Nerves transmit signals throughout the body via a combination of electrical and chemical processes. Signals begin at the dendrites, travel to the cell body, and then down the axon. This process is described in detail below.
The Journey of a Nerve Signal
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From Dendrites to Axon: The nerve impulse starts at the dendrites, branching extensions of a neuron. The impulse then travels to the neuron's cell body, where it's processed. Finally, the signal continues down the axon, a long, slender projection of the neuron. This electrical signal is remarkably fast; some nerve signals approach speeds of 300 miles per hour. [Caltech research on high-speed camera capturing nerve signals].
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Signal Transmission Across Synapses: When the signal reaches the end of an axon, it encounters a synapse – a gap between two neurons. Transmission across this gap isn't electrical, but chemical. A chemical transmitter substance carries the signal to the next neuron, triggering electrical stimulation and continuing the impulse. [Reference on neurone impulse conduction via chemical transmitter].
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Nerve Bundles: Smaller nerves often group together to form larger, rope-like bundles that travel throughout the body. These bundles, called peripheral nerves, extend from the spinal cord and brain to supply various parts of the body. [The Hand Society on upper extremity nerves]. Examples of these pathways include nerves traveling to the hand and arm (median nerve in carpal tunnel syndrome), or nerves in the brain stem traveling to the eye. [Mayo Clinic on pinched nerves, NCBI on cranial nerves].
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Sensory and Motor Nerves: Nerves are specialized in transmitting signals. Peripheral nerves, those traveling from the brain and spinal cord, can be sensory (carrying information to the brain) or motor (carrying signals from the brain to muscles). All nerves transmit signals, with some transmitting pain signals. [Cleveland Clinic on nerves and function; Elizabeth Rogers PT on nerve function].
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Measuring Nerve Signal Speed: The speed of nerve signals can be measured using nerve conduction studies. This involves placing electrodes along a nerve to measure the time it takes for an electrical impulse to travel between them. This measurement helps diagnose nerve disorders. [Johns Hopkins Medicine on nerve conduction studies].
Examples of Nerve Pathways
- Auditory Nerve: This nerve carries sound signals from the ear to the brain. [NIDCD on how we hear].
- Median Nerve: In the wrist, the median nerve can be compressed, causing carpal tunnel syndrome. [AAOS on carpal tunnel syndrome].
- Cranial Nerves: These nerves originate directly from the brain and travel to various parts of the head and neck. [NCBI on cranial nerves].
