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Neuro 3050: Structure & Function of the Nervous System > 11/18 Cerebellum Lecture > Flashcards

11/18 Cerebellum Lecture Flashcards

1
Q

THE CEREBELLUM ACTS AS A

_____ .

A

COMPARATOR,
middle management

The cerebellum takes the command from the cerebral cortex and makes the fine adjustments needed for efficient motor function.

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2
Q

The cerebral cortex gives the command to initiate voluntary movement.

A

But, it doesn’t give any particular guidance on how to make the movement smooth and coordinated.
This is where the cerebellum comes in.

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3
Q

Neurons in the ____ carry proprioceptive information from the ____ via several different pathways to the cerebellum.

A

Neurons in the DRG carry proprioceptive information from the Muscle via several different pathways to the cerebellum.

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4
Q

The Pathway

A

The cerebral cortex sends a message to motor neurons in the spinal cord. These innervate the muscle and it contracts.

There is a parallel pathway from the cortex to the cerebellum. This is not a direct pathway and involves relays in the Basilar Pons.

Now the cerebellum knows what the cortex is planning.
It needs some additional information, however, before making adjustments.

It needs to know something about where the body is in space, as well as the status of the muscles at an instant in time (i.e., proprioceptive information).

Neurons in the dorsal root ganglia carry proprioceptive information from the muscle via several different pathways to the cerebellum.

Now the cerebellum can compare the command from the cortex with the current status of the muscle.

The output of the cerebellum is to brainstem nuclei that project to the spinal cord to adjust the activity of motor neurons as necessary.

As middle management, the cerebellum also projects back to the cortex in another indirect route.

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5
Q

The output of the cerebellum is to _____ that project to the _____ to adjust the activity of motor neurons as necessary.

A

The output of the cerebellum is to Brainstem Nuclei that project to the Spinal Cord to adjust the activity of motor neurons as necessary.

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6
Q

FUNCTION OF THE CEREBELLUM:

Cerebellum receives sensory information from ____ in muscles and joints and other nuclei in the ____ which provide information about the state of contraction of the individual muscles or the position of the body in space.
Uses this information to do 6 things….

A

Cerebellum receives sensory information from proprioceptors in muscles and joints and other nuclei in the brainstem which provides information about the state of contraction of the individual muscles or the position of the body in space.

Uses this information to:

  1. Control posture & balance
  2. Coordinate sequential movements.
  3. Coordinate rapidly alternating movements (Diadocokinesis).
  4. Regulate Reflexes
  5. Involved in motor learning
  6. Plays a role in higher cognitive functions (e.g., attention, planning movements).
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7
Q

Dysmetria

A

Inability to fix the range of movement in muscular activity.

Movements are made with more force than necessary.

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8
Q

Ataxia

A

Inability to coordinate movement

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9
Q

Intention Tremor

A

A tremor that gets worse when a person is moving.

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10
Q

Diadocokinesis

A

the normal ability to perform rapidly alternating muscular movements, such as flexion and extension.

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11
Q

The Cerebellum controls posture & balance through connections with ______ .

A

the vestibular system

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12
Q

the cerebellum has several functions …..

A

It controls posture and balance through connections with the vestibular system.

One function of the cerebellum is controlling eye movements.
Executing Complex, Smooth Pursuit Eye Movements

It is essential for performing sequential movement, such as reaching out for something requiring contraction of shoulder, elbow, wrist, and digital muscles in a specific sequence.

Several terms are applied when movement is not smooth:

Dysmetria means the range of movements is not properly set. Movements may be made very fast, or with more force than necessary.

Ataxia is the inability coordinate movement.

With cerebellar lesions, there may be an Intention Tremor as the limb moves back and forth trying to home in on a target.

The cerebellum is essential for performing alternating movements like using a screwdriver or opening a door.

It regulates reflexes.
In primates, in particular, it is involved in motor learning. The first time you ride a bike you may be very clumsy, but ultimately you become very smooth and coordinated. That’s because there are circuits that allow the cerebellum to learn and become more efficient.

Finally, it plays a role in higher cognitive functioning, such as attending to our environment or in planning movements.

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13
Q

Cerebellar lesion that effects the eye:

A

Saccadic overshoot

Dysmetria

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14
Q

Saccadic overshoot

Dysmetria

A

Cerebellar lesion effecting the eye

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15
Q

Execute Complex, Smooth Pursuit Eye Movements

A

One function of the cerebellum is controlling eye movements.

