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Note to the learner

This glossary contains neuronatomical terms, as well as terms commonly used clinically to describe neurological symptoms and physical findings of a neurological examination; few clinical syndromes are included.

Abadie’s Sign — Abadie’s sign is the absence or diminution of pain sensation when exerting deep pressure on the Achilles tendon by squeezing. This is a frequent finding in the tabes dorsalis variant of neurosyphilis (i.e., with dorsal column disease).
Cross References Argyll Robertson pupil

Abdominal Paradox — see PARADOXICAL BREATHING

Abdominal Reflexes — Both superficial and deep abdominal reflexes are described, of which the superficial (cutaneous) reflexes are the more commonly tested in clinical practice. A wooden stick or pin is used to scratch the abdomi- nal wall, from the flank to the midline, parallel to the line of the der- matomal strips, in upper (supraumbilical), middle (umbilical), and lower (infraumbilical) areas. The maneuver is best performed at the end of expiration when the abdominal muscles are relaxed, since the reflexes may be lost with muscle tensing; to avoid this, patients should lie supine with their arms by their sides.

Superficial abdominal reflexes are lost in a number of  circum- stances:

  • normal old age obesity
  • after abdominal surgeryafter
  • multiple pregnancies
  • in acute abdominal disorders (Rosenbach’s sign).

However, absence of all superficial abdominal reflexes may be of localizing value for corticospinal pathway damage (upper motor neu- rone lesions) above T6. Lesions at or below T10 lead to selective loss of the lower reflexes with the upper and middle reflexes intact, in which case Beevor’s sign may also be present. All abdominal reflexes are preserved with lesions below T12.
Abdominal reflexes are said to be lost early in multiple sclerosis, but late in motor neurone disease, an observation of possible clinical use, particularly when differentiating the primary lateral sclerosis vari- ant of motor neurone disease from multiple sclerosis. However, no prospective study of abdominal reflexes in multiple sclerosis has been reported.
Cross ReferencesBeevor’s sign; Upper motor neurone (UMN) syndrome


Abducens nerve — 6th cranial nerve (CN VI); to lateral rectus muscle for abduction of the eye

Abducens (VI) Nerve Palsy — Abducens (VI) nerve palsy causes a selective weakness of the lateral rectus muscle resulting in impaired abduction of the eye, manifest clin- ically as diplopia on lateral gaze, or on shifting gaze from a near to a distant object.
Abducens (VI) nerve palsy may be due to:

  • Microinfarction in the nerve, due to hypertension, diabetes mellitus
  • Raised intracranial pressure: a “false-localizing sign,” possibly caused by stretching of the nerve in its long intracranial course
    over the ridge of the petrous temporal bone
  • Nuclear pontine lesions: congenital (e.g., Duane retraction syn- drome, Möbius syndrome).

Isolated weakness of the lateral rectus muscle may also occur in myasthenia gravis. In order not to overlook this fact, and miss a poten- tially treatable condition, it is probably better to label isolated abduc- tion failure as “lateral rectus palsy,” rather than abducens nerve palsy, until the etiological diagnosis is established.
Excessive or sustained convergence associated with a midbrain lesion (diencephalic-mesencephalic junction) may also result in slow or restricted abduction (pseudo-abducens palsy, “midbrain pseudo- sixth”).
Cross ReferencesDiplopia; “False-localizing signs”

Absence — An absence, or absence attack, is a brief interruption of awareness of epileptic origin. This may be a barely noticeable suspension of speech or attentiveness, without postictal confusion or awareness that an attack has occurred, as in idiopathic generalized epilepsy of absence type (absence epilepsy; petit mal), a disorder exclusive to childhood and associated with 3 Hz spike and slow wave EEG abnormalities.
Absence epilepsy may be confused with a more obvious distanc- ing, “trance-like” state, or “glazing over,” possibly with associated automatisms, such as lip smacking, due to a complex partial seizure of temporal lobe origin (“atypical absence”).
Ethosuximide and/or sodium valproate are the treatments of choice for idiopathic generalized absence epilepsy, whereas carba- mazepine, sodium valproate, or lamotrigine are first-line agents for localization-related complex partial seizures.
Cross ReferencesAutomatism; Seizures

Abulia — Abulia (aboulia) is a “syndrome of hypofunction,” characterized by lack of initiative, spontaneity and drive (aspontaneity), apathy, slowness of thought (bradyphrenia), and blunting of emotional responses and response to external stimuli. It may be confused with the psychomotor retardation of depression and is sometimes labeled as “pseudodepres- sion.” More plausibly, abulia has been thought of as a minor or partial form of akinetic mutism. There may also be some clinical overlap with catatonia. Abulia may result from frontal lobe damage, most particularly that involving the frontal convexity, and has also been reported with focal lesions of the caudate nucleus, thalamus, and midbrain. As with akinetic mutism, it is likely that lesions anywhere in the “centromedial core” of the brain, from frontal lobes to brainstem, may produce this picture.
Pathologically, abulia may be observed in:

  • Infarcts in anterior cerebral artery territory and ruptured anterior communicating artery aneurysms, causing basal forebrain dam- age.
  • Closed head injury
  • Parkinson’s disease; sometimes as a forerunner of a frontal lobe dementia
  • Other causes of frontal lobe disease: tumor, abscess
  • Metabolic, electrolyte disorders: hypoxia, hypoglycemia, hepatic encephalopathy

Treatment is of the underlying cause where possible. There is anec- dotal evidence that the dopamine agonist bromocriptine may help.
Cross ReferencesAkinetic mutism; Apathy; Bradyphrenia; Catatonia; Frontal lobe syndromes; Psychomotor retardation


