Skeletal Muscle Types

There are mainly three types of muscles in our body- smooth muscles, which are found in the involuntary organs of our body; cardiac muscles, which are responsible for the proper functioning of the heart; and skeletal muscles, which help us perform voluntary movements. These muscle types exist in different proportions in our body and work together to smoothly perform different functions.

There are mainly three skeletal muscle types, based on the type of movement they perform and the type of energy they produce. These three variations are- Slow oxidative type or the muscles that contract in a relatively slow fashion and utilize oxygen to produce energy.

The fast oxidative type, or the muscles that contract quite fast and use oxygen, but can still use anaerobic respiration to produce energy; and the fast glycolytic type, or muscles that contract quite quickly, and only use anaerobic respiration to produce energy. These three skeletal muscle types are utilized for different types of movements and movements in different parts of the body. 

The muscular system

Our body’s muscular system helps us to perform a wide variety of motions and tasks by working in tandem with the skeletal system. There are mainly three types of muscles:

• Smooth muscles: smooth muscles are found in places like the blood vessels, the uterus, or the gastrointestinal tract. Smooth muscles are controlled by the autonomic nervous system, which means that they are involuntary muscles- how they contract or relax is automatically determined by the body. As the name suggests, these muscles are smooth and do not have any striations. These muscles contract slowly and rhythmically.
• Cardiac muscles: Cardiac muscles are situated in the walls of our heart. These muscles are also controlled by the autonomic nervous system, and thus we have an explanation as to why the heartbeats on until our deaths. Cardiac muscles are structured like smooth muscles, but also feature striations or horizontal stripes. Cardiac muscles experience strong, rhythmic contractions
• Skeletal muscles: Skeletal muscles are the most frequently found muscle in our body. These muscles come under the control of the central nervous system. This means that these muscles can be directly controlled by us. They are attached to the bones and work in cooperation with the skeleton, which enables us to exhibit different movements. These muscles are striated and tough. 

Types of skeletal muscles

Skeletal muscles have different variations based on the type of movements they perform (slow and fast) and how these muscles produce energy (aerobic respiration or glycolysis). Different skeletal muscle types tire out at different times, as the energy they produce is used up at different speeds. Here are the different skeletal muscle types. This should also work as the answer to the question, “How many types of skeletal muscles are there?”

• Slow Oxidative muscle fibres: These muscles have a slow rate of contraction and relaxation. These muscles feature a high number of mitochondria, a rich supply of capillaries, and a high concentration of myoglobin (a substance that enhances the delivery of oxygen to the muscles). These muscles can function for a long time without fatiguing, which makes them great  for maintaining posture and making small, frequent movements that do not require too much energy
• Fast Oxidative muscle fibres: These muscles have a fast rate of contraction and relaxation. They also have a lot of mitochondria but have a low myoglobin count. These muscles can also exhibit glycolysis, and are mostly used for movements that require high energy but are not explosive. An example of such a movement would be walking.
• Fast Glycolytic muscle fibres: These muscles use anaerobic respiration as the primary source of energy. These muscles have a large diameter and have large amounts of glycogen, the substance needed for glycolysis. They have a small number of mitochondria and almost no myoglobin, as they perform anaerobic respiration. As these muscles fatigue easily, they are used for quick, powerful movements like jumping and sprinting.

Types of respiration in skeletal muscles

• Aerobic respiration: Here, the glucose in the blood is completely broken down to form ATP. It is a relatively slow reaction, and the only residue it leaves is carbon dioxide, which is then carried back through the bloodstream.
• Anaerobic respiration or glycolysis: Here the glucose goes through partial decomposition to form lactic acid and ATP. This process produces less ATP, but is a faster reaction than aerobic respiration, due to which it can provide a lot of energy for a small-time.  The lactic acid is stored in the muscles and is broken down into carbon dioxide and water once the exercise stops.

Conclusion

We saw how even small movements in our body require such a complex process to be performed, and how there are different types of muscles for almost every movement that happens in our body. In this article, we learned about the types of skeletal muscle fibres examples. Different types of movements associated with these muscles were also provided.