Functional unit of the nervous system-neuron, Science

Functional unit of the nervous system-neuron:

The human brain is composed of more than one hundred billion (100,000,000,000  or 1011) cells called  'neurons'. This number which  is comparable  to the number of stars  in the Milky Way, gives us an idea about the size of the neurons also  -  because 10"  of  them fit in a space which slightly more than a litre of water can occupy. Since these neurons are the functional units of the whole nervous system, let us become familiar with some of their basic features. You can see some typical neurons in Fig.

Neurons can be categorised  into the following kinds according to their functions : 

a) Motor neurons  :  send signals from the nervous system to muscles and glands.

b)  Sensory neurons :  carry signals from the receptor cells in  sense organs in the body to the nervous System. For example, signals generated by  touch or smell or hearing etc. 

c)  lnter neurons  or association neurons :  process the sensory  information received from other neurons,  and convey messages. For example, when an  insect bites, the fingers are given a command  to~cratch  at ,  that point. Most of  the brain's neurons fall in this category. 

The neurons are specialised to carry iqformation from one part of the body to another. These messages are referted to as nerve  impulses. The nerve impulse occurs in response to some. stimulus  or  event which excites  them. Notice in fig that in every neuron,  fhe portion of the cell with the nucleus is called the cell body.


Posted Date: 9/28/2012 8:35:44 AM | Location : United States

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