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Biology for Advanced Level Secondary Schools
nervous system comprises the cranial and Types of neuroglia
spinal nerves, which are packed together Task 4.1
with their motor and sensory endings. Search for information from internet
The nervous tissue is the main tissue sources and the library on neuroglia.
component of the nervous system and it Note their categories and specific
FOR ONLINE READING ONLY
consists of closely packed nerve cells or functions in the nervous system.
neurones with very small intercellular There are six types of neuroglia, four
spaces. Nervous tissue contains two types of which are found in the CNS and two
of cells, namely neurones and neuroglia. in the PNS. The neuroglia found in the
Neurones are specialised nerve cells that CNS include astrocytes, microglia cells,
generate and conduct nerve impulses. ependymal cells and oligodendrocytes,
Neuroglia are non-neuronal cells which while those found in PNS include satellite
cells and Schwann cells (Figure 4.1 a to f).
assist in propagation of the nerve impulses The collection of glia cells residing within
and provision of nutrients to the neurones. the walls of intestinal tract, beginning in
Neuroglia also serve as supporting cells the oesophagus and extending down to
that provide electrical insulation and the anus are known as enteric glia. The six
types of neuroglia are explained below:
remove debris. Cells of the neuroglia
produce myelin sheath that increases the (a) Microglia cell
speed of impulses along the axon of the These are the smallest neuroglia cells
neuronal fibres and offers protection for (Figure 4.1a). They are macrophage cells
the axon. that make up the primary immune system
for the CNS. These phagocytic cells help
to remove bacteria and waste (cleaning
neuronal debris).
(a) (b) (c)
(d) (e) (f)
Figure 4.1: Types of neuroglia (a) microglia (b) astrocytes (c) oligodendrocytes (d) ependymal
(e) schwann and (f) satellite cells
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