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Flashcards in Module 3 Deck (341)
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121

- originate from brainstem

Reticulocerebellar Fibers

122

- originate from vestibular nuclei and vestibular apparatus

Vestibular Fibers

123

- central neurons with fan-shaped dendritic trees
- always inhibitory with GABA as its neurotransmitter

Purkinje Cells

124

- smallest and most numerous neurons in the brain
- parallel fibers are axons of granule cells
- excitatory input from mossy fibers which use glutamate as its neurotransmitter

Granule Cells

125

o small interneurons with numerous arborizations
o inhibitory in function

Golgi Type II Cells

126

o inhibitory star-shaped cells found in superficial cerebellum

Stellate Cells

127

o inhibitory cells whose axons form baskets around Purkinje fibers and are found in deep cerebellar layers

Basket Cells

128

o complex of synapses having a mossy fiber at its core
o synapsing with axons of Golgi type II neurons and dendrites of granule cells

Glomerulus

129

- modulate Purkinje cell output
- all of the cerebellar interneurons are inhibitory EXCEPT granule cells
o granule cells have excitatory input to basket cells, stellate cells, Golgi II cells, and Purkinje cells
o basket cells and stellate cells inhibit Purkinje cells (via parallel fibers)
o Golgi II cells inhibit granule cells, thereby reducing their excitatory effect on Purkinje cells

Cerebellar Interneurons

130

Output of the Cerebellar Cortex

- Purkinje cells are the only output of the cerebellar cortex
o output is always inhibitory, using GABA as NT

- inhibitory output modulates the output of the cerebellum and regulates rate, range, and direction of movement (synergy)

131

Efferent Signals from the Cerebellum

vermis - projects to fastigial nucleus, vestibular nucleus and reticular formation

intermediate zones - project to globose and emboliform nuclei (interposed nuclei)

lateral hemispheres - project to the dentate nucleus, ventral anterior thalamic nuclei and cerebral cortex

132

CEREBELLAR PATHWAY

Cortex
Pons*
Cerebellum
Dentate nucleus*
Red Nucleus
Thalamus
Corticospinal tract

133

o consists of the small flocculonodular lobes
o for control of balance and eye movement

Vestibulocerebellum

134

o consists of lateral zones of cerebellar hemispheres
o for planning and initiation of movement

Cerebrocerebellum

135

o consists of vermis and intermediate zones
o for control of rate, force, range, and direction of movement (synergy)

Spinocerebellum

136

- during nearly every movement, certain muscles must be rapidly turned on and then quick turned off
- made possible by interplay of mossy and climbing fibers and Purkinje cells

Turn On/Turn Off Function

137

o climbing fibers modify sensitivity to parallel fiber input
o when mismatch between anticipated result of movement and its actual result occurs, climbing fiber input is more vigorous
o as movement is practiced, mismatch declines gradually

Motor Learning

138

o during any movement, momentum develops and must be overcome to stop the movement
o appropriate learned, subconscious signals from spinocerebellum stop the movement precisely at the intended point

Damping Function

139

- patient with cerebellar lesion assumes unsteady stance and reeling gait (like a drunk person)
- to compensate, he assumes a broad-based stance and a broad-based gait

Ataxia

140

- failure to meter the contractions that set the distance of motion

Dysmetria

141

- inability to perform rapid alternating movements

Dysdiadochokinesia

142

- failure of a movement to be terminated at a proper time

Past Pointing

143

- difficulty in maintaining position against sudden unexpected displacement

Overshooting

144

- slowness and slurring of speech

Dysarthria

145

- volume of voice varies from low to high from peak to peak

Scanning Speech

146

- tremor of intentionally maintained head or trunk posture or of a limb suspended in front of the body

Postural, Positional Or Static Tremor

147

- unsteady oscillations of the head or trunk

Tiutubation

148

o tremor as a limb approaches its target
o results from cerebellar overshooting and failure of the cerebellar system to "damp" the motor movements

Intention, End-Point Or Kinetic Tremor

149

-jerkiness of eye movement
o rapid, tremulous movements of the eyes rather than steady fixation
- due to failure of damping by the cerebellum
- occurs especially when the flocculonodular lobes of the cerebellum are damaged

Nystagmus

150

- decreased tone of the peripheral body musculature on the side of the cerebellar lesion
o results from loss of cerebellar facilitation of the motor cortex and brain stem motor nuclei
- shows rag doll appearance

Hypotonia