Lesson 15: Motor Control (Coordination): Cerebellum Flashcards Preview

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Flashcards in Lesson 15: Motor Control (Coordination): Cerebellum Deck (46)
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1
Q

What is the main role of the cerebellum?

How is it explained through the missile system analogy?

A

Motor control center: the cerebellum is the missile’s guidance system. Its role is to keep the missile moving smoothly, efficiently, with accuracy of sequencing, precision and synergy, ending on-target.

2
Q
In the Archi-cerebellum, what are the:
Structural Divisions
Cerebellar nuclei
Function
Cerebellar peduncles and pathways
A
  • Flocculo-nodular lobe
  • Fastigial nucleus
  • Vestibular function, equilibrium
  • Input to and output from cerebellum: inferior cerebellar peduncle to vestibular nuclei and to the vestibule-spinal tract
3
Q
In the Paleo-cerebellum, what are the:
Structural Divisions
Cerebellar nuclei
Function
Cerebellar peduncles and pathways
A
  • Anterior lobe
  • Globuse and emboliform nuclei
  • Balance of agonists – antagonists.Synergy, rate, sequencing, and degree
  • Input: Mostly via inferior cerebellar peduncles
    Output: Mostly via inferior cerebellar peduncle
4
Q
In the Neo-cerebellum, what are the:
Structural Divisions
Cerebellar nuclei
Function
Cerebellar peduncles and pathways
A

Posterior (medial) lobe Dentate nucleus
Fine movement; fine coordination
Input: middle and superior cerebellar peduncle
Output: Superior cerebellar peduncle

*only information from pons to cerebellum travels in the middle cerebellar peduncle (one way)

5
Q

What are the three functional divisions of the cerebellum?

A

Archicerebellum, paleocerebellum, and neocerebellum

6
Q

What are the folds called in the cerebellum?

A

Folia

7
Q

What are the three lobes of the cerebellum?

How is the cerebellum divided vertically?

A

Focculonodular (floculus and nodule), the anterior lobe, and posterior lobe (sometimes called medial lobe).
-Vertically into a central column (the vermis), flanked by two lateral columns (paravermal), and lateral to each of these two lateral hemispheres

8
Q

What is the archicerebellum associated with and responsible for?
What does it communicate with?

A

Is associated with the primitive vestibular system and as such is responsible for equilibrium.
It communicates with the ipsilateral vestibular nuclei, through the inferior cerebellar peduncle

9
Q

What is the paleocerebellum responsible for? Where does it receive input/output from/to?

A

Responsible for the coordination of movement, in particular the synergy between muscle groups, posture and the basis of movement generally
- Input from the spinocerebellar tracts (uncrossed), the reticular formation crossed and uncrossed), and the inferior olivary nucleus (crossed and uncrossed). Its output is to the reticular formation and inferior olivary nuclei.

10
Q

What is the role of the neocerebellum? Where does it receive info, synapse, cross?
Where do its efferent fibres synapse and project?

A

Involved in fine coordination of skilled movements, receiving cerebral cortical sensory information through the cortical-ponto-cerebellar tract (descends form the sensory cortex, synapses in the ipsilateral basis pons, and then crosses to the contralateral cerebellum.
Its efferent fibers synapse in the red nucleus (dentaorubral tract/crossed) and either project to the contralateral alpha and gamma motor neurons crossing in the rubrospinal tract or the thalamus (dentothalmic/crossed) through which it influences the motor cortex.

11
Q

Where does info entering the cerebellum synapse? Where does all info leaving the cerebellum synapse?

A

Information entering the cerebellum synapses first in the cerebellar cortex and all information leaving the cerebellum synapses in its nuclei before leaving.

12
Q

What are the efferent fibres for the neocerebellum, paleocerebellum and archicerebellum?

A

Dentate nucleus, globose and emboliform nuclei, and fastigial nuclei, respectively

13
Q

Which nuclei of the thalamus receive info from the cerebellum? (ipsiplateral or contralateral)
Which functional division is it associated with?

A

The VA and VL nuclei (motor nuclei) of the thalamus receive information from the contralateral cerebellum.
It is associated with the neocerebellum

14
Q

Where does the red nucleus receive info from?
Where does its output go?
What does stimulation of the nucleus produce?
Which functional division is it associated with?

