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What is the nervous system?

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What is the nervous system? The nervous system is made up of billions of tiny nerve cells that carry electrical signals roughout the body.

It consists of two parts: the central nervous system and the peripheral nervous system. The central nervous system is the brain and the spinal cord, which extends from the base of the brain all the way down your back. It is protected by rings of bone in your spine, called vertebrae. The peripheral nervous system is the network of small nerves that extends to all parts of the body. The nervous system is the body's main communication network, helping the whole system to work properly.

What are nerve cells?

Nerve cells, or neurones, make up the nerves that carry messages around your body. They have a star-shaped body containing the cell nucleus, with a long thread-lik e fibre called the axon. The tip of the axon is branched and touches other neurones, to which it delivers messages or nerve impulses. Neurones have many smaller threads and branches called dendrites, which receive messages from other neurones.

A long thread or axon extends from the body of a neurone, and it is along this that nerve impulses are carried.

Are there different types of nerve cell?

There are three types of neurone with different functions. Motor neurones control the way your muscles work. Sensory neurones carry messages from your sense organs. Connector neurones pass messages between different parts of the nervous system.

How are messages passed through the nervous system?

Nerve impulses that pass through the nervous system are able to jump from one neurone to the next. Inside the nerve fibre, the nerve impulse travels as an electrical signal. When it reaches the end of the long fibre, it jumps across to the next neurone by means of a chemical called a transmitter.This chemical is released from the branched ends of the fibre.

As this transmitter substance contacts the next neurone, it starts another nerve impulse.This whole process is very fast, and nerve impulses travel along the largest nerve fibres at 90 m per second. Messages travel along smaller nervs such as those in the digestive system at a slower rate.

Many nerves are named from the bones that are near them. For example, the femoral nerve is near the femur.

What is a synapse?

The point where the tiny bulbs on the tips of a nerve fibre contact another neurone is called the synapse. It is the point where transmitter substances carry the electrical signal from one neurone to the next. Some transmitter substances can switch off a nerve signal

What are nerve impulses like?

A nerve impulse is like a very simple message: either 'on' or 'off'. Because there are so many neurones which are connected to one another, this simple signal is enough to carry the most complicated messages throughout the whole of the body's nervous system.

Are nerves insulated?

A nerve impulse is an electrical signal and so it needs to be insulated if it is not to leak away. Most nerve fibres are covered with a fatty layer of insulation to stop the signal from leaking away. In diseases such as multiple sclerosis, some of this insulation disappears and the nerves no longer work properly. Some small nerves do not have this insulation. Although these smaller nerves can still pass a message, it travels much slower than in an insulated neurone.

Do nerve impulses travel straight through the nervous system?

It takes more than one nerve impulse to fire off another neurone. Each neurone receives messages saying 'Fire 'and 'Don't fire', and it will only fire off the nerve impulse if it gets more instructions to fire than to stop firing. It works a bit like the principle of voting, where a large number of'votes' are needed in order for a message to be passed on.

Which are the longest nerve fibres?

The nerve fibres that run down into the leg are the longest cells in the whole body. They can be up to one metre long.


Tags: nerves, synapse, body, brain



Category: Education  - ( Education Archive)

Date Added: 22 December '11


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