Topic 10-Cerebellum

Question 1

What happens if the cerebellum is removed in terms of perception and muscle weakness?

Answer 1

Removing the cerebellum doesn’t affect perception or muscle strength because its main role is in coordinating and fine-tuning movements rather than directly controlling those aspects.

Question 2

How does the cerebellum (little brain) regulate movement?

Answer 2

The cerebellum indirectly regulates movement by adjusting the output of major descending motor systems.

Question 3

What is the indirect function of the cerebellum, and does it have direct connections with spinal tracts?

Answer 3

The cerebellum is indirect in function and does not have direct connections with spinal tracts. It modifies the activity of upper motor neurons by adjusting the output of major motor systems.

Question 4

Three Roles of Cerebellum

Answer 4

1) Timing and spatial accuracy of movements
2) Motor learning (acquisition new motor skills)
3) “Comparator”: By comparing sensory feedback with the intended movement, which it receives as an “efference copy” or a copy of the motor plan.

Question 5

Pathway of Cerebellum

Answer 5

1) Input Sources: Primarily receives input from pre-motor and motor areas of the cerebral cortex, conveyed through pontine nuclei.

2) Additional Input: Gathers information from the spinal cord directly and via other brainstem nuclei.
3) Processing: Within the cerebellum, integrates and processes the incoming signals.
4) Output: Sends output to the ventral thalamic nucleus.
5)Thalamic Pathway: From the thalamus, the information is relayed back to the cerebral cortex.

Question 6

Describe the influence of the cerebellum on body movements.

Answer 6

The cerebellum’s impact is uncrossed and ipsilateral, meaning the right cerebellum influences the right side of the body, and vice versa.

Question 7

Where does the cerebellum primarily receive input from?

Answer 7

The cerebellum primarily receives input from pre-motor and motor areas of the cerebral cortex, conveyed through pontine nuclei.

Question 8

How does the cerebellum gather additional information?

Answer 8

[Answer] The cerebellum gathers additional information from the spinal cord directly and via other brainstem nuclei.

Question 9

What is the destination of the cerebellum’s output?

Answer 9

The cerebellum sends its output to the ventral thalamic nucleus

Question 10

What is the pathway from the thalamus in the cerebellum’s processing?

Answer 10

From the thalamus, the information is relayed back to the cerebral cortex.

Question 11

Anatomy of Cerbellum

Answer 11

1) 2 hemispheres divided by vermis
2) 3 lobes -anterior, posterior, flocculonodular
3) The cerebellar cortex is on the outside, covering the white matter located on the inside.

Question 12

How is the cerebellum connected to the brainstem?

Answer 12

The cerebellum is connected to the brainstem through three peduncles: superior, middle, and inferior.

Question 13

What is the main output pathway of the superior peduncle?

Answer 13

The superior peduncle is the primary output from the cerebellum to the cortex, projecting from deep cerebellar nuclei to various brain regions, including the red nucleus, upper motor neurons, and superior colliculus.

Question 14

What is the function of the middle peduncle?

Answer 14

The middle peduncle receives projections from the pons, which, in turn, receives input from the cortex and spinal cord.

Question 15

What does the inferior peduncle do?

Answer 15

The inferior peduncle receives input from the vestibular nucleus and outputs to the vestibular and reticular formation, contributing to arousal

Question 16

What are the three pairs of deep cerebellar nuclei through which the cerebellum receives information from the brainstem?

Answer 16

The three pairs are the fastigial, interposed (globose and emboliform), and dentate nuclei.

Question 17

How does the cerebellum’s output differ from the basal ganglia?

Answer 17

Unlike the basal ganglia, the cerebellum’s output is tonically active and excitatory, playing a role in the coordination and regulation of movements.

Question 18

Three Functional Subdivisions of the Cerebellum

Answer 18

1) Cerebrocerebellum
(lateral hemisphere)

2) Spinocerebellum (vermis and intermediate)

3) Vestibulocerebellum
(flocculonodular lobe)

Question 19

What is the focus of the Cerebrocerebellum?

Answer 19

coordinating voluntary, skilled movements, motor planning, and fine motor control.

Question 20

What is the primary concern of the Vestibulocerebellum?

Answer 20

The Vestibular Cerebellum is primarily concerned with posture and equilibrium.

Question 21

What is the primary function of the spinocerebellum?

Answer 21

primarily plays a role in controlling muscle tone, posture, and coordination of gross, automatic movements.

Question 22

Where is the Spinocerebellum located?

Answer 22

The Spinocerebellum is located down the vermis and slightly lateral (intermediate area).

Question 23

What are the two divisons of the spinocerebelleum?

Answer 23

It has a lateral part for gross movements of limbs, a middle part focusing on proximal muscles, eye movements, and responding to vestibular input.

Question 24

What is the input source for the Spinocerebellum, and what type of information does it receive?

Answer 24

The Spinocerebellum directly receives information from the spinal cord about lower limbs and some upper body proprioception.

Question 25

What are the main output connections from the cerebellar cortex, and which deep nuclei do they involve?

Answer 25

The main output connections from the cerebellar cortex are inhibitory (GABAergic), and they include: Cerebrocerebellum to dentate nucleus, Spinocerebellum to interposed and fastigial nuclei, and Vestibulocerebellum to the lateral vestibular nucleus.

Question 26

What is cerebellar ataxia, and how does it affect voluntary movements?

Answer 26

Cerebellar ataxia is damage to the cerebellum resulting in a lack of coordination among limb/body segments

Question 27

Identify and describe the symptoms of vestibulocerebellum damage.

Answer 27

Symptoms of vestibulocerebellum damage include a stumbling gait and problems with balance and coordination.

