Final answer:
The propagation of electric impulses along the axon membrane is caused by the alternation of ion channels opening and closing, allowing the movement of Na+ and K+ ions. This process leads to the creation and spreading of action potentials along the cell membrane.
Step-by-step explanation:
The propagation of electric impulses is caused by ion currents through the axon membrane, resulting from the alternation of opening and closing of ion channels such as Na+ and K+. When a stimulus triggers an action potential in one location, adjacent membranes change their permeability leading to another action potential. This process continues, causing the action potential to move slowly along the cell membrane. The movement of Na+ and K+ across the membrane during this process is equivalent to a wave of charge moving along the inside and outside of the membrane.