<< Chapter < Page Chapter >> Page >
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

The central part of the body
Alex Reply
i thought a cell is the fuctional unit of an orgarnism.
mutesi Reply
what is the name for inflammation of middle ear?
otitis media
Explain the major features and properties of the cell membrane
Robina Reply
contants ofa lipid bilayers w the enbedded proteins it is faction of the cell membaren
it is made up of protein,fat and a small portion of carbohydrates. it is semipermeable but impermeable to uncharged water molecules.
Describe an experiment to verify the law of constant composition
amazing the exprement is hard to set up can you please help us describe it for us?
hi guys
blowing your colon straight outa ya ass because you ate 4lbs of uncooked fish the night prior
What are blood vessels of will's circle
Madu Reply
vertebral arteries and cerebral arteries
What are sutures of cranial cavity ?
Madu Reply
there are four. the coronal, sagittal, squamous and lambhoidal sutured
structure of a cell
pelvic cavity contents?
unimarwat Reply
ilium ,ischium ,pubis
but that is the three parts of the hip bone
Describe the muscular skeletal system in terms of definition.. Skeleton Apendicular skeleton Axial skeleton Joints
Sherrine Reply
the basic framework of body made and cartilage is called skeleton skeleton which form limbs is called appendicular skeleton skeleton which form main axis of body is called axial skeleton the points at two or more bones meets is called joints
write short notes on ligaments,curves and moverment of vertebral column.
mutesi Reply
cranial nerves notes
what is the Analysis
what is Anatomy
it's a organs and bouns reading
Cutting Up
Cutting Up
to dissect
what usually cause blood pressurae
Abdullateef Reply
too much salt in the diet
older age
Even family history of high blood pressure
too much salt in the diet
stress is the leading factor
smoking and too much alcohol consumption
obesity can also cause hypertension
high temperature of the body high salt of the body
how does the temperature affect the blood pressure?
What sex.?
i mearnt gender,there's increased blood pressure in male than female
guys, read the question, involuntary pumping of heart causes the blood pressure in the arteries, he has not asked about high or low BP.
explain the cellular mechanism that produces tetanus and summation
Jenica Reply
epithelial cells polerity
jitendra Reply
demonstrate the fluid replacement in the body
John Reply
the red blood cells is in the long bones or flat bones?
as age increases, the bone elongates .. will the joint vanish?
Sushruth Reply

Get the best Anatomy & Physiology course in your pocket!

Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?