An example of an individual following a moving target with their eyes.

The object enters their field of view and the eyes follow it smoothly.

Then the target stops abruptly.
The normal response is for the eyes to continue in anticipation of the object continuing along its path.

Normally, the eyes will rapidly fixate on the now stationary target.

In individuals with a cerebellar lesion, the eyes overshoot in the opposite direction, and then come back and so forth until they ultimately land on the object.
This is an example of dysmetria in which the eyes move through a greater range of motion than necessary.

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16
Q

4 CEREBELLAR NUCLEI: WITHIN THE WHITE MATTER CORE OF CEREBELLUM

A

FASTIGIAL N.
DENTATE N.

The 2 INTERPOSED NUCLEI:
GLOBOSE N.
EMBOLIFORM N.

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17
Q

Cerebellar Peduncles

Details

A 
Cerebellar Peduncles (Inferior, Middle, Superior) = 
Fiber tracts that connect cerebellum to brainstem.

They are made up of:

  1. Axons entering the cerebellum that originate in the spinal cord or other parts of the brainstem (e.g., medulla, pons). These axons will terminate in the cerebellar nuclei and cerebellar cortex.
  2. Axons leaving the cerebellum that originate in one of the cerebellar nuclei. These are destined for brainstem targets.
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18
Q

Middle Cerebellar Peduncle

A

Only carries information TO cerebellum.

MCP connects the pons to the cerebellum.

Largest peduncle.

Exclusively an input pathway.

Pathway crosses in the pons.

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19
Q

Inferior Cerebellar Peduncle

A

Mostly carries information TO cerebellum.

Carries some info from the cerebellum

ICP connects the spinal cord & medulla to the cerebellum.

Mainly an input pathway.

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20
Q

Superior Cerebellar Peduncle

A

Mostly carries information FROM cerebellum.

Carries some info to the cerebellum.

SCP connects the cerebellum to the brainstem and diencephalon.

Axons leaving the cerebellum cross in the midbrain.

Major output pathway from the cerebellum to the brainstem.

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21
Q

The Largest Peduncle

A

Middle Cerebellar Peduncle

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22
Q

The smallest of the peduncles is the _____ .

A

inferior cerebellar peduncle (ICP).

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23
Q

Major output pathway from the cerebellum to the brainstem?

A

Superior Cerebellar Peduncle

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24
Q

Connects the pons to the cerebellum.

A

Middle Cerebellar Peduncle

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25
Q

Mainly an input pathway.

A

Inferior Cerebellar Peduncle

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26
Q

Connects the spinal cord and medulla to the cerebellum.

A

Inferior Cerebellar Peduncle

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27
Q

CEREBELLAR PEDUNCLES:

Long Summary

A

The smallest of the peduncles is the inferior cerebellar peduncle (ICP).
It extends from the rostral medulla to the cerebellum.
This is a pathway that brings information into the cerebellum from the spinal cord and medulla.
It courses a bit inferior to the MCP.

The largest cerebellar peduncle is the middle cerebellar peduncle (MCP).
The middle cerebellar peduncle connects the pons and the cerebellum.
It also is an input pathway carrying axons from neurons in the basilar pons into the cerebellum.

The superior cerebellar peduncle arises from the rostral pole of the cerebellum and courses toward the midbrain.
This is the major output pathway of the cerebellum.

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28
Q

The major output pathway of the cerebellum.

A

superior cerebellar peduncle

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29
Q

CEREBELLAR CORTEX

A

The cerebellar cortex is highly infolded forming deep ridges. If it was completely unfolded it would extend up to 1 meter in length.
This clearly reflects the importance of this structure in brain function.

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30
Q

Primary fissure

A

Divides the cerebellum into Anterior and Posterior lobes.

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31
Q

Flocculonodular lobe

A

The most primitive part of the cerebellum.

very small lobe.

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32
Q

Rostral-Caudal Organization

A

Primary fissure: Divides the cerebellum into Anterior and Posterior lobes.

On the inferior view, a third very small lobe is defined as the Flocculonodular lobe; most primitive part of the cerebellum.

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33
Q

Prime example of a disabled cerebellum:

A

a drunk person

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34
Q

Vermis

A

Narrow midline portion that extends through all lobes.

