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Brain and Nerves Glossary

Terms used to explain Brain and Nerves can sometimes be confusing. To help you fully understand the articles and features related to this very important health topic, we have compiled a glossary of terms that can help.

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Absence Seizure

ab*sence seizure
Pronunciation: \ˈab-sən(t)s-\


Function: noun
: a nonconvulsive generalized seizure that is marked by the transient impairment or loss of consciousness usu. with a blank stare, that begins and ends abruptly and is usu. unremembered afterward, and that is seen chiefly in mild types of epilepsy —called also absence, petit mal

Acetylcholine

ace*tyl*cho*line
Pronunciation: \ə-ˌset-əl-ˈkō-ˌlēn, -ˌsēt-; ˌas-ə-ˌtēl-\


Function: noun
: a neurotransmitter C7H17NO3 released at autonomic synapses and neuromuscular junctions, active in the transmission of nerve impulses, and formed enzymatically in the tissues from choline

Akinesia

aki*ne*sia
Pronunciation: \ˌā-kī-ˈnē-zh(ē-)ə\


Function: noun
: loss or impairment of voluntary activity (as of a muscle)

Allodynia

al*lo*dyn*ia
Pronunciation: \ˌal-ə-ˈdin-ē-ə\


Function: noun
: pain resulting from a stimulus (as a light touch of the skin) which would not normally provoke pain; also: a condition marked by allodynia

Aneurysm

an*eu*rysm
Function: noun
: an abnormal blood-filled dilatation of a blood vessel and esp. an artery resulting from disease of the vessel wall

Anticholinergic

1an*ti*cho*lin*er*gic
Pronunciation: \-ˌkō-lə-ˈnər-jik\


Function: adjective
: opposing or blocking the physiological action of acetylcholine

Antidepressant

1an*ti*de*pres*sant
Pronunciation: \ˌant-i-di-ˈpres-ənt, ˌan-ˌtī-\


Function: adjective
: used or tending to relieve or prevent psychic depression

Antiepileptic

1an*ti*ep*i*lep*tic
Pronunciation: \-ˌep-ə-ˈlep-tik\


Function: adjective
: tending to suppress or prevent epilepsy <antiepileptic[1] treatment>

Apnea

ap*nea
Function: noun

1: transient cessation of respiration whether normal (as in hibernating animals) or abnormal (as that caused by certain drugs) see sleep apnea
2: see: asphyxia

Arrhythmia

ar*rhyth*mia
Pronunciation: \ā-ˈrith-mē-ə\


Function: noun
: an alteration in rhythm of the heartbeat either in time or force

Arteritis

ar*ter*i*tis
Pronunciation: \ˌärt-ə-ˈrīt-əs\


Function: noun
pl -te*rit*i*des
Pronunciation: \-ˈrit-ə-ˌdēz\
: arterial inflammation see giant cell arteritis

Astrocytoma

as*tro*cy*to*ma
Pronunciation: \ˌas-trə-sī-ˈtō-mə\


Function: noun
pl -mas
also -ma*ta
Pronunciation: \-mət-ə\
: a nerve-tissue tumor composed of astrocytes

Ataxia

atax*ia
Pronunciation: \ə-ˈtak-sē-ə, (ˈ)ā-\


Function: noun
: an inability to coordinate voluntary muscular movements that is symptomatic of some nervous disorders

Atrial Fibrillation

atrial fibrillation
Function: noun
: very rapid uncoordinated contractions of the atria of the heart resulting in a lack of synchronism between heartbeat and pulse beat —called also auricular fibrillation

Aura

au*ra
Pronunciation: \ˈor-ə\


Function: noun
pl auras
also au*rae
Pronunciation: \-ē\
: a subjective sensation (as of voices or colored lights or crawling and numbness) experienced before an attack of some nervous disorders (as epilepsy or migraine)

Automatism

au*tom*a*tism
Pronunciation: \o-ˈtäm-ə-ˌtiz-əm\


Function: noun

1: an automatic action; esp: any action performed without the doer's intention or awareness
2: the power or fact of moving or functioning without conscious control either independently of external stimulation (as in the beating of the heart) or more or less directly under the influence of external stimuli (as in the dilating or contracting of the pupil of the eye)

