A08 - Posture, Balance and Gait

Question 1

Which structures border the cerebellum superiorly and inferiorly?

Answer 1

• The fourth ventricle is inferior to the cerebellum.

- The tentorium cerebelli is superior to the cerebellum, separating it from the occipital lobe.

Question 2

To which embryological division of the brain does the cerebellum belong?

Answer 2

The hindbrain (rhombencephalon).

Question 3

Describe the layers of the cerebellum.

Answer 3

• The surface / cortex consists of grey matter that is covered by folds / folia. It can be further divided into 3 layers:

1 - Molecular layer.

2 - Purkinje layer.

3 - Granular layer.

• The centre / medulla is composed of white matter, in which four pairs of cerebellar nuclei are embedded.

Question 4

List the phylogenetic divisions of the cerebellum.

Which is the oldest division?

Answer 4

1 - Paleocerebellum.

2 - Neocerebellum.

3 - Archicerebellum (oldest).

Question 5

What is the cerebellar vermis?

Answer 5

The cerebellar vermis is the structure that separates the hemispheres of the cerebellum by passing down the midline of the paleocerebellum, which comprises the central region of the cerebellum.

Question 6

In which structure is the archicerebellum contained?

Answer 6

The archicerebellum is contained within the flocculonodular lobe.

Question 7

List the functional divisions of the cerebellum and their corresponding phylogenetic and anatomical divisions in the cerebellum.

Answer 7

Functional - phylogenetic - anatomical:

1 - Vestibulocerebellum - archicerebellum - flocculonodular lobe.

2 - Spinocerebellum - paleocerebellum - vermis and paravermis.

3 - Pontocerebellum - neocerebellum - lateral hemispheres.

Question 8

What is the function of the vestibulocerebellum?

Answer 8

The vestibulocerebellum is concerned with the maintenance of balance.

Question 9

What is the function of the spinocerebellum?

Answer 9

The spinocerebellum is concerned with the influence of muscle tone and posture.

Question 10

What is the function of the pontocerebellum?

Answer 10

• The pontocerebellum is concerned with muscle coordination, including trajectory, speed and force of movements.
• It also compares intended movement with actual movement.

Question 11

From which area of the CNS does the vestibulocerebellum receive afferent input?

What is the name of the fibres that carry this afferent information?

Do these fibres decussate?

Through which peduncle do these afferent fibres enter the cerebellum?

Answer 11

• The vestibulocerebellum receives afferent input from the vestibular nuclei of CN VIII.
• This information is conveyed through vestibulocerebellar fibres.
• Vestibulocerebellar fibres do not decussate before synapsing in the vestibulocerebellum.
• Vestibulocerebellar fibres enter the cerebellum through the inferior cerebellar peduncles.

Question 12

From which area of the CNS does the spinocerebellum receive afferent input?

What is the name of the fibres that carry this afferent information?

Do these fibres decussate?

Through which peduncle do these afferent fibres enter the cerebellum?

Answer 12

• The spinocerebellum receives afferent input from the spinal cord.
• This information is conveyed through spinocerebellar fibres.
• Spinocerebellar fibres do not decussate before synapsing in the spinocerebellum.
• Spinocerebellar fibres enter the cerebellum through the superior and inferior cerebellar peduncles.

Question 13

From which area of the CNS does the pontocerebellum receive afferent input?

What is the name of the fibres that carry this afferent information?

Do these fibres decussate?

Through which peduncle do these afferent fibres enter the cerebellum?

Answer 13

• The pontocerebellum receives afferent input from the pontine nuclei of the pons.
• This information is conveyed through pontocerebellar fibres.
• Pontocerebellar fibres decussate before synapsing in the pontocerebellum.
• Pontocerebellar fibres enter the cerebellum through the middle cerebellar peduncles.

Question 14

Give an example of a source of afferent information to the cerebellum other than the vestibular nuclei, spinal cord and pontine nuclei.

What is the name of the fibres that carry this afferent information?

Which cerebellar nucleus receives this afferent information?

Answer 14

• The cerebellum receives afferent input from the inferior olivary nucleus.
• This information is conveyed through through olivocerebellar fibres.
• The inferior olivary nucleus synapses at the dentate nucleus in the neocerebellum.

Question 15

In which area of the cerebellum do afferent fibres terminate?

Answer 15

Afferent fibres terminate in the cortex of their respective functional division.

Question 16

Through which structure do afferent fibres enter the cerebellum?

Answer 16

Afferent fibres enter the cerebellum through the cerebellar peduncles.

Question 17

What is the name of the afferent fibres entering the cerebellum once they pass through the peduncles?

Answer 17

• After passing through the peduncles, afferent fibres become either mossy or climbing fibres, depending on their origin.
• All afferents originating from anywhere other than the inferior olivary nucleus travel as mossy fibres.
• Afferents originating from the inferior olivary nucleus travel as climbing fibres.

Question 18

In which layer of the cerebellar cortex do mossy fibres terminate?

