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114 Cards in this Set

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What is information travels within the dorsal thalmus?
sensory info to the cerebral cortex, cerebellar, basal ganglia, and limbic pathways
What are the borders of the dorsal thalmus?
medial - third ventricle; lateral - internal capsule; dorsal - hypothalmus; ventral - epithalamus
What fibers does the ventral posterior lateral nucleus receive?
medial lemniscal and spinothalamic afferents, projects to primary somatosensory cortex (area 312)
What fibers does the ventral posterior medial nucleus receive?
trigeminothalamic afferents, projects to primary somatosensory cortex (area 312)
What fibers does the ventral lateral nucleus receive and what is its function?
input from deep cerebellar nuclei via cerebellothalamic projections and minor input from the basal ganglia; functions in the execution of movements; projects to primary motor cortex (area 4)
What nuclei make up the lateral compartment of the thalamus?
Ventral tier: ventral posterior lateral(VPL), ventral posterior medial (VPM), ventral lateral (VL), ventral anterior (VA); Dorsal tier: lateral posterior (LP); Pulvinar (PUL)
What fibers does the ventral anterior nucleus receive, what is its function, and where does it project?
input from basal ganglia via afferents from the medial globus pallidus and substantia nigra, minor input from cerebellum; functions in planning movements; projects to premotor cortex (area 6) and supplementary motor cortex
What fibers does the lateral posterior nucleus receive, what is its function, and where does it project?
afferents from the superior colliculus; functions in vision and eye movement control; projects to parietal association cortex (area 5 and 7)
What fibers does the pulvinar nucleus receive, what is its function, and where does it project?
afferents from the superior colliculus; functions in vision and eye movement control; projects to secondary visual cortex (area 18 and 19); and parietal-temporal-occipital association cortex
What fibers do the mediodorsal (lateral part) and intralaminar nuclei receive, what is its function, and where does it project?
afferents from the superior colliculus, piriform olfactory cortex, and ventral pallidum; function in eye-head control and attention; project to the frontal eye fields and anterior cingulate cortex
What fibers do the mediodorsal (medial part) and midline nuclei receive, what is its function, and where does it project?
afferents from the vagal solitary nucleus, amygdala, and ventral pallidum; function in autonomic regulation and emotion; project to insular, orbitofrontal, and subcallosal cortex of frontal lobe
What nuclei make up the medial compartment of the thalamus?
mediodorsal (lateral and medial parts); works together with the intralaminar and midline nuclei of the internal medullary lamina
What fibers do the anterior and lateral dorsal nuclei receive, what is its function, and where does it project?
afferents from the hippocampus and mammillary bodies; function in sense of direction by coding head direction relative to external landmarks; projects to posterior cingulate cortex
What fibers does the lateral geniculate receive, what is its function, and where does it project?
afferents from the retina via the optic tract; functions in vision; projects to the primary visual cortex (area 17) in superior temporal gyrus
What fibers does the medial geniculate receive, what is its function, and where does it project?
afferents from the inferior colliculus via the brachium of the inferior colliculus; functions in hearing; projects to the primary auditory cortex (areas 41 and 42)
What fibers does the reticular nucleus receive, what is its function, and where does it project?
afferents from the brainstem reticular formation and thalamocortical fibers; functions in thalamic feedback circuit in regulating sleep-wakefulness cycle and awareness; projects back to the thalamic nuclei that project to it
What are the symptoms and cause of Thalamic Pain syndrome (Dejerine-Roussy)?
hemianesthesia which may improve and then result in severe pain that is intractable to anesthetics; caused by posterolateral thalamic lesion, involves sensory relay nuclei
Which thalamic nucleus projects to the prefrontal cortex?
mediodorsal nucleus
Which thalamic nucleus is associated with eye movements?
lateral posterior nucleus
Which thalamic nucleus relays basal ganglia inputs to the cortex?
ventral anterior relays basal ganglia info to the premotor and supplementary motor cortex
What is the function of the pineal gland?
secretes melatonin, a hormone important in regulating circadian rhythms
What is the internal medullary lamina?
divides the thalamus into medial and lateral compartments that hold the various thalamic nuclei, it also splits at rostral levels to create an anterior compartment; contains several intralaminar nuclei such as centromedian and parafascicular
What makes up the metathalamus?
lateral geniculate and medial geniculate
Which cortical lamina is especially well-developed in the precentral gyrus?
lamina V
What two gyri make up wernicke's area?
supramarginal gyrus, angular gyrus
Which cortical lamina is especially well-developed in the postcentral gyrus?
lamina IV (internal granular layer)
Which thalamic nucleus projects heavily to the postcentral gyrus?
ventral posterolateral and ventral posteromedial nuclei
What directional slice of the body does MRI produce best?
sagittal and coronal views
What directional slice of the body does CT produce best?
cross sectional (axial) views
What imaging modality does CT utilize?
