164
UNIT ONE
5.6
NERVOUS TISSUES
Nervous
(ner
vus)
tissues
are found in the brain, spinal cord,
and peripheral nerves. The basic cells are called
neurons,
and
they are highly specialized. Neurons sense certain types of
changes in their surroundings and respond by transmitting
nerve impulses along cellular processes called
axons
to other
neurons or to muscles or glands
(f g. 5.31)
. As a result of the
extremely complex patterns by which neurons connect with
each other and with muscle and gland cells, they can coordi-
nate, regulate, and integrate many body functions.
In addition to neurons, nervous tissue includes abun-
dant
neuroglia,
shown in F
gure 5.31. These cells support and
bind the components of nervous tissue, carry on phagocyto-
sis, and help supply growth factors and nutrients to neurons
by connecting them to blood vessels. They also play a role
Cardiac Muscle Tissue
Cardiac muscle tissue
is only in the heart
(f g. 5.30)
. Its cells,
striated and branched, are joined end-to-end, and intercon-
nected in complex networks. Each cardiac muscle cell has a
single nucleus. Where one cell touches another cell is a spe-
cialized intercellular junction called an
intercalated disc,
seen
only in cardiac tissue.
Cardiac muscle, like smooth muscle, is controlled invol-
untarily. Cardiac muscle can continue to function without
being stimulated by nerve impulses. This tissue makes up
the bulk of the heart and pumps blood through the heart
chambers and into blood vessels.
PRACTICE
22
List the general characteristics of muscle tissue.
23
Distinguish among skeletal, smooth, and cardiac muscle tissues.
Nucleus
Cytoplasm
(a)
(b)
FIGURE 5.29
Smooth muscle tissue consists of spindle-shaped cells, each with a large nucleus (1,000×).
Intercalated
disc
Nucleus
Striations
(a)
(b)
FIGURE 5.30
Cardiac muscle cells are branched and interconnected, with a single nucleus each (400×).
previous page 194 David Shier Hole's Human Anatomy and Physiology 2010 read online next page 196 David Shier Hole's Human Anatomy and Physiology 2010 read online Home Toggle text on/off