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Neuroanatomy > Basal ganglia > Flashcards

Basal ganglia Flashcards

1
Q

What is the general function of the basal ganglia?

A

To make sure some sets of mm. are active, other mm. are not, for a certain motor function to occur.

(*Overall the basal ganglia receive a large amount of input from cerebral cortex, and after processing, send it back to cerebral cortex via thalamus.)

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2
Q

What NT is most-associated w/the basal ganglia?

A

Dopamine (DA)

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3
Q

What structures make up the striatum?

A

Caudate nucleus + putamen (+ nucleus accumbens)

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4
Q

Which structure is the major efferent part of the basal ganglia?

A

Globus pallidus (pallidum)

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5
Q

Normally, what is the general effect the globus pallidus has on the thalamus?

A

GP tonically inhibits the thalamus, normally

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6
Q

What major segments are contained w/in the GP?

A 
Internal segment (GPi)
External segment (GPe)
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7
Q

What structures make up the lentiform nucleus?

A

Putamen and globus pallidus

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8
Q

What major segments are contained w/in the SN?

A 
Compact part (SNc)
Reticular part (SNr)
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9
Q

Which part of the SN secretes DA?

A

Compact part (SNc)

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10
Q

What parts of the GP and SN have similar function?

A

SNr and GPi

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11
Q

Which diencephalic nuclei are a part of the basal ganglia?

A

Subthalamic nuclei

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12
Q

In the direct pw, from what does the striatum get input?

Excitatory or inhibitory?

A

Cortex (excitatory)

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13
Q

In the direct pw, what does the striatum give output to?

Excitatory or inhibitory?

A

GPi (+ SNr) (inhibitory)

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14
Q

In the direct pw, what do GPi (+ SNr) give output to?

Excitatory or inhibitory?

A

Thalamus (inhibitory)

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15
Q

In the direct pw, what does the thalamus give output to?

Excitatory or inhibitory?

A

Cortex (excitatory)

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16
Q

In the direct pw, what input does the cortex receive? What info does it send out?
Excitatory or inhibitory?

A

Receives excitatory input from thalamus, gives off excitatory output to striatum.

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17
Q

In the direct pw, what input does the GPi (+ SNr) receive? What info does it send out?
Excitatory or inhibitory?

A

Receives inhibitory input from striatum, gives off inhibitory output to thalamus.

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18
Q

In the direct pw, what input does the striatum receive? What info does it send out?
Excitatory or inhibitory?

A

Receives excitatory input from cortex, gives off inhibitory output to GPi (+ SNr).

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19
Q

In the direct pw, what input does the thalamus receive? What info does it send out?
Excitatory or inhibitory?

A

Receives inhibitory input from GPi (+ SNr), gives off excitatory output to cortex.

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20
Q

How does the basal ganglia directly influence LMNs?

A

It doesn’t!

*influences LMNs thru cerebral cortex

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21
Q

What is the principle NT used to send excitatory signals in normal basal ganglia circuitry?

A

Glutamate

22
Q

What is the principle NT used to send inhibitory signals in normal basal ganglia circuitry?

A

GABA

23
Q

What are thalamocortical projections concerned with, regarding function?
Excitatory or inhibitory?

A
  • Motor “intention”

excitatory

24
Q

Balance of excitatory & inhibitory inputs to the ____________ determine whether thalamus is suppressed or not.

A

Striatum

25
Q

What are the names of the 4 different parallel loops of the basal ganglia (BG)?

A
  • Motor loop
  • Cognitive loop
  • Limbic loop
  • Oculomotor loop
    (all of these are integrated together)
26
Q

The cognitive loop of the BG is concerned w/what?

A

Motor “intention”

uses thalamocortical projection to go to cortex

27
Q

The limbic loop of the BG is concerned w/what?

A

Emotional aspects of motion

28
Q

The oculomotor loop of the BG is concerned w/what?

A

Voluntary eye saccades (fast eye movements)

- not important now

29
Q

The motor loop of the BG is concerned w/what?

A

*Learned movements

30
Q

What structure is part of both the lentiform nucleus and the striatum?

A

Putamen

31
Q

Which DA receptor is associated w/the direct PW of the motor circuit?
Which structures are influenced by dopamine in this pw?
What part of the SN secretes the DA?

A
  • D1
  • Caudate + putamen (striatum)
  • SN pars compacta
32
Q

In the direct pw of the motor circuit, what “inhibits the inhibitor?”

