Neurons and Glial Cells

A neuron's odd shape is the whole point. Dendrites branch out like antennae to catch incoming signals from other neurons. Those signals pool in the cell body, which houses the nucleus and decides whether to pass the message on. If the input is strong enough, an electrical signal called an action potential fires down the axon, a long single fiber, toward the axon terminals at the far end. The terminals release neurotransmitters into the synapse, the gap to the next neuron. This one-way layout, dendrite to cell body to axon to terminal, keeps information flowing in a consistent direction through a circuit instead of sloshing back and forth.

Speed matters, so many axons are wrapped in myelin, a fatty sheath made by glial cells. Myelin is not continuous; it comes in segments with small gaps between them called nodes of Ranvier. Instead of the signal crawling down every inch of membrane, it jumps from node to node, a much faster process called saltatory conduction. This is why thicker, more myelinated axons conduct signals faster than bare ones.

Glial cells get mistaken for passive packing material, but they do real work: supplying neurons with nutrients, forming and maintaining myelin, clearing away waste and dead cells, and helping regulate activity at synapses. This matters directly for disease: in multiple sclerosis, the immune system attacks myelin itself, so signals that once leapt quickly between nodes now travel slowly and unreliably, producing the numbness, weakness, and coordination problems seen in the disorder.