Flashcards in Basal Ganglia Deck (25):
Dysdiadochokinesia is ______________.
disorder of rapidly alternating movement
The basal ganglia is derived from ______________.
the ganglionic eminence – a group that becomes GABAergic
Contrast the roles of the basal ganglia and cerebellum in movement.
The cerebellum coordinates movement from sensory inputs, while the basal ganglia mediates the frontal, executive functions of movement.
The most caudal portions of the telencephalon have __________ levels of SHH.
Again, what is the nucleus accumbens?
The point where the caudate and putamen come together
Describe the direct pathway in the cortex, striatum, globus pallidus, and thalamus.
The putamen, in response to stimulation of D1 receptors, releases GABA onto the internal globus pallidus. The globus pallidus, which had been inhibiting the thalamus, is stopped and the thalamus then facilitates cortical function.
The globus pallidus externa provides tonic inhibition to the __________.
subthalamic nuclei (this is the indirect pathway)
Describe the indirect pathway.
D2 neurons in the caudate inhibit the globus pallidus externa. The globus pallidus externa then stops inhibiting the subthalamic nuclei. The subthalamic nucleus excites the globus pallidus interna, which then inhibits the thalamus. Thus, the thalamus is prevented from exciting the cortex.
In the presence of dopamine, the balance is tilted toward the ______________. That is why Parkinson's results in hypokinesia.
direct (facilitatory) pathway, because D1 is an excitatory receptor
The basal ganglia receive no _________ input and send out no _________.
direct sensory; direct motor output
True or false: unilateral basal ganglia lesions produce bilateral defects.
False. The basal ganglia coordinate with only the ipsilateral side of the cerebrum and thus produce contralateral deficits.
The substantia nigra receives a projection from the ___________.
striatum (this is in addition to its projection that it sends back to the striatum – the dopamine-releasing neurons)
The substantia nigra also projects to the ________.
True or false: both D1 and D2 receptors are stimulated by dopamine.
False. Dopamine inhibits D2 receptors.
The putamen receives input mainly from the ___________.
sensory domains of the cortex
The putamen projects onto the same cells as axons from what other structure?
The dentate nuclei of the cerebellum. They both synapse on the VA/VL nuclei of the thalamus.
Which part of the cortex connects to the caudate?
The frontal lobes (it is thought that this connection underlies the link between cognitive disorders and movement disorders)
The olfactory areas of the brain connect to which part of the basal ganglia?
The nucleus accumbens
One key to understanding the workings of the basal ganglia system is that pallidal cells have an intrinsic ___________.
What is known to increase the tremor of Parkinson's?
Parkinson's patients walk without ___________.
any extraneous movements
The symptoms of Huntington's can be mimicked by administering _______________.
Describe the pathophysiology of hemiballismus.
A stroke in the PCA near the subthalamic nucleus can lead to loss of subthalamic output on the internal globus pallidus. The loss of GPI stimulation leads to increased movement.
Decreases in the indirect pathway lead to what kind of disorders?
Hyperkinetic (because the inhibitory pathway is down)