A

Receives info from the ipsilateral cerebral cortex and the contralateral cerebellum.
Its output is through the rubrospinal tract.
Stimulation of the red nucleus produces flexion (bending) of the upper limbs and extension (straightening) of the lower limbs.
It is primarily associated with the neocerebellum

15
Q

How is the inferior olivary nucleus associated with the cerebellum?
What is its output through?
What functional division is it associated with?

A

It exchanges information with the ipsilateral and contralateral cerebellum.
Its output is through the olivospinal tract.
It is primarily associated with the paleocerebellum

16
Q

What does the reticular formation exchange info with? Where is its output?
Which functional division is it associated with?

A

Exchanges info with the ipsilateral and contralateral cerebellum.
Its output is through the reticulospinal tract.
It is primarily associated with the paleocerebellum.

17
Q

What does the vestibular nucleus exchange info with?

Which functional division is it associated with?

A

Exchanges information with the ipsilateral cerebellum. It is associated with the archicerebellum

18
Q

How many peduncles (legs) connect the cerebellum with the brainstem?

A

3

19
Q

What are the three important factors in a guidance system? How does this relate to lesions of the cerebellum?

A

• Requires constant monitoring of information during motion
• Does not change the initial intention (instruction)
• Is constantly comparing intention with performance
Therefore, lesions of the cerebellum do not lead to loss of active movement (paralysis), but to changes in the quality of movement

20
Q

Which side to the cerebellar lesion is involved in cerebellar disorders?

A

Ipsilateral

21
Q

What is: Lack of synergy (coordinated muscle recruitment) resulting in jerky movement?

A

Asynergia

22
Q

What is: Lack of smooth order and coordination in motor activities. Movements tend to be broken into segments. They can occur from a number of causes including sensory loss and cerebellar damage . Movements in cerebellar lesions tend to include bradykinesia producing slow motion and weakness in intensity?

A

Ataxia

23
Q

What is mild muscular weakness ipsilateral to the side of the cerebellar damage?
Movement may be marked with asynergia (impaired direction and force of a given movement involving paired muscles)

A

Asthenia

24
Q

What is: Impaired sequencing of body movements. (Produces staggering reeling gait) (often mistaken for alcohol impairment). It is distinguished from sensory ataxia. In sensory ataxia Romberg’s sign is present; in motor ataxia, Romberg’s sign is absent

A

Cerebellar (motor) ataxia

25
Q

What is this: uncoordinated speech breathing, inconsistent articulatory breakdowns, irregular speech rate, monoloud/monopitch, excessive monotonous stress of syllables and errors in articulating consonants often referred to as scanning speech.. People often report that they sound like they are drunk
Impaired ability to make the needed modifications and alterations in ongoing oral-facial movement, impairing motor speech.

A

Ataxia Dysarthria

26
Q

What is: slow movements (movement is slowed in order to control disconnected sequencing and timing, resulting in slow speech?

A

Bradykinesia

27
Q

What is: Weakness of intensity of movement: (weak respiration also produces poverty of sound in speech)?

A

Poverty of movement

28
Q

What is: tremor that only accompanies movement and is absent at rest. Impaired ability to dampen accessory movements during a skilled movement sequence. Tremor becomes more severe as the target is approached – as demand for the function of the cerebellum becomes more important?

A

Intention tremor

29
Q

What is: Failure to sequence alternating movements. This is tested by turning one’s hand palm up, palm down, palm up, repeatedly. It is tested in speech by saying a string of syllables (most frequently used = “pa-ta-ka”) repeatedly as fast and evenly as one can. For individuals with cerebellar issues, the output tends to be imprecise, slow and irregular/uneven
Failure in the sequential progression of motor activities displayed by clumsiness in rapid and alternating movements?

A

Dysdiadochokinesia

30
Q

What is: Movement which overshoots or undershoots the target. Voice is variably monotonous and explosive?

A

Dysmetria

31
Q

What is: Output from cerebellum to the red nucleus and thalamus that facilitates tone is reduced. Damage to the cerebellum produces characteristically hypotonic motor activity. Results in weakness of vocal output
Normal muscle tension is decreased and the muscle becomes floppy. Is ipsilateral to the side of the cerebellar dysfunction, accompanied by asthenia, a condition in which the muscles are likely to tire quickly?

A

Hypotonia

32
Q

What is: Loss of equilibrium, falls toward side of lesion

Impaired vestibular processing in the cerebellum that predominantly affects the legs. Gait is unsteady.

A

Disequilbrium

33
Q

Why is Romberg’s sign positive in sensory lesions and negative in cerebellar lesions?

