Flashcards in Basal Ganglia (17) Deck (61)
What is the function of the basal ganglia?
Voluntary movement --> decision to move, direction of movement, motor expression of emotions
*receives cortical input and provides negative feedback to cortex to modulate movement : facilitate intended movements, while suppressing unwanted movements
What are the 3 main parts of the basal ganglia? Are they white or gray matter?
3. Globus pallidus (interna and externa)
* these are all gray matter nuclei located deep in the cerebrum, or telencephalon
What two structures compose the striatum?
Caudate and putamen
What two structures make up the lentiform nucleus?
Putamen and globus pallidus
*this is old nomenclature, but may still be used, although is incorrect b/c these two are entirely different structures; caudate and putamen are considered the one striatum b/c they actually share fibers
What two structures are interconnected with the main parts of the basal ganglia, but are structurally part of the diencephalon?
1. Subthalamic nucleus
2. Substantia nigra
Although the caudate and putamen are parts of the same structure, what separates them (as can be visualized on coronal section)?
* these two are actually part of the same thing and are connected via the nucleus accumbens (a bridge at the anterior part that joins them)
What serves as the input nucleus to the basal ganglia? What kind of input does it receive from cortical and subcortical areas?
Striatum = receives mainly excitatory input from cortical and sub cortical structures
What serves as the output nucleus of the basal ganglia? What kind of output does it send and to what main structure?
Globus pallidus = sends inhibitory projections to the thalamus under normal conditions
What structure does the caudate lie just lateral to?
The lateral ventricle
The thalamus is located _______ to the putamen
What structure does the putamen lie just medial to, which is almost on the surface of the lateral aspect of the cerebrum?
Insular lobe of cortex
What structure does the tail of the caudate end as?
Amygdaloid nucleus (is inferior to the putamen )
The basal ganglia that concerns movement (the one this lecture focuses on) is also called what other two things? What is the other type?
Somatic or Dorsal basal ganglia.
The other is the limbic or ventral basal ganglia and is involved in motivation, reward, and affect
What are neostriatum and paleostriatum?
Completely inaccurate terms based on evolutionary ideas about the brain which are now known to be false
The substantia nigra is located at the base of the midbrain within what other structure?
Cerebral peduncle --> is the midbrain continuation of the internal capsule
The substantia nigra and cerebral peduncle are located at the same level as what posterior surface feature of the brainstem?
What kind of neurons are found in the substantia nigra? What two structures to they project to?
Dopaminergic neurons to the striatum and subthalamus
*no fibers to globus pallidus, which is why they are pale; neurons in and originating from the substantia nigra are dark due to the presence of melanin
In what specific region of the substantia nigra are dopaminergic fibers found? Is this the superior or inferior part?
Pars compacta---> superior part
What is the specific part of the substantia nigra that doesn't contain dopaminergic neurons? What basal ganglia structures is it similar to in terms of chemistry, shape, and function?
Pars reticulata--> is inferior part, very similar to the globus pallidus
The Subthalamic nucleus is just inferior to the thalamus and superior to ______ of midbrain. What kind of output does it send and to what 2 structures in the basal ganglia?
Tegmentum (so just superior to 4th ventricle)
*has excitatory input to globus pallidus and substantia nigra
What is a main function of the Subthalamic nucleus?
Defines the output rhythm of the basal ganglia
Which of the two main types of neurons in the striatum a make up 95% of the neuronal bulk? What do they have that the other type doesn't and what does it allow them to do?
Spiny neurons (SN)--> have dendritic spines, so can integrate info from other parts of brain; these neurons send long axons out of the striatum (the other neurons do not(
-also called projection neurons (indicating the fact they leave the striatum)
What are the other type of neurons in the striatum that make up 5% of the neurons within? What kind of neurons do they function as?
Aspiny neurons (A-neurons) ---> are interneurons, so don't send axons out of the striatum; also lack dendritic spines, so cannot integrate information coming in for other parts of brain
* these neurons do have larger cell bodies than do the spiny neurons
Which NT do ALL spiny/projection neurons from the striatum use?
Where do spiny/projection neuron subtype from the striatum that contain ENK (enkephalin) project to in the basal ganglia?
To globus pallidus externa (GPe)
Where do the spiny/projection neuron subtype from the striatum containing Substance P project to in the basal ganglia? (2 main structures)
1. Globus pallidus interna (GPi)
2. Substantia nigra (both pars compacta and pars reticulata!)
* the neurons that go to each of these 3 places are all distinct subtypes of substance P-containing spiny neurons
What other neuropeptide do Substance P-containing spiny neurons contain?
What dopamine receptor do striato-GPe neurons have? (ENK-spiny projection neurons) What is their function?
D2 receptors ; their function is to inhibit conflicting movement
What kind of dopamine receptor do all 3 subtypes of Subtance-P containing striatal neurons possess?