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Neurology > Basal Ganglia > Flashcards

Basal Ganglia Flashcards

1
Q

Basic Function of the Basal Ganglia

A

-movement & modulation

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2
Q

Parts of the Basal Gangila

A
  • Caudate Nucleus (very small ventrally placed part called tail of the caudate)
  • Putamen
  • Globus Pallidus (just internal or medial to putamen)
  • Interconnected: subthalamic nucleus
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3
Q

Substantia Nigra

A
  • black stuff which is an important cell group interconnected with the basal ganglia (black b/c there are neurons in the substantia nigra that have the black pigment melanin)
  • located at base of midbrane
  • has axons that travel into the head of the caudate, the putamen, the tail of the caudate, & form dopaminergic terminals there
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4
Q

Basal Ganglia: 2 Categories of Structure

A
  • somatic (dorsal) basal ganglia: movement control

- limbic (ventral) basal ganglia: motivation, reward, effect (nucleus accumbens, olfactory tubercle, vetral pallidum)

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5
Q

Tail of Caudate Nucleus

A

-sweeps around posteriorly, bends & comes forward and curls under the main body of the caudate, ending rostrally at the amygdaloid nucleus

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6
Q

The thalamus is located ? to theputamen?

A

medial

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7
Q

Striatum

A

-the caudate & putamen (striped in appearance due to fibers bundles passing through it to & from the cortex)

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8
Q

Organization of the Substantia Nigra

A
  • upper part: pars compacta: dopaminergic neurons are arranged in a compact layer (part with melanin)
  • below: pars reticulata: net-like mesh of fibers, few dopaminergic neurons (resemble globus pallidus in chemistry, shape & function)
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9
Q

Subthalamic Nucleus

A
  • important associated with basal ganglia

- above the cerebral peduncle, below the bulk of the thalamus

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10
Q

Stratum

A

-contains 2 main types of neurons
neurons associated with spiny dendrites & neurons with aspiny dendrites
-Aspiny: 5%, has dendrites that do not possess stubby protrusions on them, 30 microns in width at cell body
-Spiny: 95%, 15 microns in width at cell body

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11
Q

Spines

A
  • stubby portrusions coming off dendrites
  • specialized for receiving terminals from other brain regions
  • neurons that need to integrate info from diverse sources posses spines
  • transmit decision to other brain areas
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12
Q

Spiny Neuron Appearance

A

-railroad tract or ladder-like appearance
-long axon that leaves the striatum - projection neurons
(aspiny are short & do not leave the striatum-local circuit neurons or interneurons)

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13
Q

Striatal Projection Neurons

A
  • different types of spiny neurons are present in striatum
  • differ by projection target & neuropeptide content
  • Neurotransmitter: GABA

ENK Neuron: makes GABA & opioid neuropeptide (enkephalin), project to GPe (D2 Type Dopamine)
Substance P-containing striatal projection: makes substance P, project to the GPi, SNc, SNr (D1 Type Dopamine)

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14
Q

Neuropeptides

A

-adjunct neurotransmitters that neurons often use, but they can also be neurochemical signatures for defining neuron subtypes

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15
Q

Distribution of Spiny Neurons in Striatum?

A
  • intermingled Substance P & Enkephalin neurons
  • Substance P contains another neuropeptide thats also an opioid neuropeptide (dynorphin)
  • sub P project to GPi and substantial nigra pars reticulata
  • enkephalin project to GPe
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16
Q

Striato-GPe Function

A

-Inhibit conflicting movement

17
Q

Striato-GPi Function

A

-promote limb movement

18
Q

Striato-SNr Function

A

-promote eye movement

19
Q

Striato-SNc Function

A

-regulate DA neurons

20
Q

4 Types of Interneurons in Striatum

A
  1. Cholinergic: target of therapies directed at basal ganglia disease, big cell body, ACh as neurotransmitter - survive in HD
  2. Paralbuminergic: has Ca binding protein, GABA neurotransmitter, larger than projection neurons & smaller than large cholinergic interneurons
  3. Somatostatinergic: contains somatostatin (also neuropeptide), identify by neurostain, neurotransmitter is GABA/NO, same size as spiny neurons - survive in HD
  4. Calretinergic: calcium binding protein, same size as spiny neurons, GABA as neurotransmitter
    - make up 5% of neurons - survive in HD
21
Q

Huntington’s Disease

A
  • does not affect somatostatin interneurons or NPY+
  • stratum sustains severe neuron loss & atrophy
  • striatal projection neurons, which make up 90% of striatum dies
22
Q

Neurons of Globus Pallidus

A
  • have long aspiny dendrites that form a disk-shaped tree that ramifies in the vertical plane of globus pallidus (GPe, GPi)
  • many striatal neurons send their terminals onto the dendrites of any given globus pallidus neuron & any given globus pallidus neuron integrated info from the many striatal neurons that project to it
  • both GPe/GPi are GABAergic (send axons out of the globus pallidus to their target area)
23
Q

GPe

A

-projects to subthalamic nucleus

24
Q

GPi

A

-projects to motor thalamus (VP & VL)

25
Q

Motor Thalamus

A

-2 nuclei make up the motor thalamus
1. Ventral Anterior Nucleus
2. Ventral Lateral Nucleus (C - caudalis) (O - oralis)
-anterior nuclear group is toward the front, and the pulvinar is toward the back
-midline is located above the dorsomedial nucleus
VA - located at front of the motor thalamus, VL region behind the VA
VL - oral part in front, caudal part in back

26
Q

VA

A

-projects to pre-motor cortex

27
Q

VL

A

-projects to motor cortex

28
Q

What are the major sources of input to the striatum?

A

-cortex, thalamus, substantia nigra
(cerebral cortex - almost all projects)
(intralaminar thalamus)
(dopaminergic input from the substantia nigra pars compacts)

29
Q

Corticostriatal Neurons

A
  • project to striatum
  • layer 5 pyramidal neurons
  • also send motor commands to the spinal cord & pre-motor neurons of the hindbrain
30
Q

Location of Dopaminergic Terminals?

A

-caudate & putamen (not GPe & GPi)

31
Q

Inputs to Striatal Spiny Neurons?

A
  • Cerebral Cortex input ends on the tips of the spines of the spiny neurons (glutamate as neurotransmitter)
  • Substantia nigra dopaminergic input ends on the sides of the spines (modulate cortical input to spines)
  • Large aspiny neurons (ACh)
  • Meidum spiny neurons (GABA)
32
Q

Interplay of Striatal Input to Globus Pallidus & Subthalamic Nucleus Input

A
  • while the GPe projects to the subthalamic nucleus, the subthalamic nucleus mainly projects back to GPi
  • subthalamic inputs wrap around the smooth dendrites of the GPi neurons, which also receive terminals from striatal substance P-containing neurons

Neurology (18 decks)

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