Chapter 13: The Nervous System
How are the functions of neurons and neuroglia different from each other?
Neurons are the basic functional units of the nervous system. That is, they are the smallest pieces of the
system that show basic nervous system functions such as responding to stimuli and conducting impulses
from one part of the cell to another. The neuroglia, or glial cells (from the Greek
, meaning "glue"),
structurally and functionally support and protect the neurons. They outnumber neurons about 10 to 1,
but they are not directly involved in the transmission of information or impulses through the nervous
system. Rather, they are important parts of the infrastructure necessary for the neurons to do their jobs.
Name the parts of a typical neuron.
Dendrite, axon, and cell body
How are the dendrites and axons different in structure and function?
Dendrites receive stimuli, or impulses, from other neurons and conduct this stimulation to the cell body.
Dendrites also may be modified into sensory receptors that receive, or sense, stimuli such as heat, cold,
touch, pressure, stretch, or other physical changes from inside or outside the body. Dendrites tend to be
short, numerous, multibranched projections extending from the cell body.
The axon conducts nerve impulses away from the cell body toward another neuron or an effector cell (a
cell that does something when stimulated, such as a muscle or gland cell). In contrast to the short,
numerous, branched dendrites, the axon is a single structure that can be very long. For example, a single
axon in the horse may extend several feet from the spinal cord all the way to the lower leg. Axons are
often covered by a fatty substance called
What is the difference between gray matter and white matter?
White matter refers to nervous tissue containing many myelinated axons. Conversely, nervous tissue that
is made up largely of neuron cell bodies, which are not myelinated, appears darker and is called
What is the relationship between the myelin sheath and the nodes of Ranvier?
Nodes of Ranvier are small gaps in the myelin sheaths. The nodes of Ranvier and the myelin work
together to enhance the conduction of stimuli.
What are the anatomic differences between the CNS and the PNS?
The central nervous system (CNS) is anatomically composed of the brain and spinal cord, which are
found associated within the central axis of the animal’s body. Peripheral means “to the side” or “away
from the center”; therefore the peripheral nervous system (PNS) is made up of those components of the
nervous system that extend away from the central axis outward toward the periphery of the body.