the Body
Think of the body as divided into seven systems:
(click on the underlined links to learn more)
- [ bones ]
- [ brain and nerves ]
- [ muscles ]
- [ respiration ]
- [ circulation ]
- [ digestion ]
- [ glands ]
All are connected and interdependent, though each has a special network of its own.
The size of the brain has nothing to do with ability. One brain can be twice the size of another without showing any apparent difference in performance. The largest human brains, more than twice normal size, are those of diminished capacity. The brain is a soft lump of 14,000,000 cells and on the surface looks like a jigsaw puzzle fitted together with extreme precision. It usually weighs about 1.5 kgs and is so full of water that it would flop like jelly if not firmly supported. Anatomically it is symmetrical, but not in performance. Many of its functions are quite one sided. One half of the brain is inclined to be more active and some scientists think this may influence whether one is left- or right-handed.
The forebrain, the cerebrum, is the most important and is over five-sixths of the total. Here is where all higher functions occur - thought, memory and sensory impulses. Brain power is released when a number of factors, physical, mental and social, reinforce one another. The frontal lobe controls muscular movement through a narrow band of cortex which acts as the motor and nerve computer of the body, responding to every single action. An adjacent section receives sensations of warmth, cold and touch; another deals with sound messages. Visual reflexes go through the mid-brain.
The hypothalamus is situated below the cerebrum, mingled with general grey matter. It is an area smaller than a finger joint yet is involved in such diverse operations as balancing, water metabolism, temperature control, appetite, thirst, sleep, fatigue, emotions, weight regulation and sensual responses. Any damage, such as slight pressure from an adjacent tumour, can drastically change body health level, shape and mental attitude. In its control of temperature, the hypothalamus constantly regulates heat loss and gain. Heat is usually gained through metabolic or physical activity and sometimes from the environment, though this is normally cooler than the body. Shivering, which is simply involuntary activity of the skeletal muscles, lowers the temperature. Normal temperature is 36.6 degrees Centigrade. Heat is lost through radiation, convection, conduction and by evaporation through the skin.
The nervous system is closely allied to the brain. The nerve centre of the body runs through the spinal cord. Messages travel as electrical impulses, usually following the quickest route to the spinal cord, and are transmitted from there up to the brain. There are forty-three pairs of nerves; twelve go to and from the brain itself, the rest go to and from the spinal cord. Any disturbance of the spinal cord's balance can have far reaching effects. Nerves go two ways - in and out of the brain. Those passing information to the brain are sensory nerves, those taking messages out are insensory.
[ the Body ]
Think of the body as divided into seven systems:
(click on the underlined links to learn more)
- [ bones ]
- [ brain and nerves ]
- [ muscles ]
- [ respiration ]
- [ circulation ]
- [ digestion ]
- [ glands ]
All are connected and interdependent, though each has a special network of its own.
Return to [ the Body ] Index page!