What the Nervous System Does

The nervous system sends electrical and chemical signals between your brain and body to control movement, senses, thoughts, and involuntary functions like heartbeat and breathing. It acts as your body’s communication network, processing information from your environment and coordinating appropriate responses.

Core Functions of the Nervous System

Your nervous system handles three fundamental tasks that keep you alive and functioning. It collects sensory information from both inside and outside your body, processes that data in your brain and spinal cord, and sends out commands to muscles and organs. This happens continuously, whether you’re aware of it or not.

Sensory input starts when specialized nerve endings detect changes. Temperature sensors in your skin register heat or cold. Light-sensitive cells in your eyes capture visual information. Chemical receptors in your nose identify different smells. These sensors convert physical stimuli into electrical signals that travel along nerve pathways to your central nervous system.

Integration occurs mainly in your brain and spinal cord. Here, billions of neurons analyze incoming signals, compare them with stored memories and patterns, and determine what action to take. When you touch something unexpectedly sharp, your spinal cord can trigger a withdrawal reflex in milliseconds, even before your brain consciously registers pain. For more complex decisions, your brain evaluates multiple inputs and considers past experiences before choosing a response.

Motor output translates decisions into action. Electrical signals travel from your brain down through your spinal cord and out along motor neurons to specific muscles. These signals cause muscle fibers to contract in precise patterns, producing everything from a subtle facial expression to a full-body sprint. Other motor signals regulate glands, controlling processes like sweat production and hormone release.

How Signal Transmission Actually Works

Neurons communicate through a sophisticated electrochemical process that allows information to travel at speeds up to 120 meters per second. Each neuron maintains an electrical charge across its cell membrane, creating what physiologists call a resting potential of about -70 millivolts.

When a neuron receives sufficient stimulation, sodium channels in its membrane open rapidly. Positively charged sodium ions flood into the cell, reversing the electrical charge and creating an action potential. This electrical wave travels down the neuron’s axon like a domino effect, with each section triggering the next.

At the axon terminal, the electrical signal triggers a chemical response. Small sacs called vesicles release neurotransmitter molecules into the synapse, the narrow gap between neurons. These chemical messengers drift across the gap and bind to receptor proteins on the receiving neuron. Depending on the neurotransmitter type, this can either excite the next neuron (making it more likely to fire) or inhibit it (making it less likely to fire).

Your body produces more than 100 different neurotransmitters, each with specific effects. Dopamine influences motivation and reward. Serotonin affects mood and sleep patterns. Acetylcholine triggers muscle contractions and plays roles in memory formation. GABA generally calms neural activity, while glutamate tends to excite it. The balance and timing of these chemical signals determine how your nervous system responds to any given situation.

Division of Labor: Central vs Peripheral

Your nervous system splits into two main divisions based on location and function. The central nervous system (CNS) consists of your brain and spinal cord, protected by bone and cerebrospinal fluid. The peripheral nervous system (PNS) includes all other nerves, branching throughout your body to reach every tissue and organ.

The CNS processes information and makes decisions. Your brain contains roughly 86 billion neurons organized into specialized regions. The frontal lobe handles planning and decision-making. The parietal lobe processes touch and spatial information. The occipital lobe interprets visual signals. The temporal lobe manages hearing and memory. Meanwhile, your spinal cord serves as an information highway, carrying signals between your brain and body while also managing certain reflexes independently.

The PNS acts as a two-way communication system. Sensory (afferent) nerves carry information to the CNS, while motor (efferent) nerves carry commands outward. These nerves extend remarkable distances—the sciatic nerve, for example, stretches from your lower back down to your toes, making it the longest nerve in your body.

Voluntary Control: The Somatic Nervous System

The somatic nervous system manages conscious, voluntary movements and provides sensory feedback. When you decide to pick up a cup, your brain’s motor cortex sends specific signals through somatic motor neurons to activate precise muscle groups in your arm, hand, and fingers.

This system includes 12 pairs of cranial nerves and 31 pairs of spinal nerves. Cranial nerves handle specialized functions in your head and neck—controlling eye movements, facial expressions, taste, and hearing. Spinal nerves branch out to serve the rest of your body, with each nerve root connecting to specific body regions called dermatomes.