Accessory nerve — 11th cranial nerve (CN XI) — see spinal accessory nerve

Afferent — conduction toward the central nervous system; usually means sensory

Agnosia — loss of ability to recognize the significance of sensory stimuli (tactile, auditory, visual), even though the primary sensory systems are intact

Agonist — a muscle that performs a certain movement of the joint; the opposing muscle is called the antagonist

Agraphia — inability to write due to a lesion of higher brain centers, even though muscle strength and coordination are preserved

Akinesia — absence or loss of motor function; lack of spontaneous movement; difficulty in initiating movement (as in Parkinson's disease)

Alexia — loss of ability to grasp the meaning of written words; inability to read due to a central lesion; word blindness

Allocortex — the phylogenetically older cerebral cortex, consisting of less than six layers; includes paleocortex (e.g., subicular region = three to five layers) and archicortex (e.g., hippocampus proper and dentate = three layers)

Alpha motor neuron — another name for the anterior (ventral) horn cell, also called the lower motor neuron

Ammon's horn — the hippocampus proper, which has an outline in cross-section suggestive of a ram's horn; also called the Cornu Ammonis (CA)

Amygdala — amygdaloid nucleus or body in the temporal lobe of the cerebral hemisphere; a nucleus of the limbic system

Angiogram — display of blood vessels for diagnostic purposes, using, x-rays, MRI or CT, usually by using contrast medium injected into the vascular system

Anopia — a defect in the visual field (e.g., hemianopia — loss of one-half of visual field; quadrantanopia — loss of one-quarter of visual field)

Antagonist — a muscle that opposes or resists the action of another muscle, which is called the agonist

Antidromic — relating to the propagation of an impulse along an axon in a direction that is the reverse of the normal or usual direction

Aphasia — an acquired disruption or disorder of language, specifically a deficit of expression using speech or of comprehending spoken or written language; global aphasia is a severe form affecting all language areas

Apopotosis — programmed cell death, either genetically determined or following an insult or injury to the cell

Apraxia — loss of ability to carry out purposeful or skilled movements despite the preservation of power, sensation, and coordination

Arachnoid — the middle meningeal layer, forming the outer boundary of the subarachnoid space

Areflexia — loss of reflex as tested using the myotatic, stretch, deep tendon reflex

Archicerebellum — a phylogenetically old part of the cerebellum, functioning in the maintenance of equilibrium; anatomically, the flocculonodular lobe

Archicortex — three-layered cortex included in the limbic system; located mainly in the hippocampus proper and dentate gyrus of the temporal lobe

Area postrema — an area involved in vomiting; located in the caudal part of the floor of the fourth ventricle, with no blood-brain-barrier

Ascending tract — central sensory pathway, e.g., from spinal cord to brainstem, cerebellum, or thalamus

Association fibers — fibers connecting parts of the cerebral hemisphere, on the same side

Astereognosis — loss of ability to recognize the nature of objects or to appreciate their shape by touching or feeling them

Astrocyte — a type of neuroglial cell with metabolic and structural functions; reacts to injury of the CNS by forming a gliotic "scar"

Asynergy — impairment of the proper sequencing in the contraction of muscles, at the proper moment, and of theproper degree, so that an action is not executed smoothly or accurately

Ataxia — a loss of coordination of voluntary movements; often associated with cerebellar dysfunction

Athetosis — slow writhing movements of the limbs, especially of the hands, not under voluntary control, caused by degenerative changes in the striatum

Autonomic — autonomic nervous system; usually taken to mean the efferent or motor innervation of viscera (smooth muscle and glands)

Autonomic nervous system (ANS) — visceral innervation; sympathetic and parasympathetic divisions system

Axon — efferent process of a neuron, conducting impulses to other neurons or to muscle fibers (striated and smooth) and gland cells

Analgesia — pain relief (see Blockade)



Babinski response — Babinski reflex is not correct; stroking the outer border of the sole of the foot in an adult normally results in a plantar (downgoing) of the toes; the Babinski response consists of an upgoing of the first toe and a fanning of the other toes, indicating a lesion of the pyramidal (cortico-spinal) tract

Basal ganglia (nuclei) — CNS nuclei involved in motor control, the caudate, putamen and globus pallidus (the lentiform nucleus); including, functionally, the subthalamus and the substantia nigra

Basilar artery — the major artery supplying the brainstem and cerebellum, formed by the two vertebral arteries

Brachium — a large bundle of fibers connecting one part with another (e.g., brachium associated with the inferior and superior colliculi of the midbrain)

Bradykinesia — abnormally slow initiation of voluntary movements (usually seen in Parkinson's disease)

Brainstem — includes the medulla, pons, and midbrain

Brodmann areas — numerical subdivisions of the cerebral cortex on the basis of histological differences between different functional areas (e.g. area 4 = motor cortex; area 17 = primary visual area)

Bulb — referred at one time to the medulla but in the context of "cortico-bulbar tract" refers to the whole brainstem in which the motor nuclei of cranial nerves and other nuclei are located



Carotid siphon — hairpin bend of the internal carotid artery within the skull

CAT or CT scan — computerized (Axial) Tomography; a diagnostic imaging technique that uses x-rays and computer reconstruction of the brain

Cauda equina — "horse's tail"; the lower lumbar, sacral, and coccygeal spinal nerve roots within the subarachnoid space of the lumbar (CSF) cistern

