Nerve cells, their structure

Polymer materials have been established as excellent materials in chemistry, automotives and electronics to interconnect different components, to electrically insulate conductors and to survive harsh corrosive environments. Polyimides are the most common material class for substrate and insulation materials in combination with metals for interconnection wires and electrode sites. Therefore, it is quite natural that the medical device industry has focused its attention to polyimides for medical devices in general and especially for encapsulation and insulation of active implants. Neural implants are technical systems that are mainly used to stimulate parts and structures of the nervous system with the aid of implanted electrical circuitry or record the electrical activity of nerve cells. Their application... 

The structural design of nerve cells is a striking example of dendritic architecture, which acts as a signal transduction system. Neurons are known to send out a series of long specialized processes that will either receive electrical signals (dendrites) or transmit these electrical signals (axons) to their target cells (Fig. 5.40). 

Lewy bodies Abnormal masses inside some nerve cells. They occur in a variety of locations, and their structure and composition vary depending on location. 

Nerve cells (neurons) are easily excitable cells that produce electrical signals and can react to such signals as well. Their structure is markedly different from that of other types of cell. Numerous branching processes project from their cell body (soma). Neurons are able to receive signals via dendrites and to pass them on via axons. The axons, which can be up to 1 m long, are usually surrounded by Schwann cells, which cover them with a lipid-rich myelin sheath to improve their electrical insulation. 

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...

There are different types of neurons. Although all neurons carry electro-chemical nerve signals, they can differ in their structure (the number of processes, or axons, emanating from the cell body) and in their location in the body. 

Steroids are lipids that have the same basic cyclic structure shown in figure 2.3.2. The steroids have a notoriety of their own, but again, they serve their purpose and cannot be dispensed with entirely. Steroids are components of cell membranes, nerve cell insulation, and the basis for steroid hormones. 

Neurotransmitters are chemical agents secreted at the end of axons of nerve cells that diffuse across the synaptic gap and transmit information to adjoining cells such as neurons, muscle cells, and glands, by altering their electrical state or activity. There are many neurotransmitters with a variety of structures and functions two of the principle ones are acetylcholine and norepinephrine. Since the neurotransmitters convey information, anything that affects their behavior affects the function of the organism. 

---