Generation and Conduction of Nerve Impulses

Before an impulse can travel, the axon has to be electrically 'primed' by an uneven distribution of ions across its membrane. Inside the axon, the cytoplasm (the intracellular fluid, ICF) is rich in potassium and magnesium phosphate along with negatively charged proteins and other organic molecules. Outside the axolemma, the extracellular fluid (ECF) is rich instead in sodium chloride, along with bicarbonates, nutrients and oxygen the cell needs, and it carries away carbon dioxide and metabolic waste. This asymmetry — potassium-rich inside, sodium-rich outside — is what creates the electrical potential that a nerve impulse rides on, and it is maintained by specific membrane proteins that act as ion channels, regulating exactly which ions are allowed to cross and when. …