Biomedical Engineering Reference
In-Depth Information
Fig. 6.1
White and gray matter in the brain as detected by MRI imaging
The nervous system is composed of the central NS (CNS) and peripheral NS
(PNS) [
1
-
3
]. The CNS consists of the brain and spinal cord. The PNS have the cra-
nial and spinal nerves. The CNS has grey and white matter. Grey matter in the brain
is composed of neuronal cell bodies, neuropil, glial cells, and capillaries. On the
other hand, white matter has no cell bodies and mostly consists of bundles of
myelinated axons that act as a bridge between the different grey matter regions of
the nervous system. The function of grey matter is to route sensory or motor stimuli
to interneurons of the CNS in order to create a response to the stimulus through
chemical synapse activity.
As we already know, the nervous system functions together and in accordance
with the endocrine system to maintain homeostasis. Our sensory organs have differ-
ent receptors sensitive to different signals that send signals directly to the brain
(Fig.
6.1
).
These sensory organs and their neurons are part of the central nervous system
(CNS). They can bring to the brain both external and internal signals. Information
from all the senses is integrated in the brain and spinal cord (Fig.
6.2
).
The primary components of the nervous system include the central and periph-
eral nervous system. The central nervous system is composed of the brain and spinal
cord. The peripheral nervous system is composed of the cranial and spinal nerves.
All parts of the nervous system are composed of a common cellular subunit—the
neuron.
The parts of the neuron are the cell body, dendrites, axon and ganglia. The cell
body contains the nucleus and metabolic machinery of the cell. Dendrites form the
extensions into tissues that may synapse to one or many other neurons. The axon is
a long cytoplasmic process, also called the nerve fi ber. Ganglia, which are groups of
neuronal cell bodies that lie peripheral to the central nervous system in vertebrates,
