Lecture 16 - Cerebellum Flashcards
What does the cerebellum do?
- compares motor plans with physical execution
- makes adjustments to keep movements coordinated, fluid and on target
cerebrocerebellum
- lateral zone
- receives input from contralateral cerebral cortex
- regulates complex sequences of movement including speech
spinocerebellum
- paramedain + median zones
- receives input from spinal cord
- somatopic organization
vestibulocerebellum
- caudal + inferior lobes
- receives input from the vestibular nuclei
- regulates posture + balance including some eye movements
Ataxia
reeling, wide-based gait
Decomposition of movement
inability to correctly sequence fine, coordinated acts
Dysarthria
- inability to articulate words correctly
- slurring + inappropriate phrasing
Dysdiadochokinesia
inability to perform rapid alternating movements
Dysmetria
inability to control range of movement (hypo or hypermetria)
Hypotonia
decreased muscle tone
Nystagmus
- involuntary, rapid oscillation of eyeballs in horizontal, vertical or rotary direction
- fast component maximal toward side of cerebellar lesion
Tremor
- rhythmic, alternating, oscillatory movement of limb at it approaches target
- or of proximal musculature when fixed posture or weight bearing is attempted
What are 3 cerebellar outputs?
- Dentate
- Interposed
- Fastigial
Dentate
Input: from cerebrocellebellar zone
Projects to: contralateral premotor cortex + association cortices of frontal lobe (planning)
Interposed
Input: spinocerebellar zone
Projects to: contralateral motor cortex (executing movement)
Fastigial
Input: spinocerebellar zone
Projects to: upper motor neurons in ipsilateral brainstem (executing movement)
Where does the vestiublocerebellum project?
to the vestibular nuclei
What are peduncles?
fiber bundles carrying inputs and outputs
What are 3 cerebellar peduncles?
- superior
- middle
- inferior
What characterizes the superior peduncle?
- efferent pathway (mainly)
- made of fibers exiting from deep cerebellar nuclei
What characterizes the middle peduncle?
- afferent pathway
- made of fibers carrying info from cortex (via pons)
What characterizes the inferior peduncle?
- afferent fibers from brainstem + spinal cord
- efferent fibers from vestibulocerebellum
What does the cerebral cortex control? What does it project?
- the contralateral side of the body
- projects to the ipsilateral pontine nuclei
Where does each cerebellar hemisphere receive input from? What does it control?
- receives ascending input from same (ipsilateral) side of body
- controls movements on same side of body
pathways from the cerebral cortex to the cerebellum will cross the ________ at some _____
midline, point
What is the cerebrocerebellum?
influences premotor cortex via the dentate (motor planning)
What is the spinocerebellum?
influences motor cortex via the interposed nuclei (motor execution)
how does the spinocereellum influence brainstem structures?
via fastigial nucleus (motor execution)
Where does the vistibulocerebellum project?
directly to the vestibular nuclei (motor adjustment, balance)
What are the 3 layers of the cerebellar cortex?
- molecular layer (ML)
- Purkinje cell layer (PL)
- Granule cell alyer (GL)
what is the molecular layer made up of?
- mainly dendrites of Purkinje cells
- axons of granule cells (parallel fibers)
What is the Purkinje cell layer made up of?
Purkinje cells and basket cells
Where do climbing fibers convey input from?
inferior olive
Where does the inferior olive receive input from?
- cerebral cortex
- spinal cord
- red nucleus
Each purkinje cell receives input from a single _______ _____
climbing fiber
What is the Purkinje cell’s response to input form a climbing fiber?
cells fire a complex spike
Where do mossy fibers come from?
the pontine nuclei
What are the pontine nuclei?
relay input from the cerebral cortex, spinal cord, vestibular nuclei
What do mossy fibers synapse with?
granule cells
Each Purkinje cell receives _______ of inputs from parallel fibers
hundreds of thousands
What do purkinje cells fire in response to input from parallel fibers?
“simple”
motor learning means that the cerebellum can “learn” to ____ for ______
compensate, changes in the status quo
What are the 2 types of cerebellar loops?
- direct loop
2. cortical inhibitory loop from mossy fibers
What happens in a direct loop from mossy fibers
- afferent sensory information
- from mossy fibers
- to deep cerebellar nuclei
- to motor system (reflex pathway)
What happens in a cortical inhibitory loop?
- from mossy fibers to granule cells
- via parallel fibers
- to Purkinje cells
- to deep cerebellar nuclei + motor system
- fine-tune reflexes
What is the cortical inhibitory loop involved in?
fine tuning reflexes
What is the climbing fiber loop involved in?
- mediates motor learning
- involves complex spikes
Where do climbing fibers originate?
-in inferior olive
Where do mossy fibers originate?
pontine nuclei
