1.1 Neurons and Glia

• Neurons receive information and transmit it to other cells.
• Glia serve many functions that are difficult to summarize, and we shall defer that discussion until later in this module.
• Dendrites are branching fibers that get narrower near their ends.
• The dendrite’s surface is lined with specialized synaptic receptors, at which the dendrite receives information from other neurons.
• The greater the surface area of a dendrite, the more information it can receive. Many dendrites contain dendritic spines, short outgrowths that increase the surface area available for synapses.
• The cell body, or soma, contains the nucleus, ribosomes, and mitochondria. Most of a neuron’s metabolic work occurs here.
• Cell bodies of neurons range in diameter from 0.005 millimeter (mm) to 0.1 mm in mammals and up to a millimeter in certain invertebrates. In many neurons, the cell body is like the dendrites— covered with synapses on its surface.
• The axon is a thin fiber of constant diameter. The axon conveys an impulse toward other neurons, an organ, or a muscle. Axons can be more than a meter in length.
• A motor neuron, with its soma in the spinal cord, receives excitation through its dendrites and conducts impulses along its axon to a muscle.
• A sensory neuron is specialized at one end to be highly sensitive to a particular type of stimulation, such as light, sound, or touch.