The Brain and Nervous system

The pons, a saddle-like mass of coarse fibers, connects the medulla with the higher brain centers. The medulla, or spinalbulb, just below the pons and at the upper end of the spinal cord, is a switching center for nerve impulses to and from higher brain centers.

 It also contains centers which, as we will see, work through the autonomic nervous system to control heart action, changes in artery walls, breathing, and other activities that go on without our conscious effort. The cerebellum, or little brain, is divided into hemispheres like the cerebrum. The front and back areas control muscle tone. Equilibrium is the concern of an area behind the back lobe. The two main hemispheres coordinate voluntary movements.

It is characteristic of the intricate organization of brain and nervous system that the cerebellum receives nervous messages from the balance mechanism of the inner ears, from the muscles and joints, and from centers deep in the brain, and then sends impulses to the muscles adjusting their tone and coordinating their action. Are you able, with eyes closed, to touch the tip of your nose? Can you both rub your stomach and pat your head simultaneously? Then your cerebellum is still at work.

Protection for the Brain

The brain is an excellent example of built-in protection provided by nature for a vital organ, Despiteprocesses in the brain, brain tissue itself is quite sturdy stuff, tough and resilient. It is protected against injury in a number of ways. A tough bony cage, the skull, surrounds the brain completely. It takes a very strong blow to break the skull. The skull itself is protected by the scalp, which can absorb some tough blows. The scalp is made up of five layers which medical students remember by an acrostic: S is for skin (and hair in which in women constitutes considerable protection), and the skin of the scalp is the thickest in the body; C is for the cutaneous tissue, a layer under the skin; A is for the aponeurosis, a tough layer of fibrous tissue which helps the scalp slide around; L is for some loose tissue;

Still more protection is provided

 Inside the brain are four reservoirs, the ventricles, which contain cerebrospinal fluid. This fluid circulates around the brain. Thus, the brain practically floats on and in fluid. And engineers will tell you that this is an ideal "shock absorber" system. Finally, inside the bone of the skull the brain is wrapped in layers of tissue. One of these layers, the dura mater, is particularly tough and helps protect the brain against blows. But nature cannot provide infinite protection, and it has not foreseen the demands of modern society. It did not anticipate that man would ride motorcycles at 100 miles an hour, and might hurtle over the handle-bars.

Or that children would go out on hard turf and play football. Or those workmen would walk under skyscraper construction projects where a bolt falling from the fortieth floor would develop the speed of anartillery projectile. So we need additional protection: adequate helmets for motorcyclists and athletes, steel hats for workmen exposed to possible head injuries. Parents must realize, too, that babies fall off beds and, at some stage, jump out of cribs. These must be guarded against and a baby doctor can advise. Beyond protecting the brain from injuries, you can protect it so there is no interference with its efficient operation.