Nerves are your body’s wiring system. They carry electrical and chemical signals between your brain, spinal cord, and every other part of your body, allowing you to move, feel, think, and keep vital organs running without conscious effort. Every sensation you experience, every muscle you flex, and every heartbeat happens because nerves are transmitting signals at high speed through an intricate network.
The Three Types of Nerves
Your nervous system relies on three functionally distinct types of nerve cells, each with a specific job.
Sensory nerves carry information inward, from your skin, eyes, ears, nose, and tongue to your brain and spinal cord. They’re responsible for everything you perceive: temperature, pain, pressure, vibration, taste, smell, sight, and sound. Without them, you’d have no awareness of the world around you or even of your own body’s position in space.
Motor nerves carry signals outward, from your brain and spinal cord to your muscles and glands. When you decide to pick up a glass of water, motor nerves deliver the command that makes your arm and hand muscles contract in the right sequence. They also handle functions you don’t consciously control, like breathing and salivating.
Interneurons sit between sensory and motor nerves inside the brain and spinal cord. They process incoming information, make connections, and coordinate responses. When you touch something hot, interneurons help link the sensory signal (“this is burning”) to the motor command (“pull your hand away”) in a fraction of a second.
How Nerves Send Signals
Nerve signaling is both electrical and chemical, and it happens remarkably fast. Inside a nerve cell, the signal travels as a brief electrical pulse called an action potential. This pulse lasts about one millisecond and races down the long, cable-like part of the nerve cell called the axon.
When that electrical pulse reaches the end of the axon, it hits a tiny gap between one nerve cell and the next. This gap is incredibly small, only about 20 to 40 nanometers wide. The electrical signal can’t jump across, so the nerve cell converts it into a chemical one. It releases messenger molecules into the gap, and those molecules drift across and latch onto the receiving nerve cell on the other side. Once they attach, they trigger a new electrical signal in that next cell. So the system constantly converts electrical signals to chemical ones and back again, relaying messages from cell to cell across your entire body.
A fatty coating called the myelin sheath wraps around most nerve fibers, working like the plastic insulation on an electrical cord. It does three things: protects the nerve, speeds up signal transmission, and keeps the signal strong as it travels long distances. When myelin is damaged, as in conditions like multiple sclerosis, signals slow down or fail entirely.
The Central and Peripheral Divide
Your nervous system splits into two major parts. The central nervous system (your brain and spinal cord) acts as the command center, processing information and making decisions. The peripheral nervous system is the vast network of nerves that branches out from the brain and spinal cord to reach your limbs, organs, and glands. Think of the central nervous system as a power plant and the peripheral nerves as the cables running electricity to every building in a city, while also sending status reports back.
Peripheral nerves that carry information toward the brain are called afferent nerves. Those that carry commands away from the brain to muscles and organs are called efferent nerves. This two-way communication runs constantly, keeping your brain updated on what’s happening throughout your body and allowing it to respond.
Running Your Body Without Your Input
A large portion of what nerves do happens without you ever thinking about it. The autonomic nervous system is the branch responsible for involuntary functions, and it has three divisions.
The sympathetic division handles your “fight or flight” response. When you’re startled or stressed, these nerves speed up your heart rate, widen your airways, and redirect blood flow to your muscles so you can react quickly. The parasympathetic division does the opposite, managing “rest and digest” functions. It slows your heart, stimulates digestion, and conserves energy when you’re calm. The enteric division specifically manages your digestive tract.
Together, these autonomic nerves regulate your heart rate, blood pressure, breathing, digestion, bladder function, sweating, and even when your pancreas releases insulin. Your peripheral nerves constantly monitor the internal state of your organs and relay that information to your brain without you being consciously aware of it.
Reflexes: Nerves That Bypass the Brain
Some nerve responses are so urgent they can’t wait for your brain to weigh in. Reflexes are pre-wired circuits that process signals at the spinal cord level, shaving precious milliseconds off your reaction time. The classic example is the knee-jerk reflex your doctor tests with a small hammer.
A reflex arc follows a specific sequence: a receptor detects a stimulus (like a stretch in your tendon), a sensory nerve carries the signal to your spinal cord, an interneuron in the spinal cord connects it to a motor nerve, and that motor nerve fires a signal back to the muscle, causing it to contract. The entire loop can happen through as few as two nerve cells in the simplest reflexes. Your brain still receives a copy of the sensory information through separate pathways, so you become aware of what happened, but only after the reflex has already fired.
What Happens When Nerves Stop Working
Because nerves control so many functions, damage to them produces a wide range of symptoms depending on which type is affected. Peripheral neuropathy, one of the most common forms of nerve damage, illustrates this clearly.
When sensory nerves are damaged, you may feel numbness, tingling, or prickling that often starts in the hands and feet and spreads inward. Some people develop extreme sensitivity to touch or feel burning, jabbing pain from activities that shouldn’t hurt at all, like the weight of a blanket on their feet. Others describe the sensation of wearing gloves or socks when they aren’t.
Motor nerve damage shows up as muscle weakness, loss of coordination, and difficulty moving. In severe cases, affected muscles may stop responding altogether. Autonomic nerve damage is less obvious but can disrupt digestion, bladder control, sweating, blood pressure regulation, and heart rate. Some people develop heat intolerance or find they can no longer sweat normally.
Diabetes is one of the most common causes of peripheral neuropathy, but injuries, infections, toxins, and autoimmune conditions can also damage nerves.
Nerve Repair and Recovery
One important distinction: nerves in the peripheral nervous system can regrow after injury, while those in the brain and spinal cord generally cannot. Peripheral nerves regenerate at roughly 1 millimeter per day, though the actual rate varies with the severity of the injury, how close it is to the spinal cord, and individual health factors.
That 1 mm/day rate means recovery timelines scale directly with how far the signal needs to travel. An injury 10 centimeters from the target muscle or skin might recover in 3 to 4 months. A 30-centimeter gap could take 9 to 12 months. For longer distances, like a nerve injury high in the arm that needs to regenerate all the way to the fingertips (around 60 centimeters), recovery can take 18 to 24 months. Clinicians use this estimate to set realistic expectations, but full recovery is never guaranteed, especially after severe trauma.