Specialization

Nervous tissues are specialized to:

a. Receive stimuli. Cells receiving stimuli are said to be "irritable" (as are all living cells somewhat).

b. Transmit information.

c. "Store" information.

Section II. THE NEURON AND ITS "CONNECTIONS"

5-3. DEFINITION OF A NEURON

A neuron (Figure 5-1) is a nerve cell body and all of its branches.

Figure 5-1. A neuron. 5-4. TYPES OF NEURON BRANCHES

There are two types of neuron branches--dendrites and axons.

a. Dendrite. A dendrite is a neuron process that carries impulses toward the cell body. Each neuron may have one or more dendrites. Dendrites receive information and transmit (carry) it to the cell body.

b. Axon. An axon is a neuron branch that transmits information from the cell body to the next unit. Each neuron has only one axon.

c. Information Transmission. Information is carried as electrical impulses along the length of the neuron.

d. Coverings. Some neuron processes have a covering that is a series of Schwann cells, interrupted by nodes (thin spots). This gives the neuron branch the appearance of links of sausages. The Schwann cells produce a lipid (fatty) material called myelin. This myelin acts as an electrical insulator during the transmission of impulses.

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