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18 Chapter 3<br />
Sensory (receptor) neurons<br />
Motor neuron<br />
Olfactory<br />
Auditory<br />
Cutaneous<br />
Dendrites<br />
Dendritic zone<br />
Axon hillock<br />
Initial segment<br />
Node<br />
of Ranvier<br />
Myelin sheath<br />
Axon<br />
Axon collaterals<br />
Schwann cell<br />
Telaxon<br />
Synaptic endings (terminal boutons)<br />
Neuromuscular junction<br />
Figure 3-1 Types of nerve cells. Olfactory neurons are bipolar and unmyelinated. Auditory neurons are bipolar and<br />
myelinated. Spinal (posterior root) ganglion cells (cutaneous) are pseudounipolar and myelinated. Motor neurons are<br />
multipolar and myelinated. Arrows indicate input through the axons of other neurons. (Modified from Carpenter MB,<br />
Sutin J. Human <strong>Neuroanatomy</strong>. Baltimore, MD: Williams & Wilkins; 1983:92, with permission.)<br />
B. Slow Anterograde Transport—responsible for transporting fibrillar cytoskeletal and protoplasmic<br />
elements. This process occurs at the rate of 1 to 5 mm/day.<br />
C. Fast Retrograde Transport—returns used materials from the axon terminal to the cell body<br />
for degradation and recycling at a rate of 100 to 200 mm/day. It transports nerve growth factor,<br />
neurotropic viruses, and toxins, such as herpes simplex, rabies, poliovirus, and tetanus toxin. It<br />
is mediated by neurotubules and dynein.<br />
IV<br />
Anterograde (Wallerian) Degeneration—characterized by the<br />
disappearance of axons and myelin sheaths and the secondary proliferation of Schwann cells. It<br />
occurs in the central nervous system (CNS) and the peripheral nervous system (PNS).<br />
V<br />
Chromatolysis—the result of retrograde degeneration in the neurons of the CNS and<br />
PNS. There is a loss of Nissl substance after axotomy.<br />
VI<br />
Regeneration of Nerve Cells
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