53 Locomotion and Cerebellum

Question 1

16-17 MB:

What are central pattern generators, and what are their roles in generation of locomotion?

Answer 1

Spinal cord

• generate locomotor patterns without sensing sensory input
• contains inhibitory/excitatory neuron with an inhibitory interneuron in one half
• when either side is activated, the other side will be inhibited
• inhibitory output will fatigue after fixed time > other side takes place
• allow alternative contraction of flexors and extensors to allow rhythmic activities in locomotion

Question 2

2 features of CPG (Central pattern generator)

Answer 2

Only spinal cord alone is enough to generate different locomotor pattern

No afferent input is needed

Question 3

The first part of locomotion is? Then patterning network will be formed by spinal interneurons.

Answer 3

Rhythm generation by the CPG

Question 4

What are the 3 neural mechanisms to provide flexibility to stereotypical locomotor patterns?

Answer 4

1. Proprioceptive afferent from muscles and joints (ascending signals)
2. Brainstem (descending signals)
3. Motor cortex (posterior parietal cortex)

Question 5

In locomotion, proprioceptive and cutaneous signals from muscles and joints function to?

Answer 5

1. trigger locomotion
2. fine-tune locomotor rhythm (ventral spinocerebellar tract for monitoring discrepancy between actual and desired state)

Question 6

In locomotion, brainstem serves to?

Which parts of the brainstem are involved?

Answer 6

1. Initiate locomotions
2. Set speed of locomotion

Parts of brainstem involved:

• midbrain locomotor center
• subthalamic motor region
• pontine reticular formation

Question 7

In locomotion, posterior parietal cortex (motor cortex) serves to ?

Answer 7

For the storage of visual information (working memory) involved in the modulation of the locomotor pattern for precise walking

Question 8

With the influence from ascending and descending signals, the patterning network will be sent to ___________ and thus generate motor pattern.

Answer 8

Motor neurons

Rhythm generator > patterning network > motor neurons > motor pattern

Question 9

For humans, in addition to spinal CPGs, __________________ also plays an important role in triggering and maintenance of locomotor patterns.

Answer 9

motor cortical inputs to spinal cord

Question 10

For humans, in addition to spinal CPGs, motor cortical inputs to spinal cord also plays an important role in _______ and _________of locomotor patterns.

Answer 10

triggering;

maintenance

Question 11

Cerebellum provide necessary _______________to motor outputs for flexibility and precision of movement.

Answer 11

modulation

Question 12

Hindbrain consists of?

Answer 12

Cerebellum, Pons, Medulla

Question 13

The cerebellar cortex consists of _____ layers, with regular and repetitive circuitries across the layers. Name the layers

Answer 13

3 
(High to low) 
1. Molecular layer 
2. Purkinje layer
3. Granular layer

Question 14

Briefly describe the arrangement of the circuitries in the cerebellar layers.

Answer 14

Input:

• mossy fiber
• climbing fiber (from inf. olivary nucleus > purkinje cells)

Intermediate:
- Granule cell and other cell types (part of purkinje cells)

Output: Purkinje cell

Question 15

Vestibulocerebellum is associated with the ____________ lobe.

Answer 15

Flocculonodular

Question 16

What is the main function of spinocerebellum?

Answer 16

• For comparing the expected/desired state and the actual sensory/ muscle and joint status
• correction of motor command

Question 17

What are the 2 afferents of spinocerebellum? What are their respective functions?

Answer 17

1. VSCT: receive signals from interneurons, CPG and descending motor pathway (direct copy of descending signals from motor cortex)

> > > generation of expected sensory

2. DSCT: from Clarke’s nucleus/ accessory nucleus (cuneocerebellar pathway)

> > > generation of actual sensory

Question 18

Spinocerebellum receiving afferent from VSCT is for generating ________ sensory.

Answer 18

expected

Question 19

Spinocerebellum receiving afferent from DSCT is for generating ________ sensory.

Answer 19

actual

Question 20

Efferent of spinocerebellum?

Answer 20

Brainstem nuclei (spinal interneurons)

Question 21

______________ (part of cerebellum) is involved in the motor planning and precise timing of the movement (modifier of motor signals).

Answer 21

Cerebrocerebellum/ Pontocerebellum

Question 22

The cerebellum modulate and refine activities of spinal cord , cerebral cortex and brainstem through loops.
Examples of loops? (not very important)

Answer 22

1. Vestibular nuclei
   > vestibulocerebellum
   > fastigal nucleus
   > vestibular nuclei
2. Cortex > pontine nucleus
   > pontocerebellum
   > dentate + interpositus nucleus > red nucleus/ thalamus
   > cortex

Question 23

___________ (part of the cerebellum) is involved in the feedback control in motor execution.

Answer 23

Spinocerebellum

Question 24

Cerebrocerebellum is involved in ____________ and ____________of movement.

Answer 24

motor planning;

precise timing

Question 25

What is ataxia?

Answer 25

lack of coordination during execution of multi-joint movement

Question 26

What are the movement deficits in cerebellar diseases? Examples?

Answer 26

Errors in both motor planning and execution 1. Range of movement errors (finger to nose test) 2. Patterned movement error 3. Delayed movement