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Flashcards in Basal Ganglia Deck (32):
1

Basic Function of the Basal Ganglia

-movement & modulation

2

Parts of the Basal Gangila

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

3

Substantia Nigra

-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

4

Basal Ganglia: 2 Categories of Structure

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

5

Tail of Caudate Nucleus

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

6

The thalamus is located ? to theputamen?

medial

7

Striatum

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

8

Organization of the Substantia Nigra

-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)

9

Subthalamic Nucleus

-important associated with basal ganglia
-above the cerebral peduncle, below the bulk of the thalamus

10

Stratum

-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

11

Spines

-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

12

Spiny Neuron Appearance

-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)

13

Striatal Projection Neurons


-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)

14

Neuropeptides

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

15

Distribution of Spiny Neurons in Striatum?

-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

16

Striato-GPe Function

-Inhibit conflicting movement

17

Striato-GPi Function

-promote limb movement

18

Striato-SNr Function

-promote eye movement

19

Striato-SNc Function

-regulate DA neurons

20

4 Types of Interneurons in Striatum

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

Huntington's Disease

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

22

Neurons of Globus Pallidus

-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

GPe

-projects to subthalamic nucleus

24

GPi

-projects to motor thalamus (VP & VL)

25

Motor Thalamus

-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

VA

-projects to pre-motor cortex

27

VL

-projects to motor cortex

28

What are the major sources of input to the striatum?

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

29

Corticostriatal Neurons

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

30

Location of Dopaminergic Terminals?

-caudate & putamen (not GPe & GPi)

31

Inputs to Striatal Spiny Neurons?

-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

Interplay of Striatal Input to Globus Pallidus & Subthalamic Nucleus Input

-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