Basal Nuclei: Movement And Disorders Flashcards
Where do voluntary movement signals originate
Cerebral cortex
Where are the voluntary movements that originate in the cortex fine tuned
They are fine tuned and made smooth and pieces by basal nuclei
What are the basal nuclei involved in
- motor activities
- sensorimotor integration and cognitive functions: learning and mastering of new , complex movements (dancing, skiing, swimming)
- Affects (pleasure) which helps us “remember it”
Pyramidal
Pathway mediated by corticospinal neurons
Extrapyramidal
Basal nuclei, cerebellum, or descending brainstem pathways
The dorsal basal nuclei
Caudate nucleus Putamen Globes pallidus Subthalamic nucleus Substantial nigra
What is considered to be the striatum of the dorsal basal nuclei
Caudate nucleus
Putamen
What is considered to be the lenticular nucleus of the dorsal basal nuclei
Putamen
Globus pallidus
What separates the dorsal and ventral basal nuclei
Anterior commisure
What are the ventral basal nuclei involved with
Emotional cortex, pleasure for successful movements
What are the components of the ventral basal nuclei
- nucleus accumbens: a continuation of the lenticular nucleus
- substantia innominata: a continuation of the pallidum
- nucleus basalis of Meynert
- olfactory tubercle
What is the ventral region of the basal nuclei involved with
Potions of the amygdala and ventral tegmental area
What does the neostriatum (striatum) consist of
The caudate nucleus
The putamen
What is the putamen functionally tightly connected with
The caudate nucleus
What is the caudate nucleus and the putamen separated by
The internal capsule
What is the ventral striatum composed of
Nucleus accumbens
What is the pallidal complex composed of
Globus pallidus and the ventral pallidum
Anatomy of the globus pallidus
Has a medial and lateral part divided by medullary lamina
Anatomy of the ventral pallidum
Synonymous with the substantia innominata
The main input TO the pallidum
Is from the striatal complex (putamen)
The main output FROM the pallidum is
To the thalamus
How do the pallidothalamic fibers exit the globus pallidus
As two bundles: the ansa lenticularis and the lenticular fasciculus
What are the two divisions of the substantia nigra
- a cell dense portion called the paras compacta
- reticulated portion called the pars reticulata
Major afferents to the nigra complex
Striatal (putamen)
Pallidal complexes
What does the substantia nigra do
Helps other basal nuclei work in concert
Substantia nigra-pars compacta
Contains melanin containing neurons, whose dark color gives the name “black substance”
Neurons in the pars compacta of the substantia nigra
Use dopamine and project primarily to the neostriatum (putamen and caudate nucleus) as nigostriatal fibers
What kind of NT does substantia nigra use
Dopamine
Function of the dopamine released form the substantia nigra
May excite or inhibit striatal neurons depending on the type of receptor on the postysynaptic membrane
What is the pars reticulata of the substantia nigra formed by
Loose aggregations of GABAergic neurons that are indistinguishable from those of the medial pallidum
Neurons of the pars reticulata of the substantia nigra
Have axons with an extensive system of collaterals; consequently they may project to inhibit one or mroe target structure (neostriatum or thalamus)
What part of the substantia nigra have a high rate of discharge and tonically inhibit their targets
Pars reticulata
Lens shaped cell group that makes up the largest part of the ventral thalamus
Subthalamic nucleus
How does the subthalamic nucleus sit in comparison to the substantia nigra
It is rostral to the substantia nigra
What does the subthalamic nucleus receive projections from
- the lateral pallidal division
- cerebral cortex
- nigral complex
What connections are an essential part of the indirect pathway underlying basal nuclear function
The subthalamic nucleus projecting to both pallidal divisions and to the substantia nigra
Formed from the axons of the neurons in the globus pallidus internal (GPi) and go to the thalamus
Ansa lenticularis
Lenticular fasciculus
What are the main bridges from the pallidus to the thalamus
Ansa lenticularis
Lenticular fasciculus
Fibers of the ansa lenticularis and the lenticular fasciculus join together to form the _________ which enters the thalamus
Thalamic fasciculus
What do the fibers of the thalamic fasciculus terminate in
The ventral anterior and ventral lateral nuclei of the thalamus
The _______ is a principal efferent nucleus of the basal nuclei
Medial division of the pallidal complex
The _______ carries fibers of the indirect pathway from the external segment of the globus pallidus to the subthalamic nucleus and from the subthalamic nucleus to the internal segment of the globus pallidus
Subthalamic fasciculus
Blood supply to the basal nuclei
The blood supply of the striatum and globus pallidus is mainly from the lenticulostriate branches of the MCA
There are some possible variations
- medial GP is often supplied by the anterior choroidal artery
- the caudate head and anterior portions of the lentiform nucleus are often supplied by the recurrence artery of Heubner
What is the gerenalized pathway of the basal nuclei
Cortex-putamen-GPe + GPi-thalamus-cortex
What does the basal nuclei loop constant do
Monitors movements surrender happening. They are multiple and parallel. Function simultaneously for multiple movements at same time
D1 receptors
Dopamine receptor type 1
-activates the neuron if expressed
D2 receptors
Dopamine type II receptors
-deactivates the neuron if expressed
Information flow through the basal nuclei is separated into _______ distinct ______ circuits
Multiple and parallel
Where do the basal nuclei circuits originate from
Functionally distinct regions of the cerebral cortex, pass through distinct regions of each basal nuclear component, affect different areas of the thalamus, and return to functionally distinct cortical regions
All the basal nuclei circuits can be divided into _____ and ______ pathways that have OPPOSING actions on the activity of motor nuclei of the thalamus and thalamocortical projections
Direct and indirect
What pathway facilitates thalamic activity
Direct pathways
What pathways inhibits the flow for thalamic activity
Indirect pathway
What do the direct and indirect pathways create
A balance in the inhibitory outflow of the basal nuclei
What NT has a major role in both direct and indirect pathways
Dopamine
The main input to the basal nuclei comes from the _______ to the striatum
Cerebral cortex
The ________ is the most important input nucleus of the striatum for motor control pathways
Putamen
Most cortical inputs to the striatum are excitatory and use _________ as the NT
Glutamate
The main outputs from the basal nuclei are from the
Internal segment of the globus pallidus
Output pathways of the internal segment of the globus pallidus
Inhibitory and use the NT GABA
What are the main output pathways of the internal globus pallidus to
Ventral lateral and ventral anterior nuclei of the thalamus via the thalamic fasciculus
Motor loop (direct pathway) at rest
Neurons of the internal segment of the globus pallidus and of the substantia nigra pars reticulata that project to the thalamus have high rates of spontaneous activity and tonically inhibit the thalamic neurons
What tonically inhibits the thalamic neurons
Neurons of the internal segment of the globus pallidus and of the substantia nigra pars reticulata
During the motor loop (direct pathway) when there is cortical activity and voluntary movement is intended
The Cortex sends as an excitatory, glutamatergic signal to the putamen
What activated the putamen in the direct pathway?
