Explain how the nerve impulse passes along the neuron

Resting membrane potential of a neuron is maintained by active transport of sodium (Na+) out of the cell and potassium (K+) into the cell through the Na+/K+ pump. Due to the negative charge of Cl- and some amino acids located intracellularly, the charge is negative on the inside of the cell and positive on the outside, creating a concentration gradient that builds up the electrical potential (measured in millivolt).

The incoming nerve impulse from the presynaptic neurons caused the opening of first Na+ channels but needs to reach threshold level to create an action potential. A wave of Na+ channels opens to let ions diffuse into the neuron down the axon. This causes the membrane to depolarize. In response, K+ ions diffuse out of the cell through ion channels to repolarise the membrane, creating a 2-stage action potential. The nerve impulse will reach the axon terminal and cause to initiate another action potential in the next neuron. Myelinated axons carry the action potential faster than unmyelinated axons due to its insulation effects on the current. Soon after the passage of the action potential, the active transport of ions is reactivated to return to the resting membrane potential.