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A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them.
However, granule cell dendrites are not an essential component of senile plaques and these plaques have no direct effect on granule cells in the dentate gyrus. The specific neurofibrillary changes of dentate granule cells occur in patients with Alzheimer's, Lewy body variant and progressive supranuclear palsy .
Cerebellar granule cells form the thick granular layer of the cerebellar cortex and are among the smallest neurons in the brain. (The term granule cell is used for several unrelated types of small neurons in various parts of the brain.) Cerebellar granule cells are also the most numerous neurons in the brain: in humans, estimates of their total ...
Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges , blood vessels , and ducts. The two main types of cells in the brain are neurons , also known as nerve cells, and glial cells , also known as neuroglia. [ 1 ]
Recent research has elucidated the regulatory effect of GABA on neural stem cells. GABA's well-known inhibitory effects across the brain also affect the local circuitry that triggers a stem cell to become dormant. They found that diazepam (Valium) has a similar effect. [158]
The arachnoid mater covering the brain is referred to as the arachnoidea encephali, and the portion covering the spinal cord as the arachnoidea spinalis. The arachnoid and pia mater are sometimes considered as a single structure, the leptomeninx, or the plural version, leptomeninges ( lepto , from the Greek root meaning "thin" or "slender").
Oligodendrocyte progenitor cells (OPCs), also known as oligodendrocyte precursor cells, NG2-glia, O2A cells, or polydendrocytes, are a subtype of glia in the central nervous system named for their essential role as precursors to oligodendrocytes and myelin. [1] They are typically identified in the human by co-expression of PDGFRA and CSPG4.
Such cells have been called hybrid brain cells because they exhibit both neuron-like and glial-like properties. Unlike traditional neurons , these cells not only transmit electrical signals but also provide supportive roles typically associated with glial cells , such as regulating the brain's extracellular environment and maintaining overall ...