Cortex
What do signals from the putamen do
Inhibit neurons in the internal segment of the globus pallidus and in the substantia nigra pars reticulata (GABA)
When the putamen is activated, what does it in turn do in the direct pathway
Deactivates Gpi and substantia nigra
In the direct pathway, when the putamen deactivates the Gpi and the substantia nigra what happens
This stops the inhibitory inputs to thalamocortical neurons and the thalamus is disinhibition, net effect is excitation of the cerebral cortex
What is the net effect of the direct pathway
Excitation of the cerebral cortex
Which pathway is inhibitory, direct or indirect
Indirect
The indirect pathway at rest
The pallido-subthalamic fibers (GABA) have high spontaneous firing rates and tonically inhibit subthalamic neurons
In the indirect pathway what happens when the pallido-subthalamic,ic fibers get inhibited
It is done by the neostriatum that releases the subthalamic cells from their tonically inhibited state.
What do the striatopallidal neurons involved in the indirect pathway contain
GABA and enkephalin
In the indirect pathway, what do the subthalamic neurons do
They have spontaneous activity that activates the internal globus pallidum
In the indirect pathway, what does the activation of the internal globus pallidum by the subthalamic neurons do
Increases the firing rate of glutamatergic subthalamopallidal fibers to the medial pallidal segment
In the indirect pathway, what does increasing the firing rate of glutamatergic subthaalmopallidal fibers to the medial pallidal segment do
The firing rate of the inhibitory pallidothalamic fiber is increased, with a resultant decrease in the activity of thalamocortical neurons
What is the net effect of the indirect pathway
To decrease activity of the thalamus and consequently to decrease activity of the cerebral cortex
Where does the motor loop originate
In the supplementary motor, primary motor, and promoter cortices
Where do the corticostriatal projections in the motor loop terminate in
Putamen
In the motor loop, where do efferent from the putamen go
Terminate in the internal segment of the GPi and substantia nigra pars reticulata
In the motor loop, where does the GPi project to
The ventral lateral nucleus of the thalamus. These areas project back to the supplementary, premotor, and motor cortices
What does the basal nuclear pathway for the motor loop affect
Both cortical motor and brainstem motor centers
What sends signals to the putamen during movements to determine whether or not to inhibit or excite
Substantia nigra
-can be excitatory or inhibitory depending on the type if the receptors for dopamine
This receives most of the inputs form the motor and somatosensory areas of cortex and projects by way of the globus pallidus and thalamus to the motor, premotor, and supplementary motor areas. Thus it is involved in the motor functions of the basal ganglia
Putamen
What is involved in the motor functions of the basal ganglia
Putamen
This receives most of tis inputs form association areas of cortex and projects by way of GPi-SNr and the thalamus mostly to prefrontal areas. Thus it is involved more predominantly in cognitive functions and less directly movements
Caudate nucleus
What basal ganglia is more involved with cognitive functions and less directly in movement
Caudate nucleus
This indicate its probable role in the initiation of drive-related behaviors
The limb ic connections of the ventral striatum
This allows us to learn new complex movements
Caudate nucleus
What basal ganglia is most involved with the executive loop
Caudate nucleus
What are executive functions
Cognitive mechanisms that allow the individual to optimize function when multiple tasks need to be performed at the same time
What basal ganglia is not really involved in the executive loop
Putamen
What is the pathway of the executive loop
Prefrontal cortex–caudate nucleus—GPi, SNr–VA/MD
Motivational loop
- pleasure helps remember movement
- this loop includes lateral orbitofrontal cortex, anterior cingulate cortex, medial prefrontal cortex, amygdala, and hippocampus
- these project to the caudate nucleus and the ventral striatum (VS)
- then to the GPi, nucleus accumbens, and others
- then to VA, DM of the thalamus
Visuomotor loop
Similar to cognitive loop
-FEF–Caudate nucleus—GPi+SNr–VA/MD—FEF
