Final answer:
Myelin increases the speed of electrical conduction between neurons by insulating axons and facilitating the efficient transmission of nerve impulses through the creation of a myelin sheath.
Step-by-step explanation:
Myelin functions by insulating the axons of many neurons, which results in the faster transmission of electrical signals. This insulation is crucial for the efficient conduction of nerve impulses. The myelin sheath is a lipid-rich layer formed by oligodendrocytes in the CNS and Schwann cells in the PNS, which wraps around the axon, leaving gaps known as Nodes of Ranvier.
These nodes allow nerve impulses to jump from one node to the next, increasing the speed of neural transmission and preventing the electrical signal from dissipating as it travels down the axon. Disorders that lead to a reduction of myelin, such as PKU and multiple sclerosis, can cause serious impairments including cognitive deficits and loss of motor control. Contrary to option b, myelin does not decrease but rather increases the speed of electrical conduction between neurons.