Basal Ganglia Flashcards
How does the basal ganglia communicate with the LMN? Is this ipsilateral or contralateral?
communicates w/ LMN via the cortex. Then those UMN end up communicating with the LMN.
This is contralateral.
How does the cerebellum communicate with LMNs-ipsilaterally or contra laterally?
ipsilaterally
Which structures make up the striatum?
the caudate & putamen
- *this is the receiving zone
- *both of these parts have similar inputs & outputs, give output to GP
Which structures make up the lenticular nucleus?
the putamen & globus pallidus
What makes up the efferent zone of the basal ganglia?
globus pallidus
substantia nigra
Which part of the substantia nigra is a part of the basal ganglia?
the pars reticulata-this is the outer portion
What are some other structures that are a part of the basal ganglia that we haven’t talked about yet?
the sub thalamic nucleus
Describe the loop of the basal ganglia communicating with the outside world.
Basal Ganglia–Thalamus-Cortex–>Basal Ganglia
Where do you find the substantia nigra?
you find it in the midbrain sitting right above the cerebral peduncles
Which part of the internal capsule are you looking at when you see the thalamus & the lenticulate nucleus?
you are looking at the posterior limb
What are the 2 parts of the substantia nigra?
compacta (internal part)
reticulata (external part)
**one deals with input & one with output
Is the subthalamic nucleus located rostrally or caudally in relation to the substantia nigra?
it is located rostrally
What composes the basal ganglia proper?
caudate
putamen
globus pallidus
T/F Caudate and putamen are the receiving zone of the BG, are functionally similar in terms of their afferents, but they receive slightly different efferents.
False. They are similar in their efferents, but vary in their afferents.
The striatum is called the receiving zone. Where does it receive information from?
all areas of the cortex except: primary visual & auditory areas.
**this is made anatomically possible b/c the caudate is everywhere!!
The striatum gets dopaminergic input from a part of the substantia nigra. Which part?
it gets input from the compacta (internal) part.
**Note the reticulata part is a part of the basal ganglia’s efferent division.
The caudate follows the course of which structure?
the lateral ventricles
Describe the direct pathway in detail.
The cortex stimulates a neuron in the striatum. The nerve in the striatum inhibits the nerve in the GPinternal. the nerve in the GP internal inhibits the nerve in the VA/VL motor thalamus. The nerve in the thalamus is then free to activate the motor cortex. The motor cortex sends down commands via the corticospinal trunk. The CST decussates @ the pyramids. It turns into the lateral corticospinal tract & synapses w/ LMN eventually. The LMN stimulates muscles.
What type of a neuron are the following: Neuron from Cortex-->Striatum Neuron from Striatum-->GPint Neuron from GPint-->VA/VL motor thalamus Neuron from VA/VL-->Motor Cortex
Neuron from Cortex–>Striatum: excitatory by nature
Neuron from Striatum–>GPint: inhibitory by nature–gabanergic.
Neuron from GPint–>VA/VL motor thalamus: inhibitory by nature–>gabanergic.
Neuron from VA/VL–>Motor Cortex: excitatory by nature.
What are 2 names for the special structure that the neuron passes thru to get from GPint to VA/VL?
the lenticular fasciculus or ansa lenticularis
What is the end result of the direct pathway of the basal ganglia?
it increases the transmission from VA/VL to the motor cortex. Therefore, it increase motor activity. : )
If you have too much activity of the direct pathway…what happens?
you get a hyperkinetic syndrome
Which of the following lesions of the basal ganglia would increase motor activity via the direct pathway?
A lesion to the GP internal
A lesion to the VA/VL motor thalamus
The lesion to the GP internal would increase motor activity. It would destroy the cell body of the inhibitory neuron of the thalamus.
The lesion to the VA/VL would actually destroy the cell body of the neuron that activates the motor cortex. Therefore, it would turn down motor activity.
Describe in detail the indirect pathway of the basal ganglia.
The cortex sends an excitatory neuron to the striatum. This activates the next neuron, which is inhibitory, and goes to the GP external. This inhibits the next neuron, which is inhibitory, and ends up at the sub thalamic nucleus. This activates the next neuron, which is excitatory, and goes to the GP internal. This activates the next neuron, which is inhibitory, and goes to the VA/VL motor thalamus. This inhibits the next neuron, which is excitatory, and goes to the motor cortex. Less activation of the next neuron which descends via the corticospinal trunk & decussates @ the pyramids. Then it continues descending via the lateral corticospinal tract. It synapses w/ a LMN (activating it) & stimulating muscles.