X-rays in various planes that are reconstructed into axial images, the images are based on electron density, this prevents exposure to ionizing radiation
What imaging modality does MRI utilize?
the hydrogen nuclei density of different substances, the time to turn to baseline spin after magnetic pull
What color is acute blood on CT? edema?
acute blood = white; edema = dark
What is the function of PET scan?
low resolution image but gives functional information, ie the sugar uptake of a region of tissue
What color is edema on a T1 image without contrast?
dark gray
What color is edema and a lesion on a T1 image with contrast?
lesion is white; edema is dark
What color is fluid/fat on T2 image?
fluid/fat is white; bone is black
What color is fat on a CT?
dark
What is the basal ganglia?
an anatomically and functionally related set of nuclei located in the telencephalon, diencephalon, and midbrain; comprise the main elements of the extrapyramidal motor system
What are the major components of the basal ganglia?
caudate nucleus and putamen (both form the striatum); globus pallidus (lateral and medial); substantia nigra (pars reticulata and dopaminergic pars compacta); subthalamic nucleus
What is the claustrum?
a thin sheet of gray matter between the putamen and the insular cortex
What are the afferents of the striatum (caudate and putamen)?
cerebral cortex (frontal, parietal, occipital, temporal lobes); intralaminar nuclei of thalamus; substantia nigra pars compacta; raphe nuclei
What are the efferents of the striatum (caudate and putamen)?
project to medial and lateral globus pallidus and substantia nigra pars reticulata
What part of the basal ganglia form the input side?
caudate and putamen (striatum)
What part of the basal ganglia form the output side?
medial globus pallidus and substantia nigra pars reticulata
What are the afferents of the medial globus pallidus and substantia nigra pars reticulata?
from caudate and putamen
What are the efferents from the medial globus pallidus?
project to the ventral anterior and ventral lateral thalamic nuclei by two routes, lenticular fasciculus and ansa lenticularis
What are the efferents from the substantia nigra pars reticulata?
project to the mediodorsal thalamic nucleus, brainstem reticular formation, and superior colliculus
What are the inputs and projections of the lateral globus pallidus?
input from the striatum; projects to the subthalamic nucleus which then projects to the medial globus
What is the direct pathway through the basal ganglia?
the striatum to the medial globus pallidus to ventral anterior and ventral lateral thalamic nuclei
Does the direct pathway through the basal ganglia facilitate or inhibit movement?
facilitates because the striatum inhibits the medial globus pallidus, thus reducing the medial globus pallidus' inhibition of ventral anterior and ventral lateral thalamic nuclei, resulting in more thalamic activation of the cortical motor areas and more movement (inhibition of an inhibition is equivalent to excitation)
What is the indirect pathway through the basal ganglia?
striatum to lateral globus pallidus to subthalamic nucleus to medial globus pallidus to ventral anterior and ventral lateral thalamic nuclei
Does the indirect pathway through the basal ganglia facilitate or inhibit movement?
inhibits because the striatum inhibits the lateral globus pallidus, and reduces its inhibition of the subthalamic nucleus, this causes more excitatory drive to the medial globus pallidus, which produces more inhibition of the ventral anterior and ventral lateral thalamic nuclei causing less activation of the cortical motor areas and less movement
What are the primary symptoms of parkinson's disease?
akinesia, resting tremor, rigidity, and postural instability
What is the etiology of parkinson's disease?
degeneration of the substantia nigra pars compacta, which normally provides dopaminergic innervation to the striatum which dysfacilitates the direct pathway and disinhibits the indirect pathway
What are the treatments for parkinson's disease?