Autonomic Nervous System

autonomic nervous system
Function: noun
: a part of the vertebrate nervous system that innervates smooth and cardiac muscle and glandular tissues and governs involuntary actions (as secretion, vasoconstriction, or peristalsis) and that consists of the sympathetic nervous system and the parasympathetic nervous system —called also vegetative nervous system, compare central nervous system peripheral nervous system

Benign

be*nign
Pronunciation: \bi-ˈnīn\


Function: adjective

1: of a mild type or character that does not threaten health or life <benign malaria> <a benign tumor> compare malignant 1
2: having a good prognosis : responding favorably to treatment <a benign psychosis>

Biofeedback

bio*feed*back
Pronunciation: \-ˈfēd-ˌbak\


Function: noun
: the technique of making unconscious or involuntary bodily processes (as heartbeat or brain waves) perceptible to the senses (as by the use of an oscilloscope) in order to manipulate them by conscious mental control

Biopsy

1bi*op*sy
Pronunciation: \ˈbī-ˌäp-sē\


Function: noun
pl -sies
: the removal and examination of tissue, cells, or fluids from the living body

Blood-brain Barrier

blood–brain barrier
Function: noun
: a naturally occurring barrier created by the modification of brain capillaries (as by reduction in fenestration and formation of tight cell-to-cell contacts) that prevents many substances from leaving the blood and crossing the capillary walls into the brain tissues abbr. BBB

Bradykinesia

bra*dy*ki*ne*sia
Pronunciation: \-kī-ˈnē-zh(ē-)ə, -kə-, -zē-ə\


Function: noun
: extreme slowness of movements and reflexes (as in catatonic schizophrenia or in weightless spaceflight)

Bradyphrenia

bra*dy*phre*nia
Pronunciation: \-ˈfrē-nē-ə\


Function: noun
: a condition characterized by slowness of mental processes

Brain Stem

brain stem
Pronunciation: \-ˌstem\


Function: noun
: the part of the brain composed of the midbrain, pons, and medulla oblongata and connecting the spinal cord with the forebrain and cerebrum

CIS

CIS
Function: abbreviation
carcinoma in situ

CSF

CSF
Pronunciation: \ˌsē-(ˌ)es-ˈef\


Function: noun
: see: colony-stimulating factor

CT Scan

CT scan
Pronunciation: \(ˈ)sē-ˈtē-\


Function: noun
: see: cat scan

Caffeine

caf*feine
Pronunciation: \ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən\


Function: noun
: a bitter alkaloid C8H10N4O2 found esp. in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic

Carotid Artery

carotid artery
Function: noun
: either of the two main arteries that supply blood to the head of which the left in humans arises from the arch of the aorta and the right by bifurcation of the brachiocephalic artery with each passing along the corresponding anterolateral aspect of the neck and dividing opposite the upper border of the thyroid cartilage into an external branch supplying the face, tongue, and external parts of the head and an internal branch supplying the brain, eye, and other internal parts of the head —called also carotid, see common carotid artery external carotid artery internal carotid artery

Cerebral

ce*re*bral
Pronunciation: \sə-ˈrē-brəl, ˈser-ə-\


Function: adjective

1: of or relating to the brain or the intellect
2: of, relating to, affecting, or being the cerebrum <cerebral blood flow> <cerebral toxoplasmosis>

Cerebrovascular

ce*re*bro*vas*cu*lar
Pronunciation: \sə-ˌrē-brō-ˈvas-kyə-lər, ˌser-ə-brō-\


Function: adjective
: of or involving the cerebrum and the blood vessels supplying it <cerebrovascular disease>

Cerebrum

ce*re*brum
Pronunciation: \sə-ˈrē-brəm, ˈser-ə-brəm\


Function: noun
pl -brums
or -bra
Pronunciation: \-brə\

1: see: brain 1
2: an enlarged anterior or upper part of the brain; esp: the expanded anterior portion of the brain that in higher mammals overlies the rest of the brain, consists of cerebral hemispheres and connecting structures, and is considered to be the seat of conscious mental processes : see: telencephalon

Chemotherapy

che*mo*ther*a*py
Pronunciation: \-ˈther-ə-pē\


Function: noun
pl -pies
: the use of chemical agents in the treatment or control of disease or mental disorder

