Lecture 18: Basal Ganglia

Question 1

Basal ganglia is a collection of _____ matter nuclei deep within each cerebral hemisphere.

Answer 1

Gray

Question 2

Basal ganglia receives info from the ______ . It also sends info to the _____ via the _____. Additionally sends info to the _____ directly.

Answer 2

Cerebral cortex.
cerebral cortex
thalamus.
brainstem.

Question 3

What are four functions of the basal ganglia?

Answer 3

1. Important role in higher order control of posture and voluntary movement.
   -selecting, reinforcing,
   scaling desired motor
   output patterns
   -initiating and preparation
   for movement
   -automatic execution of
   previously learned
   movement patterns
2. control of eye movements
3. cognitive functions
4. emotional functions

Question 4

Define Hyperkinetic movement disorders. Give 1 example.

Answer 4

Uncontrolled involuntary movements which give rise to a random pattern of jerks and twists.
ie. Huntingtons disease

Question 5

Define Hypokinetic movement disorders. Give 1 example.

Answer 5

Rigidity, slowness of movement, marked difficulty in initiating movements.
ie. Parkingson’s Disease

Question 6

What 5 components make up the basal ganglia??

Answer 6

Caudate nucleus
Putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra

Question 7

Which component of basal ganglia follows the contour of the lateral ventricle and lies lateral to thalamus?

Answer 7

Caudate nucleus (C-shaped)

Question 8

What fuses with the head of caudate anteriorly?

Answer 8

Putamen

Question 9

Together the caudate and putamen are called the?

Answer 9

Corpus Striatum

Question 10

In between the putamen and caudate nucleus you can find the _____ joining them.

Answer 10

cellular bridges

Question 11

What is located medial to the putamen?

Answer 11

Globus pallidus

Question 12

How many segments of the globus pallidus? Name them.

Answer 12

2. The internal and external segments

Question 13

Together the ____ and ____ are referred to as the ____ nucleus.

Answer 13

Putamen and globus pallidus.

= Lentiform nucleus

Question 14

Which component is located in the midbrain, just dorsal to basis pedunculi?

Answer 14

Substancia nigra

Question 15

Substantia nigra has two portions; ventral and dorsal. Name these 2.

Answer 15

Ventral portion: pars reticulata

Dorsal portion: pars compacta

Question 16

Which portion of the substantia nigra do you find dopamine-containing neurons? (name the portion)

Answer 16

Dorsal portion: pars compacta

Question 17

What can you find off the caudate nucleus that does NOT belong to the basal ganglia?

Answer 17

Amygdala

Question 18

Nearly all inputs from other parts of the brain reach the basal ganglia by way of the ____ and ____. (called the ____ ____)

Answer 18

caudate nucleus and putamen. (called the corpus striatum).

Question 19

All areas of the cerebral cortex have massive projections to corpus striatum called _________.

Answer 19

corticostriatal pathway

Question 20

What neurotransmitter is used mostly in the corticostriatum pathway?

Answer 20

glutamate

Question 21

Corticostriatal pathway projections from cerebral cortex to striatum are mostly _____.

Answer 21

excitatory

Question 22

Besides the corticostriatal pathway another projection to the striatum is the ___ ___ ___ ___ containing dopamine.

Answer 22

substantia nigra pars compacta

Question 23

Are the substancia nigra pars compacta inputs to striatum excitatory or inhibitory to the striatum?

Answer 23

Both. Excitatory to some cells and inhibitory to other cells in striatum.

Question 24

Where do the outputs from basal ganglia leave from? (2- be specific)

Answer 24

1. internal segment of globus pallidus

2. substantia nigra pars reticulata

Question 25

Majority of outputs from basal ganglia project to ____ and ____ nuclei of ____.

Answer 25

Ventral lateral (VL) and ventral anterior (VA) nuclei of thalamus.

Question 26

the outputs sent to the VL and VA of thalamus then project to ____ areas of cortex. Then influence the lateral and anterior ____ tract.

Answer 26

motor. | corticospinal tract

Question 27

Besides the thalamus outputs of the basal ganglia, where are the other two outputs to? which tracts do they influence?

Answer 27

1. Pontomedullary reticular formation - influences descending reticulospinal tract (for automatic posture and gait related movements- anterior motor system pathways) 2. Superior colliculus - influence tectospinal tract for coordination of head and eye movements

Question 28

Basal ganglia influence ___ and ___ motor systems.

Answer 28

lateral and medial

Question 29

What is the "direct pathway" in the basal ganglia?

Answer 29

From the striatum directly to internal segment of globus pallidus and substantia nigra pars reticulata

Question 30

What are the 3 functions of the direct pathway?

