Motor Control and the Basal Ganglia

Question 1

What is the main function of the cerebellum?

Answer 1

Acts as a functional comparator; It receives information from the sensory system located in the muscles, ‘bows’ to the vestibular system, and the visual system and compares the information with

Question 2

How is the Cerebellum connected to the the rest of the brain?

Answer 2

Connected to the posterior aspect of the brainstem, by the superior middle and inferior cerebella peduncle.
(A peduncle is a bundle of nerve fibres).

Question 3

The superior peduncle connects the cerebellum to the ____?

Answer 3

The Superior peduncle connects the cerebellum to the midbrain.

Question 4

The middle peduncle connects the cerebellum to the ____?

Answer 4

The middle peduncle connects the cerebellum to the pumps.

Question 5

The inferior peduncle connects the cerebellum to the ____?

Answer 5

The inferior peduncle connects the cerebellum to the medulla.

Question 6

How many hemispheres does the cerebellum have?

Answer 6

2

Question 7

What connects the 2 hemispheres of the cerebellum?

Answer 7

A narrow median vermis

Question 8

What is the vermis?

Answer 8

Responsible for the control of the muscles on the long axis of the body.

Question 9

Which parts cerebral hemispheres control which limbs/movements?

• Intermediate zone
• Most lateral zones

Answer 9

They control the distal limbs, in what’s called the intermediate zone and the sequential movement in the most lateral zones.

Question 10

What main lobes make up the cerebellum?

Answer 10

• Anterior
• Posterior
• Flocculo-nodular lobe

Question 11

What divides the anterior and posterior lobes of the cerebellum?

Answer 11

Primary fissure.

Question 12

What divides the Posterior and Flocculo-nodular lobe?

Answer 12

Overall nodal fissure.

Question 13

What divides/separates the Superior and inferior surfaces?

Answer 13

Deep horizontal fissures

Question 14

What is the Cerebrocerebellum?

(aka “Neocerebellum”)

What is its function, where does it connect?

And where does it Communicate with in the brain?

Answer 14

Its one of the 3 different regions of the cerebellum, they’re divided according to evolution and their connections.

• “Neocerebellum” as its the most recent in terms of evolution.
• Involved in motor planning and cognitive functions.
• And “connects” to the thalamus (ventrolateral nucleus)
• The most / highest specialised part of the cerebellum.

Question 15

What is the Spinocerebellum?

What is its function, where does it connect?

And where does it Communicate with in the brain?

Answer 15

Its one of the 3 different regions of the cerebellum, they’re divided according to evolution and their connections.

• Spinocerebellum aka “paleocerebellum”
• Its function is related to posture.
• It connects to the red nucleus in the midbrain.

Question 16

What is the Vestibulocerebellum?

What is its function, where does it connect?

And where does it Communicate with in the brain?

Answer 16

Its one of the 3 different regions of the cerebellum, they’re divided according to evolution and their connections.

• Vestibulocerebellum aka “Archicerebellum”.
• Function relates to the control of balance.
• Connects to the vestibular nuclei in the brain.

Question 17

What is the cerebral cortex?

Answer 17

A covering of grey matter that’s more superficial than the white matter, the grey matter is arranged into 3 layers, so the cortex is also divided into 3 layers.

Question 18

What are the 3 layers of the cerebral cortex?

And which cells do they each contain?

Answer 18

• Molecular layer; Contains stellate and basket cells
• Purkinje cell layer; Contains the cell body of the Purkinje cells
• Granule cell layer; contains Golgi cells

Question 19

What are the Climbing and Mossy fibres in the white matter beneath the cerebral cortex?

Answer 19

They are the 2 main lines of input to the cortex, and they are excitatory to the Purkinje cells.

Question 20

What is the significance of card no.19?

about the mossy and climbing fibres and how they interact with the cerebral cortex

Answer 20

They have an input not only to the cells in the cortex but also to the central nuclei. There is a delay where that info is elaborated to the purine cells and then its related to the nuclei.