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35
Q

3 cerebellar nuclei appear to align with the 3 sagittal divisions of the cerebellar cortex.

A

Fastigial nucleus in the vermis, i

Inerpositus nuclei in the medial hemisphere

Dentate nucleus in the lateral hemisphere.

36
Q

The most medial cerebellar nuclei

A

Fastigial nuclei

37
Q

ORGANIZATION IN PROJECTION FROM CORTEX TO CEREBELLAR NUCLEI:

FLOCCULONODULAR LOBE AND VERMIS

A

FASTIGIAL NUCLEUS

38
Q

ORGANIZATION IN PROJECTION FROM CORTEX TO CEREBELLAR NUCLEI:

MEDIAL HEMISPHERE

A

INTERPOSED NUCLEI

GLOBOSE & EMBOLIFORM

39
Q

ORGANIZATION IN PROJECTION FROM CORTEX TO CEREBELLAR NUCLEI:

LATERAL HEMISPHERE

A

DENTATE NUCLEUS

40
Q

CEREBELLAR HISTOLOGY

A

PIAL SURFACE

WHITE MATTER CORE

41
Q

PIAL SURFACE

A

MOLECULAR LAYER
PURKINJE CELL LAYER
GRANULE CELL LAYER

42
Q

PURKINJE CELL LAYER

A

Only cell with an axon that leaves the cerebellar cortex.

Terminates in one of the cerebellar nuclei; dependent on sagittal zone in which it is located.

Inhibitory to target neurons in the cerebellar nuclei (GABAergic).

43
Q

GRANULE CELL

A

Parallel fibers are intrinsic to the cortex.

Excitatory to Purkinje cells

These cells are interesting in that they stay in the sagittal plane.

44
Q

BASIC CEREBELLAR CIRCUIT

A

Cerebellar Cortex: Perkinje cells

  • –> Cerebellar Nuclei
  • –>Brainstem Nuclei, Thalamus
  • –> Spinal cord, Cerebral cortex
45
Q

Expounded CEREBELLAR CIRCUIT

A

Cerebellar Cortex: Perkinje cells.
(This projection has a precise sagittal organization. Vermal PK cells project to fastigial nucleus, medial hemisphere to interposed, and lateral hemisphere to dentate.)

—> Cerebellar Nuclei
Axon leaves the cerebellum via the superior cerebellar peduncle

  • –> Brainstem Nuclei, Thalamus
    (e. g., Reticular Formation, Red Nucleus, Vestibular Nuclei).

—> Spinal cord, where they regulate alpha and gamma motor neurons.
Cerebral cortex to provide feedback to motor neurons giving rise to corticospinal tract.

46
Q

CEREBELLAR CIRCUIT:

long version

A

At the simplest level, are the neurons in the cerebellar nuclei. These neurons have axons that leave the cerebellum. They synapse on neurons in several different brainstem nuclei that in turn give rise to the descending pathways, such as the reticular formation and vestibular nuclei. They are excitatory to these neurons.

These brainstem nuclei, in turn, project to the spinal cord, where they synapse on interneurons that regulate alpha motor neurons and thus motor activity.

This is a nice basic circuit, but it needs to be regulated. Nuclear neurons are very active and sometimes they have to be shut down. That is the role of the Purkinje cell.

Purkinje cells and nuclear neurons receive the same information, although at slightly different times. The axons of these neurons leave the cerebellar cortex, and inhibit neurons in the cerebellar nuclei.

So what regulates the activity of Purkinje cells? Afferents from different regions of the CNS carrying information either from the periphery or from the cerebral cortex.

47
Q

AFFERENT INPUTS TO CEREBELLUM

A

MOSSY FIBERS

CLIMBING FIBERS

48
Q

MOSSY FIBER

A

Source: Neurons Located In Various Nuclei In The Spinal Cord And Brainstem
(e.g., Vestibular Nuclei, Pontine Nuclei, Neurons in the spinal cord).

Morphology: Complex Large Terminals (10-12 uM).

Excitatory To Granule Cells (Glutamate)

Mossy fibers synapse on neurons in the Granule Cell Layer.
The granule cell sends its axon into the molecular layer where they terminate on Purkinje cells.
These axons are called Parallel Fibers.

