Axon

What is an Axon?

An axon is a long, thin part of a nerve cell, also called a neuron. You can find axons in most animals. Their main job is to carry electrical signals away from the nerve cell body. These signals travel to other neurons, muscles, and glands. This helps the body send messages quickly.

Axons are different from another part of the neuron called a dendrite. Dendrites receive signals, while axons send them out. Axons can be very long and often branch out to connect with many other cells. In some neurons, there are special branches at the ends of axons called telodendria. The swollen tips are known as axon terminals. These tips connect with other neurons to form important junctions called synapses.

Axons are covered by a special membrane called an axolemma. The inside of the axon is filled with a substance called axoplasm. In the human brain, bundles of axons form important pathways, like the corpus callosum. These pathways help different parts of the brain communicate.

How Axons Work

Axons can be very small, like one millimeter, or as long as a meter in some animals. In humans, the longest axons connect the spinal cord to the toes. Axons can be thin, about one micrometer wide, or thick like a pencil lead in some sea animals.

There are two main types of axons: those with a fatty coating called myelin and those without. Myelin helps speed up the messages and is made by special supporting cells. The spaces between myelin sections are called nodes of Ranvier, where the message jumps from one node to the next, making the signal travel faster.

At the end of axons are tiny branches called telodendria, which connect to other cells to pass on the message. These endings store special chemicals called neurotransmitters that help cells talk to each other.

Growing Axons

Axons grow to reach their target during the development of the nervous system. Neurons first create several similar parts, but only one becomes the axon. If an unfinished axon is cut, the longest part can become the new axon.

Growing axons move using a special tip called the growth cone, which helps them explore. These axons need sticky surfaces to grow on, provided by special molecules. Even if axons are damaged, they can regrow if the main cell part stays healthy.