Caudal — toward the tail, or hindmost part of neuraxis

Caudate nucleus — part of the neostriatum, consists of a head, body, and tail (which extends into the temporal lobe)

Central nervous system (CNS) — brain (cerebral hemispheres), including diencephalon, cerebellum, brainstem, and spinal cord

Cerebellar peduncles — inferior, middle, and superior; fiber tracts linking the cerebellum and brainstem

Cerebellum — the little brain; an older part of the brain with motor functions, dorsal to the brainstem, situated in the posterior cranial fossa

Cerebral aqueduct (of Sylvius) — aqueduct of the midbrain; passageway carrying CSF through the midbrain, as part of the ventricular system

Cerebral peduncle — descending cortical fibers in the "basal" (ventral) portion of the midbrain, sometimes includes the substantia nigra (located immediately behind)

Cerebrospinal fluid (CSF) — fluid in the ventricles, and in the subarachnoid space and cisterns

Cerebrum — includes the cerebral hemispheres and diencephalon
but not the brainstem and cerebellum

Cervical — referring to the neck region; the part of the spinal cord that supplies the structures of the neck; C1–C7 vertebral; C1–C8 spinal segments

Chorda tympani — part of the 7th cranial nerve (CN VII) (see facial nerve); carrying taste from anterior two-thirds of tongue and parasympathetic innervation to glands

Chorea — a motor disorder characterized by abnormal, irregular, spasmodic, jerky, uncontrollable movements of the limbs or facial muscles, thought to be caused by degenerative changes in the basal ganglia

Choroid — a delicate membrane; choroid plexuses are found in the ventricles of the brain

Choroid plexus — vascular structure consisting of pia with blood vessels, with a surface layer of ependymal cells; responsible for the production of CSF

Cingulum — a bundle of association fibers in the white matter under the cortex of the cingulate gyrus; part of Papez (limbic) circuit

Circle of Willis — anastomosis between internal carotid and basilar arteries, located at the base of the brain, surrounding the pituitary gland

Cistern(a) — expanded portion of subarachnoid space containing CSF, e.g., cisterna magna (cerebello-medullary cistern), lumbar cistern

Claustrum — a thin sheet of gray matter, of unknown function, situated between the lentiform nucleus and the insula

Clonus — abnormal sustained series of contractions and relaxations following stretch of the muscle; usually elicited in the ankle joint; present following lesions of the descending motor pathways, and associated with spasticity

Conjugate eye movement — coordinated movement of both eyes together, so that the image falls on corresponding points of both retinas

CNS — abbreviation for central nervous system

Colliculus — a small elevation; superior and inferior colliculi comprising the tectum of the midbrain; also facial colliculus in the floor of the fourth ventricle

Commissure — a group of nerve fibers in the CNS connecting structures on one side to the other across the midline (e.g., corpus callosum of the cerebral hemispheres; anterior commissure)

Consensual reflex — light reflex; refers to the bilateral response of the pupil after shining a light in one eye

Contralateral — on the opposite side (e.g., contralateral to a lesion)

Corona radiata - fibers radiating from the internal capsule to various parts of the cerebral cortex — a term often used by neuroradiologists

Corpus callosum — The main (largest) neocortical commissure of the cerebral hemispheres

Corpus striatum — caudate, putamen, and globus pallidus, nuclei inside cerebral hemisphere, with motor function; the basal ganglia

Cortex — layers of gray matter (neurons and neuropil) on the surface of the cerebral hemispheres (mostly six layers) and cerebellum (three layers)

Cortico-bulbar — descending fibers connecting motor cortex with motor cranial nerve nuclei and other nuclei of brainstem (including reticular formation)

Corticofugal fibers — axons carrying impulses away from the cerebral cortex

Corticopetal fibers — axons carrying impulses toward the cerebral cortex

Cortico-spinal tract — descending tract, from motor cortex to anterior (ventral) horn cells of the spinal cord (sometimes direct); also called pyramidal tract

Cranial nerve nuclei — collections of cells in brainstem
giving rise to or receiving fibers from cranial nerves (CN III–XII); may be sensory, motor, or autonomic

Cranial nerves — twelve pairs of nerves arising from the brain and innervating structures of the head and neck (CN I is actually a CNS tract)

CSF — cerebrospinal fluid, in ventricles and subarachnoid space (and cisterns)

Cuneatus (cuneate) — sensory tract (fasciculus cuneatus) of the dorsal column of spinal cord, from the upper limbs and body; cuneate nucleus of medulla



Decerebrate posturing (rigidity) — characterized by extension of the upper and lower limbs; lesion at the brainstem level between the vestibular nuclei and the red nucleus

Decorticate posturing (rigidity) — characterized by extension of the lower limbs and flexion of the upper; lesion is located above the level of the red nucleus

Decussation — the point of crossing of CNS tracts, e.g., decussations of the pyramidal (cortico-spinal) tract, medial lemnisci, and superior cerebellar peduncles

Dementia — progressive brain disorder that gradually destroys a person's memory, starting with short-term memory, and loss of intellectual ability, such as the ability to learn, reason, make judgments, and communicate, and finally, inability to carry out normal activities of daily living; usually affects people with advancing age

Dendrite — receptive process of a neuron; usually several processes emerge from the cell body, each of which branches in a characteristic pattern

Dendritic spine — cytoplasmic excrescence of a dendrite and the site of an excitatory synapse

Dentate — (toothed or notched) dentate nucleus of the cerebellum (intracerebellar nucleus); dentate gyrus of the hippocampal formation

