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By the end of this section, you will be able to:
  • Describe the basic parts and functions of the central nervous system
  • Describe the basic parts and functions of the peripheral nervous system

The central nervous system

The central nervous system (CNS)    is made up of the brain and spinal cord and is covered with three layers of protective coverings called meninges    (“meninges” is derived from the Greek and means “membranes”) ( [link] ). The outermost layer is the dura mater, the middle layer is the web-like arachnoid mater, and the inner layer is the pia mater, which directly contacts and covers the brain and spinal cord. The space between the arachnoid and pia maters is filled with cerebrospinal fluid (CSF)    . The brain floats in CSF, which acts as a cushion and shock absorber.

Illustration shows the three meninges that protect the brain. The outermost layer, just beneath the skull, is the dura mater. The dura mater is the thickest meninx, and blood vessels run through it. Beneath the dura mater is the arachnoid mater, and beneath this is the pia mater.
The cerebral cortex is covered by three layers of meninges: the dura, arachnoid, and pia maters. (credit: modification of work by Gray's Anatomy)

The brain

The brain is the part of the central nervous system that is contained in the cranial cavity of the skull. It includes the cerebral cortex, limbic system, basal ganglia, thalamus, hypothalamus, cerebellum, brainstem, and retinas. The outermost part of the brain is a thick piece of nervous system tissue called the cerebral cortex    . The cerebral cortex, limbic system, and basal ganglia make up the two cerebral hemispheres. A thick fiber bundle called the corpus callosum    (corpus = “body”; callosum = “tough”) connects the two hemispheres. Although there are some brain functions that are localized more to one hemisphere than the other, the functions of the two hemispheres are largely redundant. In fact, sometimes (very rarely) an entire hemisphere is removed to treat severe epilepsy. While patients do suffer some deficits following the surgery, they can have surprisingly few problems, especially when the surgery is performed on children who have very immature nervous systems.

In other surgeries to treat severe epilepsy, the corpus callosum is cut instead of removing an entire hemisphere. This causes a condition called split-brain, which gives insights into unique functions of the two hemispheres. For example, when an object is presented to patients’ left visual field, they may be unable to verbally name the object (and may claim to not have seen an object at all). This is because the visual input from the left visual field crosses and enters the right hemisphere and cannot then signal to the speech center, which generally is found in the left side of the brain. Remarkably, if a split-brain patient is asked to pick up a specific object out of a group of objects with the left hand, the patient will be able to do so but will still be unable to verbally identify it.

Each hemisphere contains regions called lobes that are involved in different functions. Each hemisphere of the mammalian cerebral cortex can be broken down into four functionally and spatially defined lobes: frontal, parietal, temporal, and occipital ( [link] ).

Sagittal, or side view of the human brain shows the different lobes of the cerebral cortex. The frontal lobe is at the front center of the brain. The parietal lobe is at the top back part of the brain. The occipital lobe is at the back of the brain, and the temporal lobe is at the bottom center of the brain. The motor cortex is the back of the frontal lobe, and the olfactory bulb is the bottom part. The somatosensory cortex is the front part of the parietal lobe. The brainstem is beneath the temporal lobe, and the cerebellum is beneath the occipital lobe.
The human cerebral cortex includes the frontal, parietal, temporal, and occipital lobes.

Questions & Answers

information for blood vessels
Sumit Reply
helps pump blood through body
scott
arteries carry blood away from the heart while veins return it to the heart
Reverian
veins have thinner outer walls because blood pressure in them is very low compared to arteries with thicker outer walls to withstand the higher blood pressure.
Oliver
cell, tissue, organ, organism, organ system,
Gheida Reply
please what are the characteristics of a good respiratory system?
Salomon Reply
thin wall ,a moist inner surface ,a huge combined surface area and a rich blood supply.
Nchimunya
Help me am confused what is the cell membrane as a partially permeable membrane
Janelle Reply
it is the ability of a molecules to cross a cell membrane depending on their both size and chemical properties.
Andrews
Based on my previous understanding of biological systems, a cell membrane is a semi-permeable membrane made up of a phospholipids bi-layer. The polar head consisting of phosphate and the hydrophobic end made up of lipids.
Abayomi
Smallest bone of rabbit is
Sahrukh Reply
difference between catebolism and anebolism
Anthvanath Reply
identify the causes of infertility in human beings
Rodrick Reply
Describe how a healthy pregnancy could be maintained
Rodrick
Huaman largest bone
Sahrukh
How I can test DNY
Salamin Reply
Samllest bone
Sahrukh
How can I determine my child
AlfredOfficial Reply
by DNA tests
lasford
thanks
AlfredOfficial
How to test
Salamin
How many bones of 1 year childrean
R.k Reply
208
Rani
A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults
Manali
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R.k
A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults h
Manali
I ask you about beby bones
R.k
i cann't say about 1 year baby's bones bt on birth baby has 300 bones
Manali
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R.k
good night
Manali
have a sweat dream
Rani
it's 300 bones because it a baby
Jasper
babies have 300 bones in which it fuses to become 206 as an adult.
Andrews
it has 300 bones ,nchimunya
Nchimunya
figure of male reproduction
Rani Reply
front view of male reproductive system
Rani
front view of male reproductive system
Rani
what is Actin? I don't understand this definition
Rhonda Reply
Actin is a family of globular multi-functional proteins that form microfilaments. 
Lauren
difference between throat and lyrnx
Lone
what is the difference between a vaccine and a antiserum
Silver Reply
An antiserum contains antibodies already produced and is used to pass on immune responses. A vaccine contains a substance that stimulates the production of antibodies to create an immune response.
Nana
A vaccine a preparation of antigens for one (or more) diseases that is given to stimulate active immunity and protect against the disease (s). while an antiserum either neutralizes the "infection " or stimulates your immune system to attack an infection.
Oliver
what is deoxyribonucleic acid
Carlene Reply
A negatively charged molecule; polymer of nucleotides found in the nucleus of a cell ... DNA.
Abayomi
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Asali
Hi
Janelle
hi
Oliver
hello
Rani
how are you doing?
Jasper
DNA is genetic material which is present in cell DNA is made up of nitrogen base,phosphate group and pentose sugar.
Manali
hi
Jasper
give a front view of male reproductive system
Rani
to maintain certain biological activities of cell
jeeni Reply

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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