internal capsule and basal ganglia Flashcards
basal ganglia function
- fine-tune voluntary movements
- goal-directed voluntary movements
basal ganglia receive info from ?, processes it, and send it to ?
cerebral cortex; adjusted info back to cerebral cortex
cortex sends adjusted info to ? via ?
skeletal muscles; pyramidal system
basal ganglia definition
- a group of subcortical nuclei
- responsible primarily for motor control, motor learning, executive functions and behaviors, and emotions
- extrapyramidal system (involuntary)
5 pairs of nuclei in basal ganglia
- caudate nucleus
- putamen
- globus pallidus
- subthalamic nucleus
- substantia nigra
lentiform nucleus
- putamen
- globus pallidus
striatum
- caudate nucleus
- putamen
internal capsule
a big group of white matter axonic tracts
caudate nucleus
- elongated c-shaped nucleus lateral to the lateral ventricles
- head, body, tail
- continuous with putamen
- connects with amygdala
caudate nucleus tail forms ?
roof of the inferior horn of the lateral ventricles
caudate nucleus function
- sends information to the thalamus about body and limb position
- goal-oriented behavior, learning, emotion
underactive caudate nucleus associated with ?
depression and schizophrenia
putamen
- encircled by the caudate nucleus
- most lateral structure of the basal ganglia
- regulates motor functions
globus pallidus
- medial to the putamen
- external and internal segments
- control conscious and proprioceptive movements
substantia nigra
- in the midbrain but part of the basal ganglia
- contains neuromelanin
- two subcomponents: pars compacta and pars reticulata
pars compacta
- dorsal subcomponent of substania nigra
- melanin-filled neurons
- unknown function but dopamine neuron death causes Parkinson disease
pars reticulata
- ventral subcomponent of substantia nigra
- controls eye movement
large number of motor and sensory fibers travel to and from the cortex via ?
internal capsule
3 subdivisions of the internal capsule
- anterior limb
- genu
- posterior limb
anterior limb of internal capsule
- frontopontine fibers
- thalamocortical fibers
genu of internal capsule
corticobulbar fibers
posterior limb of internal capsule
- corticospinal fibers
- ascending sensory fibers
frontopontine fibers
frontal cortex to pons
thalamocortical fibers
thalamus to frontal lobe
corticobulbar fibers
cortex to brainstem
corticospinal fibers
cortex to spinal cord
extrapyramidal system function
involuntary and automatic control of movements, posture, and muscle tone
extrapyramidal system structures involved
- basal ganglia
- red nucleus
- substantia nigra
- reticular formation
- cerebellum
basal ganglia input
all of cortex (except primary visual and auditory cortices)
corticostriatal pathways
pathways that give input to basal ganglia
axons from striatum synapse with ?
globus pallidus or pars reticulata
basal ganglia output structures
- globus pallidus
- pars reticulata
basal ganglia output (globus pallidus)
- axons synapse with thalamus
- thalamus relays info back to motor cortex (feedback loop)
basal ganglia output (pars reticulata)
- axons synapse with upper motor neurons in the superior colliculus
- regulate eye movement
basal ganglia dysfunction
damage or degeneration to basal ganglia results in involuntary movements or motion impairment
types of basal ganglia dysfunction
- involuntary movement disorders
- impairments to motion disorders
- parkinson’s disease
- huntington’s disease
involuntary movement disorders
- tremor (often resting tremor)
- athetosis
- chorea
- ballism
- dystonia
athetosis
slow involuntary writing or twisting movements
chorea
fast or jerky involuntary writing movements of the extremeties
ballism
- similar to chorea
- associated with more proximal extremities like shoulders and hips
dystonia
involuntary contractions of muscles
impairments to motion disorders
- akinesia
- bradykinesia
- shuffling gait
- speech difficulties
- loss of postural reflexes
akinesia
lack of movement
bradykinesia
slow movement
parkinson’s disease is a type of ?
parkinsonism
parkinsonism
umbrella term for bradykinesia, tremor, rigidity
parkinson’s causes
- death of dopamine secretion in the substantial nigra
- exact cause in unknown
- associated with exposure to toxins, historical head trauma, infection, genetics
parkinson’s treatment
- L-DOPA
- deep brain stimulation
L-DOPA
- dopamine precusor that helps to alleviate symptoms
- initially effective
- 50% of patients develop DOPA-induced dyskinesia after 5-10 years
DOPA-induced dyskinesia
- involuntary erratic movements
- result of L-DOPA treamtent for 5-10 years
deep brain stimulation
high frequency deactivate subthalamic nucleus
increased activity of ? in parkinson’s
subthalamic nucleus
huntington’s disease causes
- progressive atrophy of the striatum
- genetic
huntington’s disease treatment
- xenazine
- antidepressants/antipsychotic drugs
xenazine
- suppresses involuntary movements
- multiple side effects (drowsiness, restlessnes, psychiatric conditions)
why does huntington’s disease have antidepressants/antipsychotic drugs as a treatment
high comorbidity rates
output nuclei of basal ganglia are inhibitory/excitatory
inhibitory
how does cortex signal to striata to disinhibit the thalamus
- output nuclei maintain a high tonic level of discharge (suppresses activity)
- phasic decrease in firing rate releases target regions from inhibition
- strong tonic inhibitions allows basal ganglia to regulate
voluntary motor control of basal ganglia
- procedural learning (routine behavior/habits)
- eye movement
- cognition
- emotional function
which functions of basal ganglia use loops
- voluntary motor control
- movement initiation
- movement regulation
- procedural learning (routine behavior/habits)
- cognitive functions
- emotional functions
- eye movements
basal ganglia motor loop
- putamen circuit
- learned movement
basal ganglia cognitive loop
- caudate circuit
- cognitive control of motor pattern sequence
- motor intentions
cognition
thinking process using sensory input with info already stored in memory
basal ganglia limbic loop
- give motor expressions to emotions
- smiling, aggressive, submissive posture
basal ganglia occulomotor loop
voluntary eye movement
