A volume could easily be written on the different parts and functions of the brain. In fact, in our library we have a book on human neuroanatomy which amounts to nearly one thousand pages of solid facts and figures about the brain. Here we are only interested in briefly describing the basic functions so that you can appreciate the importance of perfect functional efficiency of the brain. If you are interested in studying the subject further then you should read a suitable textbook.
The brain can be very roughly divided into three sections: the lower, middle and upper. At the lowest level are the activities which govern the blood pressure, the depth and rate of breathing, the body temperature, the digestive process and so forth. There are also many automatic or reflex centres in the spinal cord which carry out many body functions that have no need to be controlled from the brain itself.
The midbrain acts like an intricate switchboard. It receives impulses from every part of the body, sorts them out and transmits relevant impulses to the higher brain centres. It acts like a sluice gate that prevents unnecessary information going to the higher centres. It is the guardian of the gate, which only allows certain data to pass through. It thereby prevents the upper brain being overwhelmed by irrelevant information.
The upper or higher section of the brain is called the cerebral cortex. It is this part of the brain that structurally distinguishes man from animals. Fish and birds have little or no cerebral tissue; chimpanzees have the largest cerebral cortex of all animals; while man has easily the largest of all earthbound creatures.
The cerebral cortex fills the dome of the head and is divided down the middle; each half is automatically separated from the other. Each half is cross connected with nerves so that one side controls the other side of the body – the left side of the cerebral cortex controlling the right side of the body, and the right side of the cortex controlling the left side of the body. In most people the functions of the left hemisphere of the cortex are dominant; it is associated with speech, hearing and analytical undertakings such as mathematical problem solving. The right hemisphere is primarily concerned with spatial perception, synthesis of ideas and appreciation of art and music. The two hemispheres are connected together through a bundle of nerve fibres called the corpus callasum.
The cerebral cortex includes the centres that receive incoming data from the body via the midbrain and interpret them in a sensible manner. These centres decipher all external data coming from the surroundings through the sense organs of the eyes, ears, etc. All incoming information is interpreted by comparison with previous memories and from this suitable conclusions are reached. Appropriate actions are then instigated and carried out by the body. The cells and centres of the cerebral cortex act as receivers and transmitters of thought. They are the junction at which the mind-brain liaison takes place.