Dermatome — a patch of skin innervated by a single spinal cord segment (e.g., T1 supplies the skin of the inner aspect of the upper arm; T10 supplies umbilical region)

Descending tract — central motor pathway (e.g., from cortex to brainstem or spinal cord)

Diencephalon — consisting of the thalamus, epithalamus (pineal), subthalamus, and hypothalamus

Diplopia — double vision; a single object is seen as two objects

Dominant hemisphere — the hemisphere responsible for language; this is the left hemisphere in about 85 to 90% of people (including left-handed individuals)

Dorsal column — fasciculus gracilis and fasciculus cuneatus of the spinal cord, pathways (tracts) for discriminative touch, conscious proprioception and vibration

Dorsal root — afferent sensory component of a spinal nerve, located in the subarachnoid (CSF) space

Dorsal root ganglion (DRG) — a group of peripheral neurons along the dorsal root, whose axons carry afferent information from the periphery; their central process enters the spinal cord

Dura — dura mater, the thick external layer of the meninges (brain and spinal cord)

Dural venous sinuses — large venous channels for draining blood from the brain; located within dura of the meninges

Dysarthria — difficulty with the articulation of words

Dyskinesia — purposeless movements of the limbs or trunk, usually due to a lesion of the basal ganglia; also difficulty in performing voluntary movements

Dysmetria — impairment of the ability to control the range of movement in muscular action, causing under- or overshooting of the target (usually associated with cerebellar lesions)

Dysphagia — difficulty with swallowing

Dyspraxia — Impaired ability to perform a voluntary act previously well performed, with intact movement, coordination, and sensation



Efferent — away from the central nervous system; usually means motor to muscles

Emboliform — emboliform nucleus of the cerebellum, one of the intracerebellar (deep cerebellar) nuclei; with globose nucleus forms the interposed nucleus

Entorhinal — associated with olfaction (smell); the entorhinal area is the anterior part of the parahippocampal gyrus, adjacent to the uncus

Ependyma — epithelium lining of ventricles of the brain and central canal of spinal cord; specialized tight junctions at the site of the choroid plexus

Extrapyramidal system — an older clinically used term, usually intended to include the basal ganglia portion of the motor systems and not the pyramidal (cortico-spinal) motor system



Facial nerve — 7th cranial nerve (CN VII); motor to muscles of facial expression; carries taste from anterior twothirds of tongue; also parasympathetic to two salivary glands, lacrimal and nasal glands (see also chorda tympani)

Falx — dural partition in the midline of the cranial cavity; the large falx cerebri between the cerebral hemispheres, and the small falx cerebelli

Fascicle — a small bundle of nerve fibers

Fasciculus — a large tract or bundle of nerve fibers

Fasciculus cuneatus — part of dorsal column of spinal cord; ascending tract for discriminative touch, conscious proprioception and vibration from upper body and upper limb

Fasciculus gracilis — part of dorsal column of spinal cord; ascending tract for discriminative touch, conscious proprioception and vibration from lower body and lower limb

Fastigial nucleus — one of the deep cerebellar (intracerebellar) nuclei

Fiber — synonymous with an axon (either peripheral or central)

Flaccid paralysis — muscle paralysis with hypotonia due to a lower motor neuron lesion

Flocculus — lateral part of flocculonodular lobe of cerebellum (vestibulocerebellum)

Folium (plural folia) — a flat leaf-like fold of the cerebellar cortex

Foramen — an opening, aperture, between spaces containing CSF (e.g., Monro, between lateral ventricles and third ventricle; Magendie, between fourth ventricle and cisterna magna; Luschka, lateral foramen of fourth ventricle)

Forebrain — anterior division of embryonic brain; cerebrum and diencephalon

Fornix — the efferent (noncortical) tract of the hippocampal formation, arching over the thalamus and terminating in the mammillary nucleus of the hypothalamus and in the septal region

Fourth (4th) ventricle — cavity between brainstem and cerebellum, containing CSF

Funiculus — a large aggregation of white matter in the spinal cord, may contain several tracts



Ganglion (plural ganglia) — a collection of nerve cells in the PNS — dorsal root ganglion (DRG) and sympathetic ganglion; also inappropriately used for certain regions of gray matter in the brain (i.e., basal ganglia)

Geniculate bodies — specific relay nuclei of thalamus — medial (auditory) and lateral (visual)

Genu — knee or bend; middle portion of internal capsule; genu of facial nerve

Glial cell — also called neuroglial cell; supporting cells in the central nervous system — astrocyte, oligodendrocyte, and ependymal — also microglia

Globus pallidus — efferent part of basal ganglia; part of the lentiform nucleus with the putamen; located medially

Glossopharyngeal nerve — 9th cranial nerve (CN IX); motor to muscles of swallowing and carries taste from posterior one-third of tongue; nerve for the gag reflex

Gracilis (gracile) — sensory tract (fasciculus gracilis) of the dorsal column of spinal cord; nucleus gracilis of medulla

Gray matter — nervous tissue, mainly nerve cell bodies and adjacent neuropil; looks "grayish" after fixation in formalin

Gyrus (plural gyri) — a convolution or fold of the cerebral hemisphere; includes cortex and white matter



Habenula — a nucleus of the limbic system, adjacent to the posterior end of the roof of the 3rd ventricle (part of the epithalamus)

Hemiballismus — violent jerking or flinging movements of one limb, not under voluntary control, due to a lesion of subthalamic nucleus

