Basal Ganglia Flashcards
do the basal ganglia have a direct connection to the LMN pool?
no, they provide and regulate info coming out of UMNs
what is the result of that basal ganglia having no direct connection to the LMN pool?
lesions don’t affect strength of muscles but will effect inhibition of movement and suppression of movement
what behaviors do the basal ganglia control?
goal-directed behavior, social behavior, and some emotional responses
what are the structures of the basal ganglia
caudate, putamen, globus pallidus, subthalamic nucleus, and substantia nigra
what structures make up the striatum?
caudate and putamen
what structures make up the lenticular nucleus?
putamen and globus pallidus
what structure of the basal ganglia is not in the cerebrum, but rather in the midbrain?
the substantia nigra
what are the two parts of the GP?
GPi (globus pallidus internal) and GPe (globus pallidus external)
what are the two parts of the SN?
SNpc (substantias nigra pars compacta) and SNr (substantia nigra reticulata)
what is the area surrounding the 4th ventricle and what does it do?
PEG (periaqueductal grey)
it plays a big role in pain modulation (suppresses pain by releasing endogenous opioids)
what are the 5 cortico-BG-thalamic circuits?
2 motor:
- motor
- oculomotor
3 non-motor:
- goal-directed behavior
- emotion/motivation
- social behavior
what structures are involved in the motor basal ganglia circuit? what is the function of the circuit?
putamen and GP
skeletal muscle contraction, muscle force, multi joint movement, movement sequencing, motor planning
what structures are involved in the oculomotor BG circuit? what is the function of the circuit?
caudate body and SNr
spatial awareness and eye movement
what structures are involved in the goal-directed behavior BG circuit? what is the function of the circuit?
caudate head and GP
decision-making, information evaluation, planning, choosing actions in context
what structures are involved in the emotion/motivation BG circuit? what is the function of the circuit?
ventral striatum and ventral pallidum
regulates emotional expression, reward-seeking behavior
what structures are involved in the social behavior BG circuit? what is the function of the circuit?
caudate head and SNr
recognizes social cues, self-control, attention to social disapproval, and selective attention
what 3 things are involved in all BG circuits?
BG, cortical structure, and thalamic nuclei
what 3 things are involved in the 3 non-motor and 2 motor BG circuits?
prefrontal cerebral cortex
BG
thalamic nuclei
what are the BG afferents?
all areas of the cerebral cortex
PPN
dorsal raphe nuclei
what is the NT of the cerebral cortex?
glutamate
excitatory
always excitatotry input from the cortex
what are the 2 NTs of the PPN?
ACh (excitatory or inhibitory)
glutamate (excitatory)
what is the PPN responsible for?
attention, reward, voluntary movement, etc.
what is the NT of the dorsal raphe nuclei?
serotonin (usually inhibitory)
inputs enter the BG through what strucures?
striatum (caudate and putament)
subthalamic nucleus (STN)
what are the 3 main sources of input?
PPN, dorsal raphe nuclei, and cerebral cortex
what is the intrinsic circuitry of the BG?
SNpc to striatum (dopamine=excitatory or inhibitory)
striatum to GP and SN (GABA=inhibitory)
GPe to STN (GABA=inhibitory)
STN to GPi and SNr (glutamate=excitatory)
- only soley excitatory pathway
what are the efferents of the BG?
GPi (globus pallidus interna) to thalamus (VL and VA) and SNr (substantia nigra reticulata) to superior colliculus
tracts in the GPi to thalamus of BG
corticospinal
corticopontine
corticobrainstem
efferent info from GPi to thalamus
provide info for descending system from cerebral cortex
efferent info from SNr to superior colliculus
contributes to directing visual attention to the stimulus
superior colliculus inhibited by SNr
midbrain locomotor region inhibited
what are the 3 movement control pathways?
Go (direct)
No-Go (indirect)
Stop (hyperdirect)
normal movement requires all pathways
how does the BG control movement?
the BG controls movement by controlling what’s happening in these circuits
the SN to putamen will activate which 2 pathways depending on the signal?
go or no-go
what is disinhibition?
double inhibition=activation
silent inhibitory neuron activated and inhibits another inhibitory neuron which always excitation
stop (hyperdirect) pathway
inhibition of the motor thalamus
goal: inhibit ongoing, irrelevant movement
motor cortex activates STN
STN excites GPI
GPi inhibits motor thalamus
go (direct) pathway
goal: getting info from SNpc; facilitate movement
disinhibition of motor thalamus
motor cortex activates D1 receptor of putamen
D1 inhibits GPi (inhibiting inhibitory nucleus)
motor thalamus is disinhibited (activated)
no-go (indirect) pathway
goal: inhibit/suppress unnecessary movements
inhibition of motor thalamus
suppress competing movements
motor cortex excites D2 receptor of putamen
putamen inhibits GPe
GPe disinhibits STN
STN excites GPi
GPi inhibits motor thalamus
Control of movement from the GPi
voluntary movement
postural control
walking
LMN: control of voluntary movement
GPi inhibits the motor thalamus
motor thalamus excites motor cortex
motor cortex excites corticospinal tracts
corticospinal tracts contribute to voluntary movements
LMN: postural and girdle muscles
GPi inhibits the PPN
PNN inhibits reticulospinal tracts
disinhibition of postural and girdle muscles
stepping pattern generators/LMN for walking
GPi inhibits midbrain locomotor region
midbrain locomotor region has cholinergic effects on reticulospinal tracts
reticulospinal tracts activate SPG/LMN for walking
movement disorders of the BG
affect balance of the function of the 3 pathways
hypokinetic disorders
less movement
down regulation of go pathways, up regulation of no-go pathway
Parkinson’s disease: postural instability
hyperkinetic disorders
too much movement
up regulation of go pathway, down regulation of no-go pathway
Huntington’s disease
Tourette’s syndrome
