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Basal Ganglia I
2-Basal Ganglia I
31
Anatomy
Graduate
03/30/2011

Additional Anatomy Flashcards

 


 

Cards

Term
What do the basal ganglia do?
Definition

produce internally generated mvmts

(freeing individuals from stimulus bound responses or goal oriented mvmts)

 

Learning & retention of complex motor tasks (Procedural/Habit Learning)

 

Term
Disorders of Basal Ganglia affect primarily:
Definition
Movement
Term
Hypokinetic disorders
Definition

movement is dramatically reduced

 

Parkinson's

Term
Hyperkinetic disorders
Definition

excessive & uncontrollable involuntary mvmts

 

Huntington's chorea

Term
What are the basal ganglia?
Definition

Five areas of gray matter in the telencephalon

 

1. Caudate nucleus

2. Putamen

3. Globus Pallidus

4. Nucleus Accumbens

5. Olfactory Tubercle

Term
5 structures of BG can be grouped according to anatomical features
Definition

Lentiform nucleus: putamen, GP

 

Corpus Striatum: putamen, GP, caudate

 

Dorsal Striatum: putamen, caudate

 

Ventral Striatum: putamen, caudate, nucleus accumbens, olfactory tubercle

 

Term
Other strucutres that play a role in the circuitry of the BG
Definition

1. Substantia nigra (in mesencephalon)

2. Subthalamic nucleus (at junction b/t mesencephalon & diencephalon)

Term
Internal Structures of the BG
Definition

1. Striatum (MSN)

2. Globus pallidus (GPi, GPe)

3. Subthalamic nucleus

4. Substantia nigra (pars reticulata, pars compacta)

Term
Striatum
Definition

-receives most of the inputs to the BG

 

-origin of the BG output circuitry

-made up of the caudate & putamen (have indentical internal structures but are separated by the internal capsule from e/o)

 

-2 types of neurons (MSN, small interneurons)

 

 

Term
Small interneurons
Definition
axons remain w/in the striatum & innervate MSN
Term
Medium-sized spiny neurons
Definition

-send axons out of the striatum

 

-dendritc spinde of MSN are plastic (change shape & properties)

 

-Can be divided into 2 types based on the types of circuits they participate in

Indirect: enkephalin, D2 dopamine receptors

Direct: dynorphin, subs. P, D1 dopamine receptors

Term
Dendritic spines of MSNs are thought to be the
Definition
substrate for information storage in the striatum
Term
all MSNs release the NT
Definition

GABA- From their axon terminals & INHIBIT the activity of their target cells

 

However, MSNs are "usually quiet"-have to be excited to inhibit

Term
Globus Pallidus
Definition

whitish appearance due to large number of myelinated axons

 

contains LARGE NEURONS that contain GABA (like MSN) and are INHIBITORY to their targets

 

Divided into two compoents:

GPi and GPe

Term
Though GP neurons receive a large number of inhibitory inputs (mostly from MSNs) they are constantly active & firing at a high frequency
Definition
Term
Subthalamic Nucleus
Definition

separted from BG by the crus cerebri

 

Neurons send their axons to the BG & contain the EXCITATORY NT-GLUTAMATE

Term
Substantia nigra components
Definition

pars reticulata (SNR)

 

pars compacta (SNC)

Term
Pars Reticulata (SNR)
Definition

strucuturally similar to GPi

 

SNR & GPi are the output structures of the BG

 

Cells release GABA from their axon terminals & like GP are constantly active

Term
Pars Compacta (SNC)
Definition

neurons contains the NT DOPAMINE

 

the neurons provide Dopaminergic innervation of the striatum (nigrostriatal pathway) which ends on MSNS and internueurons

 

GP & subthalamic nucleus are innervated by SNC also

 

dopaminergic neurons in the SNC degenerate in Parkinson's

Term
Two types of circuit in BG
Definition

Closed Loops: connect up with the same cortical area providing the input

 

Open Loops: connect up with cortical areas different from the input area

Term
Cortical Inputs
Definition

All cortical areas send axons to the striatum...These corticostratiate projections are EXCITATORY and use amino acids (Glutamate) as the NT

 

Projections end mostly on the dendritic spines of MSNs

 

 

Term
Different cortical areas send axons to different components of the striam....
Definition

Frontal lobe areas= head of caudate

 

Parietal lobe= body of caudate

 

Occipital & Temporal areas=tail of caudate

 

Premotor cortex= send axons directly to subthalamic nuclesus

 

Somatosensory & motor cortices= putamen

Term
Different cortical termination patterns form the basis for...
Definition

segregated loop circuits thru the BG

 

Term
NOTE: most striatal MSNs are usually "quiet" and require simultaneous activation of a combination of cortical inputs to fire
Definition
Term
Basal Ganglia outputs
Definition

Major output target= thalamus (whose nuclei innervate the cerebral cortex)

 

 

Term
Main thalamic nuclei receiving axons from the GPi/SNR are=
Definition

1. Ventral Anterior (VA) nucleus

2. Mediodorsal (MD) nucleus

3. Posterior intralaminar nucleus

Term
Ventral Anterior (VA) nucleus
Definition

GPi=innervates the LATERAL VA which connects with PREMOTOR & SUPPLEMENTARY MOTOR cortical areas

 

SNR= innervates the MEDIAL part of VA connected with FRONTAL EYE FIELDS which control voluntary eye mvmts

Term
Mediodorsal (MD) nucleus
Definition
SNR= innervates MD which connnects with the PRE-FRONTAL CORTEX (responsible for complex cognitive control over mvmt
Term
Posterior Intralaminar Nuclei
Definition

Centomedian-parafascicular (CM/PF) complex (intralaminar) receives input from GPi and SNR

 

CM/PF = innervate the striatum, subthalamic nucleus, & premotor and supplementary motor areas AND motor cortex area 4 (unlike VA)

Term
Function of intralaminar nuclei
Definition

unclear

 

lesions lead to unilateral motor neglect

Term
Other outputs of BG are:
Definition

1. Superior Colliculus

SNR sends axons to the sup. colliculus & influences control of SACCADIC EYE MOVEMENTS

 

2. Midbrain tegmentum

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