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Which motor control system is the Basal Ganglia a part of?
extrapyramidal (developed before pyramidal)
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What does the basal ganglia control?
- involuntary, instinctive skeletal m activity (don't have to think about it)
- reflexive
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Where is the basal ganglia?
deep seated nuclei w/in white matter of cerebral hemispheres of telencephalon
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What are the primary players of the basal ganglia?
- caudate nucleus
- lenticular nucleus
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What makes up the lenticular nucleus?
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What structures make up the extrapyramidal system?
- basal ganglia
- red nucleus (midbrain)
- substantia nigra (midbrain)
- subthalamic nucleus (diencephalon)
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Does the basal ganglia have a direct connection with the SC?
no, indirect relationship to LMN
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How does the basal ganglia communicate with the SC (how does it carry out reflexive motor control to the LMN)?
by using reticulospinal, corticospinal, nigroreticular, and thalamocortical tracts
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How does the basal ganglia use the reticulospinal tract?
- sends info to reticular formation
- which sends it to ventral horns of SC to influence LMN (alpha)
- biased toward extensor activity
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How does the basal ganglia use the corticospinal tract?
- sends info to pre-central gyrus (influences UMN in precentral gyrus)
- to in turn influence LMN
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How does the basal ganglia use the nigroreticular tract?
sends info to substantia nigra in midbrain to reticular formation to reticulocortical tract to influence LMN
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How does the basal ganglia use the thalamocortical tract?
sends info to thalamus which sends info to cortex through thalamocortical tract to influence corticospinal tract
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What does the basal ganglia utilize to carry out functions?
inhibitory processes
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Is the basal ganglia intimately integrated with pyramidal system?
yes, the two can't work in isolation of one another
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What are the functions of the basal ganglia?
- assists in inhibiting co-contraction in aantagonistic mm of limbs
- assists in adjusting body position during movement for a specific task
- works at subconscious or reflexive level
- determines direction, speed, force of movement
- involved with CPG
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What is an example of the basal ganglia assisting in inhibiting co-contraction in antagonistic mm of the limbs?
- thalamocortical influence (info is from thalamus to caudate nucleus to precentral gyrus)
- utilizes Renshaw cells
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What are the basal ganglia inhibitory mechanisms?
- determines direction, speed, force of movement
- involved with CPG
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What is an example of the basal ganglia determining direction, speed, force of movement?
if you want to hit someone with a pillow, you would use your BG so it can recruit the UMN to tell LMN to work
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How is the basal ganglia involved w/ CPG?
where they are remembered. Start as voluntary and w/ repetition they become remembered (CPGs stored in BG)
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Characteristics of Basal Ganglia Damage: Parkinson's disease/Parkinsonian symptoms
hypkinesia (akinesia)
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Hypokinesia:
- reduction in the initiation, implementation, and facilitation of execution of movement (slow movement)
- movements initiated slowly and stop with difficulty
- voluntary movements
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akinesia:
when you can't move something at all
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What are characteristics of hypokinesia?
- hypertonia
- rigidity
- conscious movements may be suppressed w/ hypokinesia
- abnormal postures may be assumed
- reciprocal arm swing during gait is absent
- DTR usually normal
- facial expression masked
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hypertonia:
- reason they are moving slower
- increase in m tone w/ resistance to PROM
- if disruption involved the whole body (all mm)=rigidity
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Rigidity:
associated w/ hypokinesia and hypertonia, implying that entire body presents it
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cogwheel rigidity:
- increased jerky resistance for PROM (jerky like a cogwheel)
- due to increases in m tone
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Plastic rigidity (lead pipe)
increased resistance to PROM that is constant, continuous, and smooth
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What abnormal postures may be assumed w/ hypokinesia?
stooped, lean to one side
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How are facial expressions masked with hypokinesia?
hard to laugh or smile, etc b/c requires motor function
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Pathology of Parkinson's Disease: Degeneration of substantia nigra of midbrain
normally there are neurons in substantia nigra that release dopamine (an inhibitory NTM) to basal gagnlia
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Pathology of Parkinson's Disease: Decreased amounts of neurons leads to dopamine-depleted basal ganglia
decreased levels of dopamine = decreased inhibition
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Pathology of Parkinson's Disease: Disinhibition-
- basal ganglia can't be inhibited and will do things in an uncontrolled manner
- causing activity that you don't want (hypotonia), involuntary movements
- disinhibition Phenomenon
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Disinhibition Phenomenon:
involuntary movement b/c basal ganglia is no longer inhibiting movement
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What are the involuntary movements associated with basal ganglia damage?
hyperkinesia-hyperkinetic (involuntary movements)
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What are the symptoms of hyperkinesia-hyperkinetic?
- static tremor
- alternating tremor
- athetosis
- chorea
- ballism
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Static tremor:
- hallmark of basal ganglia dysfunction
- rhythmic, fine, involuntary tremor when extremity is in fixed position
- associated w/ Parkinson's
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What dysfunction causes static tremor?
substantia nigra dysfunction
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How do you differentiate b/w cerebellar dysfunction and basal ganglia dysfunction?
- cerebellar = intentional tremor (starts as you approach a target)
- basal ganglia = static (fixed)
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Alternating tremor is due to:
alternating contraction of opposing mm groups
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Alternating tremor, aka:
pill rolling
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Alternating tremor:
hyperkinesia characterized by regular, symmetrical, to and fro movements produced by patterned, alternating contraction of mm and their antagonists
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Is alternating tremor associated with Parkinson's?
no
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Does alternating tremor continue when pt does voluntary skeletal mm activity?
no, tremor stops
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Does alternating tremor stop during sleep?
usually
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What dysfunction causing alternating tremor?
caudate nucleus dysfunction
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Athetosis:
involuntary movement characterized by slow, writhing (squirmy), worm-like movements of the fingers
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Is Athetosis associated with Parkinson's?
no
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When does athetosis occur?
at rest or during involuntary or voluntary movement
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What dysfunction causes athetosis?
putamen dysfunction
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Chorea:
sudden, involuntary, jerky movements w/ grimacing or twitching of facial mm and faulty vocalization
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Is chorea associated with Parkinson's?
no
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What disease is associated with chorea?
Huntington's chorea
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Huntington's chorea:
- autosomal dominant disorder
- caudate nucleus atrophies or breaks down and becomes disinhibited
- manifests in 4th decade of life
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What dysfunction causes Huntington's chorea?
caudate nucleus damage
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When does chorea happen?
at rest or voluntary movement
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What dysfunction causes chorea?
caudate nucleus
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Ballism:
- involuntary movements of an entire limb
- begins proximally and proceeds distally
- movements are quite dramatic
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Is ballism associated with Parkinson's?
no
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What causes ballism?
subthalamic stroke (dysfunction of subthalmic nucleus
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Is the subthalmic nucleus part of the basal ganglia?
no, but still part of extrapyramidal system which helps w/ voluntary movements
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Which basal ganglia NT/NM are excitatory?
- ACh-acetylcholine
- Glutamate
- Aspartate
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Which basal ganglia NT/NM are inhibitory?
- GABA
- Dopamine (damage in Parkinson's)
- Glycine (major inhibitory NT in NS)
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