The significance of this is that the mossy & climbing fibres have a excitatory activity on the deep cerebellar nuclei, and the same info is processed by the purkinje cells that have an inhibitory effect on the nuclei.

Question 21

Does a lesion on one hemisphere of the cerebellum give rise to symptoms on the same or opposite side of the body?

Answer 21

Same side, they are ipsilateral as the fibres from the cerebellum do not cross over.

Question 22

Where does the efferent information from the nuclei in the cerebral cortex go?

Answer 22

Go to the brain and spinal cord.

Question 23

What nuclei are present on the cerebellum?

Laterally –> medially

Answer 23

• Dentate nucleus
• Emboliform nucleus
• Globose nucleus
• Fastigial nucleus

Question 24

What is the Thalamus?

Answer 24

The thalamus is a nucleus (of cell bodies, grey matter) in the brain and is medial to the internal capsules.

Related to the control of movement as it relays information to the cortex and to other structures, and receives info from these structures as well as being involved in ascending and descending pathways.

Question 25

Why is the Thalamus known as the gateway for sensory inputs to the brain?
or
Why does the Thalamus play an important role in the control of movement?

Answer 25

Every nucleus in the Thalamus apart from the reticular nucleus, sends axons to specific parts of the cortex. And in turn every part of the cerebral cortex sends reciprocal fibres back through the Thalamus.

Question 26

What are the ventral lateral nuclei related to?

Answer 26

To the motor areas in the cortex areas.

Question 27

What are the Basal Ganglia?

Answer 27

A series of nuclei deep in the thalamus. They sit at the base of the brain.

They Basal Ganglia are formed by different nuclei.
The general structure is;
- Corpus striatum 
- Amygdaloid nucleus
- Claustrum

Clinically tend to include substantia nigra, subthalamic nucleus

Question 28

What is the Corpus striatum made up of?

Answer 28

The;

• Caudate nucleus
• Lentiform nucleus, which is made of the:
• Putamen
• Globus pallidus

Question 29

Note about Basal ganglia pathway

Answer 29

see LC at 19:35

Question 30

What are the 2 dopamine “loops”/ pathways (involves the Basal ganglia)

Answer 30

1: Direct
- dopamine excitation, dopamine released from the substantia nigra (SN) binds to D1 receptors.
- Results in increased motor activity.

2: Indirect
- dopamine inhibition, pretty much same as above but D2 receptors instead.
- Results in decreased motor activity.

Question 31

What is the effect of a dopamine imbalance; reduced dopamine?

Answer 31

Indirect loop is overactive and the direct loop is underactive, the effect is reduced movement.

Net effect reduced motor activity; hypokinetic diseases (e.g. Parkinson’s)

Question 32

What is Parkinson’s disease?

Answer 32

• Its a basal ganglia disorder, a hypokinetic disease caused by the loss of dopamine secreting neurons in the substantia nigra.6.
• Tends to affect older people as Dopamine receptors are naturally lost as we age so 80+ are more at risk.

Question 33

What are the 3 main symptoms of Parkinson’s disease?

Answer 33

• Tremor
• Rigidity
• Bradykinesia (slowness)

Question 34

What are the Basal Ganglia responsible for?

Answer 34

As Basal ganglia disorders such as Parkinson's disease show us the basal ganglia are responsible for;
- Postural tone
- Velocity of movement
- Initiation of movement 
- Changes in movement 
-

Question 35

What is the effect of a dopamine imbalance; increased dopamine?

Answer 35

The direct loop becomes over active as the indirect loop becomes underactive, due to the increase in dopamine.

The net effect is increased motor activity; hyperkinetic disease (e.g. Huntington’s)

Question 36

What is Huntington’s disease?

Answer 36

It is a hyperkinetic disease, caused by the unbalanced dopamine secreting neurons in the substantia nigra, as they are overactive.

• Tends to affect younger people vs Parkinson’s.
• Leads to Choreiform movements (exaggerated movements).

Also lead to progressive dementia.