49
Q

mossy fiber details

A

A histological preparation of a mossy fiber (MF).
The long black structure is the MF axon that is connected to a neuron located outside the cerebellum.
This axon entered the cerebellum through either the inferior or middle cerebellar peduncle and coursed to the cortex after giving off a branch in the cerebellar nuclei.
Once it reached the cerebellum, the axon terminals were formed.
Mossy fibers originate from neurons located throughout the CNS, including Clarke’s Nucleus in the spinal cord and the external cuneate nucleus in the brainstem.
Remember: these nuclei relay proprioceptive information from muscles to the cerebellum.
Mossy fiber afferents also come from neurons located in the vestibular nuclei, which are essential for fulfilling the role of the cerebellum in balance.
Finally, the pontine nuclei in the basilar pons also are a source of afferents to the cerebellum.
These relay information from the cerebral cortex.

Thus, mossy fibers are essential components of the “comparator circuitry.”
Morphogically, the axon terminals are large, measuring 10-12 um in diameter.
Mossy fibers are excitatory to neurons in the granule cell layer.
Neurons in this layer relay the excitatory information to the Purkinje cell.
The axons of these second order neurons are called Parallel Fibers.

50
Q

CLIMBING FIBER

A

Sole Source: Inferior Olivary Complex

Characteristics:
One-to-one Relationship With Purkinje Cell.
Courses Along Primary Dendrites Giving Off Varicosities that Synapse With Primary and Secondary Dendrites.

Powerful Excitatory Input To Purkinje Cells (Glutamate)

Climbing Fibers “Climb” Along The Primary And Secondary Dendrites Of Purkinje Cells.

51
Q

CLIMBING FIBER

detailsss…

A

A climbing fiber looks very different from a mossy fiber. These axons arise from neurons located in only 1 place – the inferior olivary nucleus in the medulla. No other areas of the brain give rise to climbing fibers.
These axons have unique relationship with Purkinje cells. They form a 1 to 1 relationship. That is, Purkinje cells receive input from only 1 climbing fiber. There is no convergence of information from different olivary neurons.
This is unique and there are no other neurons with this type of relationship.
Unlike Mossy fibers that have a relay in the granule cell layer, climbing fibers go directly to the Purkinje cell where the literally climb along the dendrites of the neuron.
They are a powerful source of excitation to the Purkinje cell releasing glutamate.
Because it is a one to one relationship, all of the terminals release their transmitter at the same time depolarizing the entire dendritic tree.
This is important.

52
Q

AFFERENTS TO THE CEREBELLUM

Longggg version

A

Inputs.
There are 2 anatomically distinct afferents that project to the cerebellum: mossy fibers and climbing fibers.

As both afferents enter the cerebellum, they give off branches to the cerebellar nuclei that are excitatory to nuclear neurons.
The same afferents continue on to the cortex.
This is where the 2 afferent systems differ.

Climbing fibers project directly to Purkinje cells and provide a direct, powerful excitation of these neurons.

The information carried by mossy fibers does not go directly to Purkinje cells, but is relayed by the granule cell.
The axon of the granule cell, the parallel fiber, enters the molecular layer, runs parallel from medial to lateral (hence its name) passing through the dendrites of numerous Purkinje cells. Synaptic junctions between parallel fibers and the spines of Purkinje cells are excitatory.

53
Q

Mossy Fiber Input to Sagittal Zones of the Cerebellum

A

????

54
Q

FUNCTIONAL DIVISIONS OF THE CEREBELLUM

A

Spinocerebellum
Pontocerebellum
Vestibulocerebellum

55
Q

VESTIBULOCEREBELLUM

A

FLOCCULONODULAR LOBE

Function: Control balance and equilibrium (in trunk and axial muscles especially).

Input: Neurons related to vestibular system.
Axons of these neurons enter cerebellum via ICP.

Neurons in the Fastigial nucleus.
Purkinje cells in flocculonodular lobe.

Neurons in the vestibular nuclei which project to spinal cord.
Excitatory to interneurons that regulate activity of α and λ motor neurons in ventral horn of spinal cord.

56
Q

SPINOCEREBELLUM

A

Vermis and adjacent medial portion of hemisphere.

FUNCTION: Control muscle tone and muscle synergy (coordination across and between joints)

Input: Proprioceptors in muscles via nuclei in spinal cord and brainstem.
Carry information on position or tension in muscle or tendon.
This is UNCONSCIOUS PROPRIOCEPTION.