Question 28

What are the symptoms of spinocerebellum damage, and how does it impact movements?

Answer 28

Spinocerebellum damage leads to movements that are either too short or too far.

Question 29

Explain the symptoms associated with cerebrocerebellum damage.

Answer 29

Cerebrocerebellum damage results in speech problems and difficulties with fine motor skills.

Question 30

Define intention tremor and describe its characteristics.

Answer 30

An intention tremor is involuntary shaking during purposeful movements, becoming more pronounced as the person gets closer to the target and appearing during movement execution, not at rest.

Question 31

Three types of cerebellar ataxia

Answer 31

1) Vestibulocerebellar Ataxia
2) Spinocerebellar Ataxia
3) Cerebrocerebellar Ataxia:

Question 32

What is the main regulatory loop in the cerebellar cortex?

Answer 32

The main regulatory loop involves communication from the brainstem to the deep cerebellar nuclei, back to the nuclei ,regulating info from brain to spinal cord

Question 33

What is the function of the secondary loop in the cerebellar cortex?

Answer 33

The secondary loop regulates the main loop and involves the cerebellar cortex.

Question 34

How does the structure of the cerebellar cortex differ from the cerebral cortex?

Answer 34

The cerebellar cortex has three layers (granule, Purkinje cell, and molecular layers) compared to the six layers in the cerebral cortex.

Question 35

What is the main output mechanism of the cerebellar cortex?

Answer 35

The main output comes from Purkinje cells, which receive input from parallel fibers (axons of granule cells).

Question 36

What are the main inputs to the cerebellar cortex?

Answer 36

The main inputs include mossy cells and climbing fibers, the latter originating from the inferior olive in the brainstem.

Question 37

Who are the primary interneurons in the cerebellar cortex?

Answer 37

Granule cells.

Question 38

What is the role of granule cells in the cerebellar cortex?

Answer 38

Granule cells send axons parallel to form parallel fibers, stimulating the dendritic trees of Purkinje cells and contributing to the main output mechanism.

Question 39

What is the primary route for output from the cerebellar cortex to deep nuclei?

Answer 39

All output from the cerebellar cortex to deep nuclei is mediated through inhibitory Purkinje cells, which release the neurotransmitter GABA.

Question 40

What are the two main types of afferent input to the cerebellar cortex?

Answer 40

The two main types of afferent input are mossy fibers and climbing fibers.

Question 41

How do mossy fibers interact with the cerebellar cortex circuitry?

Answer 41

Mossy fibers synapse directly with deep cerebellar nuclei and indirectly with Purkinje cells via granule cell parallel fibers.

Question 42

How do climbing fibers interact with the cerebellar cortex circuitry?

Answer 42

Climbing fibers synapse directly with both deep cerebellar nuclei and Purkinje cells.

Question 43

What is the role of the cortical circuit involving mossy fibers and climbing fibers?

Answer 43

The cortical circuit modulates the effectiveness of the main loop in the cerebellar cortex.

Question 44

What type of spike does mossy fiber stimulation result in?

Answer 44

Mossy fiber stimulation results in a simple spike, leading to an action potential

Question 45

What type of spike is produced by climbing fiber stimulation?

Answer 45

Climbing fiber stimulation results in a complex spike, generating a large signal.

Question 46

How does climbing fiber stimulation impact Purkinje cell firing?

Answer 46

Climbing fiber stimulation has a significant impact on Purkinje cell firing, leading to inhibitory signals that shut down the deep cerebellar nucleus.

Question 47

What is the role of climbing fibers in the cerebellum?

Answer 47

Climbing fibers are thought to represent a motor error signal, altering Purkinje cell output and signaling motor errors back to the cerebellar nuclei.

Question 48

What is the long-term impact of changes in motor errors on Purkinje cells?

Answer 48

Over time, changes in motor errors cause a long-term reduction in Purkinje cell response to parallel fiber inputs.

Question 49

What role do Purkinje cells play in the cerebellar circuitry?

Answer 49

Purkinje cells act as “relaxation couplers,” linking time events to specific muscle activities and enabling temporal control of output (the regulation and coordination of the timing of signals or activities)

Question 50

How does the circuitry involving Purkinje cells contribute to temporal control?

Answer 50

The circuitry allows the cerebellum to control its output over time. Purkinje cells help coordinate muscle activities by temporally linking synchronized volleys of activity to dynamic events.

Question 51

What happens in the deep nuclei during an error in movement?

Answer 51

When an error occurs, climbing fibers send a powerful signal (complex spike), inhibiting all activity in the deep nuclei.

Question 52

What is the purpose of the synchronized volley of activity in the cerebellar circuitry?

Answer 52

The synchronized volley of activity, occurring after inhibition, serves to reset and coordinate individual activities in the deep nuclei, contributing to the temporal linking of events.

Question 53

How does the cerebellum recover and coordinate its output after an error?

Answer 53

During the recovery phase, a synchronized volley of activity resets and coordinates individual activities in the deep nuclei, allowing the cerebellum to recover and time-control its output.

Question 54

Somatotoptic Maps in Cerebellum

Answer 54

Different parts of cerebellar cortex are concerned with different parts of body.

Question 55

What are two cerebellar disorders?

Answer 55

1) Dysmetria
2) Dysdiadochokinesia

Question 56

Dysmetria

Answer 56

Refers to the inability to coordinate complex motor activity involving several muscle groups, such as difficulty keeping the heel on the shin.

Question 57

Dysdiadochokinesia

Answer 57

The inability to perform rapid alternating movements and results from the inability to coordinate antagonist muscles, often observed as difficulties in supinating the hands.