Biomedical Engineering Reference
In-Depth Information
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Figure 2.4
The neuron.
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Figure 2.5
Synaptic junction between beurons.
Figure 2.4. There are three parts—soma or cell body, dendrites and axon. The
soma is the central component of the cell which contains the nucleus where
protein synthesis occurs. The axon is a projection that extends some distance in
comparison with the soma, depending on the particular function of the cell.
Close in proximity to soma is the axon hillock, where there is a high density of
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channels. The axon itself contains structures called nodes of Ranvier
(constrictions) and is 'coated' with a myelin sheath. Filament-like dendrites in
great numbers, and displaying a high level of branching, emanate from the
soma. Signals from other neurons are received by the soma via the dendrites
and signals from the axon terminal are transmitted to other cells. The signaling
mechanism has components of electrical and chemical processes which occur
via the synapse (Figure 2.5). (The human adult brain possesses some 10
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synapses!) In this structure, close proximity is exhibited by bilayer lipid
membranes which, intrinsically, display high electrical resistance due to the
