Last time we covered a very basic overview of our skeletal system – the bony framework that maintains our body shape, protects vital organs, and provides a system of muscle levers that allow body movement. And although it allows body movement - our skeletal system cannot move on its own. In order to “move”, our bodies require a structure system that maintains and supports skeletal structure and gives the skeleton the ability to move - we need “muscles.” There are close to 640 muscles in the human body.
There isn’t just one muscle type - there are three basic types of muscle tissue in the human body. Skeletal muscle (also called striated or voluntary muscle) is attached by tendons to the skeletal bones or in some cases directly attaches to bone. Usually the two ends of a skeletal muscle are attached to two different bones across a joint. The only thing a muscle can do is contract, and when it contracts (shortens) it brings the two bones closer together. This causes movement of the skeleton – such as walking or bringing a glass of wine to the mouth.
Remember that the function of skeletal muscle is to move the skeleton. Other skeletal muscles, such as those between vertebrae and between the ribs, play a more structural role, helping the skeleton to maintain its proper shape. Our skeletal muscle is under voluntary control, which means that you control when a skeletal muscle contracts.
Another type of muscle tissue is smooth muscle, called that because it lacks striations. Probably the best example of smooth muscle is the stomach and intestines. Your digestive tract is a huge muscular tube which propels food from one end to the other end. Your intestines are ringed by circular bands of muscular tissue which squeeze the food through the tube when they contract.
Smooth muscle is not under voluntary control, but instead is controlled by the autonomic nervous system. The autonomic nervous system receives input from the brain, but at the subconscious level. The autonomic nervous system has two divisions: the parasympathetic division which speeds up movement of food through the digestive tract, and the sympathetic division which slows down movement.
The third type of muscle tissue is cardiac muscle, found exclusively in the heart. It’s somewhere between striated muscle and smooth muscle. It does have striations like skeletal muscle but the fibers are arranged more like smooth muscle, so it has elements of both. Cardiac muscle is referred to as an involuntary muscle, but it can be influenced through internal factors. For example, being nervous or scared will speed up your heart rate, while relaxing will slow down your heart rate.
Heart muscle has some very special properties which allow it to do its job. For one thing, it has a built in “pacemaker” which causes the heart to spontaneously contract all by itself. Surprisingly - you can cut all the nerves going to the heart and it will still beat just fine, this is what makes the heart transplants possible.
When a muscle is stimulated by a nerve – which is responding to some stimulation from the brain, a series of chemical reactions involving Calcium and Adenosine Triphosphate (ATP) takes place, causing certain reactions in the very small fibers of the muscles. This reaction in turn causes the muscle to contract - - and remember, that is all a muscle lives to do – contract.
Understanding our muscle anatomy gives us a clear picture of why we should exercise – without exercise: muscle fiber decreases (our muscles get smaller), muscles become shorter and lose flexibility, the ability to contract with force is greatly reduced – you bet, we lose our strength. In order to keep our muscular systems in “good shape” – we need to exercise, stretch, get adequate sleep, and “feed” them with meals that are balanced and nutritional. Exercise is essential for those with MS, Stroke, MD and Parkinson’s – period…
Chris and I send our best wishes for peace, health and love. Please make and take the time to exercise. Keep in mind how precious you are to those who love you – and don’t forget – “You have Stroke – don’t let Stroke have you”. See you at the Rec Center for “Opening Doors”.