Basal Ganglia Flashcards
Corpus striatum
. Caudate, putamen, and globus pallidus
Striatum (Neostratium)
Caudate and putamen
. Contains neurons that use either ACh or GABA
. Most inputs to here
Lenticular (lentiform) nucleus
Putamen and globus pallidus
Globus pallidus
. Composed of internal and external segments
. Use GABA
. Internal segment (GPi): major output of corpus striatum projecting to VA/VL nuclei in thalamus, receives input from striatum, external globus pallidus, and subthalamus (most outputs from here)
. External segment (GPe): input from striatum, projects to internal segment and subthalamus
Substantia nigra
. Ventral portion of midbrain tegmentum
. Pars compacta: dopamine, have neuromelanin to give black appearance
. Pars reticula: uses GABA
. Prinicpal source of dopamine to the striatum via nigtostriatal tract
Sub thalamic nucleus
. Just ventral to thalamus
. Connected to striatum and substantia nigra
Inputs to basal ganglia
. Striatum receives input from all areas of cerebral cortex, esp. premotor and supplemental motor cortices
. Project to ispsilat. Striatum via corticostriate projections
GABAergic spiny neurons
. Contains many dendritic spine
. Main type of neurons involved in both direct and indirect pathway
. Activation leads to inhibition of neuromodulation of their target neurons
Cholinergic interneurons
. Uses ACh
. Function to modulate local activity w/in striatum
. Constitutively active neurons
D1 group of receptors in striatum
. When dopamine binds it is excitatory on postsynaptic neuron
. Plays role in direct pathway
D2 group of receptors in striatum
. When dopamine binds it has inhibitory effect on postsynaptic neuron
. Plays role in indirect pathway through basal ganglia
Striatopallidal projections
. Striatum projects onto GPe and GPi
. Utilize GABA and are inhibitory
Striatonigral fibers
. Striatum projects to substantia nigra
. Use GABA, inhibitory
Subthalamus nucleus projects to ____
. GPi
. Use Glu, excitatory
Outputs of basal ganglia
. GPi main source
. Projects to VA and VL thalamic nuclei
. Pallidothalamic projections utilize GABA and are inhibitory
Basal ganglia interconnections are ipsilateral or contralateral?
. Ipsilateral
. Indirect effects on cerebral cortice influence motor control of contralat. Side of body though corticospinal system
Direct pathway
. Facilitates flow of info through thalamus
. Utilizes D1 group
. Thalamic activity is inc. by activation
. Cortical activity is inc. and so are movements
. Cortex to striatum fibers using Glu to excite spiny neurons D1 and turn them on
. D1 neurons send out GABA to GPi to turn off inhibitory neurons
. Disinhibition of the inhibitor neuron releases the thalamus from inhibition and allows thalamus to be activated
. Thalamic fiber to M-1 send Glu and excite neurons to inc. motor cortex firing
Indirect pathway
. Inhibits flow of info through thalamus
. Uses D2 dopamine receptors
. Subthalamic nucleus is key part
. Thalamic activity and cortical activity are dec.
. Cortex sends Glu to striatopalladal D2 neurons to turn them on
. D2 sends GABA and inhibits GPe that normally inhibit subthalamus
. Nothing is inhibiting subthalamus and its glutamanergic neurons excite GPi neurons
. Inhibitory pallidothalamic neurons activate and inhibit the thalamocortical projections dec. movement
. When thalamus is inactivated it can’t activate M-1
T/F nigral and pallidal inputs to thalamus are tonically active
T
T/F D1 receptors and direct pathway is excited when dopamine is released
T
Positive feedback pathway when dopamine is released
. D1 receptors turned on and D2 turned off
. Striatum sends GABA projections to cells in pars reticulata
. Causes further disinhibition of thalamus by inhibiting pars peticulata inhibitory neurons
. Inhibits the inhibitory projections of pars reticulata to pars compacta to enhance further dopamine release
Parkinsonism
. Loss of dopaminergic inputs from striatum from substantia nigra
. Indirect system is dominant due to ACh leading to serious lack of movement
How ACh affects pathways
. Excites D2 and inhibits D1 activating the indirect pathway
Chorea
. Loss of cholinergic interneurons in striatum
. Direct system dominant
. Leads to excessive, unwanted movements
T/F basal ganglia influence motor movements even though they have no direct connections to lower motor neurons
T