Interposed Nuclei, Fastigial Nucleus, Purkinje cells in the vermis, Purkinje cells in the medial hemisphere

57
Q

SPINOCEREBELLUM:

Interposed Nuclei

A

Interposed Nuclei

  • —> Axons leave via SCP and synapse on neurons in Red Nucleus or Ventral Lateral Thalamic nucleus (NOT the VPL).
  • –> Spinal cord (rubrospinal tract) or back to motor cortex (thalamocortical axons)
58
Q

SPINOCEREBELLUM:

Fastigial Nucleus

A

Fastigial Nucleus

  • –> Axons leave via ICP and synapse on neurons in reticular formation
  • –> Spinal cord to interneurons to control motor neurons via reticulospinal tract.
59
Q

ASCENDING AXONS FROM THE INTERPOSED NUCLEI

A

Some axons terminate in Red Nucleus.
These neurons give rise to the rubrospinal tract that descends to contralateral spinal cord.
Returns to same side of body from which PSCT originated. Cerebellum controls ipsilateral side of body.

Remaining axons in SCP continue on to contralateral VL complex of thalamus.
Neurons in the thalamus project to pyramidal neurons in the motor cortex to provide feedback on state of movement.
Axons of pyramidal neurons project to spinal cord via corticospinal tract.

60
Q

ASCENDING AXONS FROM INTERPOSED NUCLEI

LONG VERSION

A

Ascending axons arising from the interposed nuclei.
These axons leave the cerebellum via the SCP, cross in the rostral pons in the decussation of the SCP and ascend to the midbrain and diencephalon.
The majority of axons terminate in the Red Nucleus to modulate the activity of neurons giving rise to the rubrospinal tract.

There is an influence of the cerebellum on neurons that project to the spinal cord to influence motor neurons in the ventral horn.
These axons return to the same side of the body from which proprioceptive information carried by the posterior spinocerebellar tract originated.

The cerebellum controls the ipsilateral side of the body.

Finally, a few axons continue to the thalamus where they terminate in the ventral lateral (NOT ventral POSTERIOR lateral) nucleus.
The axons of VL neurons project back to motor cortex to provide feedback to “the boss”. These neurons in the motor cortex project back to the spinal cord via the corticospinal tract.

61
Q

PONTOCEREBELLUM

A

= Lateral portion of hemisphere

FUNCTION:
Fine coordination of movement.
Planning and controlling movement, especially distally.

Input: Indirectly from neurons in cerebral cortex.
Neurons in cerebral cortex synapse on neurons in the basilar pons.
Neurons in the basilar pons cross the midline and project to the lateral part of the cerebellum via the MCP.

Dentate Nucleus
—> Majority of neurons in the dentate nucleus synapse on neurons in VA/VL thalamus that project to cortex (feedback to motor cortex) to influence corticospinal tract.

Purkinje cells in the lateral hemisphere synapse on neurons in the dentate nucleus. Inhibitory input (GABAergic)

62
Q

CORTICO-PONTO-CEREBELLAR INPUT

A

Cortical Input Derived From All Areas Of Cortex

Synapse On Pontine Neurons

Axons Of Pontine Neurons Cross Midline And Enter Contralateral Cerebellum Via MCP.

63
Q

CORTICO-PONTO-CEREBELLAR INPUT

Details

A

Input to the lateral hemisphere.

Axons from all areas of the cortex descend and synapse on neurons in the pontine nuclei located within the basilar pons.

The axons of these neurons cross the midline and form the large middle cerebellar peduncle which relays cortical information to the lateral hemisphere.

64
Q

PROJECTIONS OF DENTATE NUCLEUS

- LATERAL HEMISPHERE

A

Axons leave via ipsilateral SCP, decussate in rostral pons.

Tract continues from decussation and terminate in contralateral Red nNucleus.

Axons of olivary neurons cross the midline and project to the cerebellum as climbing fibers. Feedback loop between cerebellum red nucleus, and inferior olive.

Majority of axons continue on to VL/VA complex of thalamus. Neurons in the thalamus project to pyramidal neurons in the motor and premotor cortex to provide feedback on state of movement.

Axons of pyramidal neurons project to spinal cord via corticospinal tract.