Chorea

cho*rea
Pronunciation: \kə-ˈrē-ə\


Function: noun
: any of various nervous disorders of infectious or organic origin marked by spasmodic movements of the limbs and facial muscles and by incoordination —called also Saint Vitus' dance, see huntington's disease sydenham's chorea

Cluster Headache

cluster headache
Function: noun
: a headache that is characterized by severe unilateral pain in the eye or temple, affects primarily men, and tends to recur in a series of attacks —called also histamine cephalalgia, histamine cephalgia, Horton's syndrome

Convulsion

con*vul*sion
Pronunciation: \kən-ˈvəl-shən\


Function: noun
: an abnormal violent and involuntary contraction or series of contractions of the muscles often used in pl.<a patient suffering from convulsions>

Craniotomy

cra*ni*ot*o*my
Pronunciation: \ˌkrā-nē-ˈät-ə-mē\


Function: noun
pl -mies

1: the operation of cutting or crushing the fetal head to effect delivery <fetal craniotomies…performed to save the life of the mother R. E. Frisch>
2: surgical opening of the skull

DNA

DNA
Pronunciation: \ˌdē-ˌen-ˈā\


Function: noun
: any of various nucleic acids that are usu. the molecular basis of heredity, are constructed of a double helix held together by hydrogen bonds between purine and pyrimidine bases which project inward from two chains containing alternate links of deoxyribose and phosphate, and that in eukaryotes are localized chiefly in cell nuclei —called also deoxyribonucleic acid, see recombinant dna

Dopamine

do*pa*mine
Pronunciation: \ˈdō-pə-ˌmēn\



Function: noun
1: a monoamine C8H11NO2 that is a decarboxylated form of dopa and occurs esp. as a neurotransmitter in the brain and as an intermediate in the biosynthesis of epinephrine see intropin

Dura

dura
see lamina dura

Dysarthria

dys*ar*thria
Pronunciation: \dis-ˈär-thrē-ə\


Function: noun
: difficulty in articulating words due to disease of the central nervous system compare dysphasia

Dyskinesia

dys*ki*ne*sia
Pronunciation: \ˌdis-kə-ˈnē-zh(ē-)ə, -kī-\


Function: noun
: impairment of voluntary movements resulting in fragmented or jerky motions (as in Parkinson's disease) see tardive dyskinesia

Dysphagia

dys*pha*gia
Pronunciation: \dis-ˈfā-j(ē-)ə\


Function: noun
: difficulty in swallowing

Dystonia

dys*to*nia
Pronunciation: \dis-ˈtō-nē-ə\


Function: noun
: a state of disordered tonicity of tissues (as of muscle)

EEG

EEG
Function: abbreviation
electroencephalogram; electroencephalograph

Electrode

elec*trode
Pronunciation: \i-ˈlek-ˌtrōd\


Function: noun
: a conductor used to establish electrical contact with a nonmetallic part of a circuit

Endarterectomy

end*ar*ter*ec*to*my
Pronunciation: \ˌen-ˌdärt-ə-ˈrek-tə-mē\


Function: noun
pl -mies
: surgical removal of the inner layer of an artery when thickened and atheromatous or occluded (as by intimal plaques)

Ergot

er*got
Pronunciation: \ˈər-gət, -ˌgät\


Function: noun

1 a: the black or dark purple sclerotium of fungi of the genus Claviceps that occurs as a club-shaped body which replaces the seed of various grasses (as rye)
b: any fungus of the genus Claviceps
2: a disease of rye and other cereals caused by fungi of the genus Claviceps and characterized by the presence of ergots in the seed heads compare ergotism
3 a: the dried sclerotial bodies of an ergot fungus grown on rye and containing several ergot alkaloids
b: see: ergot alkaloid

Febrile

fe*brile
Pronunciation: \ˈfeb-ˌrīl also ˈfēb-\


Function: adjective
: see: feverish

Flexor Muscle

flexor muscle
Function: noun
: see: flexor

Focal Seizure

focal seizure
Function: noun
: see: partial seizure

Generalized Seizure

generalized seizure
Function: noun
: a seizure (as an absence seizure or tonic-clonic seizure) that originates in both cerebral hemispheres compare partial seizure

Globus Pallidus

globus pal*li*dus
Pronunciation: \-ˈpal-ə-dəs\


Function: noun
: the median portion of the lentiform nucleus —called also pallidum