L-dopa, precursor to dopamine which crosses the BBB; Pallidotomy (medial globus pallidus lesion to reduce its inhibition of the ventral anterior and ventral lateral thalamic nuclei); subthalamic nucleus electrical stimulation (disrupts the activation of the medial globus pallidus, reducing its activity)
What is hemiballismus?
violent throwing movements of one arm or leg
What is the cause of hemiballismus?
damage to the contralateral subthalamic nucleus (loss of normal inhibition of movement by indirect pathways)
What is chorea?
involuntary, purposeless, quick, jerky, dancing movements of extremities, face, and tongue
What is the cause of Huntington's disease?
degeneration of the striatal neurons resulting from CAG repeat mutation in gene on chromosome 4 that codes for huntingtin protein
What is Sydenham's chorea?
rapid aimless involuntary movements of arms, legs, and trunk; associated with rheumatoid fever with a typical onset at 5-15 years of age
What is athetosis?
slow, writhing, worklike involuntary movements of the extremities or head and neck, caused by various lesions of cortical, striatal, pallidal, or thalamic nuclei
What is akinesia?
difficulty in initiating movements; primary negative symptom of parkinson's disease
What is compulsory approaching?
inability to shift one's attention away from a stimulus; caused by large caudate lesion
What two nuclei compose the striatum of the basal ganglia?
caudate and putamen
What mental illness is treated with dopaminergic-receptor-blocking drugs such as haloperidol?
Schizophrenia is often treated with heloperidol. The abnormal function of dopaminergic inputs to the ventral striatum and prefrontal cortex may be involved in this illness
What is the ventral striatal system?
cognitive-emotional basal ganglia system which has a parallel wiring to the classical extrapyramidal motor basal ganglia system
What are the components of the ventral striatum?
nucleus accumbens (ventral to caudate nucleus); and olfactory tubercle (deep to the anterior perforated substance)
What are the cortical afferents of the ventral striatum?
limbic cortex (hippocampus, piriform cortex, cingulate cortex, entorhinal cortex)
What are the dopaminergic afferents of the ventral striatum?
ventral tegmental area of the midbrain
What is the efferent target of the ventral striatal system?
ventral pallidum
What is the ventral pallidum?
located ventral to the globus pallidus and anterior commissure; includes substantia innominata; relays ventral striatal inputs to the mediodorsal nucleus of the thalamus to be sent to prefrontal and anterior cingulate cortex to regulate eye-head movements and emotions
What are symptoms of huntington's disease?
chorea, and dementia
What are the components of the motor servo?
alpha and gamma motor neurons, spindle receptors, golgi tendon organs, spinal reflex circuitry, muscle and its load
What is the overall function of the motor servo?
regulates muscle stiffness (ratio of change in force to change in length) at a relatively constant and moderate value by combining length regulation (spindles), force regulation(tendon organs), and muscle mechanical properties
What muscle property does the motor servo control?
muscle stiffness (slope of length/tension curve), ths makes a muscle behave consistently and predictably whether it is stretched or released
What physical device does the motor servo make muscle behave like?
a spring
What are the intrinsic properties of muscle?
intrinsic mechanical resistance to stretch; family of length-tension curves that depend on the level of muscle activity; the longer the muscle the more force it produces; force-velocity curves (shorter muscle, smaller force)
What is a central pattern generator?
a hardwired, spinal control of complex patterns of movement in locomotion without supraspinal input, ie walking, chewing, breathing
What descending motor pathways preferentially control distal muscles of the limbs?
lateral motor system: lateral corticospinal and rubrospinal tracts
What descending motor pathways preferentially control axial and proximal muscles?
medial motor system: tectospinal, reticulospinal, vestibulospinal, anterior corticospinal tracts
What is spasticity?
muscles that are hypertonic and hyperreflexive (increase in resistance of a passively stretched muscle) and display the clasp-knife reflex
What causes spasticity?
UMN lesion that interupts both the corticospinal tract and the descending cortical projections to the brain stem reticular formation cells that give rise to the dorsolateral reticulospinal tract (lose the inhibition provided by the DLRtST)
What is the function of the dorsolateral reticulospinal tract?
tonic inhibition of spinal interneurons activated by group II, III, IV afferents
What causes the clasp knife reflex?
loss of inhibition of the inhibitory interneurons relaying group II, III, IV afferent signals that are only activated at relatively high thresholds
What is the recruitment order of motor units in a spastic muscle?
large motor units are recruited first followed by small motor units, this produces large force increments too soon.
