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How do neurons transmit information through the nervous system?
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Physiology
Adenosine triphosphate (ATP) is the power source of many biochemical reactions. It is produced in the cell structures and system listed at the left to energize the important life processes listed on the right. An abbreviated chemical formula of the structure of ATP is also shown. The two high-energy P―O―P bonds are responsible for its power.
Neurons transmit information through the nervous system using a combination of electrical and chemical signals.12
Transmission Within the Neuron
Information travels along a single neuron as an electrical impulse known as an action potential. This impulse is generated at the axon hillock and propagates down the axon like a wave of depolarization and repolarization. In many vertebrates, this process is accelerated by myelin, an insulating layer that allows the impulse to jump between nodes of Ranvier in a process called saltatory conduction. Because action potentials do not vary in size, the nervous system encodes information through the frequency and number of impulses fired.341
Transmission Between Cells
When an impulse reaches the axon terminal, it must cross the synapse to reach the next cell:35
- Chemical Transmission: This is the most common method. The arrival of an action potential triggers the influx of calcium ions, causing synaptic vesicles to release neurotransmitters into the synaptic cleft via exocytosis. These chemicals bind to receptors on the postsynaptic membrane, potentially triggering a new action potential.653
- Electrical Transmission: In some cases, cells are connected by gap junctions, allowing ionic current to flow directly between neurons for faster, synchronized communication.35