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Chapter 5 CARE OF THE PATIENT WITH NEUROLOGICAL NEEDS 211

nerve cells and fibers together. This glue also provides nourishment and protec-
tion of the neurons. Spaces where impulses hop scotch from one neuron to
another are called synapses. Neurons make contact with other target cells
through synaptic spaces. A synaptic transmission is described as a chemical
process that can only occur with the release of excitatory and inhibitory neu-
rotransmitters such as dopamine, norepinephrine, acetylcholine, serotonin, gly-
cine, glutamic acid, and γ-aminobutyric acid. The myelin sheath is a membranous
covering of lipid protein and white matter that is formed in the central nervous
system (CNS) and it surrounds and protects the nerve fibers.
The nervous system is divided into the

Central nervous system – composed of at least 12 billion neurons including
the brain and spinal cord

Peripheral nervous system – contains the cranial and spinal nerves

The Central Nervous System

The central nervous system includes the brain, meninges, blood-brain barrier,
and cerebrospinal fluid (CSF). Table 5–1 reviews the components of the brain
and Figure 5–1 shows the sections of the brain. Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.

The Protecting Layers
The brain is surrounded by three tough layers that protect it and the spinal
column. They are called the meninges and they help circulate cerebral spinal
fluid (CSF) from the ventricles of the brain to the spinal column. They include
Pia mater – The inner layer of tissue that lies directly next to the brain.
Arachnoid – This middle layer contains a large vascular supply of oxygen and
nutrients that are provided to the brain cells.
Dura mater – Sometimes nicknamed the “the tough mother” because it is
durable. The thickest layer of the three membranes, the dura mater lies in
the outermost layer adjacent to the bones that surround the CNS.
The subarachnoid space is positioned between the pia and arachnoid layer.
It contains CSF supplying nutrients to the CNS, but not oxygen. This space also
serves as a protective function to cushion the brain and spinal cord.
The blood-brain barrier is another method of protection that prevents many
undesirable elements or substances from being exchanged between the blood and
the brain due to an extremely tight connection between the endothelial and astrocyte
cells. Lipid-soluble materials easily cross the blood-brain barrier, while larger, heavier
proteins like molecules cannot cross the blood-brain barrier. The blood-brain