Muscles are more than just the firm tissue beneath your skin. Your muscles give your body contour, movement and posture. More importantly, your muscular system is linked to nearly every other major system in your body, providing support to some and depending on others.
Muscle Types
Muscles are created from two different strands of protein that slide past each other as the muscle contracts. The three types of muscular tissue are skeletal tissue, which is under your voluntarily control, smooth tissue, which lines your organs and works automatically, and cardiac tissue, which is combination of both types and is a only found in your heart.
Muscular and Skeletal System
Skeletal muscles are attached to bones and allow them to move independently. Because they can only contract, skeletal muscles are typically grouped in pairs around joints, with each muscle in each pair performing antagonistic, or opposite, functions with the other. This means when one muscle in a pair contracts, the other relaxes and vice versa.
Muscular and Nervous System
Every muscle in your body is under the direct control of your nervous system, which continuously relays messages to and from your brain through the use of your nerves. Sometimes these messages are in response to your direction, such as when you choose to move a muscle group. Other times, they are in response to outside stimuli. For example, if your body temperature drops, your nerves tell your muscles to contract and relax rapidly to produce heat. Nerves also control all of your automated heart and organ muscle functions.
Muscular and Respiratory System
Your respiratory system is controlled by your diaphragm. Your diaphragm is a smooth muscle, but you do have limited control over it and you can deliberately alter your breathing patterns. Your lungs contain no muscles of their own, and your diaphragm actually does all of the work of breathing when you are sedentary. When you breathe hard due to exercise or exertion, muscles in your ribcage help the diaphragm along.
Muscular and Digestive System
Powerful muscles in your esophagus push food downward into your stomach. The muscles in your stomach, along with stomach acid, actively churn your food into a soupy mixture and help empty it into the large intestine. Muscles in your intestines push the mixture farther down the intestinal tract.
Muscular and Circulatory System
Your heart is arguably the most important muscle in your body. About the size of your fist, your heart powers your entire circulatory system, bringing nutrients and oxygen to each cell in your body. Your heart will beat up to 3 million times in your lifetime. Like other muscles, your heart becomes stronger when it's consistently exercised, so physical activity that keeps your heart rate elevated for an extended period of time will go a long way toward keeping it healthy.
