The odor of a smelly shower drain can be eliminated by removing debris from the drain. Discarding the odor-causing material in the garbage outside the home ensures the smell does not invade other areas. Boiling water dissolves oils and grease deposited on the sides of the pipe in the drain, which add to the smell.
Luckily for us, Nernst derived an equation that allows us to determine at what point the two forces (chemical and electrical gradients) balance each other - in other words, at what point we have an ionic equilibrium.
This is a region where, in each nephron, the distal convoluted tubule touches the afferent arteriole. The juxtaglomerular cells are part of the afferent arteriole and the macula densa is part of the distal tubule. Renin is secreted from the JG cells and is important in regulating systemic blood pressure.