Biology Tutorials > Human Neurology > The Central Nervous System

The Central Nervous System

Oligodendrocyte and Schwann cell

Oligodendrocytes in the central nervous system (unlike the Schwann cells in the peripheral nervous system) form segments of myelin sheaths of numerous neurons at once.

Myelin Sheath

Myelin is a substance that forms the myelin sheath associated with nerve cells. This sheath is a layer of phospholipids that increases the conductivity of the electrical messages that are sent through the cell. Diseases such as multiple sclerosis are a result in a lack of this myelin sheath, with the effect is that the conductivity of signals is much slower severely decreasing the effectiveness of the nervous system in sufferers.

In total, there are 43 main nerves that branch off the Central nervous system (CNS) to the peripheral nervous system. (The peripheral nervous system is the nervous system outside the CNS.) These are the efferent neurons that carry signals away from the CNS to the peripheral system.

Somatic Nervous System

These efferent fibers are divided into the somatic nervous system and the autonomic nervous system. The somatic fibers are responsible for the voluntary movement of our body, i.e. movement that you consciously thought about doing.

Autonomic Nervous System

The autonomic nervous system incorporates all the impulses that are done involuntarily, and are usually associated with essential functions such as breathing, heartbeat, etc. However, this type of system can further be broken down into the sympathetic and parasympathetic systems which keep one another in check in a form of negative feedback such as the release of insulin and glucagon in sugar control of the blood.

All of the actions executed by the autonomic nervous system are unconsciously done.

These informational pulses executed in our nervous system allow us to do our daily functions. The processing of this information is done in the CNS, the brain, a highly developed mass of nerve cells. The inner workings of the brain are investigated on the next tutorial, Types and Causes of Brain Damage.


Credit: Creative Learning



Complete the excerpt by selecting the correct answers from the dropdown.

The efferent neurons carry signals ___________ the peripheral nervous system.
The efferent fibers are divided into somatic nervous system and autonomic nervous system. The somatic nervous system is responsible for the ___________ movements of the body.
The autonomic nervous system, in turn, is responsible for the ___________ movements of the body.
Thus, activities, such as breathing and heartbeat, are carried out by the ___________.
Conversely, activities that are consciously thought about doing, such as running and eating, are carried out by the ___________.

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Biology Tutorials > Human Neurology > The Central Nervous System

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