With which cells do they synapse?

What do these cells do?

Answer 18

• Mossy fibres branch to supply several folia in the granular layer.
• Here, the mossy fibres synapse with granule cells, which then provide two parallel fibres that synapse at the molecular layer.
• The mossy fibres also give rise to axon collaterals that synapse with the cerebellar nuclei.

Question 19

In which layer of the cerebellar cortex do climbing fibres terminate?

With which cells do they synapse?

What do these cells do?

Answer 19

• Climbing fibres synapse in the Purkinje layer.
• They supply input to Purkinje cells, which then provide inhibitory input to cerebellar nuclei.
• The climbing fibres also give rise to axon collaterals that directly excite neurones of the cerebellar nuclei.

Question 20

What is the arbor vitae?

Answer 20

• ‘Tree of life’ - arbor vitae is the cerebellar white matter.
• It brings afferent and efferent information to and from the cerebellum.

Question 21

List the nuclei contained within the paleocerebellum.

How many of each nuclei are contained in each hemisphere?

Answer 21

1 - Globose nuclei (2 per hemisphere).

2 - Emboliform nuclei (1 per hemisphere).

Question 22

List the nuclei contained within the neocerebellum.

How many of each nuclei are contained in each hemisphere?

Answer 22

Dentate nuclei (1 per hemisphere).

Question 23

List the nuclei contained within the archicerebellum.

How many of each nuclei are contained in each hemisphere?

Answer 23

Fastigial nuclei (1 per hemisphere).

Question 24

What is the greatest source of afferent input to the cerebellar nuclei?

Answer 24

The greatest source of afferent input to the cerebellar nuclei is the purkinje cells of the cerebellar cortex.

Question 25

What is the function of the cerebellar nuclei?

Answer 25

The cerebellar nuclei integrate information and constitute the primary source of efferent fibres from the cerebellum.

Question 26

List the areas of the brain to which efferent fibres originating in the dentate nuclei project.

What is their effect here?

Through which structure do these efferent fibres leave the cerebellum?

Do these fibres decussate?

Answer 26

The dentate nucleus gives efferent fibres to:

1 - The contralateral red nucleus, where they influence the rubrospinal tract.

2 - The ventral lateral nucleus of the thalamus, where they influence fibres projecting to the motor cortex.

• The efferent fibres leave the cerebellum through the superior cerebellar peduncle.
• The efferent fibres decussate in the caudal midbrain before reaching the red nucleus and VLNT.

Question 27

List the areas of the brain to which efferent fibres originating in the globose and emboliform nuclei project.

What is their effect here?

Through which structure do these efferent fibres leave the cerebellum?

Do these fibres decussate?

Answer 27

• Efferent fibres originating in the globose and emboliform nuclei project to the contralateral red nucleus.
• Here, they influence the rubrospinal tract.
• The efferent fibres leave the cerebellum through the superior cerebellar peduncle.
• The efferent fibres decussate before reaching the red nucleus.

Question 28

List the areas of the brain to which efferent fibres originating in the fastigial nuclei project.

What is their effect here?

Through which structure do these efferent fibres leave the cerebellum?

Do these fibres decussate?

Answer 28

1 - Back to the vestibular nuclei (remember, this is the source of afferent input to the vestibulocerebellum), where they influence the vestibulospinal tract.

2 - The reticular formation, where they influence the reticulospinal tract.

• The efferent fibres leave the cerebellum through the inferior cerebellar peduncles.
• Most of the efferent fibres decussate before reaching the vestibular nuclei and reticular formation, but some do not.

Question 29

Summarise the paleocerebellum by listing:

1 - The functional division that primarily consists of the paleocerebellum.

2 - The nuclei involved.

3 - The source of afferent information.

4 - The target of efferent information.

Answer 29

1 - The paleocerebellum constitutes most of the spinocerebellum.

2 - The paleocerebellum contains the globose and emboliform nuclei.

3 - Afferent fibres are from the spinal cord.

4 - Efferent fibres synapse at the red nucleus.

Question 30

Summarise the archicerebellum by listing:

1 - The functional division that consists of the archicerebellum.

2 - The nuclei involved.

3 - The source of afferent information.

4 - The target of efferent information.

Answer 30

1 - The archicerebellum alone constitutes the vestibulocerebellum.

2 - The archicerebellum contains the fastigial nuclei.

3 - Afferent fibres are from the vestibular nuclei.

4 - Efferent fibres synapse at the vestibular nuclei and the reticular formation.

Question 31

Summarise the neocerebellum by listing:

1 - The functional division that primarily consists of the paleocerebellum.

2 - The nuclei involved.

3 - The source of afferent information.

4 - The target of efferent information.

Answer 31

1 - The neocerebellum constitutes most of the pontocerebellum.

2 - The neocerebellum contains the dentate nuclei.

3 - Afferent fibres are from the pontine nuclei.

4 - Efferent fibres synapse at the red nucleus and ventral lateral nucleus of the thalamus.