Lecture 13: Contributions of Cerebellum & Basal Nuclei to Motor Function II

Question 1

What does the basal nuclei function to do?

Answer 1

Help to plan and control complex patterns of muscle movements, controlling relative intensities of the separate movements, directions of movements, and sequencing of multiple successive and parallel movements.

Question 2

What does the basal nuclei do?

Answer 2

• plan and execute motor commands in concert with cerebral cortex; help cortex execute subconscious but learned pattern.
• help plan multiple parallel sequential patterns.
• control complex patterns of motor activity.

Question 3

Where does the basal nuclei receive most of its input from?

Answer 3

cerebral cortex

Question 4

Where does the basal nuclei return mots of its output to?

Answer 4

cerebral cortex

Question 5

What is the principle role of the basal nuclei?

Answer 5

Work with corticospinal system to modulate thalamic output to the motor cortex to plan and execute smooth movements.

Question 6

Which paired nuclei make up the basal nuclei?

Answer 6

- striatum 
  > caudate nucleus 
  > putamen 
- globus pallidus 
- substantia nigra 
- subthalamic nucleus

Question 7

What are the two major basal nuclei circuits?

Answer 7

• Putamen circuit (direct)

- Caudate nucleus circuit (indirect)

Question 8

What is the putamen circuit (direct pathway) for?

Answer 8

For subconscious execution of learned patterns of movement.

Question 9

Does the putamen circuit (direct pathway) bypass the caudate nucleus?

Answer 9

Yes

Question 10

True or False:

The putamen circuit (direct pathway) is overall excitatory, thus tending to decrease motor activity.

Answer 10

False - tends to increase motor activity (overall excitatory).

Question 11

What is the pathway of the putamen circuit (direct pathway)?

Answer 11

Cerebral cortex -(+)->
Putamen (substantia nigra compacta) -(-)->
Blobus pallidus (internal) and substantia nigra reticularis -(-)->
Thalamic relay nuclei (ventroanterior and ventrolateral nuclei) -(+)->
Primary motor cortex (and premotor/supplementary)

Question 12

In the putamen circuit (direct pathway), the connections between the striatum and the substantia nigra use what neurotransmitter?

Answer 12

Dopamine

Question 13

What receptor does dopamine bind to for an inhibitory effect?

Answer 13

D2 Receptors (indirect pathway)

Question 14

What receptor does dopamine bind to for an excitatory effect?

Answer 14

D1 Receptors (direct pathway)

Question 15

Is the action of dopamine in the putamen circuit (direct pathway) overall excitatory or inhibitory?

Answer 15

excitatory

Question 16

What happens when the putamen is excited?

Answer 16

The putamen inhibits the IGP/SubNigRet and allows the thalamus to send excitatory signals to the motor cortex.

Question 17

You know that the IGP/SubNigRet is normally active, thus sending what signals to the thalamus?

Answer 17

Sends inhibitory signals to the thalamus.

Putamen inhibits IGP/SubNigRet and allows the thalamus to send excitatory signals to the motor cortex

Question 18

What does a lesion in the globus pallidus cause?

Answer 18

> Leads to spontaneous and often continuous writhing movements of a hand, an arm, the neck, or the face.

> These movements are called athetosis.

Question 19

What does a lesion in the subthalamic nuclei cause?

Answer 19

> Leads to sudden flailing movements of an entire limb.

> A condition called hemiballismus.

Question 20

What does a lesion in the striatum cause?

Answer 20

Need to look up.

Question 21

What does a lesion in the substantia nigra cause?

Answer 21

> Leads to the common and extremely severe disease of rigidity, akinesia, and tremors known as Parkinson’s disease.

Question 22

What is the caudate circuit (indirect pathway) used for?

Answer 22

> Cognitive planning of sequential and parallel motor patterns.

plays major role in cognitive control of motor activity

Question 23

What does the caudate circuit (indirect pathway) play a major role in?

Answer 23

In cognitive control of motor activity.

Question 24

Overall, is the caudate circuit (indirect pathway) inhibitory or excitatory?

Answer 24

Over all inhibitory – tends to decrease motor activity.

Question 25

Does the caudate circuit (indirect pathway) tend to decrease or increase motor activity?

Answer 25

Tends to decrease motor activity.

Question 26

What is the neurotransmitter used between the substantia nigra and caudate nucleus and putamen?

Answer 26

Dopamine (inhibitory)

Question 27

What is the neurotransmitter used between: caudate nucleus and putamen --> globus pallidus and substantia nigra

Answer 27

GABA (inhibitory)

Question 28

What is the neurotransmitter used between: | Cortex --> caudate nucleus and putamen?

Answer 28

Acetylcholine (excitatory)

Question 29

What neurotransmitter is used in multiple pathways from the brain stem?

Answer 29

> norepinephrine > serotonin (inhibitory) > encephalin

Question 30

What do multiple glutamate pathways provide?

Answer 30

Provide most of the excitatory signals.

Question 31

What is anther name for Parkinson's?

Answer 31

Paralysis agitans

Question 32

What is Parkinson's a result of?

Answer 32

From widespread destruction of pars compacta of substantia nigra that sends dopaminergic fibers to caudate nucleus and putamen. Dopaminergic pathways to direct and indirect pathways are lost. The direct pathway loses some of its excitatory input and the indirect pathway loses some of its inhibitory input. In both cases there is decreased motor activity.

Question 33

What are the characteristics of a patient with Parkinson's?

Answer 33

> rigidity of much of body musculature > involuntary tremors of involved areas even at rest at a fixed rate > serious difficulty in initiating movement (akinesia) > postural instability > dysphagia, speech disorders, gait disturbances, fatigue

Question 34

When do Huntington's patients typically become symptomatic?

Answer 34

around 30-40 years of age

Question 35

What are the characteristics of a patient with Huntington's?

Answer 35

> flicking movements of individual muscles > progressive severe distortional movements of entire body > severe dementia > motor dysfunctions

Question 36

What are the abnormal movements in Huntington's patients probably caused by?

Answer 36

Loss of most of cell bodies of GABA-secreting neurons of caudate nucleus and putamen and of Ach neurons in other parts of the brain. Indirect pathway no longer has inhibitory influence on direct pathway and motor activity is increased.

Question 37

What do GABA neurons normally inhibit part of?

Answer 37

> globus pallidus | > substantia nigra

Question 38

True or False: In patients with Huntington's, the indirect pathway no longer has inhibitory influence on direct pathway and motor activity is increased.

Answer 38

True

Question 39

What is the pathway of the caudate circuit (indirect pathway)?

Answer 39

``` Cerebral cortex -(+)-> Caudate nucleus -(-)-> Globus pallidus (external) -(-)-> Globus pallidus (internal) -(-)-> Thalamic relay nuclei (ventroanterior and ventrolateral nuclei) -(+)-> Premotor and supplementary motor cortex ``` **the substantia nigra compacta sends inhibitory signals to caudate nucleus**

Question 40

Draw out Direct and Indirect Pathways!!

Answer 40

Figures 57-12 and 57-11