The figure below shows the two main families of acetylcholine receptors: muscarinic and nicotinic. In structural terms, muscarinic receptors are G-coupled protein receptors, while nicotinic receptors are ligand-gated ion channels. They can be found on both sides of the synaptic cleft (presynaptic and postsynaptic).
After the pressure drops below 40 psi, the electrical switch turns on the pump and the pressure in the tank increases. Any failure in any component or loss of electricity can cause a well to suddenly stop producing water when a faucet is turned on.
While water intoxication is rare, it can happen if you drink too much water too quickly. Drinking a gallon of water is safe if you spread it out throughout the day, but if you consume it in less than an hour, you risk getting water intoxication, which can be deadly. Water intoxication can happen with levels as low as 3 liters, a little less than a gallon, per hour.