Hemicrania

hemi*cra*nia
Pronunciation: \-ˈkrā-nē-ə\


Function: noun
: pain in one side of the head compare amphicrania

Hemorrhagic Stroke

hemorrhagic stroke
Function: noun
: stroke caused by the rupture of a blood vessel with bleeding into the tissue of the brain

Hydrencephalus

hy*dren*ceph*a*lus
Pronunciation: \-ˈsef-ə-ləs\


Function: noun
pl -li
Pronunciation: \-ˌlī\
: see: hydrocephalus

Hyperventilation

hy*per*ven*ti*la*tion
Pronunciation: \-ˌvent-əl-ˈā-shən\


Function: noun
: excessive ventilation; specif: excessive rate and depth of respiration leading to abnormal loss of carbon dioxide from the blood —called also overventilation

Hypoxia

hyp*ox*ia
Pronunciation: \hip-ˈäk-sē-ə, hī-ˈpäk-\


Function: noun
: a deficiency of oxygen reaching the tissues of the body

Idiopathic

id*io*path*ic
Pronunciation: \ˌid-ē-ə-ˈpath-ik\


Function: adjective
: arising spontaneously or from an obscure or unknown cause : see: primary<idiopathic epilepsy> <idiopathic thrombocytopenic purpura>

Insomnia

in*som*nia
Pronunciation: \in-ˈsäm-nē-ə\


Function: noun
: prolonged and usu. abnormal inability to obtain adequate sleep —called also agrypnia

Intracerebral

in*tra*ce*re*bral
Pronunciation: \-sə-ˈrē-brəl, -ˈser-ə-\


Function: adjective
: situated within, occurring within, or administered by entering the cerebrum <intracerebral bleeding>

Lacrimation

lac*ri*ma*tion
Function: noun
: the secretion of tears; specif: abnormal or excessive secretion of tears due to local or systemic disease

Lennox-Gastaut Syndrome

Len*nox–Gas*taut syndrome
Pronunciation: \ˈlen-əks-gas-ˈtō-\

Function: noun
: an epileptic syndrome esp. of young children that is marked by tonic, atonic, and myoclonic seizures and by atypical absence seizures, that is associated with mental retardation, that is prob. caused by various forms of brain damage (as from cerebral hemorrhage, encephalitis, or developmental or metabolic disorder), and that is characterized between seizures by an EEG having a slow spike and wave pattern

Lewy Body

Lewy body
Pronunciation: \ˈlü-ē-, ˈlā-vē-\


Function: noun
: an eosinophilic inclusion body found in the cytoplasm of neurons of the cortex and brain stem in Parkinson's disease and some forms of dementia

Lumbar Puncture

lumbar puncture
Function: noun
: puncture of the subarachnoid space in the lumbar region of the spinal cord to withdraw cerebrospinal fluid or inject anesthetic drugs —called also spinal tap

MRI

MRI
Pronunciation: \ˌem-(ˌ)är-ˈī\


Function: noun
: see: magnetic resonance imaging; also: a procedure in which magnetic resonance imaging is used

MS

MS
Function: abbreviation

1 mass spectrometry
2 master of science
3 multiple sclerosis

Malignant

ma*lig*nant
Pronunciation: \mə-ˈlig-nənt\


Function: adjective

1: tending to produce death or deterioration <malignant malaria> ; esp: tending to infiltrate, metastasize, and terminate fatally <malignant tumors> compare benign 1
2: of unfavorable prognosis : not responding favorably to treatment <psychotic reactions with a malignant trend>

Myelin

my*e*lin
Pronunciation: \ˈmī-ə-lən\


Function: noun
: a soft white somewhat fatty material that forms a thick myelin sheath about the protoplasmic core of a myelinated nerve fiber

Myelin Basic Protein

myelin basic protein
Function: noun
: a protein that is a constituent of myelin and is often found in higher than normal amounts in the cerebrospinal fluid of individuals affected with some demyelinating disease (as multiple sclerosis) abbr. MBP

Myelogram

my*e*lo*gram
Pronunciation: \ˈmī-ə-lə-ˌgram\


Function: noun

1: a differential study of the cellular elements present in bone marrow usu. made on material obtained by sternal biopsy
2: a radiograph of the spinal cord made by myelography

