What is the fatty protein layer that covers some axons and increases the speed of transmission?

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The speed of neural signaling depends on insulating the axon with a fatty sheath called myelin. This sheath, produced by glial cells (oligodendrocytes in the brain and spinal cord, Schwann cells in the peripheral nerves), wraps around the axon in segments with gaps called nodes of Ranvier. The fatty, lipid-rich insulation allows electrical impulses to jump from node to node in a process called saltatory conduction, so the signal travels much faster without having to depolarize every point along the membrane. The myelin sheath is essential for rapid transmission; when it’s damaged, as in demyelinating diseases like multiple sclerosis, conduction slows or fails. In contrast, the soma is the cell body, dendrites are inputs that receive signals, and neurotransmitters are the chemical messengers released at synapses.