Chapter 19 - Modulation of Movement by the Cerebellum

Question 1

In contrast to the upper motor neurons, the efferent cells of the cerebellum do not project directly to the local circuits of the brainstem and spinal cord that organize movement, nor do they contact the lower motor neurons that innervate muscles. Instead the cerebellum influences movements primarily by …

Answer 1

modifying the activity patterns of upper motor neurons.

Question 2

Anatomically, the cerebellum has two main gray matter structures. Which?

Answer 2

1. Cerebellar cortex on the surface

2. Deep cerebellar nuclei buried deep in the white matter of the cerebellum.

Question 3

What is the primary function of the cerebellum?

Answer 3

The primary function of the cerebellum is to detect the difference, or “motor error”, between an intended movement and the actual movement, and, through its influence over upper motor neurons, to reduce the error.

Question 4

The cerebellar hemispheres can be subdivided into three main parts based on differences in their sources of input. Which?

Answer 4

1. Cerebrocerebellum
2. Spinocerebellum
3. Vestibulocerebellum

Question 5

The cerebellar hemispheres can be subdivided into three main parts, cerebrocerebellum, spinocerebellum and vestibulocerebellum, based on what?

Answer 5

The cerebellar hemispheres can be subdivided into three main parts based on differences in their sources of input.

Question 6

The cerebrocerebellum receives its input indirectly from …

Answer 6

many areas of the cerebral cortex.

Question 7

The spinocerebellum receives its input directly from …

Answer 7

the spinal cord.

Question 8

The vestibulocerebellum receives its input directly from …

Answer 8

the vestibular nuclei in the brainstem.

Question 9

What seems to be the main feature of the cerebrocerebellum?

Answer 9

The cerebrocerebellum is concerned with the regulation of highly skilled movements, especially the planning and execution of complex spatial and temporal sequences of movement.

Question 10

What seems to be the main feature of the spinocerebellum?

Answer 10

The spinocerebellum is primarily concerned with the movement of disteal muscles, and the median strip of the spinocerebellum -the vermis - is primarily concerned with movements of proximal muscles.

Question 11

What seems to be the main feature of the vestibulocerebellum?

Answer 11

The vestibulocerebellum is primarily concerned with the vestibulo-ocular reflex and the regulation of movements that maintain posture and equilibrium.

Question 12

The connections between the cerebellum and other parts of the nervous system are made by three large pathways called .. .

Answer 12

the cerebellar peduncles.

Question 13

The x is by far the largest source of input to the cerebellum, and the major destination of this input is the Y.

Answer 13

The cerebral cortex is by far the largest source of input to the cerebellum, and the major destination of this input is the cerebrocerebellum.

Question 14

The input from the cerebral cortex to the Purkinje cells in the cerebellum is indirect. Neurons in the pontine nuclei receive a massive projection from the cerebral cortex and relay the information to the contralateral cerebellar cortex. The axons from the pontine nuclei - and most other sources of cerebellar input in the brainstem and spinal cord -are called …

Answer 14

The axons from the pontine nuclei - and most other sources of cerebellar input in the brainstem and spinal cord -are called mossy fibers because of the appearance of their synaptic terminals.

Question 15

The axons from the pontine nuclei - and most other sources of cerebellar input in the brainstem and spinal cord -are called mossy fibers because of the appearance of their synaptic terminals. Mossy fibers synapse on …

Answer 15

Mossy fibers synapse on neurons in the deep cerebellar nuclei and on granule cells in the granule cell layer of the cerebellar cortex.

Question 16

Mossy fibers synapse on neurons in the deep cerebellar nuclei and on granule cells in the granule cell layer of the cerebellar cortex. Cerebellar granule cells give rise to ..

Answer 16

Cerebellar granule cells give rise to axons called parallel fibers that ascend to the molecular layer of the cerebellar cortex.

Question 17

Cerebellar granule cells give rise to axons called parallel fibers that ascend to the molecular layer of the cerebellar cortex. The parallel fibers bifurcate in the molecular layer to form T-shaped branches that extend for several millimeters parallel to the orientation of the small cerebellar gyri (called folia); there, they form excitatory synapses with …

Answer 17

The parallel fibers bifurcate in the molecular layer to form T-shaped branches that extend for several millimeters parallel to the orientation of the small cerebellar gyri (called folia); there, they form excitatory synapses with the dendritic spines of Purkinje cells.

Question 18

The parallel fibers bifurcate in the molecular layer to form T-shaped branches that extend for several millimeters parallel to the orientation of the small cerebellar gyri (called folia); there, they form excitatory synapses with the dendritic spines of Purkinje cells. The Purkinje cells have dendrites that extend …

Answer 18

The Purkinje cells have dendrites that extend into the molecular layer, branching extensively in a plane at right angles to the trajectory of the parallel fibers.

Question 19

The Purkinje cells have dendrites that extend into the molecular layer, branching extensively in a plane at right angles to the trajectory of the parallel fibers. The Purkinje cells also receieve a direct modulatory input …

Answer 19

Purkinje cells also receieve a direct modulatory input on their dedritic sharfts from the climbing fibers, all of which arise in the inferior olive.

Question 20

Purkinje cells also receieve a direct modulatory input on their dedritic sharfts from the climbing fibers, all of which arise in the inferior olive. What do the climbing fibers do?

Answer 20

The climbing fibers provide a “training” signal that modulates the effectiveness of the parallel fiber connection with the Purkinje cells.

Question 21

The Purkinje cells project to …

Answer 21

The Purkinje cells project to the deep cerebellar nuclei.

Question 22

The Purkinje cells project to the deep cerebellar nuclei. They are the only output cells of the cerebellar cortex. Purkinje cells release what kind of neurotransmitter?

Answer 22

Purkinje cells are GABAergic.

Question 23

Since the Purkinje cells are GABAergic, the output of the cerebellar cortex is wholly inhibitory. However, the neurons in the deep cerebellar nuclei also receive excitatory input from ..

Answer 23

Since the Purkinje cells are GABAergic, the output of the cerebellar cortex is wholly inhibitory. However, the neurons in the deep cerebellar nuclei also receive excitatory input from the collaterals of the mossy and climbing fibers.

Question 24

What are the hallsmarks of patients with cerebellar damage?

Answer 24

Difficulty producing smooth, well-coordinated, multi-jointed movements.

Question 25

What is the diagnosis for the movement difficulties observed in patients with cerebellar damage?

Answer 25

Cerebellar ataxia.

Question 26

Mention a lesion study in animals that illustrate the motor error theory of the cerebellum.

Answer 26

Cutting part of the tendon to the lateral rectus muscles in one eye of a monkey weakens horizontal eye movements by that eye. When a patch is then placed over the normal eye to force the animal to use its weak eye, the saccades performed by the weak eye are initially hypometric - they fall short of visual targets. Over the next few days, the amplitude of the saccades gradually increases until they again become accurate. If the patch is then switched to cover the weakened eye, the saccades performed by the normal eye are now hypermetric. Lesions in the vermis of the spinocerebellum eliminate this ability to reduce motor error.

Question 27

A patient is suffering from movement errors consistent with symptoms of cerebellar damage. The errors are only shown when the patient is using his right hand. Where in the cerebellum would you suggest to look for damage?

Answer 27

As sensory and motor information is represented ipsilaterally in the cerebellum, as opposed to contralaterally, i’d look for damage in the right cerebellar hemisphere.

Question 28

A rare but devastating neurological disorder characterized by cerebellar ataxia, myoclonic jerks, seizures, and the fulminant progression of dementia. What’s the name?

Answer 28

Creutzfelt-Jakob disease (CJD).