[EN] Types of muscles

Without muscles the human body would not function. Muscles enable us to walk upright and move around in any desired direction. Our heart, as one big muscle, pumps our blood through our whole body, which brings oxygen and nutrients to where they are needed. And there are muscles making up most of our organs like our stomach, intestines, bladder, blood vessels and more. 

In this article I'll share basic details about different muscle types that exist in our bodies.

Types of muscles

Muscles are working units in our body that are made up of tens of thousands of fibres, which are called muscle fibres. Depending on their structure and function, the muscles in our bodies are grouped into three types - skeletal muscles, cardiac muscle, and smooth muscles. 

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Skeletal muscles

Skeletal muscles are the muscles that are connected to our bones and are used for all our movements. They are voluntary in nature, which means we can control them and decide which direction they should move and what specific movement they should perform. 

Being voluntary, they get into action when we need them. Our brain sends a nerve signal that stimulates the muscle to move in a specific way whenever needed. Our skeletal muscles are elastic in nature, and they can contract and stretch temporarily from their natural state. When they are in action, these muscles produce heat as a byproduct. 

The skeletal muscles are made up of muscle fibres. And each of these muscle fibres are made up of many microfibrils. And each of these microfibrils are made up of many power generating units called Sarcomeres. I'll share more about these in the upcoming blogposts. 

There are two types of muscle fibres - slow-twitch (ST) and fast-twitch (FT). Depending on the type of movement we need, one of these muscle fibres plays a dominant role during the movement. The constitution and ratio of these two muscle fibre types in any muscle depends on our trained activity level, activity type, and age.  Here is the main difference between these two muscle fibre types -

• Slow-twitch fibres have more capacity to store oxygen and therefore are able to do long-term exercises like long distance runs. These fibres can endure their use for longer periods. 
• Fast-twitch fibres have less storage capacity for oxygen, but are able to create intense power for a short period of time like sprints. These fibres get tired quickly.

Cardiac muscle

Our heart is one of the main organs that keeps us alive. The heart is largely made up of one type of muscle tissue called cardiac muscle. Unlike the skeletal muscles, which are voluntary, the cardiac muscle functions involuntarily. 

The cardiac muscle produces the heart beat with a contraction movement. These movements are stimulated by an electrical signal coming from the sinus node which is located in the right atrium of the heart. The movement of these electrical signals through the heart contracts the heart and produces a heartbeat. 

Smooth muscles

The third type of muscles is called visceral muscles, which are often referred to as smooth muscles. They are found in the walls of most of our organs like the stomach, intestines, bladder, blood vessels etc. These muscles also function involuntarily. 

They normally respond to either a nerve signal, hormonal signals, or local factors like the oxygen/carbon levels in the blood or the surrounding temperature. The fibres in these muscles are tightly connected and create a network of fibres. Due to this they respond to a signal in a wave like contraction. 

In the upcoming articles, I'll share more details about how muscles generate power, how they change with age, and what exercises one can do to keep their muscles healthy. 

Stay healthy and enjoy finding joy in health!