5.1 Basal Ganglia Flashcards
What is the function of the basal ganglia?
- Planning and controlling motor movement/intensity of movement
- Gates proper initiation of movement
What are the two components of the striatum?
- Caudate nucleus
- Putamen
What are the four principal structures of the basal ganglia?
- Striatum
- Globus pallidus
- Substantia nigra
- Subthalamic nucleus
Describe the shape of the caudate nucleus. What are its three components?
- C-shaped (c for caudate)
- 3 parts: head, body, tail
Why is the striatum named the striatum?
Named after the stripes created by cellular bridges between the putamen and the caudate nucleus
What are the components of the lentiform nucleus?
- Putamen
- Globus pallidus
What are the two divisions of the substantia nigra?
Dorsal: pars compacta
Ventral: pars reticulata
What is the major input structure to the basal ganglia? Where does IT recieve input from?
- Major input structure is striatum
- Recieves glutamatergic input from cortex and dopaminergic input from pars compacta of substantia nigra
What type of neurons are most abundant in the striatum? What neurotransmitter do they release, and does this make them excitatory or inhibitory?
- Medium spiny neurons
- Release GABA
- Therefore, inhibitory
What are the two output nuclei of the basal ganglia?
- SNr (ventral)
- GPi
Which of the following have a high/zero tonic firing rate: striatal medium spiny neurons, globus pallidus, and SNr
MSN: zero
Globus Pallidus: high
SNr: high
Which thalamic nuclei do GPi and SNr disinhibit upon MSN activation in the striatum?
Ventral anterior and ventral lateral nuclei (VA and VL)
True or false: since we are constantly moving around slightly, almost all basal ganglia activity is at a tonic level
- False
- Most of it is transient; only Globus Pallidus and SNr are tonic
What are the four channels that the thalamus excites when disinhibited by the basal ganglia?
- Motor loop (motor control)
- Oculomotor loop (regulation of eye movements)
- Prefrontal loop (frontal-lobe dependent cognition)
- Limbic loop (emotional/motivational regulation)
Considering the basal ganglia, do the direct/indirect pathways promote/inhibit motor function?
Direct: promotes
Indirect: inhibits
What are the two kinds of dopamine receptors? Which is excitatory/inhibitory?
D1: excitatory
D2: inhibitory
Dopaminergic receptors are G coupled receptors. Signal transduction via these receptors stimulates the production of a secondary messenger known as…
cyclic AMP (cAMP)
Describe, with mention of dopamine receptors, the balance between the two sources of input to the indirect pathway of the basal ganglia
- Glutamatergic input from the cortex is excitatory
- Due to D2 receptor expression, dopaminergic input from SNc is inhibitory
Therefore: net effect depends on which input is greater
True or false: neurons from the GPe have a high tonic firing rate, and are GABAergic/inhibitory
True (read that again)
Are the neurons from the subthalamic nucleus in the basal ganglia excitatory or inhibitory?
Excitatory
Which of dopamine/glutamate promote/prevent activity in the indirect pathway of the basal ganglia?
Glutamate promotes, dopamine prevents
Outline the direct pathway of the basal ganglia
- Glutamate and dopamine from cortex/SNc excite mesium spiny neurons in striatum
- These MSNs inhibit inhibitory neurons in the GPi
- This disinhibits the thalamus, leading to movement
Describe the indirect pathway of the basal ganglia (assuming glutamate is greater than dopamine)
- Dopamine inhibits MSNs, and glutamate excites
- MSNs inhibit inhibitory neurons in the GPe
- Inhibitory neurons in the GPe no longer inhibit excitatory nuclei in the subthalamic nuclei
- STN nuclei promote GABAergic neurons in GPi/SNr
- This inhibits the thalamus, preventing motor movement initiation