Sensory neurons in this system constantly update your brain about body position (proprioception), touch, pressure, temperature, and pain. This feedback allows you to adjust grip strength, maintain balance, and avoid injury. The rapid communication enables complex coordinated movements like typing on a keyboard or playing a musical instrument.

Automatic Processes: The Autonomic Nervous System

Your autonomic nervous system operates largely outside conscious awareness, regulating vital functions that keep you alive. It controls heart rate, blood pressure, digestion, body temperature, and numerous hormonal processes. This system works continuously, making thousands of micro-adjustments every day.

The sympathetic branch activates during stress or danger, triggering the famous “fight-or-flight” response. It increases heart rate and blood pressure, dilates pupils and airways, releases stored energy, and redirects blood flow to muscles. Sympathetic nerves also inhibit non-essential functions like digestion, allowing your body to focus resources on immediate survival.

The parasympathetic branch dominates during rest and recovery. It slows heart rate, stimulates digestion, promotes nutrient storage, and facilitates tissue repair. Parasympathetic activation helps you feel calm and allows your body to perform maintenance functions. The vagus nerve, the longest cranial nerve, carries most parasympathetic signals to your heart, lungs, and digestive organs.

The enteric nervous system specifically manages your digestive tract. This “second brain” contains roughly 500 million neurons embedded in the walls of your esophagus, stomach, and intestines. It can regulate gut motility, enzyme secretion, and blood flow relatively independently, though it communicates extensively with your brain through the vagus nerve.

Maintaining Healthy Nerve Function

Several lifestyle factors directly impact nervous system health and performance. Your neurons require specific nutrients, adequate oxygen, proper hydration, and protection from toxins to function optimally.

Diet matters significantly. Omega-3 fatty acids from fish, flaxseeds, and walnuts support nerve cell membranes and neurotransmitter function. B vitamins, particularly B12 found in eggs, dairy, and meat, are essential for maintaining myelin sheaths that insulate nerve fibers. Antioxidant-rich foods like berries and leafy greens protect neurons from oxidative damage. Adequate protein provides amino acids needed to build neurotransmitters.

Physical activity strengthens neural pathways. Exercise increases blood flow to the brain, promotes the growth of new neurons (neurogenesis), and enhances synaptic plasticity—your brain’s ability to form new connections. Studies show regular aerobic exercise can increase hippocampal volume by 2%, improving memory and learning capacity. Strength training also benefits nerve health by maintaining neuromuscular junctions.

Sleep enables crucial maintenance. During deep sleep stages, your brain clears metabolic waste products through the glymphatic system. Sleep also consolidates memories by strengthening important neural connections while pruning less useful ones. Most adults need 7-9 hours of consecutive sleep for optimal nervous system restoration.

Stress management protects neural health. Chronic stress elevates cortisol levels, which can damage neurons in the hippocampus and impair memory formation. Effective stress-reduction techniques include meditation, deep breathing exercises, time in nature, and maintaining strong social connections. These practices activate the parasympathetic nervous system, promoting recovery and resilience.

Avoiding neurotoxins is essential. Excessive alcohol damages neurons and disrupts neurotransmitter balance. Smoking reduces blood flow to the brain and increases stroke risk. Some environmental toxins, including heavy metals and certain pesticides, can cause lasting nerve damage. Protecting your nervous system means minimizing exposure to these harmful substances.

Common Conditions Affecting the Nervous System

Neurological disorders can result from injury, infection, degeneration, genetic factors, or vascular problems. Understanding major categories helps in recognizing symptoms and seeking timely treatment.

Degenerative diseases involve progressive loss of neurons or their function. Alzheimer’s disease destroys neurons in memory-related brain regions, affecting roughly 6.7 million Americans over age 65. Parkinson’s disease specifically damages dopamine-producing neurons in the substantia nigra, causing tremors and movement difficulties. Multiple sclerosis occurs when the immune system attacks myelin sheaths, disrupting signal transmission throughout the central nervous system.

Vascular disorders happen when blood supply to nervous tissue becomes compromised. Stroke—affecting nearly 800,000 Americans annually—occurs when brain tissue dies due to blocked or ruptured blood vessels. The effects depend on which brain region loses blood flow, potentially causing paralysis, speech difficulties, or cognitive impairment. Transient ischemic attacks (TIAs) are temporary episodes with similar symptoms that resolve within 24 hours but signal increased stroke risk.

