Nervous Tissue

Learning Objectives

  • Describe the structure and function of nervous tissue
  • Discuss how nervous tissue mediates perception and response

Nervous tissue is characterized as being excitable and capable of sending and receiving electrochemical signals that provide the body with information. Two main classes of cells make up nervous tissue: the neuron and neuroglia (Figure 4.16). Neurons propagate information via electrochemical impulses, called action potentials, which are biochemically linked to the release of chemical signals.  Neurons display distinctive morphology, well suited to their role as conducting cells.  They have three main parts: (1) the cell body includes most of the cytoplasm, the organelles, and the nucleus (2) dendrites branch off the cell body and appear as thin extensions; dendrites receiving incoming stimuli and conduct information toward the cell body (3) the long “tail”  is the axon and extends from the neuron body; the axon conducts impulses away from the cell body.

Neuroglia play an essential role in supporting neurons and modulating their information propagation.

This figure shows a diagram of a neuron and a micrograph showing two neuron cells. The body of the neuron contains a single, purple nucleus. The cell is irregularly shaped, having many projections emerging from its surface. Six sets of dendrites project from the top, right, and bottom edges of the cell. The dendrites are yellow and branch many times after leaving the cell, taking on the appearance of tiny trees. The axon projects from the left edge of the cell. The axon is a long cable like structure that branches into several finger like projections at its end. This is where the neuron makes contact with other cells. A label also notes that the area where the axon emerges from the cell body contains microfibrils and microtubules. The micrograph is considerably less magnified than the diagram. The neurons stain darkly and their nuclei are clearly visible. Their irregular cell body is also visible, along with the beginning of the axons.
Figure 4.16. The Neuron
The cell body of a neuron, also called the soma, contains the nucleus and mitochondria. The dendrites transfer the nerve impulse to the soma. The axon carries the action potential away to another excitable cell. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)
 

Follow this link to learn more about nervous tissue. What are the main parts of a nerve cell?