The nervous system serves as the primary master control and communication network of the body. Working alongside the endocrine system, it maintains homeostasis by detecting changes, processing information, and orchestrating responses.
Division of labor within this network separates structures into the central and peripheral components, each specialized for specific operational speeds and pathways.
The brain acts as the command center, divided into major regions with distinct responsibilities:
The spinal cord functions as a vital two-way conduction pathway between the brain and the body, while also serving as a major integration center for spinal reflexes. Protected by the vertebral column, its internal gray matter forms an H-shape containing cell bodies, while the surrounding white matter contains myelinated axon tracts ascending to the brain or descending to the body.
A reflex arc bypasses conscious brain processing to yield an immediate protective response. Sensory input travels through a dorsal root into the cord, synapses directly or via an interneuron, and sends a motor command out through the ventral root to a muscle.
The peripheral nervous system connects the central nervous system to limbs and organs. It splits functionally into somatic and autonomic branches.
The somatic nervous system governs conscious, voluntary actions by sending motor signals from the central nervous system to skeletal muscles. In contrast, the autonomic nervous system operates involuntarily, regulating visceral functions of smooth muscle, cardiac muscle, and glands.
The autonomic system further divides into the sympathetic division—which drives the fight-or-flight response during stress—and the parasympathetic division, which promotes rest-and-digest maintenance activities during calm periods.
Nervous tissue consists of two principal cell types: neurons and neuroglia. Neurons are the structural units of the nervous system specialized for transmitting electrical signals. Each typically features a cell body, branching dendrites that receive inputs, and a single axon that transmits signals away.
Neuroglial cells, or glia, outnumber neurons and provide vital support, insulation, and nourishment. In the central nervous system, astrocytes maintain the blood-brain barrier, oligodendrocytes form myelin sheaths, microglia act as phagocytes, and ependymal cells line fluid-filled cavities. In the periphery, Schwann cells form myelin, and satellite cells cushion cell bodies.
Communication within the nervous system relies on electrochemical impulses. At rest, a neuron maintains a negative electrical charge inside compared to the outside, known as the resting membrane potential.
When a stimulus reaches threshold, voltage-gated sodium channels open, causing a rapid influx of positive sodium ions that depolarizes the membrane. This spike is an action potential. Repolarization follows as potassium channels open and potassium ions rush out.
Once the action potential reaches the axon terminal, it triggers the release of neurotransmitters into the synaptic cleft. These chemical messengers bind to receptors on the next cell, continuing or stopping the signal.
Delicate central nervous system tissue requires robust physical protection. Three connective tissue membranes called meninges encase the brain and spinal cord:
Cerebrospinal fluid circulates through the subarachnoid space and internal brain ventricles, cushioning neural structures, supplying nutrients, and removing metabolic waste.
Nurses rely on baseline neurological assessments to detect subtle changes in patient status. Evaluating orientation, cranial nerve integrity, motor strength, and sensory response helps identify early signs of increased intracranial pressure or localized brain injury.
The Glasgow Coma Scale provides a standardized tool to monitor level of consciousness by scoring eye opening, verbal response, and motor performance. Any unexplained drop in score signals worsening cerebral function, requiring immediate clinical intervention and medical notification.