Nerve cell migration

The nervous system consists of two main units the central nervous system (CNS), which includes the brain and the spinal cord and the peripheral nervous system (PNS), which includes the body s system of nerves that control the muscles (motor function), the senses (the sensory nerves), and which are involved in other critical control functions. The individual units of the nervous system are the nerve cells, called neurons. Nenrons are a nniqne type of cell becanse they have the capacity to transmit electrical messages aronnd the body. Messages pass from one nenron to the next in a strnctnre called a synapse. Electric impnlses moving along a branch of the nenron called the axon reach the synapse (a space between nenrons) and canse the release of certain chemicals called neurotransmitters, one of which, acetylcholine, we described earlier in the chapter. These chemicals migrate to a nnit of the next nenron called the dendrites, where their presence canses the bnild-np of an electrical impnlse in the second nenron. 

The coexistence of lipid and water solubility in the same molecule is essential for the action of a local anaesthetic drug. Lipophilicity permits the migration of drug across the phospholipid membrane of the nerve cell hydrophilicity is essential for the ionisation of the drug within the nerve. It follows that lipid and water solubility are the external and internal facilitators of local anaesthetic action in the nerve cell. Both within and without the nerve cell the unionised and ionised forms coexist in dynamic equilibrium. Outside the nerve, the active species is the unionised tertiary amine form. Conversely, inside the cell the ionised form predominates. The lower intracellular pH induces a shift in the equilibrium in favour of ionisation (Figure 5.5). 

Fig. 8 Nerve cells adjust their adhesion and migration to the corresponding structure, as seen here on random (a, c) and aligned (b, d) cells, (a, b) SEM pictures of PCL nanofibers where gioma cells adhered and followed the fiber alignment (see asterisk in b). (c, d) Motion cell-tracking 20 individual trajectories were traced manually after a total tracking period of 36 h. Scale bars (a, b) 10 pm. Reprinted, with permission, from [178] copyright (2009) Mary Ann Liebert...

The adult (somatic) stem cells migrate with the tissue they form. For a while it was believed that blood stem cells gave rise to blood tissue only, but recently it s been shown they possess plasticity, that is, they can give rise to a number of different cells, such as nerve cells and liver cells. 

Figure 20.1. Hypothetical scheme of the immune response in acute inflammatory demyelinating polyradiculoneuropathy (AIDP) Inflammatory cells migrate from the systemic immune compartment through the damaged blood-nerve barrier into the endoneurium. Inflammatory infiltrates, which contain T-lymphocytes and macrophages cause marked segmental demyelination and secondary axonal degeneration (B B-cell T T-cell M4> Macrophage).

Schoen SW, Graeber MB, Toth L, Kreuzberg GW (1988) 5 -Nucleotidase in postnatal ontogeny of rat cerebellum a marker for migrating nerve cells Dev. Brain Res., 39, 125-136. 

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