Hemiparesis — muscular weakness affecting one side of the body

Hemiplegia — paralysis of one side of the body

Herniation — bulging or expansion of the tissue beyond its normal boundary

Heteronymous hemianopia — loss of different halves of the visual field of both eyes, as defined by projection to the visual cortex of both sides; bitemporal for the temporal halves and binasal for the nasal halves

Hindbrain — posterior division of the embryonic brain; includes pons, medulla, and cerebellum (located in the posterior cranial fossa)

Hippocampus or hippocampus "proper" — part of limbic system; a cortical area "buried" within the medial temporal lobe, consisting of phylogenetically old (threelayered) cortex; protrudes into floor of inferior horn of lateral ventricle

Homonymous hemianopia — loss of the same visual field in both eyes (i.e., left or right) as defined by the projection to the visual cortex on one side — involving the nasal half of the visual field in one eye and the temporal half in the other eye; also quadrantanopia

Horner's syndrome — miosis (constriction of the pupil), anhidrosis (dry skin with no sweat), and ptosis (drooping of the upper eyelid) due to a lesion of the sympathetic pathway to the head

Hydrocephalus — enlargement of the ventricles, usually due to excessive accumulation of cerebrospinal fluid within the ventricles (e.g., obstruction)

Hypoglossal nerve — 12th cranial nerve (CN XII); motor to muscles of the tongue

Hypo/hyper reflexia — decrease (hypo) or increase (hyper) of the stretch (deep tendon) reflex

Hypo/hyper tonia — decrease or increase of the tone of muscles, manifested by decreased or increased resistance to passive movements

Hypokinesia — markedly diminished movements (spontaneous)

Hypothalamus — a region of the diencephalon that serves as the main controlling center of the autonomic nervous system and is involved in several limbic circuits; also regulates the pituitary gland

Herpes (zoster, simplex) — a virus that attacks nerve root sheath and manifests itself as a rash with blisters soreness (see Neuralgia)



Infarction — local death of an area of tissue due to loss of its blood supply

Infundibulum (funnel) — infundibular stem of the posterior pituitary (neurohypophysis)

Innervation — nerve supply, sensory and/or motor

Insula (island) — cerebral cortical area not visible from outside view and situated at the bottom of the lateral fissure (also called the island of Reil)

Internal capsule — white matter between lentiform nucleus and head of caudate nucleus, and thalamus; consists of anterior limb, genu and posterior limb Ipsilateral On the same side of the body (e.g., ipsilateral
to a lesion)

Ischemia — a condition in which an area is not receiving an adequate blood supply

Ischemic penumbra — a region adjacent to or surrounding an area of infarcted brain tissue that is not receiving sufficient blood; the neurons may still be viable

Ischemia — reduction of blood flow in organs or tissues of a living organism (see Stroke, microstroke)



Kinesthesia — the conscious sense of position and movement



Lacune — a pathological small "hole" remaining after an infarct in the internal capsule; also irregularly-shaped venous "lakes" or channels draining into the superior sagittal sinus

Lateral ventricle — CSF cavity in each cerebral hemisphere; consists of anterior horn, body, atrium (or trigone), posterior horn, and inferior (temporal) horn

Lemniscus — a specific pathway in CNS (medial lemniscus for discriminative touch, conscious proprioception, and vibration; lateral lemniscus for audition)

Lentiform — lens-shaped; lentiform nucleus, a part of the corpus striatum; also called lenticular nucleus; composed of putamen (laterally) and globus pallidus

Leptomeninges — arachnoid and pia mater, part of meninges

Lesion — any injury or damage to tissue (e.g., vascular, traumatic)

Limbic system — part of brain associated with emotional behavior

Locus ceruleus — a small nucleus located in the uppermost pons on each side of the fourth ventricle; contains melanin-like pigment, visible as a dark-bluish area in freshly sectioned brain

Lower motor neuron — anterior horn cell of spinal cord and its axon; also the cells in the motor cranial nerve nuclei of the brainstem; called the alpha motor neuron; its loss leads to atrophy of the muscle and weakness, with hypotonia and hyporeflexia; also fascicluations are to be noted



Mammillary — mammillary bodies; nuclei of the hypothalamus that are seen as small swellings on the ventral surface of diencephalon (also spelled mamillary)

Massa intermedia — a bridge of gray matter connecting the thalami of the two sides across third ventricle; present in 70% of human brains (also called the inter-thalamic adhesion)

Medial lemniscus — brainstem portion of sensory pathway for discriminative touch, conscious proprioception and vibration, formed after synapse (relay) in nucleus gracilis and nucleus cuneatus

Medial longitudinal fasciculus (MLF) — a tract throughout the brainstem and upper cervical spinal cord that interconnects visual and vestibular input with other nuclei controlling movements of the eyes and the head and neck

Medulla — caudal portion of the brainstem; may also refer to the spinal cord as in a lesion within (intramedullary) or outside (extramedullary) the cord

Meninges — covering layers of the central nervous system (dura, arachnoid, and pia)

Mesencephalon — the midbrain (upper part of the brainstem)

Microglia — the "scavenger" cells of the CNS, i.e., macrophages; considered by some as one of the neuroglia

Midbrain — part of the brainstem; also known as mesencephalon (the middle division of the embryonic brain)

Motor — associated with movement or response

Motor unit — a lower motor neuron, its axon, and the muscle fibers that it innervates

MRI/NMR — magnetic resonance imaging (nuclear magnetic resonance), a diagnostic imaging technique that uses an extremely strong magnet, not x-rays

Muscle spindle — specialized receptor within voluntary muscles that detects muscle length; necessary for the stretch/myotatic reflex (DTR); contains muscle fibers within itself capable of adjusting the sensitivity of the receptor

