Movement L6 Flashcards
give soem elemetns of cerebral ataxia
Hypotonia - weakness
Dysmetria - inappropriate displacement e.g. overreaching
Dysdiadochokinesis - inability to make rapid alternating movement,
Decomposition of movement - lack of co-ordination of different joint movements
He also observed that: ‘after a cerebellar lesion……it is as if each movement is being performed for the first time’.
Cerebellar lesions profoundly affect movement leaving it _______.
Cerebellar lesions profoundly affect movement leaving it uncoordinated.
describe the cerebellar structure
The cerebellum has a simple, but very precise organisation.
It comprises a superficial sheet of tissue (cerebellar cortex) that buries the output structures (deep cerebellar nuclei).
Cerebellar cortex is simple and highly organised, making it one of the best understood brain areas in terms of connectivity and circuit organisation.
The output of the cerebellar cortex is exclusively from which cells?
The output of the cerebellar cortex is exclusively from the Purkinje cells.
purkinje cells dendrites are ?
planar
what do purkinje cells project to?
Purkinje cells project to and inhibit (GABA) cells in the cerebellar nuclei, which are the output neurons of the cerebellum and project to motor structures.
largest cereberllar nucleus in man>?
denate nucleus
where does the dentate nucleus project to?
the dentate nucleus, which projects to the parts of the thalamus (VL & VA) that supply motor and motor association areas of the cerebral cortex.
cerebellar strucutre
which are the only excitatory cells in the cerebellum?
granule cells
quantity of grasnule cells in the cerebellum?
huge numbers
lots
granule cells give rise to ___ ____ which excite?
Granule cells are the only excitatory neurons; they are found in huge numbers (the most numerous cells in the brain) and give rise to parallel fibres that excite Purkinje cells
3 pooints about cerebellar cotex
- highly ordered, (the neurons are precisely laid out) in a geometric organisation
- uniform over the whole cortex & (unlike the cerebral cortex, all areas look the same)
- conserved between species (all vertebrates have a similar cerebellum)
inputs to cerebellum coem from?
mossy fibres
mossy fibres excite?
granule cells
decrbie the purkinje cell dendritic tree?
HUGE
Purkinje cells through their massive dendritic trees the can do what?
Purkinje cells through their massive dendritic trees the can ‘listen’ to inputs from as many as 200 000 different granule cells
where do mossy fibres arise from
Mossy fibres arise from many brain structures, some from sensory pathways, and (particularly in man), from the pons which is a cerebro-cerebellar relay.
Inputs to the pons include information on activity in motor cortex and motor association cortex (efference copy information on motor commands), as well as inputs from sensory areas.
where do climbing fibres arise?
inferior olive in medulla
describe climbing fibre input to purkinje cells?
each Purkinje cell receives input from a single climbing fibre.
This connection is, however, massive and always makes the Purkinje cell discharge at least one action potential.
3 cerebelum areas?
spinocerebellum - first to evovle - onvolved din whoel body movements
intermediate cerebellum - connected to motor cortex throguh thalamus - outputs to the dorsolateral descending motor pathways
lateral cerebellum- output to motor association cortex (again passing through thalamus)
describe cerebella motorm learning
climbing fibres teach purkinje cells when its appropriate to fire to a set of inputs from mossy fibres
synaptic plasticity showmn as evidence: Long Term Depression (LTD) of parallel fibre to Purkinje cell synapses following conjunctive activation of parallel fibres and climbing fibres
cerebellar LTD = involves removal of receptors and does not involve NMDA receptors
which cerebellar region is involved in eye movement
flocculus
describe what the flocculus does
A region of cerebellum called the flocculus is involved.
If the wrong amount of head movement is generated then the retinal slip will generate climbing fibre signals in the flocculus, which in turn mediate cerebellar plasticity in the flocculus, modifying its output.
fat
mamba
