Cell communication (biology)
In cells, DNA is housed in the nucleus and it never leaves. The DNA within the nucleus is transcribed by tRNA, and the transcriptions of the DNA become RNA. The RNA (ribonucleic acid) leaves the nucleus to float freely around the cytoplasm, and it contains the instructions of the DNA that are vital to the coding, decoding, regulation and expression of genes. The ribosomes then take the RNA messages and turn them into proteins that build cells. When a virus enters a cell and inserts its DNA code into the nucleus, it gets transcribed and released into the cell for the ribosome to make it into a protein. This is how viral infections occur. The cell then explodes with the overproduction of the virus, releasing it into the body to infect any and all other cells it finds. It is theorized that through evolution, cells developed a defense system called RNAi (RNA interference) to stop the production of the proteins that have suspicious mirror image messages of the RNA. They don’t just destroy the suspicious messages, but the correct messages as well to stop all production of that message. This is a cell’s self-destruct mechanism and every cell, plant and animal, have RNAi: a way to turn off the production of a certain gene inside the protein.
Anatomy of the cerebellum
The innermost layer contains the cell bodies of three types of cells: the numerous and tiny granule cells, the slightly larger unipolar brush cells and the much larger Golgi cells. Mossy fibers enter the granular layer from their main point of origin, the pontine nuclei. These fibers form excitatory synapses with the granule cells and the cells of the deep cerebellar nuclei. The granule cells send their T-shaped axons—known as parallel fibers—up into the superficial molecular layer, where they form hundreds of thousands of synapses with Purkinje cell dendrites. The human cerebellum contains on the order of 60 to 80 billion granule cells, making this single cell type by far the most numerous neuron in the brain (roughly 70% of all neurons in the brain and spinal cord, combined). Golgi cells provide inhibitory feedback to granule cells, forming a synapse with them and projecting an axon into the molecular layer.