11 - Basal Ganglia (Exam 3) Flashcards
What are the 5 nuclei found deep within the cerebral hemispheres?
- Striatum
- Globus pallidus
- Nucleus accumbens
- Subthalamic nucleus
- Substantia nigra
Where must all movement information pass through?
Basal ganglia
What 2 nuclei is the striatum composed of?
- Caudate nucleus
2. Putamen
What is the appearance of the striatum?
Striped
Where is the globus pallidus located in relation to the putamen?
Medial
What are the 2 parts the globus pallidus is divided into?
- External globus pallidus
2. Internal globus pallidus
What is another name for the globus pallidus and why does it have that name?
Lentiform nucleus
Has the appearance of a lens
What separates the lentiform nucleus from the caudate nucleus?
Internal capsule
Where does the nucleus accumbens receive input from?
From projections of dopaminergic neurons
What is the nucleus accumbens integral in?
Limbic system
Motivation and reward
Where is the subthalamic nucleus located in relation to the thalamus, tegmentum, and hypothalamus?
Inferior to thalamus
Superior to tegmentum
Caudal to hypothalamus
Where does excitatory output from the subthalamic nucleus go?
Globus pallidus and substantia nigra
Where are the substantia nigra located?
Rostral midbrain
At level of superior colliculus
Where do dopaminergic neurons of the substantia nigra project to?
Putamen
Caudate nucleus
Subthalamic nucleus
What is the main input center of the basal ganglia?
Striatum
What is the main output center of the basal ganglia?
Globus pallidus internal (GPi)
Does the GPi have an inhibitory or excitatory effect on the thalamus?
Inhibitory
What 2 pathways mediate the level of tonic inhibition of the thalamus and what are their effects on tonic inhibition?
- Direct pathway (decreases, therefore stimulates thalamus)
2. Indirect pathway (enhances, therefore inhibits thalamus)
What is the goal of the direct pathway?
Facilitate movement
What are the 4 steps of the direct pathway?
- Excitatory signal from motor cortex to striatum
- Inhibitory signal from striatum to GPi
- Cortical activity increases as a result of excited thalamus
- Excitatory signal from subthalamic nucleus to substantia nigra via D1 receptors (enhances pathway even further)
What is the goal of the indirect pathway?
Stop unwanted movement
What are the 5 steps of the indirect pathway?
- Excitatory signal from motor cortex to striatum
- Inhibitory signal from striatum to GPe
- Excitatory signal from STN to GPi
- Excitatory signal also sent from STN to substantia nigra (modulates pathway)
- Inhibitory signal from SN to striatum via D2 receptors
Inhibition of the GPi (seen in the direct pathway) has what effect on the thalamus?
Excites the thalamus
Tonic inhibition is decreased
Inhibition of the GPe (seen in the indirect pathway) has what effect on the thalamus?
Inhibits the thalamus (indirectly)
Inhibited GPe results in excitation of GPi
