Neuroscience Terms Starting With C
Neuroscience Glossary: C
Central Nervous System
/ SEN-trul NER-vus SIS-tem / · Latin centralis + nervosus + Greek systema
Central Nervous System is the brain and spinal cord, serving as the primary processing and coordination center that receives sensory information, integrates it, and directs voluntary and involuntary responses throughout the body.
The brain, enclosed within the skull, contains about 86 billion neurons organized into functional regions responsible for sensory processing, movement, cognition, emotion, and homeostatic regulation. Its companion structure, the spinal cord, transmits information between the brain and peripheral nervous system, processes simple reflexes independently of the brain, and contains motor and sensory tracts organized in anatomically distinct locations. Three meningeal membranes, a rigid bony enclosure, and the blood-brain barrier together protect the entire central nervous system from mechanical injury and circulating pathogens.
Cerebrospinal fluid, produced at a rate of roughly 500 milliliters per day by the choroid plexus, circulates through the ventricles and subarachnoid space, cushioning the brain and clearing metabolic waste.
Adult neurogenesis is robust in several mammals, especially in hippocampal and olfactory regions, but its extent and functional importance in adult humans remain debated. Studies since the 1990s have shifted the field from a strict no-new-neurons view to a more cautious model in which species, age, disease state, and detection method strongly influence the conclusion.
Fun Facts About the Nervous System →The adult central nervous system cannot repair itself at all after injury. Some axon sprouting and synaptic reorganization do occur after damage, but the degree of spontaneous regeneration is far more limited than in peripheral nerves, where Schwann cells actively support regrowth over distances of several centimeters.
The sea lamprey (Petromyzon marinus) regenerates descending spinal axons after complete spinal cord transection, restoring swimming behavior within 10 to 12 weeks. Researchers studying lampreys compare more than 30 growth-associated genes with mammalian injury responses to identify why CNS axon regeneration succeeds in this species but fails in most adult mammals.
Cerebellum
/ ser-eh-BEL-um / · Latin cerebellum (little brain)
Cerebellum is a densely folded structure at the posterior base of the brain that coordinates voluntary movement, balance, and fine motor control by comparing intended and actual movements and making real-time corrections to motor output.
The cerebellum receives input from the motor cortex, brainstem, and sensory systems, comparing movement commands with proprioceptive feedback and adjusting muscle output to produce smooth, coordinated motion. Damage to this structure produces ataxia, marked by uncoordinated movement, gait instability, and intention tremor during voluntary motion. Despite occupying only about 10 percent of total brain volume, the cerebellum contains more than half of the brain’s neurons, mostly densely packed granule cells.
Its compact architecture reflects the enormous computational demand of continuous, real-time motor correction and prediction.
Elite musicians show measurably enlarged cerebellar volumes compared to non-musicians, particularly in regions processing fine motor sequences, demonstrating that intensive motor training drives structural plasticity in this region.
Fun Facts About the Nervous System →The cerebellum initiates voluntary movement. Voluntary movement is initiated by the motor cortex; the cerebellum refines and corrects ongoing movement, which is why people with cerebellar damage can intend and begin a movement but cannot execute it smoothly.
When a cat (Felis catus) is born without a cerebellum, a condition called cerebellar hypoplasia, it can still walk and eat but moves with a pronounced whole-body wobble, showing that the cerebellum is not required for movement itself. The cerebellum is required for movement precision, and the affected cat cannot land gracefully from a one-meter fall, a jump that a healthy cat executes without error.
Cerebral Cortex
/ SEH-ree-brul KOR-teks / · Latin cerebralis + cortex (bark, rind)
Cerebral Cortex is the outer layer of gray matter covering the cerebral hemispheres, organized into functional regions that process sensory perception, generate voluntary movement, support language and reasoning, and underlie conscious experience.
At two to four millimeters thick, the human cerebral cortex would cover roughly 2,500 square centimeters if unfolded flat. Deep folding into gyri and sulci packs this surface area inside the skull. Six distinct cell layers run through its thickness, each with characteristic neuron types and connectivity patterns.
Functionally, the cortex divides into frontal, parietal, temporal, and occipital lobes, each associated with different sensory, motor, and cognitive operations.
The primary motor cortex maps the body as a distorted figure called the homunculus, where the hand and face occupy far more cortical space than the trunk or legs, reflecting the precision of motor control rather than body-part size.
The cerebral cortex divides into clearly discrete regions, each with a single function. Most cognitive operations, including language comprehension and spatial reasoning, involve distributed networks spanning multiple cortical areas working simultaneously.
Plasticity of the cerebral cortex causes the somatosensory hand area to expand into adjacent regions in congenitally blind individuals who learn Braille. Functional imaging studies show that heavily used reading fingers can gain cortical representations several millimeters larger than those of sighted non-readers within months of sustained practice.
Cerebral Ventricle
/ VEN-trih-kul / · Latin ventriculus (little belly)
Cerebral Ventricle is one of the four interconnected, cerebrospinal-fluid-filled cavities inside the brain that produce and circulate cerebrospinal fluid through the central nervous system.
Cerebrospinal fluid is produced by the choroid plexus within the ventricles and circulates through the ventricular system before flowing into the subarachnoid space surrounding the brain and spinal cord, where it is reabsorbed into the venous system at arachnoid granulations. The total volume of cerebrospinal fluid in an adult is about 150 milliliters, and the choroid plexus replaces this entire volume roughly three to four times per day. Hydrocephalus occurs when CSF drainage is obstructed, causing ventricular enlargement and elevated intracranial pressure that compresses surrounding brain tissue.
Ependymal cells lining the ventricles bear motile cilia whose coordinated beating contributes to directional CSF flow.
