Cerebellum, balance and coordination Flashcards
(43 cards)
what are the names of the three pundcles that attach the cerebellum to the brain stem
- Inferior Cerebellar Peduncle (ICP)
- Middle Cerebellar Peduncle (MCP)
- Superior Cerebellar Peduncle (SCP)
Which peduncles deal mainly with input
- Middle Cerebellar Peduncle (MCP)
- Superior Cerebellar Peduncle (SCP)
Which peduncles deal mainly with output
- Inferior Cerebellar Peduncle (ICP)
where does the superior Cerebellar Peduncle (SCP) connect to
the midbrain
where does the - Middle Cerebellar Peduncle (MCP) connect to
the pons and deals mainly with voluntary movements
what are the three lobes of the cerebellum
anterior
posterior
flocculonodular
• Vestibulocerebellum
this is at the very back of the cerebellum
– consists of flocculonodular lobes (white)
– input from vestibular & visual areas
– output to vestibular nucleus – controls equilibrium and eye movements
Spinocerebellum - middle strip
– consists of vermis of posterior and anterior cerebellum + adjacent
intermediate zones on both sides of vermis
– input from spinocerebellar & auditory, visual, vestibular systems & sensorimotor cortex
– output from vermis to fastigial nuclei to vestibular & reticular formation of pons and medulla
• Control antigravity muscles in posture and locomotion
– output from intermediate zone to interposed nuclei to red nucleus to thalamus then cortex
• Act on stretch reflexes & other somatosensory reflexes
Cerebrocerebellum - outer areas
– consists of lateral zones of the cerebellar hemispheres (pink/flesh)
– input from cerebral motor cortex & adjacent premotor & somatosensory cortices
– output to dentate nucleus to thalamus to motor and premotor cortices
– creates a feedback with the cortical sensorimotor system to plan sequential voluntary body and limb movements
what are the three layers of the cerebellum
molecular layer
purkinje cell layer
Granule cell layer
what are the two main input fibres
- climbing fibres
- mossy fibres
mossy fibres
these indirectly stimulate purkunje fibres
inputs from pontine nuclei and other sources
climbing fibres
these directly stimulate purkunje fibres
inputs from inferior olivary nucleus
cerebellar output occurs via the deep nuclei, from lateral to medial what are they ?
dentate nuclei emboliform nuclei globose nucleus fastigial nuclei vestibular nucelus
alcohol effects on the cerebellum
alcohol intoxication – depression of cerebellar circuits (truncal ataxia)
how does the cerebellum act as a comparator
– Cerebellum compares descending supraspinal motor signals with ascending afferent feedback
information
– Movement smoothly and accurately coordinated
how does the cerebellum act as a timing device
– Pontocerebellum – creates a sequence for motor activation
– Vestibulocerebellum – maintains balance
– Spinocerebellum – maintains posture
how does the cerebellum initiate and store movements
– Modifiable synapse (Purkinje cell)
– So can store motor information and update it
• Primary role of cerebellum thought to be to
supplement and correlate activities of other motor areas e.g. correction of rapid muscular movement initiated by cortex (typing, musical instrument)
how is the cerebellum informed of movement
by cortex before it occurs, then cerebellum processes sensory information to generate an error signal which is fed back to cortex and movement is adjusted
• Hypotonia / Reduced muscle tone
Due to reduced input from Deep Cerebellar Nuclei neurone (DCNN) via descending
motor pathways to muscle spindle
Incoordination / Ataxia
– Asynergy – inability to coordinate contraction of agonist and antagonist muscles
– Dysmetria – inability to terminate movements (intention tremor/past pointing)
– Dysdiadochokinesis – inability to perform rapidly alternating movements
Dysarthria (scanning speech)
– Inability to articulate words (slurred and delivered slowly) due to incoordinated
oropharyngeal musculature
Nystagmus
– Rapid jerky eye movements – disruption between vestibular nucleus and oculomotor nuclei
