Once stimulated, muscles contractor relax, and glands release their products (called hormones) our nervous system can be called the “first and last” system of the body.
It is the first system to develop in an embryo, and in general the last system to shut down when you die. The nervous system can be subdivided into the central, autonomic and the peripheral nervous systems. The central nervous system (CNS) consists of the brain and spinal cord,which are protected by the skull and vertebral column. The CNS may be thought of as the body’s principal control center. Here messages are received, sorted, interpreted and relayed to and from all parts of the body. The peripheral nervous system (PNS) consists of nerve cells and their associated fibers,emerging from and going to the CNS.
The PNS serves as an intermediary between the body’s muscles and organs and the CNS. The autonomic nervous system controls the body’s smooth muscles, glands and organs. As the name implies, the autonomic system controls the involuntary target organs – organs you have no direct control over. You have no authority over your digestion rate – except through drug use – and although you can change your heart rate, this is an indirect action. The nervous system conducts messages with nerve impulses. These are electrochemical changes set up between adjacent nerve cells. These chemical changes are under the control of specific ions (charged atoms), the most common being sodium, potassium and calcium. The presence or absence of one or more of these ions sets up different electrical charges between adjacent nerve cells.
These electrical differences (called potential gradients) cause the nerve cell to “fire,” the result being a nerve impulse. Another name for these ions is electrolytes. Many bodybuilders consume electrolyte drinks to replenish their supply of these important substances, which are lost in sweat during an intense workout. For proper biochemical functioning, electrolyte levels must be in balance. Too much sodium, for example, causes the body to dehydrate. Too little interferes with the nervous and muscular systems.
During a contest bodybuilders often have troubles with muscles cramping. These cramps are caused by an improper electrolytic balance, frequently brought on by diuretics (more on this in the competition and nutrition sections).From a bodybuilding perspective, it’s probably the spinal cord that causes the most problems. Even with good form and proper warm ups, sooner or later many bodybuilders develop a bad back. Most injuries are minor and consist of slight muscle strains to the spinal erectors. Reducing the weight or changing exercises should address the problem. In a few cases, however, the underlying problem is within the spinal column itself. This is a much more serious situation, so at the slightest hint of such an injury, stop your training and see your physician. To give some idea of why back injuries are so common, let’s take a closer look at the back’s structure.
The Vertebral Column
Thirty-one pairs of spinal nerves exit the spinal cord through the associated spinal bone scalled vertebrae. The great number of articulating vertebrae gives the spine tremendous flexibility. If the spine consisted of only one or two bones, such simple movements as bending over or sitting down would be almost impossible. Each vertebra has a pencil-sized hole in the middle which houses and protects the spinal cord.
Unfortunately, with improper exercise technique or too much weight, damage is often done to the spinal area, particularly the lower spinal region. Of all the exercises that may injure the lower back, perhaps none does so more frequently than the squat. The human spine was not designed to support hundreds of pounds of weight. Some medical experts argue that it does a poor job of supporting even bodyweight, given the number of bad backs diagnosed each year. One theory for this is that human brains outstripped human physiology. In short, humans stood up too quickly.
We are walking around with a spinal design that would probably be more suited to walking on all fours. Whether or not you agree with this theory, few would argue that spinal injuries are to be avoided at all costs. Later in the text I’ll look at injuries in more detail, and offer ways to avoid or treat them.
Robert Kennedy: Encyclopedia of Bodybuilding, The Complete A-Z Book On Muscle Building. 2008
Nick Evans: Bodybuilding Anatomy. 2012
Arnold Schwarzenegger: The New Encyclopedia of Modern Bodybuilding, 2013