Dendrites
Cell body
Nucleus
Astrocyte
Microglial
cell
Muscular Tissue Generates
Force for Movement
Muscular tissue is composed of elongated muscle cells
called muscle fibers. The job of muscular tissue is to
generate force, which produces motion, maintains pos-
ture, and generates heat. There are three types of mus-
cular tissue (Figure 3.26): •
You will learn the details of these muscle tissues in Chap-
ters 6, 11, and 14.
Nervous Tissue Transmits Impulses to
Coordinate Activities
Blood '
vessel
N eurons and neuroglia • Figure 3.27
Numerous projections of the cell body of the neu
ron called dendrites receive nerve impulses
from other cells. A long projection of the
neuron cell body called an axon conducts
each impulse away from the cell body to
other cells. The two types of neuroglial
cells—astrocytes and microglia—sup
port the nerve cells.
Axon
Skeletal
muscle.
These
groups
of long,
multi-
nucleated
cells
with
regular
bands
or
striations
generate force upon voluntary commands. This muscle
is usually attached to the skeleton and contracts
voluntarily.
Smooth muscle. These groups of small cells with one
nucleus each are capable of stretching and are part
of blood vessels, the stomach, intestines, uterus, and
bladder. Smooth muscle tissue has no striations and
contracts involuntarily.
Cardiac muscle. The intermediate-sized cells that
make up this tissue are connected to one another by
cell junctions called
intercalated discs.
Cardiac muscle
has striations and contracts involuntarily.
Despite the complexity of nervous system functions, ner-
vous tissue consists of only two types of cells: neurons
and neuroglia (Figure 3.27). Neurons (
NOO-ronz
), or
nerve cells, are specialized cells that are sensitive to
various stimuli. They convert stimuli into nerve impulses
and conduct these impulses to other neurons, to muscle
fibers, or to glands. Neurons can be small or large. For ex-
ample, some neurons within the brain may extend only a
few inches, while a spinal neuron from the spinal cord to
a muscle in your foot may extend well over a foot. Neu-
roglia (
noo-ROG-le-a
) are supporting cells that do not
generate or conduct nerve impulses but have many other
important supportive functions. The detailed structure
and function of neurons and neuroglia are considered in
Chapter 7.
Cells Specialize into Various Tissues 81
previous page 116 Craig Freudenrich, Gerard J  Tortora   Visualizing Anatomy and Physiology   2011 read online next page 118 Craig Freudenrich, Gerard J  Tortora   Visualizing Anatomy and Physiology   2011 read online Home Toggle text on/off