Nervous System

 Print This Post

The Brain

2.8     The brain weighing about 1.4 kg contains about 1 trillion cells, and it consists of three basic parts: the cerebrum, the cerebellum and the brain stem. The cerebrum, which is the largest part of the brain, initiates all the body’s voluntary actions. The cerebellum controls balance of the muscle movement. The brain stem, which connects the cerebrum to the spinal chord, has nerve centres that regulate swallowing, the digestive process, circulation and respiration.

2.9     Cerebral Hemispheres – The cerebrum is made up of a right hemisphere and a left hemisphere, each divided into four lobes. Each hemisphere controls the actions of the opposite side of the body. In most people, the left hemisphere is dominant. In general, the left hemisphere is responsible for speech, writing, and reading. It also plays a major role in verbal, analytical, and computational skills. The right hemisphere is more involved with nonverbal functions, such as emotion, intuition, awareness and interpretation of space and connected by a structure called the corpus callosum, and there is constant communication between the two sides.

2.10   Blood-Brain Barrier – Some substances taken into the body can interfere with the proper functioning of the brain. Fortunately, a structure called the blood-brain barrier prevents most harmful substances from passing from the capillaries of the brain into the cerebrospinal fluid. The cells lining the brain’s blood vessels are tightly joined together and play the primary role in forming the blood-brain barrier. In addition, projections from one type of glial cell cover the outside of the brain’s blood vessels, making passage into the brain even more difficult. A special carrier system allows water, oxygen, carbon-dioxide, glucose and nutrients to pass through the blood-brain barrier.

 Disorders of the Nervous System

2.11   Stroke – When the blood supply to the brain is cut off, a stroke occurs. Most strokes occur due to damage to the blood vessels, caused by high blood pressure. Nerve cells in the affected areas die, and the victim may lose the ability to carry out functions contolled by those areas of the brain such as speaking or moving a limb. A common disorder due to a stroke is the paralysis of one side of the body.