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Basal Ganglia
N/A
29
Medical
Graduate
03/10/2012

Additional Medical Flashcards

 


 

Cards

Term
Where are the basal ganglia located? Describe their bulk connections
Definition

Interconnected nuceli in the telencephalon, diencephalon, and mesencephalon

 

Input from the cerebral cortex, output to frontal lobes via thalamus and brainstem

 

No spinal connections

Term
What are the parts of the Striatum?
Definition
Caudate and Putamen (tail and shell) and accumbens septi (nucleus leaning agains the septum)
Term
What are the parts of the Globus Pallidus?
Definition

Internal Segment

 

External Segment

 

Ventral Pallidum

 

 

Term
What is the lenticular nucleus composed of?
Definition

Putamen and globus pallidus

 

Lenticular = Lens-like

Term
What are the parts of the Substantia Nigra?
Definition

Pars Reticulata (spotted)

 

Pars Compacta (dense)

Term
What do the Basal Ganglia do?
Definition

Motor Control primarily, but also involved in cognitive, emotional, and motivational mechanisms.

 

Basal Ganglia act in parallel to allow desired motor movements and simultaneously inhibit competing mechanisms.

 

Traffic cop

Term
Name the types of Neurons found in the striatum, and some characteristics
Definition

Medium Spiny (95%): extensive collateral connections

 

Large Aspiny (1%): Ach transmitter

 

Medium Aspiny (1%): Somatostatin Transmitter

 

GABAergic interneurons (1%): Fast spiking

Term
What is the input to the striatum?
Definition

Excitatory, glutamatergic input from most of the cerbral cortex.

 

Excitatory input from the intralaminar thalamus (function unknown)

 

From SNpc, D1 Dopamine is excitatory, but D2 Dopamine is inhibitory (presynaptic connections to medium spiny neurons)

Term
Describe the Outputs of the striatum
Definition

Intermixed populations of neurons (medium spiny)

 

GABA/Substance P: Inhibitory, go to GPi/SNpr, express dopamine D1 (direct path)

 

GABA/Enkephalon: Inhibitory, go to GPe and also SNpc, express dopamine D2 (2 separate paths)

Term
What do the D1 and D2 neurons from the SNpc do in the striatum?
Definition

D1 facilitates the direct pathway to the GPi/SNpr

 

D2 inhibits the indirect pathway to the GPe

 

They input presynaptically, modulating medium spiny neurons in the striatum

Term
What do the SNpc neurons fire in response to?
Definition
significant events related to rewards, presentation of instructions, but not simuli that have been used over and over.
Term
Describe the center surround organization throughout the basal ganglia pathways
Definition

Striatum (center excite surround inhibit)

GABA

GPi (center inhibit surround excite)

GABA

Thalamus (center excite surround inhibit)

Term
What role does the subthalamic nucleus have in the basal ganglia?
Definition

Takes input from the frontal lobe areas (excitatory), preserves somatotopy, and sends excitatory output to both direct (GPi/SNpr) and and indirect (GPe) pathways. 

 

The hyperdirect pathway!

 

Also receives inhibitory input from the GPe.

Term
Why do spiny neurons not fire much?
Definition

They use a lot of energy, so there are a number of mechanisms to keep their firing rates down.

 

Long refractory periods, collateral inhibition

Term
What are the Basal Ganglia output Nuclei?
Definition

Globus Pallidus pars interna

 

Substantia Nigra pars reticulata

Term
Describe the neural input morphologies in the GPi
Definition

From the striatum, each neuron touches many other neurons before entwining one particular neuron. (slower pathway)

 

From the subthalamic nucleus, each neuron can entwine a number of GPi neurons. (faster pathway)

Term
Describe the receptive field of the Globus Pallidus internal portion
Definition

From the subthalamic nucleus, bulk excitation, but from the striatal cortex, center inhibition

 

off-center on surround.

Term
Describe the output of the GPi
Definition

Goes to Thalamus, which projects to the frontal lobes

 

Inhibitory GABA

 

Also collaterally projects to pedunculopontine area, projecting to reticulospinal system (coordinates bilateral movements)

Term
Describe the structure and function of the Substantia Nigra pars reticulata
Definition

Like the GPi

 

Output is GABA and inhibitory, to the thalamus (VA, VLm, MD), and the pedunculopontine area, and the Superior colliculus (Frontal eye fields)

 

 

Term
Describe the discharge patterns of different parts of the basal ganglia
Definition

 

Putamen -> almost no activity

GPi/SNpr -> large amounts of activity

STN -> focused peaks of activity

Term
When do the basal ganglia fire in relation to movement activity?
Definition

For limb movements, after the onset of muscles

 

For eye movements, the SNpr fires late to initiatory activity in the superior colliculus

Term
What is chorea?
Definition

Dance-like movements

 

Small amplitude twitches

Term
What sort of motions can compete with desired voluntary motion
Definition

Posture (righting mechanisms)

Locomotion

Term
Describe the asymmetric tonic neck reflex
Definition
When the neck is twisted, you extend the side that the face is pointing towards, and contract the side that you are not facing
Term
How are hypokinetic disorders characterized?
Definition

Slow movements, scarcity of movement, rigidity

 

Parkinson's Disease

 

Fail to excite the direct pathway enough/ excite the indirect pathway too much

Term
How are hyperkinetic disorders characterized?
Definition

Abnormal involuntary movements and postures, chorea

 

Huntington's Disease

 

Failure to inhibit the direct pathway enough (too much D1), or excite the indirect pathway sufficiently (not enough D2)

Term
Describe Parkinson's Disease: Pathology, symptoms, surgical treatments
Definition

Pathology: Degeneration of Dopaminergic neurons in the SNpc

 

Symptoms: Can't initiate movement, difficulty limiting patterns that result in abnormal coactivation and contraction.

 

Treatment: Lesion in the subthalamic nucleus decresases excitatory surround in the GPi, decreases surround inhibition at thalamus

 

Treatment: Lesion in the GPi provides less inhibition in the center, which means more excitation in the center at thalamus

Term
Describe Huntington's disease: Pathology, symptoms
Definition

Pathology: D2 enkephalon receptors die, but D1 remain, creating less inhibition of the indirect pathway. Genetically based (chrom 4)

 

Symptoms: movement all the time, shrunken brain

Term
Describe Hemiballism
Definition

Damage to the subthalamic Nucleus

 

Ballism -> large amplitude flinging movements on contralateral side compared to lesion source

 

Chorea -> small twitching movements.

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