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S2 Neuroscience > Basal Ganglia > Flashcards

Basal Ganglia Flashcards

1
Q

basal ganglia: 2 definitions

A

deep grey matter structures that develop from the telencephalon
a series of grey matter structures that are interconnected and serve a common function (this is the one we will use)

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2
Q

corpus striatum

-subdivisions

A

neostriatum or striatum

  • caudate nucleus
  • putamen
  • globus pallidus
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3
Q

neostriatum

  • divisions
  • divided by…
A

one nucleus divided into 2 parts by anterior limb of internal capsule

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4
Q

putamen and caudate make up the…

A

dorsal striatum

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5
Q

caudate nucleus

-composed of…

A

head
body
tail

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6
Q

globus pallidus (GP)

  • what are the parts
  • separated by…
A

external (GPe - lateral)
internal (GPi - medial)
separated by internal medullary lamina

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7
Q

amygdaloid nuclear complex

  • develops from…
  • functionally associated with…
A

develops from telencephalon

functionally associated with Limbic System

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8
Q

other structures functionally associated with Basal Ganglia

A

subthalamic nucleus (ST nuc.)
Substantia nigra (SN)
thalamic nuclei: VA, VL, DM, CM
pedunculopontine nucleus

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9
Q

substantia nigra

-parts

A

zona or pars compacts (SNc)

zona or pars reticulata (SNr)

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10
Q

pars compacta

  • neural neurotransmitter
  • contains…
A

dopamine neurons

contains black pigment: neuromalanin

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11
Q

pars reticulata

  • neural neurotransmitter
  • does not contain…
  • functionally similar to…
A

GABA neurons
no neuromelanin
functionally similar to medial GP (GPi)

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12
Q

pedunculopontine nucleus

  • relation to Basal Ganglia
  • function
A

RF nucleus that sets up a rhythmic cholinergic input to the striatum
plays a role in the coordination of synergistic movement

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13
Q

structures anatomically related to corpus striatum

A

lenticular nucleus

claustrum

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14
Q

lenticular nucleus

-what is it?

A

name given to GP plus putamen

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15
Q

claustrum

-bounded by…

A

external and extreme capsules

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16
Q

function of basal ganglia

A

collection of sub-cortical (suprasegmental) masses of gray matter that serve to modulate cortical control of

  • motor function
  • cognition
  • motivation
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17
Q

basal ganglia pathways

-form _____ that start in _____ and end in _____

A

form several circuits or loops that start in widespread areas of cortex and end in more circumscribed parts of motor cortex, limbic cortex or frontal lobe association cortex

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18
Q

from a functional point of view, the basal ganglia and related nuclei have been divided into…

A

dorsal and ventral striatum

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19
Q

dorsal striatum

-consists of…

A

consists of pathways involving the caudate and putamen

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20
Q

caudate is involved in…

A

cognitive processing

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21
Q

putamen involved in…

A

involved more with sensorimotor processing

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22
Q

ventral striatum

-function

A

involvement with limbic system and emotion

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23
Q

dorsal striatum

-general pathways

A

afferents
interconnections
efferents

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24
Q

dorsal striatum afferents

-location of the structures that project to the dorsal striatum

A

widespread cortex
intralaminal nucleus of thalamus
raphe nuclei fibers
pedunculopontine nuclei fibers

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25
Q

dorsal striatum afferents: widespread cortex

  • neurotransmitter
  • projects to…
A

glutamate
projects to striatum
smaller inputs to SNr (pars reticulata) and ST nuclei (subthalamic nucleus)

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26
Q

dorsal striatum afferents: intralaminal nucleus of thalamus

  • another name
  • projects to…
A

centromedial thalamic nucleus (CM)

-projects to striatum

27
Q

dorsal striatum afferents: raphe nuclei fibers

  • neurotransmitter
  • projects to…
A

serotonin

projects to all parts of basal ganglia

28
Q

dorsal striatum afferents: pedunculopontine nuclei of RF

  • neurotransmitter
  • projects to…
A

ACh

projects to SNr and GP

29
Q

dorsal striatum interconnections

-can be categorized as…

A

direct (main) circuit
indirect (auxillary) circuit
nigro-striatal-nigral pathway

30
Q

dorsal striatum interconnections: direct circuit

  • pathway
  • neurotransmitter associated with each
A

widespread areas of cortex (glutamate) –> stiratum (GABA and substance P) –> GPi and SNr (GABA) –> thalamic nuclei (glutamate) –> frontal lobe cortex

31
Q

dorsal striatum interconnections: indirect circuit

  • pathway
  • neurotransmitter associated with each
A

widespread areas of cortex –> striatum –> GPe (GABA) –> subthalamic nuclei (glutamate) –> SNr and GPi (GABA) –> thalamic nuclei –> frontal lobe cortex

32
Q

dorsal striatum interconnections: nigrostriatal pathway

  • neurotransmitter
  • from
  • to
A

dopamine-containing fibers from SNc to striatum

GABA fibers from striatum back to SNc

33
Q

dorsal striatum efferents

-no direct output of…

A

basal ganglia to brainstem or spinal cord LMNs

34
Q

dorsal striatum efferents

  • major efferents are from…
  • to
  • function of each area they go to
A

GPi (largest number) and SNr to the

  • VA and VL
  • -motor function
  • DM
  • -cognitive function
  • CM
35
Q

dorsal striatum efferents from GPi and SNr directed through the thamalus
-relayed to _____ as part of _____

A

relayed to frontal lobe cortex and supplementary motor cortices as part of the direct and indirect circuits

36
Q

dorsal striatum efferents: cerebellar connections running through the thalamus end primarily in…