Myoclonus

my*oc*lo*nus
Pronunciation: \ˌmī-ˈäk-lə-nəs\


Function: noun
: irregular involuntary contraction of a muscle usu. resulting from functional disorder of controlling motor neurons; also: a condition characterized by myoclonus

Narcolepsy

nar*co*lep*sy
Pronunciation: \ˈnär-kə-ˌlep-sē\


Function: noun
pl -sies
: a condition characterized by brief attacks of deep sleep often occurring with cataplexy and hypnagogic hallucinations compare hypersomnia 2

Night Terror

night ter*ror
Pronunciation: \-ˈter-ər\


Function: noun
: a sudden awakening in dazed terror that occurs in children during slow-wave sleep, is often preceded by a sudden shrill cry uttered in sleep, and is not remembered when the child awakes usu. used in pl.—called also pavor nocturnus

Nocturnal

noc*tur*nal
Pronunciation: \näk-ˈtərn-əl\


Function: adjective

1: of, relating to, or occurring at night <nocturnal myoclonus>
2: characterized by nocturnal activity <a nocturnal form of filariasis>

Pallidotomy

pal*li*dot*o*my
Pronunciation: \ˌpal-i-ˈdät-ə-mē\


Function: noun
pl -mies
: the surgical inactivation of the globus pallidus or a part of it in the treatment of involuntary movements (as in Parkinson's disease)

Paresthesia

par*es*the*sia
Function: noun
: a sensation of pricking, tingling, or creeping on the skin having no objective cause and usu. associated with injury or irritation of a sensory nerve or nerve root

Parietal Lobe

parietal lobe
Function: noun
: the middle division of each cerebral hemisphere that is situated behind the central sulcus, above the sylvian fissure, and in front of the parieto-occipital sulcus and that contains an area concerned with bodily sensations

Photophobia

pho*to*pho*bia
Pronunciation: \ˌfōt-ə-ˈfō-bē-ə\


Function: noun

1: intolerance to light; esp: painful sensitiveness to strong light
2: an abnormal fear of light

Pituitary

1pi*tu*i*tary
Pronunciation: \pə-ˈt(y)ü-ə-ˌter-ē\


Function: adjective

1: of or relating to the pituitary gland
2: caused or characterized by secretory disturbances of the pituitary gland <a pituitary[1] dwarf>

Plaque

plaque
Function: noun

1 a: a localized abnormal patch on a body part or surface and esp. on the skin <psoriatic plaque>
b: a sticky usu. colorless film on teeth that is formed by and harbors bacteria
c: an atherosclerotic lesion
d: a histopathologic lesion of brain tissue that is characteristic of Alzheimer's disease and consists of a dense proteinaceous core composed primarily of beta-amyloid that is often surrounded and infiltrated by a cluster of degenerating axons and dendrites —called also senile plaque
2: a visibly distinct and esp. a clear or opaque area in a bacterial culture produced by damage to or destruction of cells by a virus

Plasmin

plas*min
Pronunciation: \-mən\


Function: noun
: a proteolytic enzyme that dissolves the fibrin of blood clots

Post-traumatic

post–trau*mat*ic
Pronunciation: \-trə-ˈmat-ik, -tro-, -trau-\

Function: adjective
: occurring after or as a result of trauma <post-traumatic epilepsy>

Prodromal

pro*dro*mal
Pronunciation: \(ˈ)prō-ˈdrō-məl\


Function: adjective
: see: precursory; esp: of, relating to, or marked by prodromes <the prodromal stages of a disease>

Ptosis

pto*sis
Pronunciation: \ˈtō-səs\


Function: noun
pl pto*ses
Pronunciation: \-ˌsēz\
: a sagging or prolapse of an organ or part <renal ptosis> ; esp: a drooping of the upper eyelid (as from paralysis of the oculomotor nerve)

Pulsatile

pul*sa*tile
Pronunciation: \ˈpəl-sət-əl, -sə-ˌtīl\


Function: adjective
: marked by or occurring in pulsations <a pulsatile glandular secretion>

Radiation Therapy

radiation therapy
Function: noun
: see: radiotherapy

Rapid Eye Movement

rap*id eye movement
Pronunciation: \ˈrap-əd-\


Function: noun
: a rapid conjugate movement of the eyes associated esp. with REM sleep —called also REM

