Nerves are your body’s communication wires. They carry electrical and chemical signals between your brain and every other part of your body, allowing you to feel sensations, move your muscles, and keep vital organs running without conscious thought. Every heartbeat, every breath, every sensation of warmth or pain travels along nerve pathways.
How a Nerve Signal Travels
A nerve cell, or neuron, has three basic parts: a cell body containing the nucleus, branch-like extensions called dendrites that receive incoming signals, and a long tail-like fiber called an axon that sends signals outward. When a neuron fires, it creates a tiny electrical pulse that races down the axon toward the next cell in the chain.
That electrical pulse works through a rapid exchange of charged particles. At rest, the inside of a nerve cell sits at a negative charge compared to the outside. When the cell is triggered, channels in its membrane open and allow positively charged sodium to rush in, flipping the charge positive. This wave of charge reversal travels down the length of the axon. Immediately behind it, potassium channels open to let potassium flow out, resetting the cell back to its resting state. The whole cycle happens in milliseconds.
Many nerve fibers are wrapped in a fatty insulating layer called myelin, produced by specialized support cells. Myelin doesn’t coat the entire axon. It leaves tiny gaps, and the electrical signal jumps from gap to gap rather than crawling along the full length. This jumping pattern increases signal speed by more than tenfold compared to uninsulated fibers.
Passing Signals Between Nerve Cells
Neurons don’t physically touch each other. Between the end of one neuron’s axon and the next cell’s dendrite is a tiny gap called a synapse. When the electrical signal reaches the end of an axon, it triggers the release of chemical messengers called neurotransmitters into that gap. These chemicals drift across and bind to receptors on the receiving cell, converting the chemical message back into an electrical one. The entire handoff can happen in a fraction of a millisecond for fast-acting signals, though some chemical messengers require sustained bursts of activity over several seconds before they’re released.
Sensing the World Around You
Sensory nerves are the reason you can feel a hot stove, hear a conversation, or sense where your foot is without looking at it. These neurons carry information from your skin, eyes, ears, and other sense organs up to your brain for processing.
Not all sensory signals travel at the same speed. Your body has different types of sensory nerve fibers designed for different jobs. Lightly insulated fibers handle the sharp, immediate “something just happened” sensation of pain, the kind that makes you pull your hand away from a flame. A separate set of completely uninsulated fibers carries slower, duller pain signals, the lingering ache that follows. The difference in speed between these two fiber types is why a stubbed toe produces a sharp flash of pain first, followed by a throbbing ache a moment later.
Controlling Movement
Motor nerves run in the opposite direction from sensory nerves. They carry commands from the brain and spinal cord out to your muscles. When you decide to pick up a cup of coffee, your brain sends a signal down through your spinal cord to motor neurons, which deliver that command to the specific muscle fibers in your arm and hand. Those muscles contract, and you lift the cup.
Motor nerves also participate in reflexes, the responses that happen before your brain even gets involved. When a doctor taps your knee and your leg kicks, sensory fibers in the stretched muscle send a signal to the spinal cord, which immediately routes a response back through motor neurons to contract the muscle. The whole loop bypasses your brain entirely, saving precious time when speed matters.
Running Your Organs on Autopilot
A third category of nerves handles everything your body does without you thinking about it: heart rate, digestion, blood pressure, body temperature, pupil size, bladder control, and breathing rate. This is the autonomic nervous system, and it operates through two opposing branches.
The sympathetic branch activates your body’s stress response. When you’re startled or threatened, it speeds up your heart, raises your blood pressure, dilates your pupils, triggers sweating, and diverts energy away from digestion. The parasympathetic branch does the opposite. It slows the heart, stimulates digestion and nutrient absorption, promotes pancreatic secretion, contracts the pupils, and triggers urination. These two systems constantly balance each other to keep your body functioning in the right mode for the situation.
The single most important nerve in this system is the vagus nerve, which runs from the brainstem down through the neck and into the chest and abdomen. It touches nearly every major organ. In the throat, it controls the muscles responsible for swallowing and vocalization. In the chest, it slows the heart. In the gut, it regulates smooth muscle contraction and glandular secretion. It also carries a massive amount of information in the other direction, sending data about the state of your internal organs back up to the brain. This two-way communication is the foundation of what researchers call the gut-brain axis.
Support Cells That Keep Nerves Working
Neurons can’t function alone. They depend on support cells that insulate, feed, and protect them. In the peripheral nervous system (everything outside the brain and spinal cord), cells called Schwann cells produce the myelin insulation that enables fast signaling. But their role goes well beyond insulation.
Schwann cells act as energy depots for nerve fibers, supplying fuel during periods of rapid firing or after injury. Sensory neurons in particular depend on Schwann cells for survival. When Schwann cell metabolism is disrupted, whether through disease or toxic exposure, the nerve fibers they support can degenerate. This pattern of insulation breakdown followed by nerve fiber damage is a common feature of many inherited and acquired nerve disorders.
Schwann cells also have a remarkable ability that brain support cells lack: after a peripheral nerve is injured, they can reprogram themselves into a more primitive state that actively promotes nerve regrowth. This is a major reason why nerves outside the brain and spinal cord can regenerate while those inside generally cannot.
How Nerves Heal After Injury
Damaged peripheral nerves regrow at a fairly consistent rate of about 1 millimeter per day, roughly one inch per month. That means recovery from a nerve injury depends heavily on how far the damaged point is from the muscle or skin it serves. An injury near the wrist might recover in weeks, while one near the shoulder could take many months as the regenerating fiber slowly works its way down the length of the arm.
What Happens When Nerves Stop Working
When nerves are damaged or diseased, signaling breaks down in three ways: signals that should be sent aren’t, signals fire when they shouldn’t, or messages get distorted along the way. The symptoms depend on which type of nerve is affected.
Damage to sensory nerves causes tingling, numbness, pain, loss of reflexes, and difficulty sensing vibrations or temperature changes. People with sensory nerve damage may struggle to coordinate movements like walking or buttoning a shirt, especially with their eyes closed, because they’ve lost the ability to sense where their limbs are in space. Damage to motor nerves leads to muscle weakness, painful cramps, visible twitching under the skin, and eventually muscle wasting if the nerve supply isn’t restored. When autonomic nerves are affected, problems can show up in heart rate regulation, digestion, blood pressure, or bladder control.
The most common causes of peripheral nerve damage include diabetes, physical injury, infections, and exposure to toxins. Because nerves touch virtually every system in the body, dysfunction in even a small number of nerve fibers can produce symptoms that feel disproportionately large.