The motor system- Lecture 21 Flashcards
(23 cards)
What percentage of neurones in the brain are in the cerebellum?
82%
What volume of the brain is the cerebellum?
10%
What are some characteristic movements of cerebellum lesions?
Tremor, hypermetria (overreaching) dysdiadochokinesia, ataxic gait
What are the four nuclei of the cerebellum?
Dentate, emboliform, globose and fastigial
Which two nucleus are interposed?
Emboliform an globose
What is a fundamental feature of the cerebellum?
The lateral, intermediate and medial cerebellum are divided
Describe the lateral cerebellum pathway
This is the cerebrocerebellar. The dentate nucleus receives input from the cortex via the pontine nuclei. the dentate projects to the ventrolateral nucleus of the thalamus which goes back to the cortex.
What cortex area does the cerebrocerebellar receive inputs from?
association cortex
What nucleus does the cerebrocerebellar receive inputs via?
The pontine nucleus
What nucleus does the dentate nucleus project to?
The ventrolateral nucleus of the thalamus
What is the only output cell of the cerebellum?
The Purkinje cell- GABA inhibitory cell
What layer is the Purkinje cell dendritic tree in?
The molecular layer
What are the two inputs to Purkinje cells?
From parallel fibres and climbing fibres
What are parallel fibres?
The axons of granule cells which are in the granule layer. Their axons reach up and bifurcate to cross the dendritic trees at right angles.
Where do granule cells get their inputs from?
Mossy fibres and golgi cells
Where do golgi cells get input from?
Descending axons of parallel fibres
Describe gain control in the cerebellum layers
Granule cells get excitatory input from mossy fibres and inhibitory input from golgi cells. Golgi cells are innervated by parallel fibres which are the axons of the granule cell so there is feedback about activity
What rule of neuroscience do Purkinje cells break?
That APs are all or nothing
What do simple spike APs arise from?
Temporal summation of parallel fibre input to Purkinje cells
What is the rate of simple spikes?
100Hz
What do complex spikes arise from?
One-to-one input from a climbing fibre to Purkinje cell
What rate do complex spikes occur at?
1Hz
Describe Marr and Albus’s thinking of how the cerebellum could automate movement.
When Purkinje cells are activated by climbing fibres when doing a movement for the first time, synapses of mossy fibres are strengthened. So when we do that movement again, the mossy fibres are able to activate the Purkinje cell
