Cerebellum Flashcards
The brains largest cell is found in the Cerebellum. What is the name of this cell?
Purkinje cell
The most numerous cell in the brain is found in the Cerebellum. What is the name of this cell?
Granule cell
Explain the reasoning behind the structure of the Purkinje cell?
Having huge flat plates with flat dendritic arbor allows the Purkinje cell to make many connections to other cells ( 100,000).
Purkinje cells can produce either a simple or a complex spike. What are the fundamental differences between these two spikes.
Simple spikes is the usual spike.
Complex spike has a leading spike, similar to a simple spike. It is then followed by spikelets, a series of smaller spikes. The complex spike has a far larger refectory period.
What is the ratio of Purkinje cells to climbing fibres?
1:1
Each Purkinje cell has its own climbing fiber which winds up around it.
Explain the connection between the mossy fibres and the Granule cell.
The Granule cells receive inputs from many different parts of the brain along the mossy fibres.
Each Granule cell will combine inputs from 3 or 4 mossy fibres.
How is the Granule cell linked to the Purkinje cell?
The parrallel fibre carries spikes from the Granule cell to the Purkinje cell.
The parallel fibres carry information to the Purkinje cell from the Granule cell.
Explain the other input to the Purkinje cell?
The other input is the climbing fibres. This carries information from the Inferior Olive.
What is the Inferior Olive?
It is fundamental in motor control. It is a major source of input to the cerebellum.
The Purkinje cells recieve inputs from the Inferior olive via the cimbing vibres. The Purkinje cell then send inhibitory signals where? What does this do?
The Purkinje cells then send inhibitory signals to the Deel Cerebellar Nucleus (DCN).
The DCN has inhibitory neurons which act on the Inferior olive and excititary neurons which act of the motor system.
If inhibitory signals stop neurons from firing, how does an inhibitory connection between the Purkinje Cell and the Deep Cerebellar nucleus result in movement?
The Purkinje cells inhibit other inhibitory cells in the Deep cerebellar Nucleus. Turning off the ‘DONT MOVE’ mechanism.
People with parkinson’s often lose this connection, hence why shaking hands is a common symptom.
Can you have many complex spikes in quick succession?
No, a complex spike is followed by a long refractory period during which time spiking is not possible.
Typical complex spike refectory period is 50ms.
Which connection within the Cerebellum act as a perceptron
Parrallel fibres to the Purkinje cells.
What is the difference of having positive and negative errors in the perceptron?
Remember, the connection is inhibitory.
Positive errors and associated with synaptic depression. This is a result of climbing fibre activity being greater than average.
Negative errors associated with synaptic potentiation. This is a result of the climbing fibre activity being less than average.
Synapse from the parallel fibre can only be positive. Give a limitation of this?
Inability to learn complex models, e.g the XOR function.
