Basal Ganglia Flashcards
name the 5 ares of gray matter in the inferior and medial telencephalon that make up the basal ganglia
- caudate nucleus
- putamen
- globus pallidus
- nucleus accumbens
- olfactory tubercle
gray matter collection in the brain that is responsible for:
• Production of internally generated movements
• Procedural learning
• Selecting/activating desired movements, and suppressing unwanted ones
• Controlling activity in the premotor cortex (PMA and SMA)
basal ganglia
the caudate and putamen make up the dorsal striatum of the basal ganglia, and are separated by what structure?
anterior limb of the internal capsule
the lentiform nucleus of the basal ganglia refers to what two structures?
putamen and globus pallidus
most of the neurons in the dorsal striatum are this type of “quiet” neuron, low spontaneous activity and release the inhibiting neurotransmitter GABA
medium spiny neurons (MSNs)
medium spiny neurons can be divided into 2 classes based on the type of circuit they participate in: one class contains the peptides ____ and _____, and has mostly D1 dopamine receptors. (Are these neurons excited or inhibited by dopamine binding?)
dynorphin and substance P;
excitated by dopamine binding
medium spiny neurons can be divided into 2 classes based on the type of circuit they participate in: one class contains the peptide ____, and has mostly D2 dopamine receptors. (Are these neurons excited or inhibited by dopamine binding?)
enkephalon; inhibited by dopamine binding
how are globus pallidus neurons like the MSNs of the striatum? How are they different?
globus pallidus neurons use GABA, and so inhibit their target neurons, just like MSNs; but they have fewer spines and a high rate of spontaneous, tonic activity
the subthalamic nucleus lies below the thalamus in the diencephalon, and is excitatory to its target, the _____. This results in what overall effect?
GPi (internal globus pallidus); this results in the release of GABA, and an overall inhibitory effect on its target
the substantia nigra consists of two parts: the pars ______, which is functionally analgous to GPi, and the pars ______, which synthesizes dopamine.
reticulata; compacta
corticostriate projections to the MSNs in the striatum are always excitatory, and usually use ____ as their neurotransmitter
glutamate
the main output target for the basal ganglia is the _____, specifically what nucleus?
thalamus; ventral anterior (VA) nucleus
The steps below highlight the (direct or indirect) pathway of the internal basal ganglia circuit:
Cortex (+GLU) –> D1 receptors of MSN in the striatum (-GABA) –> GPi/SNr (-GABA) –> (disinhibition) VA of thalamus –> (+) Cortex
direct pathway (in words: when the execution of a specific motor loop is desired, the cortex sends an excitatory signal (via Glutamate) to the striatum, where medium spiny neurons are excited at their D1 receptors. The MSNs then release their inhibitory neurotransmitter GABA. GABA disinhibits the internal global pallidus and substantia nigra reticulata, whose resting function is inhibition of the thalamus. So, we've just inhibited the inhibitor. Now the thalamus (newly disinhibited!) is free to relay the signal back to the cortex, bringing the desired movement to the forefront of consciousness.
in the default state, the global pallidus and substantia nigra reticulata are _____ the VA nucleus of the thalamus
inhibiting
The steps below highlight the (direct or indirect) pathway of the internal basal ganglia circuit:
Cortex (+GLU) –> MSN in the striatum (-GABA) –> GPe (-GABA) –> (disinhibition) subthalamic nucleus (+GLU) –> GPi/SNr (-GABA) –> Thalamus –> disruption of signal relay to cortex
indirect pathway (in words: when it's time to cease a specific motor loop, the cortex sends an excitatory signal (via Glutamate) to the striatum, where medium spiny neurons are excited at their D2 receptors. The MSNs then release their inhibitory neurotransmitter GABA which inhibits the external global pallidus, whose resting function is inihibition of the subthalamic nucleus. So, we've just inhibited the inhibitor. Now the subthalamic thalamus (newly disinihibited!) is free to send its excitatory signal (glutamate) to the Gpi/SNr, who send inhibitory signals via GABA to the thalamus. The thalamus is once again inhibited, and this prevents signalling from that particular loop to any longer reach the cortex.
