The Neuroscience on
the Web Series:
Glossary of
Neuroscience Terms F-L |
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T |
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Z
F
- Facial Nerve (Cranial Nerve VII):
- innervates the lip muscles including the obicularis oris and the zygomaticus.
The muscles must contract during the oral preparatory and oral transport stages of the
swallow to prevent food from dribbling out of the mouth. The facial also innervates the buccinator
muscles of the cheeks. These must remain tense during the oral component of the swallowing
process to prevent the pocketing of food between the teeth and the cheeks.
Sensory Component carries information about taste from the anterior 2/3 of the tongue.
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- falx cerebelli:
- separates the lobes of the cerebellum; the falx cerebelli is formed by the dura mater
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- falx cerebri:
- separates the lobes of the cerebrum; the falx cerebri is formed by the dura mater
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- festinating movements:
- movements which become increasingly rapid and uncontrolled
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- final common pathway:
- lower motor neurons traveling to the muscles of the body on the only route by which
information from any of the upper motor tracts can reach the periphery. Thus, when lower
motor neurons are damaged, the parts of the body that they innervate are deprived of input
from the pyramidal and extrapyramidal tract as well as cerebellar pathways. Thus,
voluntary, automatic and reflexive movements are all affected.
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- finger agnosia:
- an inability to recognize objects through the sense of touch; may be the result of
damage to the angular gyrus in the hemisphere dominant for speech and language
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- fissure:
- a particularly deep sulcus
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- fissure of Rolando (central sulcus):
- the sulcus that separates the frontal and parietal lobes
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- fissure of Sylvius (lateral fissure):
- the fissure that separates the frontal and temporal lobes
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- flaccid (lower motor neuron) dysarthria:
- the only form of dysarthria that results from damage to lower motor neurons.
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- Fluent Aphasias:
- Fluent aphasias are the result of lesions affecting the post Rolandic area.
Problems with meaning are associated with posterior lesions.
- Phoneme selection and sequencing as well as syntax are preserved. Speech is
characterized by a facility of articulation and many long runs of words combined using a
variety of grammatical constructions. However, fluent speech is not equivalent to
meaningful speech. Often the speech of fluent aphasics sounds like
"jabberwocky." Typically, there are word-finding problems that affect nouns and
picturable action words. Comprehension is typically poor with fluent/posterior lesion
aphasias. (Conduction aphasia would be the exception to this). The amount and type of
paraphasias, the presence of auditory receptive impairments and of impaired repetition are
variable in fluent aphasias, depending upon the exact site of lesion.
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- flocculi:
- the most ancient part of the cerebellum; the flocculi are part of flocculonodular lobe
-
- flocculonodular lobe:
- the lobe of the cerebellum that consists of the flocculi and the nodulus; the
flocculonodular lobe is involved in the maintenance of equilibrium
-
- focal lesions:
- generally small and just in one area, focal lesions can affect the language and
swallowing centers of the brain, they can cause symptoms similar to those seen as a result
of a left cerebral vascular accident including apraxia, dysarthria, aphasia,
dysphagia, agnosia, anomia, and dysphonia. Focal lesions can
also cause more general impairments that affect language, similar to those resulting from
right hemisphere damage. These include attentional, perceptual and pragmatic deficits.
-
- foramina of Luschka:
- two lateral openings (along with the medial foramen of Magendie) which serve to connect
the fourth ventricle to the subarachnoid space
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- foramen of Magendie:
- a medial opening (along with the lateral foramina of Luschka) which serves to connect
the fourth ventricle to the subarachnoid space
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- foramina of Munro (interventricular foramina):
- two openings which connect the lateral ventricles to the third ventricle
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- fornix:
- a subcortical component of the limbic system; the fornix is a group of fibers that arise
from the hippocampus and connect the rhinencephalon to the thalamus and hypothalamus; the
fornix is connected to the septal nuclei and the mamillary bodies
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- fourth ventricle:
- one of the four ventricles of the brain; it is filled with cerebrospinal fluid; the
fourth ventricle is located between the cerebellum and the pons
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- frontal lobe:
- the most anterior lobe of the brain; it is bounded posteriorly by the central sulcus and
inferiorly by the lateral fissure; this lobe is associated with higher cognitive functions
and is involved in the control of voluntary muscle movement
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- fusiform layer (multiform layer):
- the sixth and most inferior layer of the cortex
G
- GABA:
- Gamma Amino Butric Acid; a neurotransmitter that is involved in the inhibitory function
of the basal ganglia; it is a glutamate
-
- gag reflex:
- a good example of a true reflex. It is "triggered" whenever a noxious
substance touches the back of the tongue, back of the pharynx, or soft palate. The swallow
response, on the other hand, cannot be initiated by touching any particular area in the
oral cavity. The gag reflex and the swallow response also differ in terms of neurological
control. The gag reflex is completely controlled by the brain stem. The swallow, on the
other hand, is only partially controlled by the brain stem. It also receives cortical
input, and input from muscle spindles, including feedback from tongue movements.