65
Q

PROJECTIONS OF DENTATE NUCLEUS
- LATERAL HEMISPHERE

Dteails

A

The projection of the dentate nucleus is very similar to that of the interposed nuclei with the exception that there is not a descending limb.

The axons leave via the ipsilateral SCP and decussate in the rostral pons.
The Red Nucleus neurons that receive this input are NOT the ones that give rise to the rubrospinal tract!!!
Rather, these red nucleus neurons terminate in the Inferior Olive, the source of climbing fibers to the cerebellum.
Axons of olivary neurons cross the midline and project to the cerebellum as climbing fibers.

This pathway represents a feedback loop between the cerebellum, red nucleus, and inferior olive that regulates climbing fiber activity.

The majority of the dentate nucleus axons continue on to the VL nucleus of the thalamus.
These axons project to the motor cortex to provide feedback to neurons giving rise to the corticospinal tract.

66
Q

Flocculonodular Lobe:

ALL THE MAIN POINTS

A

FUNCTION:
Maintenance Of Equilibrium

MOSSY FIBER INPUT:
Vestibular Neurons

OUTPUT:
Fastigial Nucleus To Vestibular Nucleus

67
Q

Medial Hemisphere

A

FUNCTIONS:
- Descending Tract:
Postural Adjustments

  • Ascending Tract (Interposed):
    Via Rubrospinal And Corticospinal Tracts

MOSSY FIBER INPUT:

  • Spinal Cord
  • Reticular Formation
  • Pontine Nuclei (Relay from cerebral cortex)

OUTPUT:
Fastigial & Interposed Nuclei To:

Descending Tract:

  • Vestibular Nuclei (Fastigial)
  • Reticular Formation (Interposed)

Ascending Tract (Interposed):

  • Red Nucleus
  • VA/VL Thalamus
68
Q

Lateral Hemisphere

A

FUNCTION:
Planning & Programming of Voluntary Movements, esp. Learned, Skillful Movements that become More Rapid with Practice.

MOSSY FIBER INPUT:
Corticopontine Axons

OUTPUT:

  • Dentate Nucleus
  • Red Nucleus
  • VA/VL Thalamus
69
Q

CLIMBING FIBER INPUT:

INPUTS TO THE INFERIOR OLIVE

A
  • SPINAL CORD
  • CEREBRAL CORTEX
  • VESTIBULAR NUCLEI
  • RED NUCLEUS
  • RETICULAR FORMATION
  • CEREBELLUM
70
Q

CLIMBING FIBERS PLAY A ROLE IN ERROR DETECTION

A

Mossy Fibers, on the other hand, are more associated with normal, adapted-to movements.

71
Q

SUMMARY CEREBELLAR CIRCUIT:

PURKINJE CELLS

A

Only neurons with an axon that leaves the cerebellar cortex.

Role is to modulate the output of nuclear neurons.

72
Q

SUMMARY CEREBELLAR CIRCUIT:

A

Carry output of the cerebellum to brainstem nuclei and motor cortex.

Without nuclear neurons, cerebellum has no control over movements.

73
Q

SUMMARY CEREBELLAR CIRCUIT:

INPUT TO THE CEREBELLUM

A

Two afferent systems:
Mossy Fibers & Climbing Fibers

Collaterals of afferents to the cerebellum first synapse in the cerebellar nuclei before continuing on to the cerebellar cortex.

Purkinje cells in cortex project to areas of nuclei receiving same afferents.

74
Q

SUMMARY CEREBELLAR CIRCUIT:

There is a precise ____-to-____ _____ organization in the projection between the cerebellar ___ and the cerebellar ____.

A

medial-to-lateral sagittal

There is a precise medial to lateral sagittal organization in the projection between the cerebellar Cortex and the cerebellar Nuclei.

75
Q

SUMMARY CEREBELLAR CIRCUIT:

Fastigial nucleus

A

Flocculonodular lobe and Vermis

76
Q

SUMMARY CEREBELLAR CIRCUIT:

Globose & Emboliform nuclei (interposed nuclei)

A

Medial hemisphere

77
Q

SUMMARY CEREBELLAR CIRCUIT:

Dentate nucleus

A

Lateral hemisphere

78
Q

Collaterals of afferents to the cerebellum first synapse in the ____ before continuing on to the ____.

