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Neurons communicate with other cells via synapses, which are specialized connections that commonly use minute amounts of chemical neurotransmitters to pass the electric signal from the presynaptic neuron to the target cell through the synaptic gap. Neurons are the main components of nervous tissue in all animals except sponges and placozoans.
Neurogenesis is the process by which nervous system cells, the neurons, are produced by neural stem cells (NSCs). [1] This occurs in all species of animals except the porifera (sponges) and placozoans. [2]
Corticogenesis: younger neurons migrate past older ones using radial glia as a scaffolding. Cajal–Retzius cells (red) release reelin (orange). Neuronal migration is the method by which neurons travel from their origin or birthplace to their final position in the brain. There are several ways they can do this, e.g. by radial migration or ...
Neurons migrating with this mode of locomotion are bipolar and attach the leading edge of the process to the pia. The soma is then transported to the pial surface by nucleokinesis, a process by which a microtubule "cage" around the nucleus elongates and contracts in association with the centrosome to guide the nucleus to its final destination ...
The axolotl is less commonly used than other vertebrates, but is still a classical model for examining regeneration and neurogenesis. Though the axolotl has made its place in biomedical research in terms of limb regeneration, [19] [20] the model organism has displayed a robust ability to generate new neurons following damage.
The neurons that are able to re-enter the cell cycle are much more likely to undergo apoptosis and lead to the disease phenotypes. In Alzheimer’s disease, affected neurons show signs of DNA replication such as phosphorylated Mcm2 and cell cycle regulators cyclin D, Cdk4, phosphorylated Rb, E2F1, and cyclin E.
The evolution of nervous systems dates back to the first development of nervous systems in animals (or metazoans). Neurons developed as specialized electrical signaling cells in multicellular animals, adapting the mechanism of action potentials present in motile single-celled and colonial eukaryotes.
Ramón y Cajal's drawing of the cells of the chick cerebellum, from Estructura de los centros nerviosos de las aves, Madrid, 1905. The neuron doctrine is the concept that the nervous system is made up of discrete individual cells, a discovery due to decisive neuro-anatomical work of Santiago Ramón y Cajal and later presented by, among others, H. Waldeyer-Hartz. [1]