(It is important to note that the gag reflex and the swallow response are not
related. In the past, many physicians would determine feeding status based on the presence
or absence of a patient's gag. Actually, the presence or absence of a gag reflex does not
predict the status of the swallow response.)
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- gamma neurons:
- neurons of the final common pathway (located on the ventral aspect of the spinal cord);
these cells conduct slow motor impulses and their main function is to stretch muscle
spindles; gamma cells are only half as numerous as alpha cells
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- ganglionic cells:
- neurons of the autonomic system that originate within the ganglia of the autonomic
nervous system and project to post-ganglionic neurons
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- ganglionic layer:
- the fifth layer of the cortex; it contains small granular cells, large pyramidal cells,
and the cell bodies of some association fibers (the association fibers that originate here
form the Bands of Baillerger and Kaes Bechterew, which are two large fiber tracts)
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- Glasgow Coma Scale:
- developed by Jennett and Teasdale (1989), instrument most frequently used to quantify
levels of consciousness, consists of three categories: eye opening, verbal
responses and motor responses.
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- Global Aphasia:
- third most common aphasic syndrome after Broca's and Wernicke's, occurs when there are
both anterior and posterior lesions. All aspects of language are so severely impaired that
there is no longer a distinctive pattern of preserved vs. impaired components.
Articulation may be adequate in the context of stereotypical utterances. Prognosis is
poor.
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- globus pallidus:
- the more medial part of the lenticular nucleus
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- Glossopharyngeal Nerve (Craninial Nerve IX):
- considered the major nerve for the swallowing center, Motor Component innervates the 3
salivary glands in the mouth. The saliva from these glands mixes with the chewed up food
to form a bolus. Has motor, sensory, and autonomic nervous system nerve fibers. It, along
with the vagus (CN. X), provides some innervation to the upper pharyngeal constrictor
muscles (Zemlin, 1997). Innervates the stylopharyngeus muscle which elevates the
larynx and pulls it forward during the pharyngeal stage of the swallow. This action also
aids in the relaxation and opening of the cricopharyngeus muscle. Sensory components
mediate all sensation, including taste, from the posterior 1/3 of the tongue. Also carries
sensation from the velum and the superior portion of the pharynx. A lesion may impair the
gag reflex unilaterally (Zemlin, 1997).
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- graduated stick:
- may be used instead of a pacing board. Graduated sticks have bumps on
them at regular intervals and the patient must touch one bump for every syllable.
Metronomes can also be used to slow speech rate. Patients are taught to produce one
syllable per "tick" on the metronome.
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- gyrus:
- a raised fold of brain tissue
H
- hemianopsia:
- loss of sight in one half of the visual field. damage to either middle cerebral artery
can cause This blindness affects the contralateral aspect of both visual fields. For
example, a blockage in the right middle cerebral artery will cause left hemianopsia or
blindness in the left visual field of both eyes.
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- hyposthesia:
- lack or sensation
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- hemiplegia:
- complete paralysis on one side
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- hemiparesis:
- partial paralysis on one side
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- hematomas:
- or pools of congealed blood, in the parenchyma, the subarachnoid space, or the subdural
space, bleeding due to stroke, hemmorrhage or traumatic brain injury, tissue is irritated
rather than infarcted
-
- Hemophilia:
- is a thinning of the blood which prevents it from coagulating.
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- hemorrhagic strokes
- Hemorrhagic stroke occurs when a cerebral artery ruptures, causing bleeding within the
cranium. Such ruptures may be caused by aneurysms,
weak spots in arterial walls. (Aneurysms can balloon out rather than bursting. The
excess pressure resulting from this swelling can also damage brain tissue.)
