week 5- basal ganglia Flashcards
what are the output. nuclei of the BG
SNr, GPi, ventral pallidum this send the output to the thalamus
outline the direct pathway
excitation= hyperkinesia, damage = hypokinesia
Motor cortex stimulation with GLU
striatum GABA released from the putamen
inhibition of globus pallidus internus (and or substantia nigra)
decreased inhibition of thalamus (ventrolateral nucleus)
increased excitation of the motor cortex increased movement
outline the indirect pathway
excitation= hypokinesia, damage= hyperkinesia
Motor cortex stimulation with GLU
striatum GABA released from the putamen
inhibition of globus pallidus externus
decreased inhibition of subthalamic nucleus (ventrolateral nucleus)
increased stimulation of globus pallidus internus
inhibition of thalamus
inhibition of motor cortex
Describe the normal function of medium spiny neurons and what would happen if they were inhibited
reside in the stratium respond to GLU and release gaba as output from stratium
•Direct path MSNs expresses D1 receptors (dopamine excitatory here)
inhibition MSN = hypokinesia
•Indirect path MSNs expresses D2 receptors receptors (dopamine inhibitory here)
inhibition of MSN= hyperkinesia (less inhibition of GPe)
less inhibition of GPe by MSNs, so MORE inhibition of STN by GPe. More inhibition of STN means the STN cannot drive the output nuclei (SNr and GPi), so there is LESS inhibitory control of thalamus. Less inhibition of thalamus means thalamus allows increased movement.
compare D1 and D2 receptors
D1- DA excites MSNs of the direct pathway
D2- DA inhibits MSNs of the indirect pathway
what part of the BG releases dopamine
what part of the BG depends on dopamine
substantia nigra pars compacta
stratium
what pathway is upregulated in hyperkinesia and what are some examples
Increased direct, decreased indirect
Ballismus, Choreiform, Athetoid movements
what pathway is upregulated in hypokinesia and what are some examples
decreased direct, increased indirect
Akinesia, Hypokinesia, Bradykinesia, Rigidity (lead-pipe; cogwheel
what would damage to the right STN result in
CONTRALATERAL hemiballism
due to damage of the indirect pathway
for comparision HD impacts the stratium
what disease is characterized by the loss of spiny neurons
HD
will hit indirect path first = early presentation of hyperkinesia
Eventual damage to both the direct (bradykinesia, rigidity and dystonia) and indirect pathways (chorea) … involves loss of cortical and subcortical cells, decreased neurotrophins, excitotoxicity, astrocyte loss and ROS.
would lesion of the BG result in contra or ipsilateral damage
contralateral
differentiate between substantia nigra pars compacta and pars reticulara
compacta is where the dopamine is produced and the reticulara is a major output nuclei
ID the four loops of the BG
BG chisels through everything you don’t need at that time because then everything back to the cortex is excitatory
–> striatum –>output nuclei –>thalamus–>back to cortex
Motor loop:
What output nuclei: GPi
What part of thalamus: VL/VA
Oculomotor loop: FEF & posterior parietal eye fields
What output nuclei: GPi, SNr
What part of thalamus: Mediodorsal (MD)/ VA
Prefrontal:
What output nuclei: GPi, SNr
What part of thalamus: Mediodorsal (MD)/ VA
Limbic loop:anterior cingulate orbital frontal cortex (amygdala, hippocampus temporal lobe)
What output nuclei: ventral pallidum
What part of thalamus: MD
what structures does the internal capsule seperate
The anterior limb of the internal capsule separates the caudate and the putamen in anterior section
in deeper sections the internal capsule the separates the globus pallidus internus and the substantia nigra
what is the subthalmic nuclei superior to
substantia nigra and the red nucleus
