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Which motor control system is the Basal Ganglia a part of?
extrapyramidal (developed before pyramidal)
What does the basal ganglia control?
- involuntary, instinctive skeletal m activity (don't have to think about it)
Where is the basal ganglia?
deep seated nuclei w/in white matter of cerebral hemispheres of telencephalon
What are the primary players of the basal ganglia?
- caudate nucleus
- lenticular nucleus
What makes up the lenticular nucleus?
What structures make up the extrapyramidal system?
- basal ganglia
- red nucleus (midbrain)
- substantia nigra (midbrain)
- subthalamic nucleus (diencephalon)
Does the basal ganglia have a direct connection with the SC?
no, indirect relationship to LMN
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
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
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
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
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
What does the basal ganglia utilize to carry out functions?
Is the basal ganglia intimately integrated with pyramidal system?
yes, the two can't work in isolation of one another
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
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
What are the basal ganglia inhibitory mechanisms?
- determines direction, speed, force of movement
- involved with CPG
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
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)
Characteristics of Basal Ganglia Damage: Parkinson's disease/Parkinsonian symptoms
- reduction in the initiation, implementation, and facilitation of execution of movement (slow movement)
- movements initiated slowly and stop with difficulty
- voluntary movements
when you can't move something at all
What are characteristics of hypokinesia?
- 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
- reason they are moving slower
- increase in m tone w/ resistance to PROM
- if disruption involved the whole body (all mm)=rigidity
associated w/ hypokinesia and hypertonia, implying that entire body presents it
- increased jerky resistance for PROM (jerky like a cogwheel)
- due to increases in m tone
Plastic rigidity (lead pipe)
increased resistance to PROM that is constant, continuous, and smooth
What abnormal postures may be assumed w/ hypokinesia?
stooped, lean to one side
How are facial expressions masked with hypokinesia?
hard to laugh or smile, etc b/c requires motor function
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
Pathology of Parkinson's Disease: Decreased amounts of neurons leads to dopamine-depleted basal ganglia
decreased levels of dopamine = decreased inhibition
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
involuntary movement b/c basal ganglia is no longer inhibiting movement
What are the involuntary movements associated with basal ganglia damage?
hyperkinesia-hyperkinetic (involuntary movements)
What are the symptoms of hyperkinesia-hyperkinetic?
- static tremor
- alternating tremor
- hallmark of basal ganglia dysfunction
- rhythmic, fine, involuntary tremor when extremity is in fixed position
- associated w/ Parkinson's
What dysfunction causes static tremor?
substantia nigra dysfunction
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)
Alternating tremor is due to:
alternating contraction of opposing mm groups
Alternating tremor, aka:
hyperkinesia characterized by regular, symmetrical, to and fro movements produced by patterned, alternating contraction of mm and their antagonists
Is alternating tremor associated with Parkinson's?
Does alternating tremor continue when pt does voluntary skeletal mm activity?
no, tremor stops
Does alternating tremor stop during sleep?
What dysfunction causing alternating tremor?
caudate nucleus dysfunction
involuntary movement characterized by slow, writhing (squirmy), worm-like movements of the fingers
Is Athetosis associated with Parkinson's?
When does athetosis occur?
at rest or during involuntary or voluntary movement
What dysfunction causes athetosis?
sudden, involuntary, jerky movements w/ grimacing or twitching of facial mm and faulty vocalization
Is chorea associated with Parkinson's?
What disease is associated with chorea?
- autosomal dominant disorder
- caudate nucleus atrophies or breaks down and becomes disinhibited
- manifests in 4th decade of life
What dysfunction causes Huntington's chorea?
caudate nucleus damage
When does chorea happen?
at rest or voluntary movement
What dysfunction causes chorea?
- involuntary movements of an entire limb
- begins proximally and proceeds distally
- movements are quite dramatic
Is ballism associated with Parkinson's?
What causes ballism?
subthalamic stroke (dysfunction of subthalmic nucleus
Is the subthalmic nucleus part of the basal ganglia?
no, but still part of extrapyramidal system which helps w/ voluntary movements
Which basal ganglia NT/NM are excitatory?
Which basal ganglia NT/NM are inhibitory?
- Dopamine (damage in Parkinson's)
- Glycine (major inhibitory NT in NS)