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Question: How does the nervous system travel signals so quickly to different parts of your body?
Your nervous system is made of nerve cells called neurons, which are the basic working units naturally designed to transmit information to other nerve and non-nerve cells. A typical neuron has three parts: a cell body, dendrites, and an axon. The axon is a thin and fiber-like structure that starts from the cell body and ends at its nerve terminal called synapse. The axon is also called nerve fiber. The synapse is the place where information transfers between two neurons. The term synapse is a Greek word for "juncture". Dendrites are tree-like structures that extend from the cell body. The dendrite has the ability to receive information from or send to other cells. Thus, information can travel either from one neuron to another through the synapse and the dendrite or from one part of the neuron to the other part through the axon.
Let us take pain signaling as an example. When your finger is prickled by a thorn, you feel a prickling pain and quickly pull your hand away. This whole process involves many steps of transmitting signals through your nerve system. First, the broken skin tissue releases "pain" molecules that interact with the "pain" receptors at the end of the neuron. Such interaction generates an electric signal. Scientists call the signal an "action potential". The action potential then moves along the nerve fiber up to the cell body that locates in your spinal core, where the signal moves to another neuron that connects the spinal core with the motor and sensory areas of the your brain. Once your brain receives and processes the "pain" signal, it decides to move your hand away from the thorn. To accomplish this action, the brain generates a new signal. This signal then travels down to the spinal core where the signal continues traveling down along another neuron to the muscle cells. Finally, your muscle contracts and your finger moves away from the thorn.
The fastest speed of signaling in the nerve system can be more than 200 miles per hour and the lowest speed of signaling can be about 2 miles per hour. The traveling speed of a nervous signal mainly depends on the structure of the nerve fiber. This is very similar to an internet connection, whose speeds are based on the wiring material between your home and the service provider. Usually, the neurons that are involved in muscle position signaling have a nerve fiber structure suitable for the high speed of signaling (similar to the high speed internet connection); the neurons that are involved in chronic pain signaling have a nerve fiber structure for the low speed of signaling (similar to the low speed internet connection). The pathway for the prickling (acute) pain has the neurons that transmit signaling between these two extreme cases.
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