Granule cell
These parallel fibers form thousands of excitatory granule-cell–Purkinje-cell synapses onto the intermediate and distal dendrites of Purkinje cells using glutamate as a neurotransmitter.
Granule cells in different brain regions are both functionally and anatomically diverse: the only thing they have in common is smallness.
In the transmission electron microscope, these cells are characterized by a darkly stained nucleus surrounded by a thin rim of cytoplasm.
The granule cells in the dorsal cochlear nucleus are small neurons with two or three short dendrites that give rise to a few branches with expansions at the terminals.
The dendrites are short with claw-like endings that form glomeruli to receive mossy fibers, similar to cerebellar granule cells.
[5] Its axon projects to the molecular layer of the dorsal cochlear nucleus where it forms parallel fibers, also similar to cerebellar granule cells.
The main intrinsic granule cell in the vertebrate olfactory bulb lacks an axon (as does the accessory neuron).
[7] In the mammalian olfactory bulb, granule cells can process both synaptic input and output due to the presence of large spines.
[8] Cerebellar granule cells receive excitatory input from 3 or 4 mossy fibers originating from pontine nuclei.
The parallel fibers and ascending axon synapses from the same granule cell fire in synchrony which results in excitatory signals.
[14] Granule cells do not just relay signals from mossy fibers, rather they perform various, intricate transformations which are required in the spatiotemporal domain.
David Marr and James Albus suggested that the cerebellum operates as an adaptive filter, altering motor behaviour based on the nature of the sensory input.
In order for the granule cell to respond, it needs to receive active inputs from multiple mossy fibers.
[16] The cerebellar granule cells also play a role in orchestrating the tonic conductances which control sleep in conjunction with the ambient levels of GABA which are found in the brain.
Granule cells in the dorsal cochlear nucleus play a role in the perception and response to sounds in our environment.
[22] Calcium dynamics are essential for several functions of granule cells such as changing membrane potential, synaptic plasticity, apoptosis, and regulation of gene transcription.
[10] The nature of the calcium signals that control the presynaptic and postsynaptic function of the olfactory bulb granule cells spines is mostly unknown.
This is due to the fact that dentate granule cells play a critical role in the function of the entorhinal-hippocampal circuitry in health and disease.
Dentate granule cells are situated to regulate the flow of information into the hippocampus, a structure required for normal learning and memory.
The specific neurofibrillary changes of dentate granule cells occur in patients with Alzheimer's, Lewy body variant and progressive supranuclear palsy.
