Chapter 11 Part 2 Flashcards
What percentage of neurons of CNS are on the cerebellum?
50
What does the cerebellum do?
Coordinates movement and postural control by comparing actual motor output with the intended movement and then adjust the movement as necessary
What else is cerebellum involved in?
Is involved in learning timing and rhythm of movements, synchronization of movements, and learning to correct motor errors
Three layers of the cerebellum:
outer layer
middle layer
inner layer
What are the neurons of the crerebellum?
principal: purkinje fibers
interneurons
What are the afferent fibers of the cerebellum?
mossy fibers
climbing fibers
Mossy fibers:
from spinal cord, reticular formation, and vestibular system ; convey information regarding sensory, equilibrium and motor information
Climbing fibers:
from inferior olivary neucleus; convey information regarding movement error
Three lobes of cerebellum:
Anterior
Posterior
Flocculonodular
Three groups of peduncles of cerebellum:
superior cerebellar peduncles
middle cerebellar peduncles
inferior cerebellar peduncles
Superior cerebellar peduncles
to midbrain
Middle cerebellar peduncles
receives input from pons
Inferior cerebellar peduncles
bidirectional
Cerebellar nuclei from medial to lateral are
Fastigial nucleus
Globose
Emboliform
Dentate
Vertically, the cerebellum can be divided into sections:
Midline vermis
Paravermal hemisphere
Lateral hemisphere
What are the three anatomic regions or functional divisions ?
vestibulocerebellum (flocculonodular lobe)
spinocerebellum
cerebrocerebellum
Three broad classes of human movement:
Elquilibrium
Gross movement of limbs
fine, distal, voluntary movement
Equilibrium:
Is regulated by the vestibulocerebellum (flocculonodular lobe) that receives information from vestibular receptors, and sends information to the vestibular nuclei; influence eye movements and postural muscles
Gross movements of limbs:
Are coordinated by the spinocerebellum which receives proprioceptive information from muscle spindles and visual and auditory information; control ongoing movements through medial and lateral motor tracts
Fine, distal, voluntary movements:
Are coordinated by the cerebrocerebellum that is related to processing in the cerebral cortex and coordinate movements via lateral motor tracts
Unilateral lesions of cerebellum affect:
same side of the body
Why are cerebellar signs ipsilateral?
- output paths of medial tracts remain ipsilateral
- cerebellar efferents project to contralateral cerebral cortex and red nucleus whose descending tracts cross the midline
Ataxia:
describes the uncoordinated voluntary, normal-strength, jerky, and inaccurate movements that are not due to hypertonia or contracture
What results in truncal ataxia?
Lesions to vermal and flocculonodular lobe
What do prarvermal lesions result in?
gait and limb ataxia
What do lateral cerebellar lesions result in?
hand ataxia
Limb ataxia resulting from spinocerebellar lesions has what manifestations:
dysdiadochokinesia
dymetria
action tremor
Dysdiadochokinesia
inability to rapidly pronate and supinate the forearm
Dysmetria:
inability to rapidly move an intended distance
Action tremor
shaking of the limb during voluntary movement
What can also produce ataxia?
Interference with transmission of somatosensory information to the cerebellum, either by lesions of the spinocerebellar tracts or by peripheral neuropathy,
What can also produce ataxia in lower limbs?
Sensory deficits or paravermal cerebellar lesions
How is cerebellar and somatosensory ataxia differentiated?
Romberg test, tests of proprioception, vibration sense, and ankle reflexes
What is the Romberg test:
Measures the ability to use proprioceptive information for standing balance
How is Romberg test performed?
Patient stands with his or her feet together, first with eyes open for 30 seconds and then with eyes closed for 30 seconds
pass or fail
What is criteria for failure of the Romberg test?
moving the arms to maintain balance, opening the eyes during the eyes closed section, beginning to fall, or requiring assistance
How do cerebellar limb ataxia individuals present in the Romberg test:
unable to stand with feet together, with or without vision, and have normal vibratory sense, proprioception, and ankle reflexes
How to sensory ataxia individuals present?
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 impaired with sensory ataxia?
Conscious proprioception and vibratory sense are impaired, ankle reflexes are decreased or absent
