Supraspinal control Flashcards
what are the 3 ascending pathways in the spinal chord and what do they do, and where are they located/ project to?
dorsal columns: proprioception, light touch information transmitted to dorsal column nuclei in medulla, then crosses to contralateral thalamus and continues to contralateral somatosensory cortex
Spinothalamic tracts: higher threshold touch, nociceptive and temperature information crosses in the spinal cord and projects to contralateral thalamus and on to contralateral somatosensory cortex
Spinocerebellar tracts: proprioception (awareness of position of body), light and higher threshold touch, nociception and temperature through spinocerebellar tracts to the ipsilateral cerebellum
what are the descending motor pathways of the spinal cord and what are their functions?
Ventromedial pathways : vestibulospinal and tectospinal control posture of head and neck. Pontine and medullary reticulospinal tracts control posture of trunk and antigravity muscles of limbs
Lateral pathways (corticospinal and rubrospinal): mostly influence motor neurones for distal muscles
corticospinal tract: two components: the lateral corticospinal tract terminates on distal muscle MNs, the ventral CST terminates on axial and proximal muscle MNS
what are the main thalamocortical connections?
ventral lateral nucleus is the major input to the primary motor cortex
ventral anterior nucleus supplies premotor cortex and supplementary motor area
how does the cerebellum control movement ?
the flocculi-nodular lobe controls balance and eye movements
the vermis and pars intermedia adjust ongoing movement of the whole body
cerebellar hemispheres help coordinate the planning of limb movements, project in particular to premotor area
what are the cerebellar output pathways?
there are no private cerebellar output pathways, it accesses the corticiospinal, rubrospinal and vestibulospinal pathways.
Major outputs from lateral parts to the thalamus and motor cortex. Smaller output from intermediate parts to red nucleus. Important output from medial parts to vestibular nuclei
how do primary motor cortex pyramidal neurones converge/ diverege from neurones?
many pyramidal neurones attach to single spinal motorneurones (they converge)
a single pyramidal neurone connects to several motor neurone and interneurone pools (they diverge)
what do primary motor cortex neurones code for?
muscle force; some code for dynamic force, some for static force, some for both
what does the premotor cortex consist of ?
the premotor area and the supplementary motor area
how does the premotor cortex wire to other areas in the brain
the premotor area and supplementary motor area (together the premotor cortex) project to the primary motor cortex
via the thalamus the premotor area has strong inputs from the cerebellum
via the thalamus the supplementary motor area has strong inputs from the basal ganglia
what is the function of the premotor area and the supplementary motor area?
premotor area is involved in planning movements based on external (especially visual) cues
supplementary motor area is involved with planning movements based on internally generated strategies (muscle memory/ learned sequences of movement)
describe the anatomy of the cerebellum
three major sagittal divisions: central longitudinal strip of the cerebellar cortex (grey matter) is the vermis, on each side of the vermis is the narrow pars intermedia and on the outside of that are the lateral cerebellar hemispheres.
The cerebellar cortex overlies a collection of nuclei; the cerebellar deep nuclei. (fastigial, interpositus and dentate)
what are the inputs/outputs of the cerebellar deep nuclei
inputs: the cerbellar cortex
outputs: thalamus, red nucelus, brainstem.
what are the inputs to the cerebellum and where do they connect to?
inputs of cerebellum project to cerebellar cortex and give collaterals to the cerebellar nuclei:
mossy fibres from; spinal cord (proprioceptive feedback), pontine nuclei (cerebral cortical information), reticular nuclei.
Mossy fibres synapse onto granule cells which send up parallel fibres to purkinje cells- the output cells of the cerebellar cortex. Each purkinje cells receives up to 250,000 parallel fibre inputs.
Climbing fibres: only from inferior olive. Inferior olive receives inputs from spinal cord, dorsal column nuclei, cerebral cortex and red nucelus. Each olivary axon branches to give 10-15 climbing fibres. These terminate on a purkinje cell in the cerebellar cortex, via a collateral to the cerebellar nuclei. Each purkinje cell receives only one climbing fibre input although multiple synapses with same fibre
what can cerebellar lesions result in?
Hypotonus: loss of muscle tone
Ataxia: loss of co-ordination
deficiencies in velocity and rhythm of muscle contractions.
asynergia: loss of co-ordination between different muscle groups
ataxia of arms, decomposition of smooth movements with intention tremor.
what are theories of cerebellar control?
cerebellum receives copies of movement plans from other structures (e.g motor cortex) : intenal feedback/ efferency copy
it receives external feedback/ reafference about sensory consequences of movement
It uses these types of information to adjust motor outputs for fine control of movements
Cerebellum involved in motor learning involving modification of parallel fibre to purkinje cell synapses under influence of climbing fibre instructions
