Flashcards in Cerebellum and Movement Deck (83):
The cerebellum accounts for __% of the brain and __% of all of the neurons in the CNS
How does the cerebellum coordinate movement and postural control?
By comparing actual motor output with the intended movement and then adjusting the movement as necessary
What 3 things is the cerebellum involved in?
- learning timing and rhythm of movements
- synchronization of movements
- learning to correct motor errors
Does damage to the cerebellum interfere with sensory perception or muscle strength?
No, however coordination of movement and postural control are degraded.
What does the cerebellar cortex do?
How many layers are there to the cerebellar cortex? What is contained within each layer
- outer layer: interneurons
- middle layer: Purkinje cell bodies
- inner layer: interneurons
What is deep to the cortex?
White matter, which consists of the cerebellar nuclei
What cells are the output cells from the cerebellar cortex?
Purkinje cells projections ____ the cerebellar nuclei and the vestibular nuclei
What are the 2 types of afferents that enter the cerebellar cortex?
- Mossy fibers
- Climbing fibers
What type of information to the mossy fibers convey to the cerebellum?
- cerebral cortex motor information
What type of information to the climbing fibers convey to the cerebellum?
- movement errors
Climbing fibers synapse with _____ cells, whereas mossy fibers synapse with _______ that convey information to the Purkinje cells
What are the 3 lobes of the cerebellum?
Where is the flocculonodular lobe located?
tucked underneath the posterior lobe, touching the brainstem
What are the 3 cerebellar peduncles?
- Superior cerebellar peduncles
- Middle cerebellar peduncles
- Inferior cerebellar peduncles
The _____ cerebellar peduncle connects to the midbrain and contains most of the cerebellar efferent fibers
Fibers from the cerebral cortex synapse in the pons, and the information then travels via axons in the ____ peduncle into the cerebellum
The _____ peduncle brings afferent information from the brainstem and spinal cord into the cerebellum and sends efferent from the cerebellum to the vestibular nuclei and reticular nuclei in the brainstem.
List the 4 cerebellar nuclei from medial to lateral
- Fastigial nucleus
Vertically, the cerebellum can be divided into sections, what are they?
- Midline vermis
- Paravermal hemisphere
- Lateral hemisphere
What are the 3 broad classes of human movement?
- Gross movements of the limbs
- Fine, distal, voluntary movements
The ____cerebellum regulates equilibrium.
The vestibulocerebellum is the functional name from the _____ lobe why?
flocculonodular, because is receives information directly from vestibular receptors and connects reciprocally with the vestibular nuceli
The vestibulocerebellum also receives information from ____ areas of the brain to influence what?
visual, to influence eye movements and postural muscles
The spinocerebellum is the functional name of the ____ and the ____ region, why?
vermis and paravermal region, because of its extensive connections with the spinal cord
Information that converges in the spinocerebellum is used to control what?
Ongoing movement via brainstem descending tracts
Input to the cerebrocerebellum is received from where?
cerebral cortex fibers that synapse with neurons in the pons
The ____cerebellum coordinates gross limb movements.
The ____cerebellum coordinates distal limb voluntary movement.
Unilateral lesions of the cerebellum affect the ____ side of the body.
Cerebellar signs are ____, why?
ipsilateral, because the output paths of the medial descending tracts remain ipsilateral and because cerebellar efferents project to the contralateral cerebral cortex and red nucleus whose descending tracts cross the midline.
What type of movement disorder is common to all lesions of the cerebellum?
Vermal and flocculonodular lobe cerebellar lesions result in what type of ataxia?
Paravermal lobe cerebellar lesions result in what type of ataxia?
gait and limb ataxia
Lateral cerebellar lesions result in what type of ataxia?
What do lesions involving the vestibulocerebellum cause?
- difficulty maintaining sitting and standing balance (truncal ataxia)
What do paravermal and cerebrocerebellar lesions result in?
dysarthria, which is slurred, poorly articulated speech
Dysfunction of the spinocerebellum results in what?
Describe ataxic gait
wide-based, unsteady, staggering, and veering gait
What cerebellar lobe is damaged in chronic alcoholism?
anterior lobe section of the spinocerebellum due to malnutrition, resulting in the characteristic ataxic gait
Spinocerebellar lesions result in what type of ataxia?