A

Striatum (inhibits the GPi, which is inhibiting the thalamus)

33
Q

In the direct pw of the motor loop, what would be the end-effect of releasing DA from the SN pars compacta?

A
  • Stimulates the cortex (by “inhibiting the inhibitor”)
34
Q

At what rate does the thalamus talk to the cortex? What does it say?

A

Thalamus constantly spews info at cortex whenever it has it

35
Q

What’s another name for the direct pw of the motor circuit?

A

“Go” pw

36
Q

What’s another name for the indirect pw of the motor circuit?

A

“No-go” pw

37
Q

How does the SN’s role differ in the indirect pw (vs. the direct)?

A

Still releases DA, but now not only activates D1 receptors in striatum that excite the striatum, but also activates D2 receptors that inhibit the striatum

38
Q 
Which part(s) of the GP are involved in the direct pw? What about the indirect pw?
Explain whether each part excites or inhibits.
A
  • Direct: GPi (tonically inhibits thalamus)

- Indirect: GPi (tonically inhibits thalamus). GPe (inhibits GPi and tonically inhibits subthalamic nucleus)

39
Q

What is the subthalamic nucleus’s role in the direct pathway? Indirect pathway?
Also, what inhibits it?

A
  • Direct pw: no role

- Indirect pw: tonically inhibited by GPe, transiently activates GPi

40
Q

Which are the 2 steps in the either pathway that have “tonic” inhibition or excitation?

A
  • GPe tonically inhibits the subthalamic nucleus (indirect pw)
  • GPi tonically inhibits VA/VL of thalamus (both pw’s)
    (*so GP actions are tonic, every other action is transient)
41
Q

What part of the cortex do the VA/VL nuclei of the thalamus interact w/ in the direct pw? Indirect pw?

A
  • Direct: Premotor cortex

- Indirect: Motor cortex

42
Q

What part of the cortex interacts w/and transiently stimulates the striatum in both direct and indirect pw’s?

A

Association cortex

43
Q

Explain the Parkinson’s Disease (PD) role in altering the indirect pw of the motor loop of the BG by acting on D2 receptors

A
  1. PD degenerates the SN, less DA released
  2. Striatal D2 input increased
  3. GPe inhibited
  4. Subthalamic nuc disinhibited, GPi disinhibited
  5. Subthalamic nuc stimulates GPi (reinforcing)
  6. GPi inhibits thalamus
  7. Motor cortex blocked (decreased excitation)
44
Q

Explain the PD role in altering the direct pw of the motor loop of the BG by acting on D1 receptors

A
  1. PD degenerates the SN, less DA released
  2. Striatal D1 input decreased
  3. GPi disinhibited
  4. Thalamus more inhibited
  5. Motor cortex less activated
    (same effects as indirect pw)
45
Q

Discuss some sx of PD (video).

A

Movements are accurate but slowed. Unstable when standing, hard to start walking (but once moving automatic fcns take over)

46
Q

Read about the characteristics of HD:

A
  • Autosomal dom
  • Chromosome 4 – Huntingtin gene
  • Abnormal trinucleotide repeat expansion
  • Onset age 30 - 50 years of age
  • Initial symptoms chorea and alternation of mood. Disease progression – dementia worsening personality changes
47
Q

During HD, which ventricle expands?

A

Lateral ventricles

48
Q

Dicuss some sx of HD (video).

A

Fidgety, restless, spontaneous movements of face/mouth. Gait has extra movements

49
Q

Explain HD’s role in altering the indirect pw of the motor loop of the BG.

A
  1. Striatal D2 receptors degenerated
  2. GPe disinhibited
  3. GPe inhibits GPi and subthalamic nuc (subthalamic wants to stimulate GPi)
  4. Thalamus disinhibited
  5. Overactive motor cortex
50
Q

In summary, the direct pw turns __ w/DA, the indirect pw turns __ w/DA.

A

on

off

51
Q

What’s providing the main input to the subthalamic nucleus in the indirect pw?
What’s another form of input it can receive?

A
  • Tonically inhibited by GPe

- *Can also be directly stimulated by the cortex (hyperdirect pw)

52
Q

What’s hemiballismus, and how would you cause it?

A
  • Rare disorder causing flailing, ballistic, undesired movements
  • Caused by lesion to subthalamic nucleus

Neuroanatomy (20 decks)

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