Fundamentals of Anatomy and Physiology

106

thus, it pumps the blood through our body. The inter-
connected branches of cardiac muscle cells guarantee
coordination of the pumping action of the heart (to be
discussed further in Chapter 14).

Nervous Tissue

The basic unit of organization of nervous tissue is the nerve
cell or neuron (NOO-ron) (Figure 5-17). Actually, the
neuron is a conducting cell, whereas other cells of the
system called neuroglia are supporting cells. These
different types of nerve cells are discussed in greater detail
in Chapter 10. Neurons are very long cells, so like muscle
cells, they are called nerve fibers. It is ba-sically impossible
to view an entire neuron even un-der low power of the
microscope due to their length.

Chapter 5

However, we can view the parts of a neuron as we scan a

microscope slide. The cell body contains the nucleus. It

also has rootlike extensions called dendrites (DEN-drytz)

that receive stimuli and conduct them to the cell body.

Axons (AK-sonz) are long, thin extensions of the cell

body that transmit the impulse toward the axon endings.

Nervous tissue makes up the brain, spinal cord, and

various nerves of the body. It is the most highly or-ganized

tissue of the body. It controls and coordinates body

activities. It allows us to perceive our environment and to

adapt to changing conditions. It coordinates our skeletal

muscles. Its special senses include sight, taste, smell, and

hearing. It controls our emotions and our reasoning

capabilities. It allows us to learn through the memory

process.

Function Characteristics and Location Morphology

Neurons (nerve cells)

These cells have the ability

to react to stimuli.

1. Irritability —
   Ability of nerve tissue to respond
   to environmental changes.


2. Conductivity —
   Ability to carry a nerve
   impulse (message).

(^)
Nerve tissue is composed of Dendrites^
neurons (nerve cells). Neurons (^)
have branches through which (^)
various parts of the body are (^)
connected and their activities (^)
coordinated. They are found in (^)
the brain, spinal cord, and nerves. (A) Cell body

(B)

Nucleus

AxonSheath Myelin^

Axon terminal

branches

Source

Associates/Science Biophoto ©

(B) Photo

(^) ,
® Learning
Cengage
© (A)
Figure 5- 17 Views of a neuron (multipolar, motor
neuron).