Limb ataxia manifests itself in what ways?
- dysdiadochokinesia: inability to rapidly alternate movements
- dysmetria: inability to accurately move an intended distance
- action tremor
How are action tremors compensated for?
By using movement decomposition, which consists of maintaining a fixed position of one joint while another joint is moving
What do cerebrocerebellar lesions interfere with?
the coordination of fine finger movements
Is all ataxia is caused by cerebellar lesions?
What may also produce ataxia?
Interference with transmission of somatosensory information to the cerebellum, either by lesions of the spinocerebellar tracts or by peripheral neuropathy
Sensory deficits or paravermal cerebellar lesions may cause ataxia where?
in the lower limbs
What test differentiates between sensory and cerebellar limb ataxia?
What does the Rhomberg test measure?
The ability to use proprioceptive information for standing balance
How do Rhomberg test results differentiate between individuals with cerebellar limb ataxia and sensory ataxia?
- Individuals with cerebellar limb ataxia are unable to stand with feet together, with or without vision, and have normal vibratory sense, proprioception, and ankle reflexes.
- Individuals with sensory ataxia are able to stand steadily with feet together with eyes open for 30 seconds, but balance is impaired when the eyes are closed.
What is also impaired in sensory ataxia?
Conscious proprioception and vibratory sense are impaired, ankle reflexes are decreased or absent.
Are muscle strength, bulk, tone, and involuntary muscle contraction impaired in cerebellar lesions?
No, all are normal
In summary, the cerebellum and basal ganglia are called the ____ circuits and adjust what?
control circuits that adjust the level of activity in the descending tracts
What are the 3 types of movements?
Posture is controlled by which brain region?
Ambulation is controlled by which brain regions?
brainstem and spinal regions
Reaching/Grasping is controlled by which brain region?
What does postural control provide?
Orientation and balance
What is orientation?
the adjustment of the body and head to vertical
What is balance?
the ability to maintain the center of mass relative to the base of support
How is postural control achieved?
By central commands to the lower motor neurons; the central output is adjusted to the environmental context by sensory input
What 3 senses are used in order to orient to the world?
What does somatosensation provide information about?
weight bearing and the relative positions of body parts
What does vision provide information about and what does it cue for?
provides information about movement and cues for judging upright
What does vestibular input from receptors in the inner ear inform us about?
head position relative to gravity and about head movement
What 2 senses can predict destabilization?
visual and somatosensory
Which senses are used to shape the motor reaction to instability
all 3: Somatosensation, Vision, and Vestibular
What device can be used to determine sensory organization and muscle coordination?
__ sensory conditions can be tested in posturography.
Describe how the cerebral cortex, basal ganglia, cerebellum, and sensory information are used in normal human ambulation.
- Cerebral cortex provides goal orientation and control of ankle movements.
- Basal ganglia govern generation of force.
- Cerebellum provides timing, coordination, and error correction.
- Sensory information is used to adapt motor output appropriately.
During ambulation what does the swing limb do first?
First it pushes downward and then backward against the support surface, in order to get the COG moving
What 2 senses are essential for reaching and grasping?
What is the significance of vision for reaching/grasping?
It provides information for locating an object in space and assessing its shape and size.
What is the primary role of vision during reaching and grasping?
Feed-forward, or the preparation for movement
The stream of visual information used for movement ("action stream") flows from where to where?
from the visual cortex to the posterior parietal cortex
What is grasping coordinated with?
Activity of the eyes, head, proximal upper limb, and trunk
When the object one reaches for is contacted, grip force adjusts quickly, indicating feed-____ control.
After an object is grasped, what corrects any error in grip force?
What does an evaluation of the motor system assess?
- muscle bulk
- muscle tone
- movement efficiency and speed
- postural control
- abnormal movements
The purpose of nerve conduction studies in motor disorders is to differentiate among three possible sites of dysfunction, what are these 3 sites?
- Neuromuscular junction
Diagnostic EMG (using a needle electrode inserted into the muscle) is commonly used to distinguish between what 2 things?
denervated muscle and myopathy