A

lateral premotor cortex

37
Q

dorsal striatum efferents

  • other efferents
  • function
A

SNr to tectum
-modulates tectospinal path
SNr and GPe to the pedunculopontine nucleus (RF nucleus)

38
Q

the primary mechanism underlying the function of the basal ganglia is…
-explain

A

disinhibition
-inhibition of a tonically active inhibitory pathway; an inhibitiroy neuron inhibiting a tonically active inhibitory neuron

39
Q

disinhibition

-how is it accomplished

A

accomplished through a balance of signals from the direct and indirect loops converging on the output nuclei, GPi and SNr

40
Q

disinhibition

  • groups of cells in the GPi are strongly linked to…
  • the initiation in from _____ rather than _____
A

remembered motor tasks coupling them to an internally generated initiation of movement
-initiation is more from an internal direction of deciding to do something, rather than from sensory cued stimuli such as vision or proprioception

41
Q

disinhibition

-when are different groups of GPi cells active?

A

some cells are associated with specific phases of complex movements, active only during a portion (single joint) of a complex activity
other groups of cells are active throughout the entire sequence of the movement, programming sequential multi-joint activity

42
Q

disinhibition: cells of the GP
- when are they active
- controlled by…

A

spontaneously active

controlled by cortical or nigral activation of the relatively quiet striatal cells (caudate and putamen)

43
Q

what general things will be noted with lesions in the basal ganglia

A

abnormal movement and posture

44
Q

how is the basal ganglia involved in movement and posture

A

basal ganglia activity coupled to areas of the cortex that are involved in planning and execution of motor activity

45
Q

secondary proposed function of the basal ganglia

A

part of the procedural learning of motor activity

46
Q

describe procedural learning

A

more task-oriented

-i.e. ability to learn and replicate automatic motor skills

47
Q

procedural and declarative learning relation to Alzheimer’s patients

A

they can learn new motor tasks (procedural), but not new facts (declarative)

48
Q

aside from disinhibition and procedural memory, basal ganglia also involved in…

A

cognitive function

49
Q

describe basal ganglia role in cognitive function

A

head of caudate nucleus

  • recieves a large projection from frontal lobe assocation cortex
  • projects back to the same cortical area via VA and DM thalamic nuclei
50
Q

putamen role in basal ganglia cognitive function

A

primarily a motor function nucleus

functions more in habit formation and procedural or implicit memory

51
Q

basal ganglia blood supply

  • from…
  • -each supplies…
A

striatal or ganglionic arteries (small deeply penetrating brahcnes of Circle of Willis)
-supply bulk of caudate nucleus
-anterior globus pallidus
-putamen
-internal capsule
thalamo-geniculate branch of posterior cerebral artery
-subthalamic nucleus (plus thalamus and adjacent posterior limb of internal capsule)

52
Q

diffuse diseases of the CNS with multiple sites of damage

  • examples
  • produce…
  • -as a result
A

encephalitis and CP
produce a variety of dyskinesias (disorders of movement)
-makes localization of lesions difficult

53
Q

the idea that individual components of the basal ganglia and related motor areas have certain distinct functions is based on…

A

observations of two types of dyskinesias

-hyper- and hypo-kinetic in nature

54
Q

kyperkinetic disorders

-what are they

A

athetoses
choreas
ballismus

55
Q

athetoses

  • describe
  • often seen in…
  • lesion location
A

involuntary, ceaseless, slow, writhing movements (like an “oriental dancer”)
often seen in CP
lesion location is unclear, but probably involves striatum

56
Q

choreas

  • describe
  • lesion location
A

jerking, dancing, grimacing movements of varying duration and latency
-frequently appear “purposive”
when not moving, patients’ muscles exhibit hypotonia
lesions are typically in striatum or VL of thalamus

57
Q

ballismus

  • describe
  • lesion location
A

violent flinging movements due to involuntary contractions, especially of proximal limb muscles
usually on one side only = hemiballism
caused by localized lesion of subthalamic nucleus contralateral to affected limb

58
Q

why is ballismus caused by a contralateral lesion?

A

I don’t know

59
Q

hypokinetic disorder

  • lesion location
  • example
A

lesions usually in striatum and SN

Parkinsonism

60
Q

Parkinson’s disease

  • caused by…
  • characteristic
  • -caused by…
A

caused by degeneration of nigrostriatal neurons that use dopamine as their neurotransmitter
deficit may be worse on one side than the other, in which case dopamine loss is greater on the side contralateral to the worst deficits

61
Q

hyperkinesias: hypothesized mechanisms

- best interpretation from…

A

clinical observations and primate research

62
Q

hyperkinesias

  • explain the mechanism
  • -function of indirect and direct circuits
  • -what would cut the indirect circuit and what would the result be
A

basal ganglia normally has an inhibitory influence on UMNs through the indirect circuit and an excitatory influence through the direct circuit
lesions of the subthalamic nucleus would cut the indirect circuit and permit the direct circuit to drive movements unopposed

63
Q

hyperkinesias

-explanation for choreas and athetoses

A

still unknown but may involve selective loss of striatal GABA neurons that normally inhibit motor activity

64
Q

hypokinesia with rigidity

-current mechanism hypothesis

A

dopamine normally enhances the direct (excitatory) circuit and inhibits the indirect (inhibitory) circuit
loss of SNc dopaminergic neurons results in a greatly reduced ability of the cortex to initiate movement through the activation of cortical UMNs
loss of control over UMNs results in loss of voluntary control of alpha LMNs (akinesia) and decreased inhibition of the gamma loop relfex (rigidity)

S2 Neuroscience (25 decks)

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