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Cochlear implant
A cochlear implant, also called a bionic ear, is an electronic device that bypasses damaged inner-ear structures to give a sense of sound to people who are profoundly deaf.
Cochlear nerve
Cochlear nerve: auditory division of cranial nerve VIII, carrying signals from spiral ganglion neurons to the brainstem cochlear nuclei; aplasia or hypoplasia predicts poor cochlear implant outcomes, with auditory brainstem implants as the alternative.
Cochlear nucleus
Cochlear nucleus: first brainstem relay of the auditory pathway (dorsal, anteroventral, posteroventral divisions), where auditory nerve fibers split into ventral sound-localizing and dorsal pattern-recognition streams; target of auditory brainstem implants and linked to tinnitus.
Cognitive neuroscience
Cognitive neuroscience studies how brain function supports mental activities, combining cognitive psychology with brain imaging. Named by Gazzaniga and Miller in the late 1970s; fMRI is its leading tool, with reverse inference and reproducibility as key debates.
Colic
Colic: excessive, inconsolable crying in an otherwise healthy infant, defined by Wessel's rule of threes and Rome IV criteria; affects 17-25% of infants, peaks at 4-6 weeks, resolves by 3-4 months; also biliary, renal, and intestinal colic in adults.
Collateral Circulation
Collateral circulation: naturally occurring artery-to-artery backup vessels (coronary, cerebral, peripheral) that enlarge by arteriogenesis under shear stress after arterial occlusion, measured by collateral flow index, and linked to better survival in coronary disease and stroke.
Collecting duct system
Collecting duct system (kidney): ureteric bud-derived tubules draining nephrons; segments from connecting tubule to papillary duct; principal and intercalated cells; ADH/AQP2 water reabsorption, ENaC sodium handling, acid secretion; urine 0.5–10 L/day, up to 1200 mOsm/kg.
Colloid cyst
Colloid cyst: benign epithelial (neuroepithelial) cyst of the anterior third ventricle, 0.2-3% of benign intracranial tumors, causing obstructive hydrocephalus and rare sudden death; treated by endoscopic or microsurgical resection.
Coloboma
Coloboma (ocular coloboma, congenital ocular coloboma) is a birth defect in which part of the eye or eyelid tissue is missing, caused by failure of the embryonic fissure to close; affects about 1 in 10,000 people and can cause childhood blindness.
Coloboma of macula
Coloboma of macula (macular coloboma; OMIM 120300) is a rare congenital chorioretinal maldevelopment of the macula, not caused by optic fissure closure failure, causing central vision loss and distinguished from toxoplasmosis by OCT.
Color vision
Color vision: the visual system's perception of light wavelength as color, based on three S, M, L cone types, retinal cone-opponent pathways, trichromatic and opponent-process theories, color constancy, and color vision deficiency affecting about 1 in 12 men.
Coma
Coma: a state of prolonged unconsciousness with no awareness or response, caused by brain injury, stroke, toxins, diabetes, or oxygen lack; assessed with the Glasgow Coma Scale (3-15).
Commotio cordis
Commotio cordis, also called cardiac concussion, is ventricular fibrillation triggered by a blunt chest blow during a 10-20 ms vulnerable window of the heartbeat, mainly in young male athletes; survival rose from 10-15% to over 60% with rapid CPR and AED use.
Comparative auditory physiology
Comparative auditory physiology studies how vertebrate ears detect and discriminate sound across species, using differences among fish, amphibians, reptiles, birds, and mammals to interpret human hearing.
Complement system
Complement system: 40+ plasma proteins of innate immunity; classical, lectin, and alternative pathways converge on C3 cleavage, driving opsonization, inflammation, and MAC lysis; dysregulation causes aHUS, AMD, PNH, hereditary angioedema.
Complementary colors
Complementary colors are color pairs that mix to neutral (white light, grey pigment) and sit opposite on the color wheel, such as red/green, yellow/violet, and blue/orange; they drive simultaneous contrast, afterimages, and painterly contrast techniques.
Compliance (physiology)
Compliance (physiology): the ease of volume expansion per pressure change (C=ΔV/ΔP) in heart chambers and vessels; ventricular diastolic compliance, venous capacitance 30 times arterial, and clinical diastolic dysfunction.
Composition of the human body
The composition of the human body describes how body mass is partitioned and measured across five levels, from chemical elements to whole organs; water makes up about 60% of body weight.
Computational methods in neuroengineering
Computational methods in neuroengineering are the mathematical models, signal-processing algorithms, and machine-learning techniques used to analyze neural signals, decode intentions, and control devices interfacing electronics with living neural tissue.
Computational neuroscience
Computational neuroscience, also called theoretical or mathematical neuroscience, applies mathematical models, theoretical analysis, and computer simulation to nervous systems, from ion channels to whole-brain networks.
Computed tomography angiography
Computed tomography angiography (CTA, CT angiogram): imaging of blood vessels using iodinated contrast injection and CT scanning; introduced with helical CT in 1991; coronary CTA sensitivity 0.94, specificity 0.73; doses now submillisievert.
Computer vision syndrome
Computer vision syndrome, or digital eye strain, is a group of eye, vision, and musculoskeletal symptoms from prolonged screen use, affecting about 69% of users, driven by reduced blinking and accommodative fatigue, and managed mainly with ergonomics and breaks.
Concussion
Concussion, a mild traumatic brain injury from head trauma causing temporary altered mental status; also commotion cerebri. Key facts: 300,000 US sports cases yearly, 24-48h rest then early return to school, 6-step return-to-play, Amsterdam 2022 SCAT6 tools.
Concussions in American football
Concussions in American football: sport-related traumatic brain injuries in a collision sport. NFL protocol since 2011, highest football impact accelerations (83.2 g), youth incidence 1.41 per 1,000 exposures, CTE link, $1 billion settlement, Guardian Caps and kickoff rule changes.
Conductive hearing loss
Conductive hearing loss (CHL): hearing loss from blocked or faulty sound transmission in the outer or middle ear, with normal bone conduction; causes include earwax, otitis media, perforation, otosclerosis; often treatable.
Cone cell
Cone cell (cone photoreceptor): retinal photoreceptor for daylight and color vision, with S, M, and L opsins peaking at 420, 534, and 564 nm; less sensitive than rods, never saturates, adapts in minutes.
Cone rod dystrophy
Cone rod dystrophy (CORD, CRD) is a group of inherited retinal diseases in which cone photoreceptors degenerate first, then rods, causing childhood-onset vision loss, photophobia, and legal blindness by mid-adulthood; over 30 genes, chiefly ABCA4, GUCY2D, CRX, and RPGR, are implicated.
Congenital asplenia
Congenital asplenia: absence of the spleen from birth, isolated (often RPSA-related, autosomal dominant) or syndromic with heterotaxy and heart defects; marked risk of pneumococcal sepsis, managed with vaccination and penicillin prophylaxis.
Congenital cervical spinal stenosis
Congenital cervical spinal stenosis (ORPHA:831, congenital narrowing of cervical spinal canal, ICD-10 Q06.8) is a rare neurological disease with cervical canal sagittal diameter under 14 mm, predisposing to myelopathy and trauma-induced cord injury.
Congenital chylothorax
Congenital chylothorax (CCT), also called congenital chylothorax of the newborn, is chyle accumulation in the fetal or neonatal pleural space from lymphatic duct malformation; the leading cause of neonatal pleural effusion, incidence about 1:5,800-1:24,000, treated stepwise with drainage, MCT diet, octreotide, and surgery.