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- Heschl's Gyrus (anterior transverse temporal gyrus):
- the primary auditory area; it is located in the temporal lobe
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- hippocampus:
- a cortical area classified as part of the limbic system; it is a gyrus located on the
medial edge of the temporal lobe, it is involved with memory
-
- homunculus:
- "little man"; a pedagogical device that is used to explain and demonstrate the
functioning of the motor strip
-
- horizontal cut (transverse cut):
- a cut that divides the brain into upper and lower sections; perpendicular to coronal,
medial, and sagittal cuts
-
- hydrocephalus:
- a condition that occurs when too much cerebrospinal fluid is produced and the ventricles
swell, resulting in pressure being exerted on the tissue of the brain; it may be caused by
tumors
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- hydroencephali:
- a rare birth defect in which the cerebrum is absent and the space where it should be is
filled with cerebrospinal fluid; the term literally means "water brain"
-
- hyperkinetic dysarthria:
- occur when the extrapyramidal tract is damaged, specifically the basal ganglia
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- hypertension:
- blood pressure that is elevated regardless of activity level; may be a factor in stroke
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- Hypokinesia :
- "the reduced amplitude of muscle movement" (Love & Webb, 1992, p. 146).
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- Hypoglossal Nerve (Cranial Nerve XII)
- Information about motor movement is received from the muscle spindles in the tongue via
this nerve, serves as part of the swallowing center that
initiates the swallow. The hypoglossal innervates all extrinsic and intrinsic tongue
muscles. (It is strictly a motor nerve.)
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- hypopharynx (of the Pharynx):
- lower portion of the pharynx. It is also known as the laryngopharynx
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- hypothalamus:
- a subcortical structure located immediately below the thalamus, part of it is also
anterior to the thalamus and it forms the floor and part of the lateral walls of the third
ventricle; by controlling the functioning of the pituitary gland it regulates basic
biological functions (e.g., appetite, body temperature, sex drive)
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- hypokinetic dysarthria:
- occur when the extrapyramidal tract is damaged, specifically the substantia nigra
-
- Hyperuricemia:
- a risk factor for CVA, involves an elevation of the level of uric acid in the blood.
(This is the cause of gout.)
I
- infarction:
- death of tissue
-
- inferior:
- refers to the lower parts of the nervous system
-
- inferior cerebellar peduncles (restiform bodies):
- one of the three fiber bundles called cerebellar peduncles that connect the cerebellum
to the brain stem; the inferior cerebellar peduncle connects the cerebellum with the
vestibular nuclei located in the lower pons and medulla, and with the reticular formation;
proprioceptive information from the upper body (information that travels along the
dorsospinocerebellar tract) enters the cerebellum on the inferior cerebellar peduncle
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- inferior colliculi:
- structures of the midbrain that relay auditory information to the medial geniculate
bodies of the thalamus
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- insula (the Island of Reil):
- the cortical area that lies below the fissure of Sylvius; it is considered by some
anatomists as the fifth lobe of the brain; it may be associated with the viscera
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- interconnecting fibers:
- nerve fibers that connect structures within the brain; the two types of interconnecting
fibers are commisural fibers and association fibers
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- internal capsule:
- a group of myelinated ascending and descending fiber tracts that connect the cortex to
other parts of the central nervous system; although the axons that pass through it descend
to the brain stem and spinal cord, the capsule itself ends within the cerebrum; the
internal capsule is located between the lenticular nucleus and the caudate nucleus
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- internal carotid artery:
- a division of the common carotid; the internal carotid arteries supply blood to the
brain; the two main branches of this artery are the anterior
cerebral artery and the middle cerebral artery,
The internal
carotids and basilar arteries are connected via the Circle of Willis,
which allows blood to pass from one system to another in the event of blockage.
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- internal granular layer:
- the fourth layer of the cortex; it is very thin; it contains pyramidal cells in row
formation
-
- interneurons:
- association neurons of the spinal cord; interneurons connect the anterior and posterior
horns of grey matter and are involved in the reflex arc (they function within the same
segment of the spinal cord)
-
- internuncial neurons:
- association neurons of the spinal cord; internuncial neurons project (ascend) to the
brain stem and cerebellum
-
- intraparnchymal bleeding:
- can occur at a very slow rate within structure such as the thalamus, the spontaneous
recovery period following a stroke caused by this type of bleeding may be especially
lengthy. For this reason, it is justifiable to continue therapy for a longer period of
time with patients who have had parenchymal bleeding than with those who have had other
types of hemorrhages.
