Search results
Results from the WOW.Com Content Network
Pyramidal cells, or pyramidal neurons, are a type of multipolar neuron found in areas of the brain including the cerebral cortex, the hippocampus, and the amygdala. Pyramidal cells are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract .
The pyramidal cells in CA3 have a unique type of dendritic spine called a thorny excrescence or thorn, only found in CA3 pyramidal cells and hilar mossy cells. The thorn has a thin single spine with a number of heads. Clusters of thorns sit on a dendrite on a broad stem.
There is also a distinct pathway from layer 3 of the EC directly to CA1, often referred to as the temporoammonic or TA-CA1 pathway. Granule cells of the DG send their axons (called "mossy fibers") to CA3. Pyramidal cells of CA3 send their axons to CA1. Pyramidal cells of CA1 send their axons to the subiculum and deep layers of the EC.
Schaffer collaterals are the axons of pyramidal cells that connect two neurons (CA3 and CA1) and transfer information from CA3 to CA1. [5] [6] The entorhinal cortex sends the main input to the dentate gyrus (perforant pathway). From the granule cells of the dentate gyrus, connections are made to the CA3 regions of the hippocampus via mossy fibers.
The trisynaptic circuit is a neural circuit in the hippocampus, which is made up of three major cell groups: granule cells in the dentate gyrus, pyramidal neurons in CA3, and pyramidal neurons in CA1. The hippocampal relay involves 3 main regions within the hippocampus which are classified according to their cell type and projection fibers.
It is the tract of the mossy fiber projections, both inhibitory and excitatory from the granule cells of the dentate gyrus. One mossy fiber may make up to 37 connections to a single pyramidal cell, and innervate around 12 pyramidal cells on top of that. Any given pyramidal cell in the stratum lucidum may get input from as many as 50 granule cells.
Betz cells are not the sole source of direct connections to those neurons because most of the direct corticomotorneuronal cells are medium or small neurons. [3] While Betz cells have one apical dendrite typical of pyramidal neurons, they have more primary dendritic shafts, which can branch out at almost any point from the soma (cell body). [4]
The Betz cells account for only a small percentage of the corticospinal tract. By some measures, they account for about 10% of the primary motor cortex neurons projecting to the spinal cord [ 1 ] or about 2-3% of the total cortical projection to the spinal cord. [ 2 ]