Corticospinal and Cerebellar Systems Flashcards
What are the 2 streams of descending information to the spinal cord?
Ventromedial group
Dorsolateral group
Which pathways make up the ventromedial group of spinal cord inputs?
Reticulospinal
Tectospinal
Vestibulospinal
Which pathways make up the dorsolateral group of spinal cord inputs?
Corticospinal
Rubrospinal
What do medial MNs control?
Axial muscles - balance and posture
What do lateral MNs control?
Distal muscles - fine movements
What is a corticomotoneuronal cell?
Cortical neuron that projects directly to MN
What are the component of the motor cortex?
Primary motor cortex (M1)
Supplementary motor area (SMA)
Premotor area (PM)
Which aspects of muscle force do M1 cortical neurons code for?
Direction
Amplitude
What is the evidence against M1 cortical neurons as controllers and how could this be dismissed?
Fire during range of movement directions - bell-shaped directional tuning curve - not precise enough
Direction could be encoded by cooperation of cells with overlapping tuning curves - M1 neurons encode direction as population
What is the role of Purkinje cells in the cerebellar cortex?
Select relevant information for movement control from inputs (from granule cells)
Which NT do cerebellar Purkinje cells release?
GABA
Where do cerebellar Purkinje cells receive inputs from?
Granule cells
Climbing fibres
Where do cerebellar granule cells receive inputs from?
Mossy fibres
Where do cerebellar mossy fibres receive inputs from?
Most sensory modalities
Motor efference copy
Vestibular
Where do climbing fibres originate from?
Medullary olive
What is the role of climbing fibres in the cerebellar cortex?
Fires when sensory feedback different to predicted - signals error
Where do Purkinje cells in each cerebellar hemisphere project to?
Ipsilateral cerebellar nuclei
Where do interneurons in the cerebellar nuclei project to?
Inferior olive - same region climbing fibres for that zone originated from
What are the circuit loops in the cerebellum called?
Olivo-cortico-nuclear modules
What are the ascending cerebellar outputs?
Major - from lateral cerebellum - to thalamus, motor cortex
Minor - from intermediate cerebellum - to red nucleus
What are the descending cerebellar outputs?
Major - from medial cerebellum - to vestibular nuclei
What does the flocculonodular lobe control?
Balance and eye movements
What do the vermis and pars intermedia control?
Adjust ongoing whole-body movements
What do the cerebellar hemispheres control?
Coordinate planning of limb movements
What is the effect of conjuctive activation of climbing fibre and parallel fibre inputs to Purkinje cells?
LTD of parallel fibre-Purkinje cell synapses
Reduced Purkinje cell response to parallel fibre stimulation
Explain the mechanism of cerebellar LTD
Climbing fibre input depolarises Purkinje cell
VGCCs open in Purkinje cell - Ca2+ influx
Glutamate release by parallel fibre - binds to mGluRs on Purkinje cell - increases PKC
Ca2+ activates PKC - phosphorylates active AMPARs in parallel fibre-Purkinje cell synapse - decreases AMPAR conductivity
LTD
