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By the end of this section, you will be able to:
  • Identify the anatomical and functional divisions of the nervous system
  • Relate the functional and structural differences between gray matter and white matter structures of the nervous system to the structure of neurons
  • List the basic functions of the nervous system

The picture you have in your mind of the nervous system probably includes the brain    , the nervous tissue contained within the cranium, and the spinal cord    , the extension of nervous tissue within the vertebral column. That suggests it is made of two organs—and you may not even think of the spinal cord as an organ—but the nervous system is a very complex structure. Within the brain, many different and separate regions are responsible for many different and separate functions. It is as if the nervous system is composed of many organs that all look similar and can only be differentiated using tools such as the microscope or electrophysiology. In comparison, it is easy to see that the stomach is different than the esophagus or the liver, so you can imagine the digestive system as a collection of specific organs.

The central and peripheral nervous systems

The nervous system can be divided into two major regions: the central and peripheral nervous systems. The central nervous system (CNS)    is the brain and spinal cord, and the peripheral nervous system (PNS)    is everything else ( [link] ). The brain is contained within the cranial cavity of the skull, and the spinal cord is contained within the vertebral cavity of the vertebral column. It is a bit of an oversimplification to say that the CNS is what is inside these two cavities and the peripheral nervous system is outside of them, but that is one way to start to think about it. In actuality, there are some elements of the peripheral nervous system that are within the cranial or vertebral cavities. The peripheral nervous system is so named because it is on the periphery—meaning beyond the brain and spinal cord. Depending on different aspects of the nervous system, the dividing line between central and peripheral is not necessarily universal.

Central and peripheral nervous system

This diagram shows a silhouette of a human highlighting the nervous system. The central nervous system is composed of the brain and spinal cord. The brain is a large mass of ridged and striated tissue within the head. The spinal cord extends down from the brain and travels through the torso, ending in the pelvis. Pairs of enlarged nervous tissue, labeled ganglia, flank the spinal cord as it travels through the rib area. The ganglia are part of the peripheral nervous system, along with the many thread-like nerves that radiate from the spinal cord and ganglia through the arms, abdomen and legs.
The structures of the PNS are referred to as ganglia and nerves, which can be seen as distinct structures. The equivalent structures in the CNS are not obvious from this overall perspective and are best examined in prepared tissue under the microscope.

Nervous tissue, present in both the CNS and PNS, contains two basic types of cells: neurons and glial cells. A glial cell    is one of a variety of cells that provide a framework of tissue that supports the neurons and their activities. The neuron    is the more functionally important of the two, in terms of the communicative function of the nervous system. To describe the functional divisions of the nervous system, it is important to understand the structure of a neuron. Neurons are cells and therefore have a soma    , or cell body, but they also have extensions of the cell; each extension is generally referred to as a process    . There is one important process that every neuron has called an axon    , which is the fiber that connects a neuron with its target. Another type of process that branches off from the soma is the dendrite    . Dendrites are responsible for receiving most of the input from other neurons. Looking at nervous tissue, there are regions that predominantly contain cell bodies and regions that are largely composed of just axons. These two regions within nervous system structures are often referred to as gray matter    (the regions with many cell bodies and dendrites) or white matter    (the regions with many axons). [link] demonstrates the appearance of these regions in the brain and spinal cord. The colors ascribed to these regions are what would be seen in “fresh,” or unstained, nervous tissue. Gray matter is not necessarily gray. It can be pinkish because of blood content, or even slightly tan, depending on how long the tissue has been preserved. But white matter is white because axons are insulated by a lipid-rich substance called myelin    . Lipids can appear as white (“fatty”) material, much like the fat on a raw piece of chicken or beef. Actually, gray matter may have that color ascribed to it because next to the white matter, it is just darker—hence, gray.

Questions & Answers

what is oesophagus?
Bhavani Reply
What is the meaning of dissection
Beryl Reply
what's the meaning of polar?
Jackson Reply
Sign of anaemia or whitish color or Hgb luck
Kassahn
Are you talking of Polar anaemia or what, because the word polar doesnt have one meaning
Kingsley
what are the three types of adrenocorticoids hormones
Lubega Reply
glucocorticoids mineralocorticoid and catecholamines
Kartik
what is polar and non-polar
Jackson Reply
polar unequal share of electron while non polar is equal share
Quran
why are phosphate molecules negatively charged?
Jackson Reply
Bocz of unpaired elections
Javid
because of unpaired electrons
ABDULLAH
what are amphipathic molecules?
Jackson Reply
Amphipathic molecules are molecules with both polar and non polar regions
Mohammed
How does the male organ develop
MADUBULA Reply
Hw does the male organ develop
MADUBULA
Review your questions madam
Aliyu
what is anaphylaxis?
Rugut Reply
it is an imagency condition resulting from abnormal and immediate alagic response to a substance to which the body has become intensively sensitized
Lubega
different between drug and medicine
ado Reply
drugs have no medical application (cocaine, heroin, crystal meth). medicine have medical purpose (fentanyl, albuterol, aspirin, ect ect)
Jordan
medicine is a substance or preparation used in treating disease,drug is chemical compound medicine are drugs but all drugs are not medicines
Wafa
assalam o alaikum
Sidra
what happen to ECF and ICF regarding to OEDEMA
Zwanga Reply
what are the smooth muscles of the heart
Sintung Reply
stomach
Sidra
identify external features of kidney
saba Reply
kidney weight on males?
saba
and female ?
saba
Sle full name & treatment
Samim
Syplymic lupw erythematous
Samim
blood supply to spleen ?
saba
g..
saba
ya 135 g females
saba
130 on male
saba
130g on male
saba
g samim
saba
no 130grms on male
saba
mbbs
saba
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Shahab
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saba
your name?
saba
ok
saba
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saba
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Shahab
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saba
Define cranial nerves with oder
Javid
O-olfactory O-optic O-occumulator T-trochlear T-trigemenal A-abducent F-facial A-auditory G-glossopharyngeal V-vagus A-acessory
Aniee
opd mean?
Shahab
out patient department
mahesh
thnxx
Shahab
Ty Aniee singh
Javid
Ap sb us book s parhte h
Areeej
Read KD Tripathi book of Pharmacology.
mayank
Hello
mayank
CT Scan means
Sintung
what's health?
Sintung
hello
Philip
hi
Sintung
CT means - computerized tomography
Vivek
connective tissue
Dee
they link some body organs
Sintung
Difference between drug and medicine
Javid
hiii muskan
saba
what is tomography?
Gideon
tomography ☝
shahid
yes
Gideon
how hemolytic anemia cause due to gas gangrene?
Huma Reply
what's gangrene?
Sidra
why retro abdominal region called or named "flank "?
Huma Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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