Myelin — proteolipid layers surrounding nerve fibers, formed in segments, which is important for rapid (saltatory) nerve conduction

Myelin sheath — covering of nerve fiber, formed and maintained by oligodendrocyte in CNS and Schwann cell in PNS; interrupted by nodes of Ranvier

Myelopathy — generic term for disease affecting the spinal cord

Myopathy — Generic term for muscle disease

Myotatic reflex — stretch reflex, also called deep tendon reflex (DTR); elicited by stretching the muscle; causes a reflex contraction of the same muscle; monosynaptic (also spelled myotactic reflex)

Myotome — muscle groups innervated by a single spinal cord segment; in fact, usually two adjacent segments are involved (e.g., biceps, C5 and C6)

Minimally invasive — the minimum volume inflicted injuries method of surgical treatment



Neocerebellum — phylogenetically newest part of the cerebellum, present in mammals and especially well developed in humans; involved in coordinating precise voluntary movements and also in motor planning

Neocortex — phylogenetically newest part of the cerebral cortex, consisting of six layers (and sublayers) characteristic of mammals and constituting most of the cerebral cortex in humans

Neostriatum — the phylogenetically newer part of the basal ganglia consisting of the caudate nucleus and putamen; also called the striatum

Nerve fiber — axonal cell process, plus myelin sheath, if present

Neuralgia — pain - severe, shooting, "electrical," along the distribution of a peripheral nerve (spinal or cranial)

Neuraxis — the straight longitudinal axis of the embryonic or primitive neural tube, bent in later evolution and development

Neuroglia — accessory or interstitial cells of the central nervous system; includes astrocytes, oligodendrocytes, ependymal cells, and microglial cells

Neuron — the basic structural unit of the nervous system, consisting of the nerve cell body and its processes — dendrites and axon

Neuropathy — disorder of one or more peripheral nerves

Neuropil — an area between nerve cells consisting of a complex arrangement of nerve cell processes, including axon terminals, dendrites, and synapses

Nociception — refers to an injurious stimulus causing a neuronal response; may or may not be associated with the sensation of pain

Node of Ranvier — gap in myelin sheath between two successive internodes; necessary for saltatory (rapid) conduction

Nucleus (plural nuclei) — an aggregation of neurons within the CNS; in histology, the nucleus of a cell

Nystagmus — an involuntary oscillation of the eye(s), slow in one direction and rapid in the other; named for the direction of the quick movement

Neurosurgery — the section of medicine dealing with the nerve disease, whose treatment was performed mainly by surgical methods

Neurology — a branch of medicine which studies the structure and function of the nervous system in health and disease, patterns of development



Oculomotor nerve — 3rd cranial nerve (CN III); motor to most muscles of the eye

Olfactory nerve — 1st cranial nerve (CN I); special sense of smell

Oligodendrocyte — a neuroglial cell, forms and maintains the myelin sheath in the CNS; each cell is responsible for several internodes on different axons

Optic chiasm(a) — partial crossing of optic nerves — nasal half of retina representing the temporal visual fields — after which the optic tracts are formed

Optic disc — area of the retina where the optic nerve exits; also the site for the central retinal artery and vein; devoid of receptors, hence the blind spot

Optic nerve — 2nd cranial nerve (CN II); special sense of vision; actually a tract of the CNS, from the ganglion cells of the retina until the optic chiasm

Osteoporosis — depression and cortical layers of spongy bone due to partial resorption of bone substance

Osteochondrosis — a group of mainly inflammatory diseases podhryaschevogo of long tubular bones and short bones apophyses arising from specific or (less often) non-specific infections of the bones and joints



Paleocortex — phylogenetically older cerebral cortex consisting of three to five layers

Papilledema — edema of the optic disc, visualized with an ophthalmoscope (also called a choked disc); usually a sign of abnormal increased intracranial pressure

Paralysis — complete loss of muscular action

Paraplegia — paralysis of both legs and lower part of trunk

Paresis — muscle weakness or partial paralysis

Paresthesia — spontaneous abnormal sensation (e.g., tingling; pins and needles)

Pathway — a chain of functionally related neurons (nuclei) and their axons, making a connection between one region of CNS and another; a tract (e.g., visual pathway, dorsal column-medial lemniscus sensory pathway)

Peduncle — a thick stalk or stem; a bundle of nerve fibers (cerebral peduncle of the midbrain; also three cerebellar peduncles — superior, middle, and inferior)

Perikaryon — the cytoplasm surrounding the nucleus of a cell; sometimes refers to the cell body of a neuron

Peripheral nervous system (PNS) — nerve roots, peripheral nerves and ganglia outside the CNS (motor, sensory, and autonomic)

PET — positron emission tomography; a technique used to visualize areas of the living brain that become "activated" under certain task conditions; uses very shortacting biologically active radioactive compounds

Pia (mater) — the thin innermost layer of the meninges, attached to the surface of the brain and spinal cord; forms the inner boundary of the subarachnoid space

Plexus — an interweaving arrangement of vessels or nerves

Pons (bridge) — the middle section of the brainstem that lies between the medulla and the midbrain; appears to constitute a bridge between the two hemispheres of the cerebellum

Projection fibers — bidirectional fibers connecting the cerebral cortex with structures below, including basal ganglia, thalamus, brainstem, and spinal cord

Proprioception — the sense of body position (conscious or unconscious)

Proprioceptor — one of the specialized sensory endings in muscles, tendons, and joints; provides information concerning movement and position of body parts (proprioception)

