Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

NEUR 350 > Basal Ganglia > Flashcards

Basal Ganglia Flashcards

(61 cards)

Start Studying
1
Q

Where is the basal ganglia located?

A

lie deep within the cerebral hemispheres and in the anterior part of the midbrain (substantia nigra)
lateral to the thalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the four functions of the basal ganglia?

A
  1. regulating involuntary movement
  2. tuning voluntary movement
  3. maintaining posture
  4. involving in non-motor brain function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does the basal ganglia affect movement?

A

does not intitate movement directly but instead modulates movement by influencing motor circuits in the brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 3 components of the basal ganglia?

A
  1. striatum
  2. pallidum
  3. subthalamic nuclei
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 2 components of the striatum (BG)?

A
  1. caudate
  2. putamen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 2 components of the pallidum (BG)?

A
  1. global pallidus (internal and external)
  2. substantia nigra pars reticulata
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where is the location of the striatum (BG)?

A

input zone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where is the location of the pallidum (BG)?

A

output zone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the main neuronal type of the striatum (BG)?

A

medium spiny neurons (MSN)
D1 and D2 MSNs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the main neuronal type of the pallidum (BG)?

A

globulus pallidus - large inhibitory GABAergic projection neurons
substantia nigra - dopaminergic neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the physiological properties of the striatum (BG)?

A

low spontaneous activity
requires strong excitation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the physiological properties of the pallidum (BG)?

A

high spontaneous activity
continuously inhibits targets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the function of the striatum (BG)?

A

process motor and cognitive inputs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the function of the pallidum (BG)?

A

regulates movement via inhibitory outputs -> creates of smooth muscle and precise motor actions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where does the striatum receive inputs from?

A

the cortex
thalamus
substantia nigra pars compasta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where does the striatum send outputs to?

A

internal part of globus pallidus - direct pathway
external part of globus pallidus - indirect pathway

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where does the pallidum send outputs to?

A

thalamus
substantia nigra pars compasta to the striatum
substantia nigra pars reticulate to the brainstem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where doe MSN receive inputs from?

A

the cerebral cortex
local circuit interneurons of the striatum
neurons in the midline and intralaminar nuclei of the thalamus
neurons in several nuclei of the brainstem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How many neurons doesnthe striatum contain?

A

about 100 million
about 75% MSN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the function of MSN?

A

have large dendritic trees which allow then to collect and integrate input from a variety of cortical, thalamic, and brainstem structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where do axons arising from MSN converge?

A

in the pallidum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the 2 key features of MSN?

A
  1. they are GABAergic output neurons that recive dopaminergic input
  2. they have unique biophysical properties due to the expression of a specific type of potassium channels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where are dopaminergic synapses located?

A

originates in the substantia nigra pars compacta
on the base of the spine in close proximity to the cortical synapse where they selectively modulate cortical imput

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the action of D1R receptors on MSN and dopamine?