A

Sensory info is vital to the smooth harmonious production of motor activity. A failure to produce normally smooth motor acts it referred to as ataxia. Ataxia may be manifest in individual limb motions, but is more commonly evident during walking.
With ataxia, movements become jerky and uncoordinated. The CNS must be constantly appraised of the position, tone and movements of the limbs and trunk. It accomplishes this task by integrating (primarily in the cerebellum) proprioceptive input and information from the receptors for equilibrium, which are located in the labyrinths of the ear, and by relaying these data back to the appropriate motor effectors.

34
Q

Which type of ataxia: Includes conditions in which motor performance is faulty, but the motor pathways and the cerebellum are intact. This occurs because there is a defect in transmitting proprioceptive or equilibratory information to higher centers. Frequently can be compensated for by using visual input to guide limb position and the ataxia is often worse in the dark or when the eyes are closed

Is there a presence of the Romberg’s sign?

A

Sensory ataxia

[presence of Romberg’s sign].

35
Q

Which type of ataxia: Include conditions in which the sensory pathways are intact but motor performance is faulty, and there is a defect in the integration and processing of proprioceptive information. Is usually due to the disease in the cerebellum. This type of ataxia is often poorly compensated for by visual input. Therefore, it will remain essentially the same with eyes open or closed

Is there a presence of the Romberg’s sign?

A

Motor ataxia

[absence of Romberg’s sign]

36
Q

What does the Romberg test do?

A

The patient who shows little or no unsteadiness when standing with the feet together and eyes open but who displays marked unsteadiness with the eyes closed has a Romberg sign, indicating that the patient has a sensory ataxia. Patients with a motor (cerebellar) ataxia may or may not be unsteady in the Romberg position but show little or no increase in unsteadiness when they close their eyes and thus do not have a Romberg sign. Patients who have a sensory ataxia generally have difficulty with either vestibular function or proprioception, as a result of peripheral or spinal cord disease [typically dorsal columns]. Ataxia patient without a Romberg sign often show abnormalities in cerebellar function.

37
Q

Where does the cerebellum receive info from?

A

Motor cortex, brainstem reticular reflex networks, and spinal cord

38
Q

What are the two sensory body representations of the cerebellum?

A

Tactile stimulation activates potentials ipsilaterally in the anterior lobule and bilaterally in the paramedian lobules

39
Q

Why is the inferior cerebellar peduncle an important pathway?

A

Pathway through which ascending inputs from distal limbs gain rapid entry to the ipsilateral cerebellum.

40
Q

What are the fibre bundles that enter through the inferior cerebellar peduncle?
What does each fibre bundle do?

A
Vestibulocerebellar (info related to equilibrium), 
Dorsal spinocerebellar (info related to unconscious proprioception)
Olivocerebellar (info related to intended motor movement) Cuneocerebellar (info related to proprioception)
41
Q

What structures mediate the excitatory info to the outer cellular layer?
Which cells inhibit the activity of deep cerebellar nuclei?

A
  • Input axons, with branches to both the deep nuclei and cerebellar cortex, mediate excitatory (+) info to the outer cellular layer. Also excite a stripe of Purkinje cell dendrites
  • Axons of Purkinje cells project to inhibit (-) the activity of deep cerebellar nuclei – which serve as the final cerebellar output.
42
Q

What happens when there is alteration in the sequence of excitatory and inhibitory events, and/or timing interval between neuronal element?

A

Cause the deep cerebellar nuclei send faulty output signals to the brainstem. Thus, in turn, negatively affects the functional integrity of the neuronal circuitry of the motor cortex, reticular formation, and spinal cord - Consequently, motor functions become uncoordinated due to loss of muscle synergy.

43
Q

How is the cerebellum implicated with motor learning?

A

Begins with a conscious control of movement and gradually ends with the skill acquisition that no longer requires a conscious regulations of the tactile motor activities.

44
Q

What are the three characteristic symptoms of lateralized cerebellar lesions?

A

(1) an ipsilateral character to the signs
(2) deficits related to motor functions with no sensory loss and/or complete paralysis
(3) gradual natural recovery, unless there is a lesion that is progressive, massive, or bilateral in nature.

45
Q

What is rebounding?

A

Impaired motor tone adjustment as well as a loss of rapid and precise corrective response, as the patient loses the ability to predict, stop, or dampen movement.

46
Q

What would involvement of the thromboembolic or hemorrhage of the vertebrovascular artery cause?

A

System interrupts blood circulation to the cerebellum