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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 the anatomy
FAKE Reply
Anatomy is study of structure of organs.
Sneha
thanks
FAKE
The scientific study of the structure of human or animal bodies.
FAKE
I was confused as to which one would be right and I asked
FAKE
My answer and you answer both are right.
Sneha
i want to improve my study i like this app i interest physiology and anatomy
Su Reply
I also like this app am really interested in learning anatomy and physiology.
Johny
I have this book with my anatomy class it's awesome! also if look at crashcourse anatomy on you tube!
AMY
what the name
isaiah
umesh. rede
Rede
what is heart and long type answer
Lalita Reply
its a organ in the body
ay
describe about hear chambers.. valves.. arteries.. veins.. circulation.. inferior/superior venacava, aorta., tricuspid valve, mitral valve. pulmonary artery/vein, how oxigenation occur,systolic presure diastolic pressure.. stroke volume,cardiac output, ets.. heart located in which place, describe it
Sanjith
if you describe what I cited up, thogh you can write a long type answer about heart
Sanjith
autonomic functions took over
Vanarith Reply
What did they take over?
Eric
what is the average volume of blood in men and why does it varrie from women?
Esther Reply
what is the average volume of blood in men
Esther
5to6liter
Sarita
5to6liter dt
Sarita
umesh. rede
Rede
what is the definition of anatomy
Noriah Reply
Search google
killer
^of
chieng
The study of the structure or internal workings of something. "Machiavelli's anatomy 
Eric
post. communi. artey... this may be true 70% hope correct
vikash Reply
what is the strongest muscle in the human body?
Robiam Reply
masseter muscles
Om
yes masseter..... jaw muscle is the strongest muscle..
Sarita
Kidneys have direct effect on which
The function the loop
function of the loop?
Eric
the function of the loop of henle is to increase surface area for reasorbtion.
Conan
what is an atom and it's functions
Jany
An atom is the basic building block of matter.
Eric
which is the largest digestive gland in our body
Shubu
stomach
Barbara
What is the smallest bone in the body of the human being?
Kelvin
pisiform
Chulit
how many found in the head
obakunmi
4
ayesha
I think stapes is the smallest bone in human body
Sanjith
22
Sanjith
yes stapes is the smallest bone of our body
Sarita
the smallest bone is stapes in the ear
Isaac
smallest bone in human body is stapes or stirrup present in the middle ear ..
Om
stapes yes
Robiam
blood work and purification and it leads to cardiac systen
vikash
explain function of kidney
Noel Reply
filtration
Naqash
Secretagogue hormones
Sa
Organising water
Sa
hi
Jany
they help in the reproduction of sperms
Jany
Their main job is to cleanse the blood of toxins and transform the waste into urine. The kidney have several functions though. I think it is important to know them, but not in depth. But to truly understand the kindney's over all importance.
Eric
I meant to say the kidneys have.
Eric
how kidney help in reprdution of sperms?
Amir
the basic and functinal unit of kidney is Nephron
Sanjith
what us the name of the longest bone in the body
Ohuche Reply
femur
Zaini
femur
AKHILA
anatomical planes of the body
Opio Reply
sagittal plane, transverse plane and coronal plane
Ogechi
the only moveable bone in head
Sewar Reply
the only movable bone in head
Sewar
stapes. in the ear. but one could argue, all three ear bones move. malleus, Incas, and stapes.
Conan
mandible
Ankita
The mandible is.
Eric
The only unattached bone in the body is the hyod bone in the neck.
Eric
The mandible. It's the part that enables us to talk.
chieng
Mandible present in the head
Shubu
how can u protect ur self from corona
Nity Reply
how can u know that u have corona
Nity
with a test
Danielle
can protect by social distancing, following hand hygiene and standard precautions
Danielle
tq very much
sudhakar
as per the CDC incubation period 2 to 14 days. typical symptoms. typical symptoms, fever, cough, malagia, fatigue, and shortness of breath. alcohol based hand sanitizers. 60 to 85% strength, physical barriers, PPE. a face mask with three layers. Keep a physical distance of 6 feet or more.
Conan
a nasal swab test, or a blood test to confirm SARs-cov-19.
Conan
what is corona
Nity Reply
virus
Danielle
It's a virus which causes COVID 19
chieng

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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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