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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 meant by control center?
Freeman Reply
what is anatomy
Ajibola Reply
is the study of the structure of the body and their relationship to each refers to the shapes iyo sizes
Khadar
what is a blastomere?
Toluba Reply
In biology, a blastomere is a type of cell produced by cleavage (cell division) of the zygote after fertilization and is an essential part of blastula formation.
Adnan
what is cell
Shivaani
Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. ... Cells have many parts, each with a different
Adnan
function
Adnan
cell is a membrane bound unit that contains the fundamentals molecules of life
Sushma
A1
Adnan
excellent
Adnan
movement,reproduction, excretion, respiration ,growth ,nutrition, response to external stimuli.
Sushma
good
Adnan
sister excellent
Adnan
questions pushy ja sukty hy kya
Maryam
jwab forun milta hy ya ak do din k bad
Maryam
Maryam Riaz sister what you say
Adnan
i want to say that k kush questions k answer mil sukty hy mjhy
Maryam
inshallah
Adnan
zaror mere behen
Adnan
question kari
Adnan
hn mil mil sakte h na esly
Ziya
Which muscle of the gluteal region originates from lumber spine? a. Gluteus medius b. Psoas major c. Iliacus d. Gluteus maximus
Maryam
sweet sister's
Adnan
question tu kari Inshallah Allah behtar kariga
Adnan
to mcqs kia to hy
Maryam
answer ni mila abhi
Maryam
wait sister
Adnan
what is the functional unit of kidneys
Khadar
nephron is the functional unit of kidney
Maryam
Maryam Riaz sister option. d. gluteus maximus
Adnan
thanks
Maryam
sorry Maryam Riaz sister
Adnan
option b. psoas major
Adnan
right answer this one
Adnan
nephron is the functional unit of kidney
Ihsan
I discussed with to my teachers
Adnan
d
Ihsan
d. is right option bro
Adnan
yes
Ihsan
what is cell
Shilpa
cell is the smallest unit of life
Maryam
ok
Shilpa
Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. ... Cells have many parts, each with a different
Adnan
function
Adnan
Maryam Riaz sister I m clear option d. also right thank you ihan bro
Adnan
type structure function origin insertion action of muscles
DAMINI Reply
oxygn amount in our body
Tg Reply
A normal level of oxygen is usually 95% or higher. Some people with chronic lung disease or sleep apnea can have normal levels around 90%. The “SpO2” reading on a pulse oximeter shows the percentage of oxygen in someone's blood
Adnan
What is the difference between cytoplasmic and endoplasmic
Ajibola Reply
The cytoplasm is 90℅ water and 10℅ of organic and inorganic compounds. The cytoplasm contains mitochondria. ... Lysosomes of Cytoplasm contains 50 different enzymes that digest proteins, lipids, and nucleic acids. The endoplasmic reticulum produces process and transport proteins, lipids for all the
Adnan
tarsal are cube shaped broad and long whiles metatarsal they are longer than they are wide
Priscilla Reply
articular cartilage serve as shock absorber and also reduces friction
Priscilla
articular cartilage serve as shock absorber and also reduces friction
Priscilla
when a bone joint with another bone
Priscilla
to know how you body function to know the relationship between the body parts to know specific functions of a certain body parts
romeo Reply
To know our body function we shd know chemical secretion of our glands, we can map all the function of our body and also relation ship between the body parts.
KUSUMA
that z it kusuma
kanaku
can you get fungi infection by seating on a public toilet?
Calls Reply
explain how blood acts as a connective tissue in the body
Rymz Reply
how does blood act as a connective tissue in the body
Rymz
what is anatomy
Victoriah Reply
fat deficiency in the body
Agbor Reply
Explain how body exercise regulates blood pressure
dranimva Reply
thank you
Thelma
what is cillia and flangella
Kalah Reply
what are the proceduers of condactive system ?
Salua 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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