Exam #2: Basal Ganglia Flashcards
What are the two general functions of the basal ganglia?
1) Inhibition of involuntary movements at rest
2) Starting & stopping voluntary movements
Specifically, what movements does the basal ganglia inhibit?
- Tremors
- Chorea
- Tics
Specifically, what voluntary movements does the basal ganglia facilitate?
- Initiating movement
- Maintaining normal speed of movement
- Stopping movement
What are the five major nuceli that compose the basal ganglia?
1) Caudate nucleus
2) Putamen
3) Globus Pallidus
4) Subthalamic Nucleus
5) Substantia nigra
What are the two components of the “Lentiform Nucleus?”
- Putamen
- Globus Pallidus
*Note that Lentiform= “Lens-shaped” i.e. appearance on cross-section
What are the components of the “Corpus Striatum?’
- Caudate Nucleus
- Putamen
- Globus Pallidus (or pallidum)
What is the striatum?
- Putamen
- Caudate nucleus
**vs. Corpus Striatum that contains that Globus Pallidus as well
What is the Pallidum?
This is another name for the Globus Pallidus
What white matter tract runs between the lentiform & caudate?
Internal capsule
Where is the caudate in reference to the lateral ventricle?
Inferior and lateral
What is the striatum? What are the three major inputs to the striatum?
- Putamen & caudate nucleus
1) Cortex
2) Thalamus
3) Substantia nigra
What are the corticostriate fibers?
Input fibers from cortex to the striatum
What are the thalamostriate fibers?
Input fibers from the thalamus to the striatum
What are the nigrostriate fibers?
Input fibers from the SN to the striatum
What are the dopaminergic neurons from the SN primarily associated with behaviorly?
Movement
What does the loss of DA neurons in the SN result in, in PD?
Inability to INHIBIT unwanted movements
What is the two major outputs from the striatum?
Output from the Striatum is funneled to the:
1) GLOBUS PALLIDUS via striatopallidal fibers
2) SUBSTANTIA NIGRA via straitonigral fibers going to the SN
What are the two major inputs to the pallidum?
1) STRIATUM via the striatopallidal fibers
2) SUBTHALAMIC NUCLEUS via the subthalamaic fasiculus
What is the major output from the pallidum?
1) THALAMUS via pallidothalmic fibers
2) SUBTHALAMUS via pallidosubthalamic fibers i.e. the subthalamic fasiculus
What are the major divisions of the Pallidothalamic fibers? Where are they going?
1) LENTICULAR FASICULUS
2) ANSA LENTICULARIS
**BOTH are going to the THALAMUS
What nuclei are the Pallidothalamic fibers traveling to in the thalamus?
1) VENTRAL ANTERIOR nuclei of the THALAMUS
2) VENTRAL LATERAL nuclei of the THALAMUS
VA/VL–these are the motor nuclei of the thalamus
Draw the motor loop of the basal ganglia. What is the purpose of this loop?
Information relayed from basal ganglia to motor cortical areas
Cortex
- Supplementary motor cortex*
- Somatosensory cortex
- Primary motor cortex
- Premotor cortex
Striatum
Pallidum
Thalamus
Draw the association loop of the basal ganglia. What is the purpose of this loop?
Planning & direction of movement
Cortex
- Prefrontal cortex= decision making*
- Premotor cortex
- Posterior parietal cortex
Striatum
Pallidum
Thalamus
Draw the Oculomotor loop of the basal ganglia. What is the purpose of this loop?
Integration of eye movements & visual guidance
Cortex
- Frontal eye field*
- Prefrontal cortex
- Posterior parietal cortex
Striatum–>Superior colliculus
Pallidum
Thalamus
Draw the limbic loop of the basal ganglia. What is the purpose of this loop?
Emotional & motivational influences on movements
Cortex
- Anterior cingulate gyrus*
- Orbitofrontal cortex*
- Hippocampus
- Amygdala
- Entorhinal area
Striatum= specifically, the Nucleus Accumbens
Pallidum
Thalamus
Where do the “closed” loops go back to?
Cortex
What is the general function of the primary motor cortex?
Execution
What is the general function of the premotor cortex?
Orientation
What is the general function of the PFC?
Planning movement
What is the general function of the posterior parietal cortex?
Visual guidance
What is the general function of the frontal eye field?
Visual tracking
What is the general function of the superior colliculus?
Visual reflexes
What is the general function of the inferior colliculus?
Auditory reflexes
What is the general function of the amygdala?
Emotion
What is the general function of the entorhinal area?
Olfactory information
What is the nucleus accumbens?
This is a subnucleus of the striatum that processes the emotional aspects of movement
Where is the nucleus accumebens on cross-section?
Area where the caudate & putamen come together–anterior
Is the pallidum excitatory or inhibitory?
Inhibitory
Is the thalamus excitatory or inhibitory?
Excitatory
What is the general function of the indirect pathway?
Increased inhibition & suppression of inappropriate movements
What is the general function of the direct pathway?
Excitation of the cortex via disinhibition of the thalamus–allows voluntary movements
Define dyskinesia.
Unintentional, disorderly, & purposeless movements
Define athetosis.
Condition in which the individual displays slow, vermicular or “worm-like” involuntary movements
Define hemiballismus.
Condition of involuntary ballistic or striking movements on one side of the body
Define bradykinesia.
Slowness in the execution of movement
Define chorea.
Sequence of rapid, jerky, & somewhat agile flowing movements of the hands, feet, tongue, & facial muscles
What are the current diagnostic criteria for Tourette’s Syndrome?
A. Both multiple motor and one or more vocal tics have been present at some time during the illness, although not necessarily concurrently.
B. The tics may wax and wane in frequency but have persisted for more than 1 year since first tic onset.
C. Onset is before age 18 years.
D. The disturbance is not attributable to the physiological effects of a substance (e.g., cocaine) or another medical condition (e.g., Huntington’s disease, postviral encephalitis).
In Huntington’s Disease, neurons of what “loop (direct vs. indirect) degenerate?
Indirect
In Huntington’s Disease, specifically what neurons degenerate?
Striatal GABAergic neurons, which results in a loss of GABA inhibitory influence via the striatonigral pathway