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- intraparynchemal hemorrhaging:
- Due to Penetrating Brain Injury Bleeding within the structures of the brain is usually
the consequence of penetrating head wounds rather than CHI. This kind of hemorrhaging can
occur in the cortex as well as in subcortical areas. When it is the result of closed head
injury, rather than CVA, it most commonly affects the frontal and temporal lobes. Most
penetrating brain injuries result from high velocity missiles such as bullets. Low
velocity focal injuries (blows to the head-head hitting windshield) can result in bone
fragments penetrating the brain. There is a high rate of mortality following penetrating
brain injury especially to the brain stem (Brookshire, 1997).
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- ischemic:
- refers to a lack of blood-bourne oxygen. Ischemic strokes are more common than
hemorrhagic strokes and may be caused by stenosis or thrombosis of the
arteries, as well as by the presence of thrombo-emboli in the arteries. Almost
always contralateral and therefore unilateral
-
- Island of Reil (the Insula):
- the cortical area that lies below the fissure of Sylvius; it is considered by some
anatomists as the fifth lobe of the brain; it may be associated with the viscera. It has
recently been associated with programming for muscle movement involved in speech.
J
K
- kinesthesia:
- feedback from muscle spindles (a more specific term than proprioception)
L
- lateral:
- toward the sides
-
- lateral aspect:
- the part of the motor strip that is located on the lateral surface of the hemisphere; it
is responsible for motor control of the upper body (including the larynx, face, hands,
shoulders, and trunk)
-
- lateral corticospinal tract (lateral pyramidal tract):
- the fibers of the corticospinal tract that decussate at the pyramids
-
- lateral fissure (fissure of Sylvius):
- the fissure that separates the frontal and temporal lobes
-
- lateral geniculate bodies:
- the thalamic nuclei that receive visual information from the superior colliculi of the
midbrain, process, and then transmit this information to the cortex
-
- lateral pterygoid muscle of the oral cavity:
- depresses, opens, and protrudes the mandible, as well as moving it laterally
-
- lateral ventricles:
- the two large ventricles (filled with cerebrospinal fluid) that have anterior horns
located in the frontal lobes, inferior horns located in the temporal lobes, and which also
extend posteriorly into the parietal lobes
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- left middle cerebral artery:
- supplies blood to Broca's area, Wernicke's area, Heschl's
gyrus, angular gyrus and also the areas of the motor
and sensory strips from the head to the hips.
-
- left-right disorientation:
- an inability to distinguish the left from the right; may be the result of damage to the
angular gyrus in the hemisphere dominant for speech and language
-
- left side neglect:
- an impairment in the ability to recognize and respond to stimuli on the left side of the
body
-
- lenticular nucleus (lentiform nucleus):
- one of the two structures that make up the basal ganglia; it is composed of the globus
pallidus and the putamen; the lenticular nucleus is located between the caudate nucleus
and the Island of Reil with its anterior aspect attached to the head of the caudate
nucleus
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- levator veli palatini (oral cavity):
- with the palatoglossal both raise the velum. They are innervated by the vagus
nerve (CN. X).
-
- limbic system (rhinencephalon):
- the most ancient and primitive part of the brain; it is composed of both cortical and
subcortical structures located on the medial, inferior surfaces of the cerebral
hemispheres; the limbic system is involved in the processing of olfactory stimuli,
emotions, motivation, and memory, and may be involved in cortical speech and language
behavior
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- literal/phonological paraphasia:
- More than half of the intended word is produced correctly. For example, a patient may
say /pun/ instead of /spun/. In addition, transpositions of sounds can occur, e.g
tevilision for television. (Brookshire, 1997).
-
- long association fibers:
- association fibers that connect areas that are located in different lobes of the brain
(e.g., the arcuate fasciculus)
-
- longitudinal fissure (interhemispheric fissure):
- the split or gap between the right and left cerebral hemispheres that is lined with
cortex
-
- lower motor neurons:
- second order neurons; the cranial and spinal nerves; the cell bodies of the lower motor
neurons are located in the neuraxis (brain stem), but their axons synapse with the muscles of the body,
sometimes called the final common pathway
-
- lumbar puncture (spinal tap):
- a diagnostic procedure in which a needle is inserted in the lower lumbar section of the
vertebral canal to obtain a sample of cerebrospinal fluid