Movement L6

Question 1

give soem elemetns of cerebral ataxia

Answer 1

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’.

Question 2

Cerebellar lesions profoundly affect movement leaving it _______.

Answer 2

Cerebellar lesions profoundly affect movement leaving it uncoordinated.

Question 3

describe the cerebellar structure

Answer 3

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.

Question 4

The output of the cerebellar cortex is exclusively from which cells?

Answer 4

The output of the cerebellar cortex is exclusively from the Purkinje cells.

Question 5

purkinje cells dendrites are ?

Answer 5

planar

Question 6

what do purkinje cells project to?

Answer 6

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.

Question 7

largest cereberllar nucleus in man>?

Answer 7

denate nucleus

Question 8

where does the dentate nucleus project to?

Answer 8

the dentate nucleus, which projects to the parts of the thalamus (VL & VA) that supply motor and motor association areas of the cerebral cortex.

Question 9

cerebellar strucutre

Answer 9

Question 10

which are the only excitatory cells in the cerebellum?

Answer 10

granule cells

Question 11

quantity of grasnule cells in the cerebellum?

Answer 11

huge numbers

lots

Question 12

granule cells give rise to ___ ____ which excite?

Answer 12

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

Question 13

3 pooints about cerebellar cotex

Answer 13

1. highly ordered, (the neurons are precisely laid out) in a geometric organisation
2. uniform over the whole cortex & (unlike the cerebral cortex, all areas look the same)
3. conserved between species (all vertebrates have a similar cerebellum)

Question 14

inputs to cerebellum coem from?

Answer 14

mossy fibres

Question 15

mossy fibres excite?

Answer 15

granule cells

Question 16

decrbie the purkinje cell dendritic tree?

Answer 16

HUGE

Question 17

Purkinje cells through their massive dendritic trees the can do what?

Answer 17

Purkinje cells through their massive dendritic trees the can ‘listen’ to inputs from as many as 200 000 different granule cells

Question 18

where do mossy fibres arise from

Answer 18

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.

Question 19

where do climbing fibres arise?

Answer 19

inferior olive in medulla

Question 20

describe climbing fibre input to purkinje cells?

Answer 20

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.

Question 21

3 cerebelum areas?

Answer 21

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)

Question 22

describe cerebella motorm learning

Answer 22

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

Question 23

which cerebellar region is involved in eye movement

Answer 23

flocculus

Question 24

describe what the flocculus does

Answer 24

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.

Question 25

fat

Answer 25

mamba