Muscular Information

Each of the three different types of muscle tissue have their own distinct functions:

• Skeletal Muscle: skeletal muscle is the most common type of muscle found throughout the body. It is considered voluntary because you can regulate its activity. Skeletal muscle is involved in generating movement, ranging from movement of facial muscles to express emotions to movement of muscles of your limbs and back to allow you to dance, swim, and run. Intercostal muscles and the diaphragm help expand the rib cage during breathing (respiration). Skeletal muscles also help to maintain upright body posture and prevent a “slumped” appearance by constantly contracting and making adjustments. They also work with the skeletal system to allow for movement by pulling on the bones. Lastly, they surround joint capsules between bones and provide stability to the joints so that the joints do not grind together and cause wear and tear. When skeletal muscles contract, they also release heat, which helps the body regulate its temperature. 

  • Skeletal Muscle Structure:

    • skeletal muscle is under voluntary control, which means that it can be “told” what to do. Skeletal muscle fibers are typically long, striated (striped), and have multiple nuclei. 

      • There are two main types of skeletal muscle fibers: fast twitch and slow twitch.

        • Fast Twitch: fast twitch muscle fibers can give muscles large bursts of energy in a short period of time. These types of fibers are needed for sprinters or powerlifters. 

        • Slow Twitch: slow twitch muscle fibers are better at conserving energy and preventing fatigue. They are necessary for people who need a lot of endurance, like long-distance runners or ballet dancers. 

• Smooth Muscle: smooth muscle lines hollow organs and the inside of arteries and veins. Smooth muscle contracts and relaxes in a smooth, wave-like motion known as peristalsis, pushing materials (blood, food, waste) through the organ. In the arteries, smooth muscle plays a vital role in regulating blood flow and blood pressure by maintaining vessel diameter (width). In the digestive system, smooth muscle contractions move food through the digestive system and make up all sphincters. In the urinary system, smooth muscle in the bladder helps to push out urine. Piloerector muscles, the small muscles that cause hair to stand upright and give the appearance of “goosebumps”, are also made up of smooth muscle. In the eye, smooth muscles help to dilate (widen) or constrict (narrow) the pupil, regulating the amount of light that can enter the eye, and aiding in vision. In the respiratory system, smooth muscle makes up parts of the airways, allowing them to expand and contract as needed to bring air into the lungs. Lastly, smooth muscle is also involved in the reproductive system, aiding in menstruation, ovulation, ejaculation, and childbirth.

  • Smooth Muscle Structure: 

    • Smooth muscle operates under involuntary control, which means they contract automatically without thinking. Smooth muscle fibers are not striated (striped) and tend to look like long spindles with a nucleus in the center.  

• Cardiac Muscle: cardiac muscle is only found in the heart. It plays a vital role in the synchronized contraction of the heart that helps pump blood throughout the body and to the lung for oxygenation. 

  • Cardiac Muscle Structure: 

    • Like skeletal muscle fibers, cardiac muscle fibers are striated (striped). Unlike skeletal muscle, however, cardiac muscle is mononucleated (only has one nucleus) and contains intercalated discs (discs that connect cardiac muscle fibers) that control the synchronized contraction of cardiac tissues in the heart.