Download Nerve Cells (Human)

Nerve Cells (Human)
1 Neurons
Structure
Nerve cells are called neurons. They do not go
through the process of reproducing themselves
(mitosis). They are said to be amitotic: if destroyed,
they cannot be replaced. Ganglia are collections of
nerve-cell bodies outside the central nervous system.
All neurons contain the same elements:
a Cell body This includes a nucleus (control center)
and fibers called processes extending out.
b Axon This is a long, slim “trunk” that transmits
information from the cell body to other cells via
junctions known as synapses. Some axons are only
a few millimeters long; others are more than a yard
long. Axons are sheathed in a fatty substance called
myelin which helps with the conduction of electrical
impulses.
c Dendrites These are networks of short fibers that
branch out from the axon or cell body and link the
ends of axons from other neurons. Dendrites are
the cell’s receivers of information, bringing signals
to their neuron’s own cell body. Each neuron might
have hundreds of dendrites.
Functions
Neurons communicate electrochemically with one
another to transmit impulses throughout the body.
a cell body
c dendrites
b axon
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2 Neuroglia
The nervous system also contains
neuroglia cells. These do not
conduct nerve impulses. Instead,
they support and protect neurons.
They are capable of mitosis (so if
damaged can be replaced). There
are four types of neuroglia within
the central nervous system:
a star-shaped astrocytes cling to
neurons and help protect them;
b smaller microglia are spider
shaped and help get rid of dead
brain cells and bacteria;
c ependymal cells line the
ventricles of the spinal cord and
brain, and their cilia (hairlike
fronds) help circulate
cerebrospinal fluid; and
d long-extensioned
oligodendrocytes wrap around
and protect nerve fibers.
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a astrocytes
b microglia
c ependymal cells
d oligodendrocytes
Sometimes, Schwann cells and
satellite cells, found in the
peripheral nervous system, are
considered neuroglia.
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