Injuries can damage nervous tissue directly. Traumatic brain injury from falls, accidents, or impacts can cause temporary confusion or lasting cognitive and emotional changes. Spinal cord injuries may result in partial or complete paralysis below the injury site. Peripheral nerve damage from compression (like carpal tunnel syndrome), trauma, or diabetes causes numbness, tingling, pain, or muscle weakness in affected areas.

Seizure disorders involve abnormal electrical activity in the brain. Epilepsy affects approximately 3.4 million Americans, causing recurrent seizures that range from brief lapses in awareness to major convulsions. Seizures result from excessive, synchronized firing of neurons, often triggered by specific factors like sleep deprivation, flashing lights, or fever.

Infections can invade the nervous system. Bacterial meningitis inflames the membranes surrounding the brain and spinal cord, potentially causing lasting damage or death without prompt antibiotic treatment. Viral infections like herpes can affect nerve tissue, causing conditions such as shingles when dormant varicella-zoster virus reactivates in sensory nerve roots.

Warning Signs Requiring Medical Attention

Certain symptoms indicate serious nervous system problems requiring immediate evaluation. Sudden onset symptoms often signal medical emergencies that need treatment within minutes to hours for best outcomes.

Seek emergency care immediately for:

Sudden weakness or numbness affecting one side of the body
Sudden severe headache unlike any previous headache
Confusion, difficulty speaking, or trouble understanding speech
Vision loss or double vision in one or both eyes
Loss of balance, coordination, or ability to walk
Sudden severe dizziness or vertigo
Seizure, especially if it’s the first one
Loss of consciousness or altered mental state

Schedule prompt medical evaluation for:

Persistent headaches that worsen or change in character
Numbness or tingling lasting more than a few days
Progressive muscle weakness
Memory problems interfering with daily activities
Changes in coordination or frequent falls
Unexplained tremors or involuntary movements
Persistent back or neck pain with radiation to limbs
Changes in bowel or bladder control

Early diagnosis often leads to better treatment outcomes. Many neurological conditions progress gradually, and intervention during early stages can slow deterioration or prevent complications.

Frequently Asked Questions

What’s the difference between neurons and nerves?

Neurons are individual nerve cells that transmit electrical signals. Each neuron has a cell body, dendrites that receive signals, and an axon that sends signals. Nerves are bundles of many neuron axons wrapped together, similar to how individual wires bundle into a cable. A single nerve can contain thousands of axons from different neurons, carrying multiple signals simultaneously.

Can damaged nerves heal?

It depends on the location and severity of damage. Peripheral nerves outside the brain and spinal cord can regenerate slowly, typically at about 1 millimeter per day. Full recovery may take months to years depending on the distance to the target tissue. Central nervous system neurons (in the brain and spinal cord) have much more limited regenerative capacity, though research into nerve regeneration continues to advance.

How fast do nerve signals travel?

Signal speed varies by nerve type. Myelinated neurons, with insulating myelin sheaths, conduct signals at 70-120 meters per second (up to 268 miles per hour). Unmyelinated neurons transmit much slower, at 0.5-2 meters per second. The myelin sheath allows signals to “jump” between gaps in the insulation, dramatically increasing transmission speed—crucial for quick reflexes and coordinated movement.

Why do we feel pain?

Pain is your nervous system’s alarm mechanism. Specialized sensory neurons called nociceptors detect potentially harmful stimuli—excessive heat or cold, pressure, tissue damage, or inflammatory chemicals. These neurons send signals to your spinal cord and brain, which interpret the signals as pain. While unpleasant, pain serves a protective function by alerting you to threats and encouraging behaviors that promote healing.

Your nervous system represents one of biology’s most sophisticated achievements, coordinating billions of signals every second to maintain life and enable conscious experience. It adapts constantly to new information, forming new connections as you learn and pruning unused pathways to optimize efficiency. Taking care of this remarkable system through healthy lifestyle choices supports not just longevity, but quality of life at every stage.

Recommended related topics:

Understanding brain anatomy and specific regions
Neurotransmitters and their roles in mood and behavior
Neuroplasticity and how the brain changes throughout life
Peripheral neuropathy causes and management
Protective factors against neurodegenerative diseases