The lateral ventricles, the largest of the four, extend into all four lobes of the cerebral hemisphere and can be visualized on routine MRI scans, making ventricular size a useful clinical marker for conditions ranging from hydrocephalus to neurodegenerative disease.
The ventricles are simply passive fluid reservoirs. The ependymal cells lining the ventricles beat their cilia to drive CSF circulation, and the choroid plexus actively regulates the ionic composition of CSF rather than merely filtering plasma.
Circulatory System Fun Facts →In zebrafish (Danio rerio) embryos, the brain ventricles inflate with CSF within 24 hours of fertilization, expanding to roughly 30 percent of total brain volume by that stage. Blocking this inflation during the first 1 to 2 days of development can cause the forebrain to collapse, showing that ventricular pressure shapes early brain morphology.
How To Become A Sleep Doctor? →Cerebrum
/ SEH-ree-brum / · Latin cerebrum (brain)
Cerebrum is the largest division of the human brain, comprising the two cerebral hemispheres and housing the cerebral cortex, basal ganglia, and limbic structures that together support higher cognitive, sensory, motor, and emotional functions.
Developing from the embryonic telencephalon, the cerebrum constitutes about 85 percent of total brain weight in adults. The two hemispheres connect through the corpus callosum and are functionally lateralized, with the left hemisphere typically dominant for language and the right more specialized for spatial processing. Sensory signals from the body cross the midline before reaching the cerebrum, so the left hemisphere processes input from the right side of the body and vice versa.
This crossed organization means that a stroke affecting the left cerebral hemisphere typically produces language deficits and right-sided weakness.
The surface area of the human cerebral cortex, if spread flat, would cover roughly 2,500 square centimeters, about the size of a standard pillowcase, and the deep folds creating gyri and sulci allow this large area to fit inside a skull with an average volume of about 1,400 cubic centimeters.
The left and right hemispheres are independent systems with separate personalities. Both hemispheres collaborate continuously through the corpus callosum and subcortical connections, and most behaviors, including language, draw on contributions from both sides.
The cerebrum of bottlenose dolphins (Tursiops truncatus) is highly folded with a cortex that is relatively large and thick, with a surface area in adult animals reaching roughly 3,700 square centimeters. This cortex supports tool use, social behavior, and mirror self-recognition in animals whose adult brains can exceed 1,500 grams.
What Do Dolphins Eat? →Corpus Callosum
/ KOR-pus kah-LOH-sum / · Latin corpus (body) + callosus (hard, thick-skinned)
Corpus Callosum is the largest white matter structure in the human brain, consisting of approximately 200 to 250 million myelinated axons that connect the two cerebral hemispheres and coordinate interhemispheric communication.
Axons of the corpus callosum carry both excitatory and inhibitory signals between homotopic and heterotopic cortical regions, allowing the hemispheres to share sensory information, coordinate motor activity, and integrate cognitive processes. Unlike most brain structures, the corpus callosum continues to develop through childhood and adolescence, with full myelination not complete until the mid-twenties. This prolonged maturation means that interhemispheric processing speed increases steadily through adolescence and is measurable with reaction-time tasks that require cross-hemisphere coordination.
Congenital absence of the corpus callosum, called agenesis, can occur with mild or variable behavioral effects when other commissures partially compensate.
In split-brain patients whose corpus callosum was surgically severed to control severe epilepsy, information presented to only one visual field could not be named aloud, because language processing is concentrated in the left hemisphere and the right hemisphere could no longer relay what it saw.
The corpus callosum is larger in women than in men. Decades of neuroimaging studies have produced inconsistent results on this question, and large-sample analyses controlling for total brain volume find no reliable sex difference in callosal size or connectivity.
A child born with complete agenesis of the corpus callosum may show no obvious neurological symptoms in routine testing, yet takes measurably longer, sometimes hundreds of milliseconds longer, on tasks requiring one hand to mirror the movements of the other. The delay can exceed 200 milliseconds in demanding bilateral tasks, revealing the callosum's role in fine interhemispheric motor timing.
Cranial Nerve
/ KRAY-nee-ul nerv / · Latin cranium (skull) + nervus (sinew)
Cranial Nerve is any one of the twelve paired nerves that emerge directly from the brain or brainstem and carry sensory, motor, or mixed signals between the brain and structures of the head, neck, and thorax without passing through the spinal cord.
Unlike spinal nerves that exit through the vertebral column, cranial nerves exit through foramina in the skull base and are numbered I through XII in rostral-to-caudal order. Their functions span smell (CN I), vision (CN II), eye movement (CN III, IV, VI), facial sensation and chewing (CN V), facial expression (CN VII), hearing and balance (CN VIII), and swallowing (CN IX, X, XII). The vagus nerve (CN X) is the most extensive, sending parasympathetic fibers to the heart, lungs, and abdominal viscera.
Several cranial nerves carry both somatic and autonomic fibers within the same nerve bundle, so damage to a single nerve can produce a combination of sensory, motor, and autonomic deficits.
Cranial nerve zero, sometimes called the terminal nerve or CN 0, was identified in humans in the early twentieth century and runs from the nasal mucosa to the forebrain; its function in humans remains debated, but in other vertebrates it appears to carry chemosensory signals related to reproductive behavior.
Fun Facts About the Nervous System →All cranial nerves carry both sensory and motor signals. Cranial nerves I, II, and VIII are primarily sensory, III, IV, VI, XI, and XII are primarily motor, and V, VII, IX, and X carry mixed sensory and motor or autonomic fibers.
Damage to CN VII, the facial nerve, causes Bell's palsy, in which one side of the face droops completely because the motor neurons controlling all ipsilateral facial muscles lose their neural input. The condition affects roughly 40,000 Americans per year, with most cases resolving spontaneously within three to six months as the nerve regrows.