Welcome to BioBits, your quick 300 word summaries for satisfying your curiosity about the wider world of biology, medicine and science. Unlike the other articles in this blog, these summaries will not focus on recent research but instead on general topics. From what are neurons to what is evolution, from why do we sweat to how do we get colds. The idea is to educate you in a short, sweet summary using only scientific evidence and simple language. It would be wonderful if these summaries were interactive so feel free to post a topic in the comments for summarization. Below you will see the first BioBit.
Without muscles, movement would not be possible. You wouldn’t be able to scratch your nose, move your eyes, swallow, breathe or pump blood through your body. The human body has three types of muscle:
- Skeletal muscle is responsible for the voluntary movement of your skeleton. Skeletal muscles control the movement of your arms, your feet and your eyeballs. It comes in different varieties depending on its function in your body.
- Fast twitch fibers contract quickly but use up their energy fast and therefore fatigue quickly. These fibers are usually found in muscles used for sprinting, jumping or moving your eyes.
- Slow twitch fibers contract slower but can keep contracting for a while because they use their energy up slower. Muscles that are used for posture are made up of slow twitch fibers.
- Cardiac muscle is only found in your heart. This muscle is not under voluntary control and is responsible for pumping blood around your body 24 hours a day, 7 days a week, 365 days a year.
- Smooth muscle is also not under voluntary control and is found in your digestive system, blood vessels, around the airways in your lung and in your bladder. They are important in controlling bodily functions like maintaining blood pressure, swallowing, urinating and controlling your pupils.
Types of muscle (Image from Violetta Kulbitska)
The main proteins involved in the function of muscles are called actin and myosin. These two proteins interact like a ratchet system (scientifically called the cross bridge cycle) to make the muscle shorten and cause your body to move. In skeletal muscle and cardiac muscle, the actin and myosin line up to give the muscle a banding pattern under a microscope. Smooth muscle is called such because the muscle lacks the banding pattern that skeletal muscles and cardiac muscle have.