Hello! This week the musculoskeletal system series continues and this time the subject of interest is muscle. Previously I’ve written about bone (HERE), and tendons (HERE). Muscles are an interesting topic especially when it comes to training and physical performance. Probably all of us are keen on having a body that functions well and enables us to do our daily chores and as you might know this is achieved with healthy musculoskeletal system while muscles are playing an important role. Many people also want to be strong and therefore train their muscles in various ways. Not to mention that athletic and toned appearance is considered attractive and aesthetic to many and most often the muscles are the thing that shape the body to these measures. Don’t get me wrong there are various views and opinions what is attractive and aesthetic so I personally try to remember to live and let live. Lately strength training has been very popular form of exercise. I would even speak about a trend. Anyhow here you have some frenzy free information about muscles and muscle tissue. Enjoy!
I’ll start with the attributes of a muscle. So here they are:
- Muscle has electric activity – Muscles actually function with electricity.
- Irritability – When the nervous system stimulates the muscle with action potentials the muscle reacts to the stimulus by contracting.
- Distensibility – The muscle can stretch to a certain point which enables the muscle with elastic features and also makes it possible to revert to the original length after a muscle contraction.
- Contractility – Muscles contract as a result of receiving an action potential.
- Relaxation – Muscles are able to restore their features in rest.
These attributes are common to all three types of muscle tissue which are smooth muscle, heart muscle tissue and skeletal muscles. This is the rough division but muscle tissue can be divided in many different ways for example muscle tissue can be functionally divided to voluntary and non-voluntary muscle tissue wheter you can move certain muscle voluntarily or not. Smooth muscle type is found in the walls of viscera intestinals and blood vessels and is non-voluntary.
Heart muscle tissue as you probably guessed is in the heart. Actually heart is a muscle about the size of your fist. The heart is also non-voluntary so you can’t just stop your heart beating except if you are a yoga practitioner. Then there is the skeletal muscle tissue and the muscles composed of skeletal muscle tissue are the ones you can voluntarily use to move and achieve your goals.
Muscles are mostly composed of water like almost everything in the body which means that up to 75 percent of the muscle’s weight is water. The rest is proteins 20 percent and inorganic salts 5 percent. The main proteins in muscle tissue are actin and myosin. Actin and myosin form the contracting unit together with other structures. The contraction happens happens when actin and myosin slide by each other and the muscle shortens and causes the bone move to where it is attached.
As the subject of musculokeletal system is delt here I’m naturally goint to talk a bit more of skeletal muscle tissue. Skeletal muscles attach to at least two different bones and as they contract the bones come closer to each other and movement occurs. There are various different shapes represented in skeletal muscles. Some muscles are straight and flat like the rectus abdominus or they can be fusiform or triangular. The skeletal muscles are formed of individual muscle cells. The number of the cells varies between different muscles. The muscle cells in skeletal muscle appear cross-stripe in the microscope because of different proteins in the muscle cell.
To make things even more complicated the skeletal muscle cells can be divided in different groups in various different ways. This division can be done based on the power generation features or on the type of the contracting proteins. Roughly the based on the contraction and relaxation ability the muscle cells can be divided to slow type type I-muscle cells and fast type II-muscle cells. People have differences in the distribution of the muscle cells meaning some people have bigger percentage of fast type II-cells in certain muscles. The distribution also differs between muscles. Type I-cells are typically found in muscles that are responsible for maintenance of posture and are called tonic muscles. This is because the slow type I-cells have good endurance abilities so they can maintain static postures for long periods of time. The thing is only that the power generation feature in the slow type I-cells is lower and they contract slowly hence the name. As you probably guessed the fast type II-cells are found in posture changing muscles and motor muscles that we use when we actually move. These muscles are called phasic. The power generating abilities of the fast type II-cells are good and they contract quickly but they lack endurance and tire quite fast.
I’ll end this article here because there is just so much information about muscles and muscle tissue that otherwise if go all the way this article would rather be a book. So let me know if you’d be interested in more muscle related articles or if you want to know some more. There sure are topics to cover when considering muscles. Hope this article was useful and enjoyable!
Thank you for reading!
Peace & Love!