Introduction to excitable tissue
Basic anatomy
Neurons
Neurons or nerve cells are the main components making up the nervous system and are termed ‘an electrically excitable tissue’ by virtue of their ability to conduct and transmit electrochemical signals throughout the body. There are many different specialized neurons, however a typical neuron (Fig. 6.1) would consist of:
Figure 6.1 The basic structure of a myelinated neuron.
Cell body, which houses the nucleus and organelles
Dendrites, which receive signals from other neurons and carry these signals towards the cell body
Axon, which conducts signals away from the cell body and onto other neurons. The axons of some neurons are myelinated and as a result are able to conduct signals faster due to its insulation properties. Myelination occurs as a result of non-neural cells wrapping themselves around the nerve axon at intervals along its length, interspersed by gaps called the nodes of Ranvier. In the peripheral nervous system, it is Schwann cells which are responsible for this function and in the central nervous system, it is oligodendrites (S2.7).