Restless Legs Syndrome

restless legs syndrome
Function: noun
: a neurological disorder of uncertain pathophysiology that is characterized by aching, burning, crawling, or creeping sensations of the legs that occur esp. at night usu. when lying down (as before sleep) and cause a compelling urge to move the legs and that is often accompanied by difficulty in falling or staying asleep and by involuntary twitching of the legs during sleep —called also restless legs

Shunt

1shunt
Pronunciation: \ˈshənt\


Function: transitive verb
: to divert by or as if by a shunt; esp: to divert (blood) from one part to another by a surgical shunt

Sleep Apnea

sleep apnea
Function: noun
: brief periods of recurrent cessation of breathing during sleep that is caused esp. by obstruction of the airway or a disturbance in the brain's respiratory center and is associated esp. with excessive daytime sleepiness

Sleepwalker

sleep*walk*er
Pronunciation: \ˈslēp-ˌwo-kər\


Function: noun
: one who is subject to somnambulism : one who walks while sleeping —called also somnambulist

Slow-wave Sleep

slow–wave sleep
Function: noun
: a state of deep usu. dreamless sleep that occurs regularly during a normal period of sleep with intervening periods of REM sleep and that is characterized by delta waves and a low level of autonomic physiological activity —called also non-REM sleep, NREM sleep, orthodox sleep, S sleep, synchronized sleep

Soft Palate

soft palate
Function: noun
: the membranous and muscular fold suspended from the posterior margin of the hard palate and partially separating the mouth cavity from the pharynx

Spasm

spasm
Pronunciation: \ˈspaz-əm\


Function: noun

1: an involuntary and abnormal contraction of muscle or muscle fibers or of a hollow organ (as an artery, the colon, or the esophagus) that consists largely of involuntary muscle fibers
2: the state or condition of a muscle or organ affected with spasms <the renal artery went into spasm>

Spinal Tap

spinal tap
Function: noun
: see: lumbar puncture

Subarachnoid

sub*arach*noid
Pronunciation: \ˌsəb-ə-ˈrak-ˌnoid\


Function: adjective

1: situated or occurring under the arachnoid membrane <subarachnoid hemorrhage>
2: of, relating to, or involving the subarachnoid space and the fluid within it <subarachnoid meningitis>

Substantia Nigra

sub*stan*tia ni*gra
Pronunciation: \səb-ˌstan-chē-ə-ˈnī-grə, -ˈnig-rə\


Function: noun
pl sub*stan*ti*ae ni*grae
Pronunciation: \-chē-ˌē-ˈnī-(ˌ)grē, -ˈnig-(ˌ)rē\
: a layer of deeply pigmented gray matter situated in the midbrain and containing the cell bodies of a tract of dopamine-producing nerve cells whose secretion tends to be deficient in Parkinson's disease

Thalamotomy

thal*a*mot*o*my
Pronunciation: \ˌthal-ə-ˈmät-ə-mē\


Function: noun
pl -mies
: a surgical operation involving electrocoagulation of areas of the thalamus to interrupt pathways of nervous transmission through the thalamus for relief of certain mental and psychomotor disorders

Transient Ischemic Attack

transient ischemic attack
Function: noun
: a brief episode of cerebral ischemia that is usu. characterized by temporary blurring of vision, slurring of speech, numbness, paralysis, or syncope and that is often predictive of a serious stroke abbr. TIA—called also mini-stroke

Tremor

trem*or
Pronunciation: \ˈtrem-ər\


Function: noun
: a trembling or shaking usu. from physical weakness, emotional stress, or disease <tremors of the hands>

Vagus Nerve

vagus nerve
Function: noun
: either of the tenth pair of cranial nerves that arise from the medulla and supply chiefly the viscera esp. with autonomic sensory and motor fibers —called also pneumogastric nerve, tenth cranial nerve, vagus

Vertebral Artery

vertebral artery
Function: noun
: a large branch of the subclavian artery that ascends through the foramina in the transverse processes of each of the cervical vertebrae except the last one or two, enters the cranium through the foramen magnum, and unites with the corresponding artery of the opposite side to form the basilar artery

White Matter

white matter
Function: noun
: neural tissue esp. of the brain and spinal cord that consists largely of myelinated nerve fibers bundled into tracts, has a whitish color, and typically underlies the gray matter

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