12/21/16

                       The Nervous System 


   THE BODY HAS MANY ORGANS. 
Every organ has a work to do. For example, the stomach helps digest foods, the kidneys help excrete poisonous waste matter, the skin regulates the heat of the body, the heart causes the blood to circulate. Each organ must do its proper amount of 
work at the proper time, and all the organs must work together in harmony, or the body will become sick. The work of the 
nervous system is to make all parts of the body work at the right time, in the right way, and do the right amount. 

The Brain and the Spinal Cord 

The two main divisions of the nervous system are the brain and the spinal cord. The brain is protected inside the skull. The nerve fibres from the two sides of the brain come together at its base. Here they cross each other, exchanging sides and extending downward, to form the spinal cord. It is important to note that they cross, for this explains why the left 
side of the body is controlled from the right side of the brain and vice versa.
      These fibres leave the skull through an opening at its base and proceed down the-back behind the segmented spinal bones 

that form the vertebrae. The spinal cord, as tlhese fibres are collectively called, is protected within a hollow column formed by a succession of bony appendages projecting from the vertebrae and joining together to form a continuous canal.
Projecting backward from this column there is still a further bony ridge running the full length of the back, which one can feel by running his hand up and down the backbone.
        Nerves leave the spinal cord from each side through notches in the protecting bony column. These divide and subdivide as the branches of a vine until they provide muscular or sensory control over the entire body. The final divisions of the nerves are microscopic. No part of the body can be injured without some nerve being involved and relaying a sensation to the brain.

Functions of the Brain and Spinal Cord


    The brain and the spinal cord are like the governor of a province, who resides in his office in the capital. The nerves that extend out to every part of the body are like the telegraph wires that connect the governor's office with every important city in the state. Messages come in over the telegraph wire
from a city to the governor, telling him what has happened. He at once sends back a message over the wire telling the local official what to do.
      The brain not only receives the messages from the different parts of the body, but it sends out messages and causes the muscles to move. For example, if we wish to walk, the brain orders the muscles of the legs to move the legs and feet.
       The brain is the centre of our lives. It does the loving and hating, the thinking and feeling, the planning and choosing and the directing of nearly all the activities of the body. There are some physiological functions that are involuntary. That is,
they are not under the control of the will. The heart keeps on beating whether we wake or sleep. We cannot command it.We cannot stop it. The same may be said of the stomach and the intestines. Our breathing is both direct control and involuntary control.If we dive into water,for example,or are in the presence of objectionable air,we can hold our breath but if we go to sleep,breathing continues as an involuntary function.
   Other very interesting movements not under the control of the brain are the reflexes. If we accidentally place our hand

1. Canal for spinal cord ; 2. The projection below figure 2 is the spinous process that is felt when the hand is run down the back of the spinal column ; 3. Body of the vertebra.
    Note : The nerve fibres from the two sides of the brain come together at its base.
Here they cross each other, exchanging sides and extending downward to form the spinal cord.it is important to note that they cross,for this explains why the left side of the body is controlled from the right side of the brain and vice versa. So in strokes affecting the right side of the cerebrum the left side of the body is affected and vice
versa.
     Polio may affect the spinal cord at any level. It destroys some or all of the motor nerve fibres that extend from the brain to the muscles. All such muscles are paralysed in whole or in part depending on the proportion of nerve fibres that are destroyed.
   A TYPICAL THORACIC VERTEBRA SHOWING THE POSITION OF THE SPINAL CANAL

       
           On a sharp pin or a hot stove, we take it off quickly before we have time to think. If we had to wait for a message from the brain before we could remove the hand from the hot stove, it would be seriously burned. But with the help of the reflex arc, which takes over and moves the hand in an instant, the damage is minimized to a slight hurt. What happens is this. The sensation of burning goes up-the sensory nerves to the spinal cord. There it is short-circuited to the motor nerves, which send an impulse to the muscles concerned to
remove the hand.

Hygiene of the Nervous System


    The whole body must be well and strong in order for the nervous system to be healthy. Good food,pure air, sleep and proper exercise of the mind and body, are necessary in order to keep the nervous system in good condition.

Habits


  Almost everything we do, whether good or bad, becomes a habit. One can train the mind so that only good habits will be formed. On the other hand, by thinking evil thoughts over and over again and by saying and doing evil things repeatedly, one can
form bad habits. Most of our habits are fixed before we reach the age of twenty-five. How important, then, that children and youth be properly trained! They should be taught to think of things that are true and honest, just and pure, and of good report. In this way a noble character will be developed,
If good mental and physical habits are formed, disease will be more easily avoided, and a long, useful life will be more certain of attainment.

      READ ALSO: SEEING AND HEARING.
Reactions:

0 comments:

Post a Comment

Follow by Email to Receive Every Post by Mail

Advertisement

Popular Posts

Advertisement