate.