The Differences Between Skeletal, Smooth & Cardiac Muscles
Three Types of Muscles Found in the Human Body
• Skeletal (muscles that move voluntarily)
• Smooth (involuntary muscles in organs)
• Cardiac (only found in the heart)
The Function of Muscles
- To help us move and maintain posture.
- Create heat (the calories burned for energy tend to have an output of 75% heat, therefore on a cold day running is an effective way to warm up).
- Regulate organs.
- Move substances around the body (blood from the heart and food through the digestive system.
• Are directly attached to the skeleton by tendons.
• Aid in movement and locomotion.
• Are voluntarily activated.
• Appear striped under a microscope. Also called "striated" muscle.
• Fatigue more quickly than smooth or cardiac muscles.
• Are able to stretch and resume original shape.
• Striated appearance comes from formation of actin and myosin muscle fibres.
• Are capable of powerful contractions and, just as adequately, small contractions for delicate movement requiring precision.
• Stimulated by the nervous system's motor neurons.
• Well-supplied with nerves and blood vessels.
• Get their name from their smooth appearance under a microscope.
• Arranged in bundles of muscle fibre sheets.
• Contract involuntarily. Regulated by autonomic part of nervous system.
• Found in walls of hollow structures, including veins, arteries, and intestines.
• Maintain flow of fluid and food along hollow structures.
• Found in hair erectors, pupils, gland ducts, esophagus, bronchi, intestines, stomach, and blood vessels.
• Contract slowly and rhythmically.
• Fatigue slowly.
• Found only in heart and at cardiac ends of main blood vessels.
• Contract involuntarily.
• Striated when viewed under a microscope.
• Do not fatigue.
• Contract rhythmically.
• Controlled by central nervous system, but can contract without signals due to "pacemaker" cells.
• Contain high count of mitochondria and myoglobin.
• Have good blood supply.
Skeletal muscle tissue fatigues much more quickly than cardiac or smooth muscles, perhaps because skeletal movement is not essential to homeostasis and survival. It is theoretically quite possible to survive without having to use some skeletal muscles at all. At the opposite extreme, cardiac muscle tissue is under permanent tension to lesser or greater extents to deliver blood, other fluids, oxygen, nutrients, and other substances vital to survival.
Cardiac muscles have great blood supply and are designed specifically to avoid becoming fatigued. Since asphyxiation can lead to death within minutes, cardiac muscles must be able to fulfill their duty transporting oxygen in blood hemoglobin. Cardiac muscle mitochondria help with energy production rhythmic capacity, even at high force when needed.
Research has shown that skeletal muscle mass grows in correlation to the force exerted. These muscles are bigger than smooth and cardiac muscles as a result.
Conscious or Subconscious Contraction
(also known as voluntary or involuntary contraction)
Cardiac and smooth muscles operate on a subconscious, or involuntary, basis. Given the frequency of contractions this is just as well. Not only would it be nearly impossible to make a conscious decision to activate our heart and smooth muscles, but the responsibility would be too much. It is important that the heart maintains a rhythm. A heartbeat that is too fast would lead to high blood pressure. Too slow, and low blood pressure would result, resulting in low energy.
Only skeletal muscles require voluntary contraction, although sometimes movement can be a reflex action (i.e. hitting the patella region with a rubber hammer can cause flexion of the knee). Generally it must be a voluntary action, or else we would have no control over the locomotion of our body to do everyday tasks.