Answer 30

1. serves to release tonic inhibition of the thalamic neurons that project to the cortex (ie. inhibit inhibitory neurons= excitation of thalamus) 2. net effect: excitation of thalamus --> greater excitation of motor areas of cortex 3. Direct pathway "enhances movement"

Question 31

What is the indirect pathway in basal ganglia?

Answer 31

From striatum to other basal ganglia nuclei (external segment of globus pallidus and subthalamic nucleus) prior to reaching internal segment of globus pallidus and substantia nigra pars reticulata.

Question 32

What are the 3 functions of the indirect pathway?

Answer 32

1. acts to oppose the dis-inhibitory action of the direct pathway (ie. excite inhibitory neurons in thalamus) 2. net effect inhibition of thalamus - decreased excitation of motor areas of cortex 3. indirect pathway "diminishes movement"

Question 33

Motor channel (influences motor control) is the loop from primary motor, _____ and somatosensory cortex --> ______ ---> projects to ___ and ___ of thalamus -> to ____ and ______ cortex.

Answer 33

motor association. basal ganglia. VL and VA of thalamus. primary motor cortex and motor association cortex.

Question 34

Oculomotor channel (for basal ganglia regulation of eye movement) is the loops from posterior parietal and _____ --> ______-->_____ relay nuclei --> to ___ eye fields and ___ eye fields of frontal lobes.

Answer 34

pre-frontal cortex. basal ganglia. thalamic relay nuclei. frontal eye fields and supplementary eye fields of frontal lobes.

Question 35

Prefrontal channel is the loop from posterior parietal and pre-frontal cortex --> ___--> ______--> to ____ cortex.

Answer 35

basal ganglia. thalamic relay nuclei. to prefrontal cortex.

Question 36

Prefrontal channel is important for? be specific

Answer 36

Important in cognitive processes involving the frontal lobes: planning, working memory, attention and behaviour.

Question 37

Limbic channel is the loops from limbic cortex --> _____--> _____ nuclei--> outputs relay back to ____.

Answer 37

Basal ganglia. Thalamic relay. limbic cortex.

Question 38

Limbic channel is for?

Answer 38

Regulation of emotions and motivational drives | * likely key role in neuro-behavioural and psychiatric disorders*

Question 39

What is Parkinson's disease? - involves? - loss of? results in? - what type of disorder is it?

Answer 39

involves a degeneration of dopamine-containing neurons in substantia nigra pars compacta. -dopamine normally has a net excitatory effect on thalamus - loss of dopamine leads to alterations in both direct and indirect pathways of the basal ganglia. -Results in net decreased excitation of motor cortex --> diminished movement This leads to Parkinson's disease which is a HYPOKINETIC movement disorder.

Question 40

What are the 3 cardinal signs of Parkinson's disease?

Answer 40

1. resting tremors ("pill rolling") - tremors subside when doing activities but are present at rest 2. bradykinesia (generalized slowness in movements) 3. muscle rigidity

Question 41

What are other features of Parkinson's disease (not cardinal signs)? (12 total... name 6 at least)

Answer 41

1. Hypokinesia- decreased amount of movement 2. small handwriting (micrographia) 3. Akinesia - lack of movement; difficulty initiating movement 4. episodes of "freezing" during movement - during change of environment or change in direction of movement. 5. masked face, lack of expression - could be due to lack of emotion (changes in limbic channel) 6. reduced volume of speech 7. postural instability 8. Gait- decreased speed, shortened stride, shuffling feet, decreased or absent arm swing 9. Festination: difficulty stopping gait once started (CoM forwards therefore hard to stop as trying to catch CoG) 10. MSK changes: weakness, decreased muscle strength, joint contractures 11. Cardiopulmonary dysfunction 12. Swallowing difficulties

Question 42

What is Huntington's disease? what type of disorder is it? causes?

Answer 42

Autosomal dominant hereditary disorder. it is a HYPERKINETIC movement disorder -cause is atrophy of caudate and putamen (corpus stiatum) also association degeneration of cerebral cortex.

Question 43

Huntington's disease results in?

Answer 43

reduced inhibition of thalamus and therefore, excessive OUTput from motor cortex.

Question 44

When does Huntington's disease get expressed?

Answer 44

Expresses between 40-45 years old. (onset between 40-50) * numbers in notes*

Question 45

What are the clinical features of Huntington's disease?

Answer 45

1. initial clumsiness, decreased coordination 2. generalized chorea -involuntary, jerky, rapid movements - tongue protrusion, facial grimacing 3. personality changes 4. depression, psychosis 5. cognitive deficits, dementia