The myelin sheath is an insulating layer of fatty material, composed of schwann cells that are wrapped tightly around the neuron
Sodium and potassium ions can't diffuse through the layer of Schwann cells, but in between the Schwann cells, there are the nodes of Ranvier.
Ionic movements that create action potentials cant occur over much fo the length of the neuron due to the thick layer of schwann cells, they only occur in the Nodes of Ranvier.
In myelinated neurons, the local currents are therefore elongated and sodium ions diffuse along the neuron from one node of Ranvier to the next; meaning that the action potential appears to jump between nodes, also known as saltatory conduction.
the myelin sheath means that action potentials can only occur at the nodes of Ranvier. Effectively, the action potential jumps between the nodes. This speeds up the transmission of the action potential along the neuron. Myelinated neurons will conduct action potential more quickly.
