Week 8 - cerebellum

Question 1

What is the cerebellum?

Answer 1

prominent hindbrain structure - one of the most recognisable regions of the brain due to its shape and location

Question 2

What are folia?

Answer 2

gyro formations of the cerebellum

Question 3

What is the function of the cerebellum?

Answer 3

• detects differences in motor error
• aids motor cortex in producing accurate and smooth movements by modulating and refining motor cortex commands using feedback form proprioceptors and other sensory organs
• involved in sensorimotor coordination

Question 4

name the three lobes the cerebellum can be anatomically divided into

Answer 4

• anterior lobe
• posterior lobe
• flocculonodular lobe

Question 5

Does the cerebellum initiate movement?

Answer 5

no - detects differences in motor error between an intended movement and the actual movement

Question 6

is the cerebellum of a cow longer than of a human?

Answer 6

yes

Question 7

What are the major components of the cerebellum?

Answer 7

• cerebelar cortex
• deeper cerebellar nuclei
• cerebellar peduncles

Question 8

Subdivide the cerebellar cortex into its three functional zones based on differences in their sources of input

Answer 8

1. cerebrocerebellum
2. spinocerebellum
3. vestibulocerebellum

Question 9

What does the cerebrocerebellum comprise?

Answer 9

most lateral cerebellar hemisphere
largest subdivision

Question 10

What does the spinocerebellum comprise of?

Answer 10

• comprises anterior lobe and vermis
• occupies median and paramedic zone of cerebellar hemispheres

Question 11

What does the vestibulocerebellum comprise of?

Answer 11

• caudal inferior lobes include
• flocculus and nodulus

Question 12

From what areas does the cerebrocerebellum receive its inputs?

Answer 12

indirectly from the cerebral cortex

Question 13

What is the function of the cerebrocerebellum?

Answer 13

regulating highly skilled movements initiated by the motor cortex eg. speech, voluntary movement of arms and hands, hand eye coordination

Question 14

From what areas does the spinocerebellum receive its inputs?

Answer 14

directly form the spinal cord

Question 15

What is the function of the spinocerebellum?

Answer 15

regulation of muscle tone and movement of distal muscles eg. arm and legs

Question 16

From what areas does the vestibulocerebellum receive its inputs?

Answer 16

from vestibular nuclei in brainstem and processes vestibular information

Question 17

What is the function of the vestibulocerebellum?

Answer 17

regulation of the vestibule-ocular reflex - ensure stability of gaze, and movements maintaining posture and balance of the head and body

Question 18

name the three deep cerebellar nuclei

Answer 18

• dentate, interposed, fastigial nucleus

Question 19

Where are all in/out puts to the cerebellar cortex relayed to?

Answer 19

• doesn’t have ires input form or output to rest of brain, all in/outputs relayed through deep cerebellar nuclei

Question 20

name the three cerebellar peduncles

Answer 20

superior, middle, inferior

Question 21

what is the function of the cerebellar peduncles?

Answer 21

make connections between the cerebellum and other parts of the nervous system

Question 22

What does the superior cerebellar peduncle comprise?

Answer 22

output fires projecting form deep cerebellar nuclei to midbrain structures (eg. primary motor cortex)

Question 23

What does the middle cerebellar peduncle comprise?

Answer 23

comprises input fibres projecting to the cerebellum largely from base of the pons

Question 24

What does the inferior cerebellar peduncle comprise?

Answer 24

comprises input fibres projecting to the cerebellum from the spinal cord and vestibular nuclei

Question 25

From what three regions does the cerebellum receive projections?

Answer 25

cerebral cortex sensory pathways (spinal cord) Brian stem

Question 26

Where do projections form the cerebral cortex go to in the cerebellum?

Answer 26

- largest input - cortical input going to cerebrocerebellum

Question 27

Do cortical axons project directly into the cerebellum?

Answer 27

no - synapse on nucleus in pons (pontine nucleus) located on same side of brainstem as hemisphere of origin axons of pontine are transverse pontine fibres, cross midline and enter cerebellum via middle cerebellar peduncle

Question 28

How do sensory pathways project to the cerebellum?

Answer 28

- vestibular axons from 8th CN and axons form vestibular nuclei in medulla project to vesibulocerebellum - relay neurons in dorsal nucleus of Clarke in spinal coord + external cuneate nucleus of caudal medulla send their axons to spino-cerebellum

Question 29

How does the brainstem project to the cerebellum?

Answer 29

- receives modulatory input form inferior olivary nucleus in brainstem from structures such as cerebral cortex and red nucleus - olivo-cerebellar axons exit medially form inferior live and enter cerebellum via inferior cerebral peduncle

Question 30

explain output projections form the cerebellum to the cortical motor systems

Answer 30

- from dentate nucleus and interposed nucleus -> relay in VL thalamus complex -> project to motor cortex

Question 31

what do lower motor neurons in medial ventral from contribute to?

Answer 31

control of axial and proximal limb musculature

Question 32

name the three layers of the cerebellar cortex

Answer 32

1. molecular layer 2. Purkinje cell layer 3. granule cell layer

Question 33

Describe the molecular layer of the cerebellum

Answer 33

contains apical dendrites of Purkinje cells, m parallel fibres form granule cells, basket cells and stellate cells

Question 34

Describe the Purkinje cell layer of the cerebellum

Answer 34

comprises middle layer of cerebellar cortex and contains Purkinje cell body

Question 35

describe the granule cell layer of the cerebellum

Answer 35

contains granule cell bodies

Question 36

What is the ultimate destination of afferent pathways to cerebellar cortex?

Answer 36

Purkinje cells

Question 37

Is input from cerebral cortex to Purkinje cells direct or indirect?

Answer 37

indirect

Question 38

What are mossy fibres?

Answer 38

axons form pontine nuclei and most other sources of cerebellar input from brainstem and spinal cord

Question 39

Where do mossy fibres synapse?

Answer 39

on neurons in deeper cerebellar nuclei and on granule cells in granule cell layer

Question 40

What do granule cells give rise to?

Answer 40

parallel fibres that ascend to the molecular layer of the cerebellar Cortex

Question 41

How is the molecular layer of the cerebellum structured?

Answer 41

- parallel fibres fork to form T-shaped branches that form excitatory synapses with the dendritic spines of Purkinje cells

Question 42

What do Purkinje cells do?

Answer 42

- receive direct modulatory input form climbing fires which arise in inferior olivary nucleus - modulate effectiveness of parallel fibre connections - project to deep cerebellar nuclei

Question 43

What modulates inhibitory activity of Purkinje cells?

Answer 43

inputs form basket cells and stellate cells

Question 44

What is motor error correction?

Answer 44

- mediated by climbing fires that ascend form inferior olive to contact dendrites of Purkinje cells - climbing fibres modify efficacy of parallel fibre - Purkinje cell connection, producing long term changes in cerebellar output - motor learning