Prosody — vocal tone, inflection, and melody accompanying speech

Ptosis — drooping of the upper eyelid

Pulvinar — the posterior nucleus of the thalamus; functionally, involved with vision

Putamen — the larger (lateral) part of the lentiform nucleus, with the globus pallidus; part of the neostriatum with the caudate nucleus

Pyramidal system — named because the cortico-spinal tracts occupy pyramid-shaped areas on the ventral aspect of the medulla; may include cortico-bulbar fibers; the term pyramidal tract refers specifically to the corticospinal tract

Paralysis, plegia — lack of voluntary movements

Paresis — a weakening of voluntary movements

Psychotherapy — a complex therapeutic effect on emotions, judgments, and self-rights to:

  • psychological adjustment of the psyche of people with mental disorders
  • psychological assistance



Quadrigeminal — referring to the four colliculi of the midbrain; also called the tectum

Quadriplegia — paralysis affecting the four limbs (also called tetraplegia)



Radicular — refers to a nerve root (motor or sensory)

Ramus (plural rami) — the division of the mixed spinal nerve (containing sensory, motor, and autonomic fibers) into anterior and posterior

Raphe — an anatomical structure in the midline; in the brainstem, several nuclei of the reticular formation are in the midline of the medulla, pons, and midbrain (these nuclei use serotonin as the neurotransmitter)

Red nucleus — nucleus in the midbrain (reddish color in a fresh specimen)

Reflex — involuntary movement of a fixed nature in response to a stimulus

Reflex arc — consisting of an afferent fiber, a central connection, a motor neuron, and its efferent axon leading to a muscle movement

Reticular — pertaining to or resembling a net - reticular formation of brainstem

Reticular formation — diffuse nervous tissue, nuclei and connections, in brainstem; quite old phylogenetically

Rhinencephalon — in humans, refers to structures related to the olfactory system

Rigidity — abnormal muscle stiffness (increased tone) with increased resistance to passive movement of both agonists and antagonists (e.g., flexors and extensors), usually seen in Parkinson's disease; velocity independent

Root — the peripheral nerves - sensory (afferent, dorsal) and motor (efferent, ventral) — as they emerge from the spinal cord and are found in the subarachnoid space

Rostral — toward the nose, or the most anterior end of the neuraxis

Rubro — red; pertaining to the red nucleus, as in rubrospinal tract and cortico-rubral fibers

Reflex — reaction of the body caused by central nervous system during stimulation of the receptors by agents of internal or external environment

Receptor — a special sensitive education, perceiving and transforming stimuli from the external or internal environment and transmitting information about the active agent in the nervous system

Regeneration — the restoration of the body of lost or damaged organs and tissues, as well as restoration of the whole body of its parts



Saccadic — to jerk; extremely quick movements, normally of both eyes together (conjugate movement), in changing the direction of gaze

Schwann cell — neuroglial cell of the PNS responsible for formation and maintenance of myelin; there is one Schwann cell for each internode of myelin

Secretomotor — parasympathetic motor nerve supply to a gland

Sensory — afferent; to do with receiving information, from the skin, the muscles, the external environment, or from internal organs

Septum pellucidum — a double membrane of connective tissue separating the anterior horns of the lateral ventricles, situated in the median plane

Septal region — an area below the anterior end of the corpus callosum on the medial aspect of the frontal lobe that includes cortex and the septal nuclei

Somatic — used in neurology to denote the body, exclusive of the viscera (as in somatic afferent neurons from the skin and body wall); the word soma is also used to refer to the cell body of a neuron

Somatic senses — touch (discriminative and crude), pain, temperature, proprioception, and the "sense of vibration"

Somatotopic — the orderly representation of the body parts in CNS pathways, nuclei, thalamus, and cortex; topographical representation

Somesthetic — consciousness of having a body; somesthetic senses are the general senses of touch, pain, temperature, position, movement, and "vibration"

Spasticity — velocity-dependent increased tone and increased resistance to passive stretch of the antigravity muscles; in humans, flexors of the upper limb and extensors of the lower limb; usually accompanied by hyperreflexia

Special senses — sight (vision), hearing (audition), balance (vestibular), taste (gustatory), and smell (olfactory)

Spinal accessory nerve — 11th cranial nerve (CN XI); refers usually to the part of the nerve that originates in the upper spinal cord (C1–5) and innervates the muscles of the neck, the sternomastoid and trapezius muscles

Spinal shock — complete "shut down" of all spinal cord activity (in humans) following an acute complete lesion of the cord (e.g., severed cord after a diving or motor vehicle accident); usually up to two to three weeks in duration

Spino-cerebellar tracts — ascending tracts of the spinal cord, anterior and posterior, for "unconscious" proprioception to the cerebellum

Spino-thalamic tracts — ascending tracts of the spinal cord for pain and temperature (lateral) and nondiscriminative or light touch and pressure (anterior)

Split brain — a brain in which the corpus callosum has been severed in the midline, usually as a therapeutic measure for intractable epilepsy

Stereognosis — the recognition of an object using the tactile senses and also central processing, involving association areas especially in the parietal lobe

Strabismus — a squint; lack of conjugate fixation of the eyes; may be constant or variable

Stria — a slender strand of fibers (e.g., stria terminalis from amygdala)

Striatum — the phylogenetically more recent part of the basal ganglia (neostriatum) consisting of the caudate nucleus and the putamen (lateral portion of the lentiform nucleus)

