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The nervous system is the body’s intricate wiring network, translating sensations—touch, light, smell, sound—into electrical impulses that the brain interprets. The brain then orchestrates responses, managing everything from heart rate to voluntary movements. The speed and efficiency of these signals are governed by the conductivity of nerve cells.
While nerves spread throughout the body, the central nervous system (CNS) serves as the brain’s processing hub. Comprised of the brain and spinal cord, the CNS coordinates voluntary and involuntary functions and interprets incoming sensory data. Think of it as a living, biological supercomputer that relays messages between the brain and the rest of the body.
Neurons are the fundamental units of the nervous system. Each neuron features a cell body, dendrites that receive signals, and an axon—sometimes extending up to one meter (3.3 feet)—that transmits information to other neurons or tissues. Synapses, the junctions where neurons meet, facilitate communication through chemical messengers. All CNS neurons are wrapped in a myelin sheath, an insulating layer that speeds signal transmission.
A nerve signal, known as an action potential, begins when a neuron’s membrane potential becomes more positive due to the influx of sodium ions. This change propagates along the axon in a wave-like fashion. Myelin-coated axons allow the impulse to leap between gaps (nodes of Ranvier) in a process called saltatory conduction, dramatically increasing speed. In the CNS, impulses can travel at up to 112 m/s (≈250 mph).
Upon reaching the axon terminal, the action potential triggers the release of neurotransmitters—such as dopamine or adrenaline—into the synaptic cleft. These molecules bind to receptors on the adjacent neuron’s dendrites, generating a new action potential and continuing the signal’s journey. This elegant chemical-electrical relay ensures rapid and precise communication throughout the nervous system.