Are spastic springs (muscles) more or less stiff?
more
What are three mechanisms of motor impairment after disruption of the central execution of motor command?
paresis, soft tissue contracture, muscle overactivity
What is the basis of transcortical (Long loop) stretch reflexes?
reinforcement and supplemental segmental spinal reflexes which depend on afferents that ascend in dorsal columns and relay in thalamus and reach the precentral motor cortex to signal reflex
Which brain systems are important in early planning and programming of movements?
motor cortex, cerebellum and basal ganglia
How do movements in cerebellar or basal ganglia disease differ from normal?
cerebellar: difficulty monitoring the progress of the movement and correct for errors efficiently; basal ganglia: difficulty producing initial, fast, ballisitc movements or reacting, trouble learning how to improve movements
What are four sources of weakness?
lower motor neurons (peripheral nerve, plexus, root, anterior horn); muscle disease; neuromuscular junction disorder; upper motor neurons (spinal cord; brain stem; internal capsule; motor cortex)
Where is the lesion causing paralysis of the entire left face and right hemiplegia?
left pons; crossed brain stem syndrome
In which arterial territory would an infarct occur to produce paralysis of arm and face greater than leg?
middle cerebral artery
In which arterial territory would an infarct occur to produce paralysis of leg greater than arm and face?
anterior cerebral artery
What causes steppage gait?
weak foot dorsiflexion (foot drop) leading to exaggerated hip flexion and greater elevation of the leg so as not to trip over the weak foot
What causes duck waddle gait?
weak pelvic girdle muscles in myopathy make it difficult to transiently stand on one leg while walking, so the patient compensates by leaning or swaying side to side
What causes scissors gait?
with spastic paraparesis, the hypertonic adductor muscles of the thighs tend to cross ones leg over the other while walking
What signs and symptoms occur with a hemispheral cerebellar syndrome or lesion?
ipsilateral kinetic tremor, dysmetria, dysdiadochokinesia, and rebound phenomenon
What signs and symptoms occur with a vermal syndrome or lesion?
truncal unsteadiness, tremor, postural impairment, and gait ataxia
What are the 5 essential elements involved in gait?
strength; coordination; postural control; sensation; memory or concept of walking
Where is there a lesion if a patient stands steadily with feet together, but sways and breaks stance when the eyes are closed (Romberg sign)?
posterior column (proprioception is lost); visual orientation compesates for impaired proprioception
Where is there a lesion if a patient cannot stand steadily with feet together, regardless of whether the eyes are open or closed?
cerebellar disease, visual cues are unable to compensate for cerebellar deficit
What causes a broad-based ataxic gait?
posterior column (proprioception is lost) or cerebellum
What causes a hemiplegic gait (leg is rigidly extended and ipsilateral arm is flexed)?
cerebral infarct (stroke); causes the leg to be extended and arm flexed, the extended leg is circumducted to allow toes to clear the ground
What causes a tabetic gait?
impaired sensation due to neurosyphilis or damage to the dorsal columns is compensated by forcibly planting the feet to "feel" the floor
What is kinetic tremor?
rhythmic oscillations during movement of the limb toward a target
What is dysmetria?
overshooting or undershooting the target
What are common causes of cerebellar hemispheral syndrome?
ipsilateral infarct, hemorrhage, tumor, and MS
What are common causes of cerebellar vermal syndrome?
hemorrhage, tumor, MS, and degenerative disorders (alcoholism)
What are the signs and symptoms of Friedreich's ataxia?
dysfunction of the dorsal spinal cord, spinocerebellar tract lesions (limb dysmetria, gait ataxia, dysarthria); corticospinal tract lesions (weakness and Babinski sign); dorsal root and posterior columns (loss of vibration, position sense, and no reflexes); symptoms begin age 8-15.
What is dystonia?
continual contraction of muscles, causing turning and spasms, unnatural, twisted, and fixed postures
What is a tic?
brief, semipurposeful, stereotyped repetitive contraction of groups of muscles (eye blink, facial twitch, sniff)
What is myoclonus?
rapid shocklike movements of limbs usally bilateral, but often asynchronous; seen in diffuse encephalopathies
What is asterixis?
loss of postural tone of hands or feet so the extended hand or foot has a flapping tremor; seen in diffuse encephalopaties or in structural brain disease