Stroke — a sudden severe attack of the CNS; usually refers to a sudden focal loss of neurologic function due to death of neural tissue; mostly due to a vascular lesion, either infarct (embolus, occlusion) or hemorrhage

Subarachnoid space — space between arachnoid and pia mater, containing CSF (cerebrospinal fluid)

Subcortical — not in the cerebral cortex, i.e., at a functionally or evolutionary "lower" level in the CNS; usually refers to the white matter of the cerebral hemispheres, and also may include the basal ganglia

Subicular region — part of hippocampal formation; transitional cortex (three to five layers) between that of the hippocampus proper and the parahippocampal gyrus

Substantia gelatinosa — a nucleus of the gray matter of the dorsal (sensory) horn of the spinal cord composed of small neurons; receives pain and temperature afferents

Substantia nigra — a flattened nucleus in the midbrain with motor functions — consisting of two parts: the pars compacta with melanin pigment in the neurons (the dopamine neurons, which degenerate in Parkinson's disease), and the pars reticulata, which is an output nucleus
of the basal ganglia

Subthalamus — region of the diencephalon beneath the thalamus, containing fiber tracts and the subthalamic nucleus; part of the functional basal ganglia

Sulcus (plural sulci) — groove between adjacent gyri of the cerebral cortex; a deep sulcus may be called a fissure

Synapse — area of structural and functional specialization between neurons where transmission occurs (excitatory, inhibitory, or modulation), using neurotransmitter substances (e.g., glutamate, GABA); similarly at the neuromuscular junction (using acetylcholine)

Syringomyelia — a pathological condition characterized by expansion of the central canal of the spinal cord with destruction of nervous tissue around the cavity

Symptom — a sign of illness

Syndrome — a particular combination of symptoms of the disease (see symptom) caused by a single start



Tectum — the "roof" of the midbrain (behind the aqueduct) consisting of the paired superior and inferior colliculi; also called the quadrigeminal plate

Tegmentum — the "core area" of the brainstem, between the ventricle (or aqueduct) and the cortico-spinal tract; contains the reticular formation, cranial nerve and other nuclei, and various tracts

Telencephalon — rostral part of embryonic forebrain; primarily cerebral hemispheres of the adult brain

Tentorium — the tentorium cerebelli is a sheet of dura between the occipital lobes of the cerebral hemispheres and the cerebellum; its hiatus or notch is the opening for the brainstem — at the level of the midbrain

Thalamus — a major portion of the diencephalon with sensory, motor, and integrative functions; consists of several nuclei with connections to areas of the cerebral cortex

Third (3rd) ventricle — midline ventricle at the level of the diencephalon (between the thalamus of each side), containing CSF

Tic — brief, repeated, stereotyped, semipurposeful muscle contraction; not under voluntary control, although may be suppressed for a limited time

Tinnitus — persistent ringing or buzzing sound in one or both ears

Tomography — radiological images, done sectionally, including CT and MRI

Tone — referring to muscle, its firmness, and elasticity - normal, hyper, hypo - elicited by passive movement and also assessed by palpation

Tract — a bundle of nerve fibers within the CNS, with a common origin and termination, (e.g., optic tract, cortico-spinal tract)

Transient ischemic attack (TIA) — a nonpermanent focal deficit, caused by a vascular event; by definition, usually reversible within a few hours, with a maximum of 24 hours

Trapezoid body — transverse crossing fibers of the auditory pathway situated in the ventral portion of the tegmentum of the lower pons

Tremor — oscillating, "rhythmic" movements of the hands, limbs, head, or voice; intention (kinetic) tremor of the limb commonly seen with cerebellar lesions; tremor at rest commonly associated with Parkinson's disease

Trigeminal nerve — 5th cranial nerve (CN V); major sensory nerve of the head (face, eye, tongue, nose, sinuses); also supplies muscles of mastication

Trochlear nerve — 4th cranial nerve (CN IV); motor to the superior oblique eye muscle

Two-point discrimination — recognition of the simultaneous application of two points close together on the skin; distance varies with the area of the body (compare finger tip to back)

Tremor — involuntary oscillatory movement of the whole body or parts thereof



Uncus — an area of cortex - the medial protrusion of the rostral (anterior) part of the parahippocampal gyrus of the temporal lobe; the amygdala is situated deep to this area; important clinically as in uncal herniation

Upper motor neuron — neuron located in the motor cortex or other motor areas of the cerebral cortex or in the brainstem - giving rise to a descending tract to lower motor neurons in the brainstem (for cranial nerves) or spinal cord (for body and limbs)

Upper motor neuron lesion — a lesion of the brain (cortex, white matter of hemisphere), brainstem, or spinal cord interrupting descending motor influences to the lower motor neurons of the brainstem or spinal cord, characterized by weakness, spasticity, and hyperreflexia, and often clonus; usually accompanied by a Babinski response



Vagus — 10th cranial nerve (CN X); supplies motor fibers to the larynx; the major parasympathetic nerve to organs of the thorax and abdomen

Velum — a membranous structure; the superior medullary velum forms the roof of the fourth ventricle

Ventricles — cerebrospinal (CSF) fluid-filled cavities inside the brain

Vermis — unpaired midline portion of the cerebellum, between the hemispheres

Vertigo — abnormal sense of spinning, whirling, or motion, either of the self or of one's environment

Vestibulocochlear — 8th cranial nerve (CN VIII); special senses of hearing and balance (acoustic nerve is not really correct)



White matter — nervous tissue of CNS made up of nerve fibers (axons), some of which are myelinated; appears "whitish" after fixation in formalin






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