The myelin sheath is a critical fatty insulation surrounding many neurons in the nervous system. Its primary function is to increase the speed of action potentials along the axon through a process called saltatory conduction, where the impulse jumps between gaps known as nodes of Ranvier. This efficient transmission enables rapid communication between the brain and body, facilitating reflexes and coordinated movements. Damage to the myelin sheath can lead to neurological disorders, such as multiple sclerosis.