A

excitatory inputs to the MSN that project to the internal globus pallidus (direct pathway)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the action of D2R receptors on MSN and dopamine?
inhibitory inputs to the MSN that projecr to the external globus pallidus (indirect pathway)
26
What is the major functional difference between D1R and D2R receptors?
D1Rs mediate the activation of G proteins that increase cAMP D2Rs act through different G proteins that decrease cAMP -> D1Rs enhance the excitatory input from cortex and D2Rs supress this excitation
27
What is the action of inward-rectifier K+ channels?
in MSN remain open at resting potential -> stabilizing the membrane and making spontaneous diring unlikely -> MSN require strong excitatory input from multiple sources to overcome potassium conductance and fire an AP -> when the neuron depolarizes these channels close making the neurons more excitable
28
When do MSNs typically increase their rate of discharge?
before an impeding movement
29
When do MSNs typically start firing?
associated with the occurance of a movement
30
Explain the premovement neuronal activity of MSNs may encode?
the activity of these cells may encode the decision to move toward a goal rather than the direction and amplitude of the actual movement necessary to reach the goal
31
What type of neurons are in the pallidum?
efferent cells of both the globus pallidus and substantia nigra pars reticulata are GABAergic -> the main output of the BG is inhibitory
32
How many neurons is the globus pallidus comprised of?
about 700 000 cells on average more than 100 MSNs innervate each cell
33
What is the output activity of neurons in the pallidum and what does it prevent?
high levels of spontaneous activity prevent unwanted movement by tonically inhibiting cells in the thalamus and superior colliculus
34
What are the 3 main projection to the BG?
1. the corticostriatal pathway 2. the thalamostriatal pathway 3. pathway from substantia nigra pars compasta
35
What are the 3 main projection from the BG?
1. from the striatum 2. from the globus pallidus 3. from teh substantia nigra pars reticulata
36
Where does the caudate recieve projection from in the corticostriatal pathway?
multimodel association cortices motor areas in the frontal lobe that control eye movement
37
Where does the putamen recieve projection from in the corticostriatal pathway?
the primary and secondary somatosensory cortices in the parietal lobe the higher order visual cortices in the occipital and temporal lobe the premotor and primary motor cortices in the frontal lobe the auditory association areas in the temporal lobe
38
What are the direct and indirect pathways from the striatum?
direct - to internal part of the globus pallidus indirect - to external part of the globus pallidus and the substantia nigra pars reticulata
39
What is the pathway from the globus pallidius?
to the ventral anterior and ventral lateral nuclei of the dorsal thalamus -> motor areas of the cerebral cortex
40
What is the pathway from the substantia nigra pars reticulata?
to the superior colliculus that command head and eye movements, without an intervening relay in the thalamus
41
What activates the direct and indirect pathways withing the BG?
integration of cortical inputs by the striatum
42
What is the the balance of the activity mediated by the direct and indirect pathways the principal determinant of?
whether the output from the pallidum to to the thalamus or superior colliculus
43
How are the direct and indirect pathways functionally organized?
in a centre-surround fashion withing the output nuclei of the basal ganglia
44
What does co activation fo both sets of striatal neurons imporant for?
the smooth initiation and execution of new motor activites
45
Explain the direct pathway (BG)
activation leads to the focal inhibition of a more restricted "center" cluster of neurons in the internal segment -> the disinhibition of the VA/VL thalamic complex and the expression of the intended motor program cortex -> striatum (-) -> IGP (-) -> thalamus EXCITATORY
46
Explain the disinhibition circuit of the direct pathway
the pallidal cells are inhibited by activation of the MSNs -> the globus pallidus neurons provide tonic inhibition to the relay cells in the VL/VA nuclei of the thalamus -> the thalamus neurons are disinhibited and can trigger the activation of upper motor neurons in the cortex -> allows the upper motor neurons to send commands to local circuit neurons and lower motor neurons that, in turn, initiate movement
47
Explain the indirect pathways (BG)
the external segment of the globus pallidus sends projections to both the adjacent internal segment and the subthalamic nucleus of the ventral thalamus with activation of the indirect pathways, the **MSNs discharge and inhibit the tonically active GABAergic neurons** of the external globus pallidus -> the subthalamic cells become more active and due to their excitatory connections with the GABAergic cells in the internal segment of the globus pallidus and substantia nigra pars reticulata they **increase the inhibitory output of the basal ganglia** also the subthalamic nucleus recives excitatory projections from the cerebral cortex cortex ->striatum (-) -> EGP (-) -> subthalamic nucleus (+) -> IGP (-) -> thalamus INHIBITORY
48
How does teh BG contribute to saccadic eye movements?
shortly before the onset of a saccade the **tonic discharge rate of the reticulata neurons is sharply reduced** by input from GABAergic MSNs of the caudate which have been activated by signals from the cortex -> this **disinhibits the upper motor neurons** of the superior colliculus allowing them to generate the bursts of APs that command saccades -> the projections from the substantia nigra pars reticulata to the upper motor neurons act as a physiological "gate" that must be "opened" to allow either sensory or other higher order signals from cognitive centers to activate the upper motor neurons and initiate a saccade
49
What are the two classes of disorders associated with the BG?
hypokinetic movement disorders - parkinsons hyperkinestic movement disorders - huntingtons
50
What is the cause of Parkinsons?
loss of dopaminergic neurons in the substantia nigra pars compacta
51
What is parkinsons effects on pathways?
less dopamine -> overactive indirect pathway -> excess inhibiton of the thalamus -> less movement
52
What are the symptoms of parkinsons?
bradykinesia (slow movement) resting temor rigidity postural instability
53
What is the treatment for Parkinson's?
L-DOPA therapy (resotre dopamine levels) deep brain stimulation (targets STN or GPi)
54
What is the cause of huntingtons disease?
degeneration fo the MNs in the indirect pathway
55
What is huntingtons effects on pathways?
loss of indirect pathway inhibition -> excess activation of the thalamus -> uncontrolled movement
56
What are symptoms of Huntingtons?
chorea (involuntary jerky movements) cognitive decline emotional distrubances
57
What is the treatment for huntingtons?
symptomatic management with dopamine antagonsits
58
Explain how hyperkinesia is modelled in animals?
a GABA antagonist is injected into the SNr reducing tonic activity -> removes the inhibitory control over the SC leading to disinhibiton of the SCs upper motor neurons -> generates involuntary saccadic eye movements (spontaneous and irrepressible) -> direction of saccades depend on the injection site within the SNr (spatially organized with motor maps corresponding to saccade vectors in the visual field)
59
What is deep brain stimulation?
the implantaion of battery powered generator untis usually near the clavicles produce electrical discharges that are passed through subcutaneous wires to electrodes implanted bilaterally into the brain
60
What are the two most common sites for DBS in individuals with movement disorders?
the internal segment of the globus pallidus the subthalamic nucleus
61
What can the exogenous induction fo electrical currents in DBS lead to?
complex patterns of activity and inactivity in the affected neural elements as well as effects on non neural elents different intensities may lead to the local release of neurotransmitters and neuromodulators

NEUR 350 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions