Mossy fiber (cerebellum)
Encyclopedia
Mossy fibers are one of the major inputs to cerebellum
. There are many sources of this pathway, the largest of which is the cerebral cortex, which sends input to the cerebellum via the pontocerebellar pathway
. Other contributors include the vestibular nerve
and nuclei
, the spinal cord
, the reticular formation
, and feedback from deep cerebellar nuclei
. Axons enter the cerebellum via the middle and inferior cerebellar peduncles, where some branch to make contact with deep cerebellar nuclei. They ascend into the white matter of the cerebellum , where each axon branches to innervate granule cells in several cerebellar folia
.
In this case, the pathway is so named for a unique synapse formed by its projections, the mossy fiber rosette. Fine branches of the mossy fiber axons twist through the granule cell layer, and slight enlargements giving a knotted appearance indicate synaptic contacts. These contacts have the appearance of a classic Gray's type 1 synapse, indicating they are glutamatergic and excitatory. Sensory information relayed from the pons through the mossy fibers to the granule cells is then sent along the parallel fibers to the Purkinje cells for processing. Extensive branching in white matter and synapses to granular cells ensures that input from a single mossy fiber axon will influence processing in a very large number of Purkinje cells.
, which shares little similarity with its cerebellar namesake
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. There are many sources of this pathway, the largest of which is the cerebral cortex, which sends input to the cerebellum via the pontocerebellar pathway
Pontocerebellar fibers
The pontocerebellar fibers are fibers that run within the middle cerebellar peduncles, from the pons to the cerebellum.The term "corticopontocerebellar" is sometimes used to denote afferent signals from the cerebral cortex.-External links:...
. Other contributors include the vestibular nerve
Vestibular nerve
The vestibular nerve is one of the two branches of the Vestibulocochlear nerve . It goes to the semicircular canals via the vestibular ganglion...
and nuclei
Vestibular nuclei
The vestibular nuclei are the cranial nuclei for the vestibular nerve.In Terminologia Anatomica they are grouped in both the pons and medulla.-Subnuclei:There are 4 subnuclei; they are situated at the floor of the fourth ventricle....
, the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
, the reticular formation
Reticular formation
The reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...
, and feedback from deep cerebellar nuclei
Deep cerebellar nuclei
The Cerebellum has four deep cerebellar nuclei embedded in the white matter in its center.-Inputs:These nuclei receive inhibitory inputs from Purkinje cells in the cerebellar cortex and excitatory inputs from mossy fiber and climbing fiber pathways. Most output fibers of the cerebellum originate...
. Axons enter the cerebellum via the middle and inferior cerebellar peduncles, where some branch to make contact with deep cerebellar nuclei. They ascend into the white matter of the cerebellum , where each axon branches to innervate granule cells in several cerebellar folia
Folium (brain)
A folium is a wrinkle on the surface of the cerebellum. The cortex of a folium consists of three layers of cells - the top molecular layer, the Purkinje layer, and the bottom granular layer - and this cortex covers deeper white matter ....
.
In this case, the pathway is so named for a unique synapse formed by its projections, the mossy fiber rosette. Fine branches of the mossy fiber axons twist through the granule cell layer, and slight enlargements giving a knotted appearance indicate synaptic contacts. These contacts have the appearance of a classic Gray's type 1 synapse, indicating they are glutamatergic and excitatory. Sensory information relayed from the pons through the mossy fibers to the granule cells is then sent along the parallel fibers to the Purkinje cells for processing. Extensive branching in white matter and synapses to granular cells ensures that input from a single mossy fiber axon will influence processing in a very large number of Purkinje cells.
See also
Mossy fiber (hippocampus)Mossy fiber (hippocampus)
In the hippocampus, granule cells of the dentate gyrus form distinctive unmyelinated axons that project along the mossy fiber pathway to the CA3 region. The axons emerge from the basal portions of the granule cells and pass through the hilus of the dentate gyrus before entering the stratum...
, which shares little similarity with its cerebellar namesake