Lecture 10 - Basal Ganglia Flashcards Preview

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Flashcards in Lecture 10 - Basal Ganglia Deck (22):
1

Basal Ganglia overview

-gets input from many brain areas
-do complex information processing
-assist the IPSI motor cortices for proper movement, tone and posture
-play poorly understood role in cognitive and emotional functions
-lateral to lateral ventricle, next to internal capsule
-internal capsul is between the thalamus and the globus pallidus

-motor, cognition, emotion all determined

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Striatum

Caudate
putamen
-function as unit

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Globus pallidus

internal
external
-with putamen = lentiform/lenticular nucleus

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Subthalamic nucleus

ventral to thalamus

5

Substantia nigra (midbrain)

reticular
compact

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input

excitatory projections mostly from cerebral cortex to striatum

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output

inhibitory projections mostly from internal globus pallidus, reticular substantia nigra to thalamus (ventral anterior and ventral lateral nuclei)

8

Thalamus

excites motor cortex
-direct pathway increases
-indirect pathwya decreases
-initiate vs. terminate motor programs

9

Direct pathway

MORE movement
1. cortex excites inhibitory neuros in putamen (striatum)
2. striatum inhibits INT. globus pallidus and reticular substantia nigra
3. reduces globus pallidus and RSN inhibition of thalamus
4. increased excitation from thalamus to motor cortex

10

Indirect pathway

LESS movement
1. cortex excites inhibitory neurons in striatum
2. striatum inhibits EXT. globus pallidus
3. reduces inhibition of subthalamic nucleus
4. subthalamic nucleus excites int. globus pallidus and RSN more
5. int. globus pallidus and RSN increase inhibition of thalamus
6. decreased excitation from thalamus to motor cortex

11

Dyskinesias

BG dysfunction
-involuntary abnormal movements and/or postures without weakness
-"movement disorders"
hyperkinetic
hypokinetic
both

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Ballism

involuntary, fast, large proximal limb movement
-lesion in subthalamic nucleus --> less excitation of inhibitory neuros to thalamus

*** shuts down indirect --> uncontrolled direct = more movement

13

Tremor

involuntary alternating movement
-rhythmicity, amplitude, frequency, parts of body affected
rest tremor: at rest
action tremor: movement or posture
-postural tremor: with a position held against gravity
-kinetic tremor: during movement
intention tremor - when movement approaches a target (cerebellar issue)

14

Dystonia

Hyperkinetic dyskinesia
Involuntary sustained contraction of one or more muscles causing abnormal movement/posture

15

Chorea

Hyperkinetic dyskinesia
involuntary, fast, irregular, mostly distal limb movements that resemble dancing

16

Athetosis

Hyperkinetic dyskinesia
involuntary, slower, writhing, mostly distal limb movements that resemble the movement of snakes

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Myoclonus

Hyperkinetic dyskinesia
Involuntary movement that are small and rapid (a jerk), usually of bilateral proximal limbs and trunk

18

Tics

Hyperkinetic dyskinesia
seminvoluntary movements or vocalizations that relieve a progressively uncomfortable sensation and which may be briefly suppressed with concentration

19

Compact Substantia Nigra

Inputs from many brain areas
-projects dopamine to IPSI striatum via nigrostriatal tract
-influence BG by:
increasing activity of direct pathway *** more movement
decreasing activity of indirect pathway
other stuff

20

Parkinsonism

Dysfunctional nigrostriatal tract
-bradykinesia (hypokinetic) - involuntarily slowed
-rigidity (velocity-independent hypertonia)
-rest tremor (hyperkinetic) - usually distal limbs
sometimes also postural tremor

21

Acetylcholine

Neurons in and out of BG
unclear wiring
mostly favors INDIRECT pathway

22

Nonmotor functions

cognition and emotion
***nucleus accumbens (experience of reward --> motivation)