A cell may have hundreds of dendrites, but may have only one axon. The dendrites carry signals from other neurons into the soma, and the axon carries a single signal from the soma to the next neuron or to a muscle fiber.
A dendrite from one neuron and an axon from another neuron meet at a synapse, which is a very narrow gap between the two cells. When electrical impulses reach the end of an axon, they trigger the release of chemicals called neurotransmitters. These chemicals cross the synapse to the dendrite, where they trigger the flow of ions into or out of the cell.
The movement of the charged ions in the dendrite causes an electrical current, which spreads to the soma briefly before being restored to normal.
If the dendrites get lots of signals from axons, then it sets off a chain reaction. The chain reaction is a strong electrical current called an action potential that flows down the axon to the next synapse.
Fully differentiated neurons do not divide. However, stem cells in the adult brain may regenerate functional neurons throughout the life of an organism. Generally, once born, neurons do not divide. Many will live the whole lifetime of the animal.
References[change | change source]
- Chudler EH. "Brain Facts and Figures". Neuroscience for Kids. Retrieved 2009-06-20.
- Herrup K, Yang Y (May 2007). "Cell cycle regulation in the postmitotic neuron: oxymoron or new biology?". Nature Reviews. Neuroscience. 8 (5): 368–78. doi:10.1038/nrn2124. PMID 17453017.
- Gilbert, Scott F.; College, Swarthmore; Helsinki, the University of (2014). Developmental biology (Tenth ed.). Sunderland, Mass.: Sinauer. ISBN 978-0878939787.