Lecture 14 - Basal Ganglia Flashcards
What does the basal ganglia include?
Collection of gray matter nuclei WITHIN the white matter of cerebral hemispheres:
- Caudate
- Putamen
- Globus Pallidus
- Subthalamic nucleus
- striatum
- lenticular nucleus
Compared to the frontal lobes, what is the basal ganglia responsible for, in terms of movement?
frontal lobes DIRECT movement
basal ganglia responsible for TRUNCAL movements and WHOLE OF BODY movements, such as GAIT, tc
Does the basal ganglia project onto the spinal cord?
No, like the cerebellum, it synapses with other nuclei that do.
What can happen in people with basal ganglia lesions?
Hyperkinetic movement disorder
hypokinetic movement disorder
What is the striatum and what does it do
this is a the caudate nucleus and the putamen.
they are seperate, but are said to function basically as a unit, because they both receive all the input into the basal ganglia
damage this, damage input into basal ganglia
what does the caudate look like
c shaped
head, body and nail.
amygdala lies at the anterior tip of the tail
Where does input for basal ganglia come into
striatum - putamen and caudate
Where does output happen for basal ganglia
internal segment of global pallidus and substantia nigra
Describe the motor channel in the basal ganglia
input travels mainly to putamen > output from internal global pallidus and substantia nigra pars compacta > ventral anterior and ventral lateral nuclei of thalamus > supp motor area, premotor cortex and primary motor cortex
goes from somatosensory and motor cortices back to the supp, premotor and motor cortex.
What are hyperkinetic movement disorders
- seen in huntingtons
uncontrolled involuntary mvements
random pattern of jerks and twists
What are hypokinetic movement disorders
- seen in parkinsons
- rigidity,slowlness and marked difficulty initiating movements
- the inhibitory output from the basal ganglia to thalamus is increased, resulting in a relative paucity of movements.
Describe the oculomotor channel
- regulates eye movements
posterior parietal cortex and prefrontal cortex > body of caudate > globus pallidus and substatia nigra > VA MD of thalamus > frontal eye fields and supplementary eye fields of frontal lobes
What are the four main parallel channels through the basal ganglia?
- Motor Channel
- Oculomotor Channel
- Prefrontal Channel
- Limbic channel
all pass through different areas of basal ganglia, thalamus and finally frontal lobe, to create action
Describe the prefrontal channel
- important for cognitive processes that involve the frontal lobes.
postrior parietal cortex, premotor cortex > head of caudate > globus pallidus, substantia nigra > VA and MD of thalamus > prefrontal cortex.
Describe the limbic channel
- regulation of emotions and motivational drives
limbic cortex, hippocampus, amygdala > nucleus accumbens, ventral caudate, ventral putamen > ventral pallidum, globus pallidus and substantia nigra >MD VA of thalamus > anterior cingular and orbtial forntal cortex
What are the two ways intrinsic connections are made in the basal ganglia?
- direct
- indirect - reaches output nuclei via detour through subthalamic nuclei
“determinant of pathway is dopamine”
Describe the direct pathway for intrinstic basal ganglia connections
direct pathway travels from striatum directly to the internal segment of globus pallidus or substantia nigra pars reticulata
NET EFFECT: excitatory - creates movement
Describe the indirect pathway for intrinstic basal ganglia connections
this pathway takes a detour from striatum, to external segment of globus pallidus, to subthalamic nuleus, then to the internal segment of globus pallidus or substantia nigra.
NET EFFECT: inhibitory : inhibits movement
What does the cerebellum consist of
- the midline vermis, the intermediate part of the cerebellar hemisphere, and the lateral part of the cerebellar hemisphere.
- attached to dorsal portion of brainstem
What are the three functional zones of the cerebellum
- vermis - control proximal and trunk muscles and
- flocculonodular lobe - vestibulo-ocular ontrol
- intermediate- control of more distal muscles in arms and legs
- lateral - planning the motor program
What commonly happens after a cerebellar lesion
ATAXIA - irregular, uncoordinated movement
it is ipsilateral to the side of cerebellar lesion
midline lesions of the vermis or flooculonodular lobes cause unstead gait and eye movement abormalities
lesions of intermediate part of cerebellar hemisphere causes ataxia of the limbs
also causes nausea, vertigo and nystagmus bc of connections with vestibular system
What can ataxia be caused by
lesions within the cerebellum - ipsilateral side, and to the limbs if in the intermediate cerebellum hemisphere.
can also be caused by lesions in brainstem circuitry
What is spasticity
The slow, clumsy, stiff movements and hyperreflexia resulting from corticospinal, upper motor neuron lesions
^ not cerebellar lesions
what is ataxia
Irregular, uncoordinated movements caused by lesions of the cerebellar circuitry
what is dyskinesia
Abnormal movements caused by basal ganglia dysfunction
sometimes called Extrapyramidal motor disorder because the extrapyramidal system was once mistakenly thought to be an independent pathway, running parallel to the pyramidal (corticospinal) tracts, travelling from the striatum to spinal cord.
what is bradykinesia
slowed movements
hypokinesia
decreased amount of movements
akinesia
absence of movement
rigidity
increased resistance to passive movement of a limb
dystonia
abnormal, distorted position of the limbs, trunk or face that is sustained
athetosis
twisting movements of the limbs, face and trunk that sometimes merge with faster choreic movements
chorea
“dance”
nearly continuous involuntary movements that have a jerky or varying quality
ballismus
movement of proximal limb
tics
a sudden brief action preceded by an urge to perform it and followed by a sense of relief.
myoclonus
considered the faster of all movement disorders; a sudden rapid muscular jerk that can be focal, unilateral or bilateral.
tremor
rhythmic or semirhythmic oscillating movements.
What is seen in huntington’s
hyperkinetic
what is seen in parkinsons
hypokinetic
What are ways that hyperkinetic movement disorder can be caused
causing lesions to subthalamic nucleus (a part of the indiret pathway) through stroke
loss of inhibitory neurons from striatal neurons of indirect pathway in early huntingtons
