Text A The Nervous System. Brain and Nerves

1. Nerves lead from the spinal cord or from the brain to each part of the body. Then they lead from each part of the body back to the brain or spinal cord. The brain and spinal cord are the centres of this system of nerves.

2. All parts of your body are connected by nerves. The nerve cells with their fibres make up the nervous system. When we study one

Lesson 13 <► 155

Motor area

Sensory area Cerebral hemispheres Visual area Cerebellum Spinal cord

Silent area Speech area Smell and taste Auditory area Medulla

Fig. 13. Diagram to illustrate some of the more important centres in cerebral hemispheres.

nerve cell, we see that it has a long^ fibre at one end and short fibres at the other. The nerve cells send impulses to each other by means of the fibres at their ends. These fibres do not actually touch but are so close to each other that an impulse can travel from one fibre to another. Physical agents

become stimuli for nerve terminals by transferring energy from the

external %orid to the nerve terftimals:

3. Thus all rierve cells connect with each other. There are millions of
these connecting nerve cells. Thus a stimulus from any part of the body
can reach any other part of it. In the spinal cord and brain, the nerve
cells connect with each other by their connecting fibres. Outside the
spinal cord and brain, certain long fibres are grouped together forming
nerves. Each nerve is made up of thousands of nerve fibres together in a
bundle, as a cable is made up of separate wires.

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