A

Collaterals of afferents to the cerebellum first synapse in the cerebellar nuclei before continuing on to the cerebellar cortex.

79
Q

OUTPUT AND FUNCTION OF CEREBELLAR NUCLEI:

A

The vast majority of axons arising from neurons in the cerebellar nuclei leave via the superior cerebellar peduncle.

The vast majority of neurons in the nuclei give rise to an excitatory output which projects to nuclei in brainstem that are directly involved in controlling movement (e.g., vestibular nuclei, red nucleus) or provide feedback to the cerebral cortex via the thalamus.

80
Q

ALCOHOL AS A NEUROTOXIN IN THE ADULT AND DEVELOPING CEREBELLUM

ACUTE CHANGES:

A

The effect is primarily on Purkinje cells in the anterior lobe.

  1. Effect is on voltage-sensitive ionic conductances.
  2. It augments the opening of Cl- channels by GABA leading to hyperpolarization of the Purkinje cell.

*Ethanol in alcoholic beverages takes the purkinje cells out of the curciut.
Purkinje cells are inbitory and have many GABA receptors.
This is why…..

81
Q

ALCOHOL AS A NEUROTOXIN IN THE ADULT AND DEVELOPING CEREBELLUM

CHRONIC USE:

A

CHRONIC USE CAUSES DEATH OF PURKINJE CELLS IN ANTERIOR LOBE.

Decreases levels of cGMP which changes cellular metabolism and alters cellular function.

82
Q

ALCOHOL AS A NEUROTOXIN IN THE ADULT AND DEVELOPING CEREBELLUM

ADULT CLINICAL SIGNS:

A
  1. Gait ataxia: stiff legged gait with small shuffling steps
  2. Increased tone in extensor muscles.
    (change in input to reticular formation and vestibular nuclei, which alters input to motor neurons.)
83
Q

ALCOHOL AS A NEUROTOXIN IN THE ADULT AND DEVELOPING CEREBELLUM

DEVELOPMENTAL EFFECTS:
CLINICAL SIGNS

A
  1. DELAYS IN MOTOR DEVELOPMENT
  2. PROBLEMS WITH FINE MOTOR TASKS
  3. TREMORS
  4. ATAXIA
84
Q

ALCOHOL AS A NEUROTOXIN IN THE DEVELOPING CEREBELLUM

DEVELOPMENTAL EFFECTS:
ANATOMICAL

A

DENDRITIC TREE HAS FEWER BRANCHES & SPINES

85
Q

AUTISM

A

AUTISM IS A DEVELOPMENTAL, NOT A PSYCHOLOGICAL, DISORDER WITH DEFICITS IN BRAINSTEM, MIDBRAIN, FRONTAL LOBE, AND CEREBELLUM

IN CEREBELLUM, OFTEN A DECREASE IN SIZE OF VERMAL LOBULES VI & VII.
ALSO SEE ABNORMAL LEVELS OF SEROTONIN.

86
Q

MOTOR vs ATTENTION REGIONS OF THE CEREBELLUM

A

THEORY: CEREBELLUM PROVIDES INPUT TO MOTOR-ATTENTIONAL AREAS OF BRAIN, SUCH AS RETICULAR FORMATION.

ONE STUDY HAS SHOWN THAT MOTOR CONTROL AND ATTENTION INDEPENDENTLY ACTIVATE DIFFERENT REGIONS OF THE CEREBELLUM.

ATTENTION AREA IS IN AREA IMMEDIATELY POSTERIOR TO PRIMARY FISSURE - AND ADJCENT HEMISPHERE (MOST RECENTLY EVOLVED AREAS OF CEREBELLUM)

THIS IS RELEVANT TO AUTISM AS A MAJOR PROBLEM IS THE INABILITY TO SHIFT ATTENTION IN A “COORDINATED” MANNER.

THIS SUGGESTS THE CEREBELLUM PLAYS A ROLE IN HIGHER COGNITIVE FUNCTION.

87
Q

THE CEREBELLUM OF MALE MUSICIANS IS 5% LARGER THAN THOSE OF MALE NON-MUSICIANS.

A

CONCEPT:

MANY YEARS OF PRECISE FINGER EXERCISE HAD STIMULATED EXTRA NEURAL GROWTH IN THE CEREBELLUM

Neuro 3050: Structure & Function of the Nervous System (29 decks)

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