Types of Muscles

Types of muscles which make up the Human Muscular System.

There are three classifications of muscles found throughout the human body. These are, Skeletal, Cardiac, and Smooth Muscles.

Skeletal Muscles

Most muscles that make up the human body are under our conscious or voluntary control meaning we can command their movement by messages sent from our brains to the muscles via the nervous system. These muscles are called Skeletal Muscles and are usually connected to the skeletal system by bundles of collagen fibers which are more commonly known as tendons. The point at which the muscle attaches to the bone is called the origin of the muscle. This origin point tends not to move by the contraction of the attached muscle and tends to be closer to the center of the body and have greater mass than what the other end of the muscle attaches to. The opposite end of the muscle is called the insertion. The attachment point of insertion tends to be further away from the center of the body and has less mass than the site of the origin attachment. The insertion end of the muscle attachment is more likely to be the end that moves when the muscle is contracted. Skeletal Muscles never attach themselves to another muscle. that we usually So if we want to turn the water off at the kitchen sink, we would command the action via our brains which would send signals down through our nervous system to the muscles required to turn off the tap. It is important to note that skeletal muscles work in tandem with corresponding skeletal muscles to create movement. These muscles can only pull and not push so on their own they are non functioning. In most cases of Skeletal muscles you will find a pair which work together such as the biceps and the triceps or the hamstring and the quadriceps. Skeletal muscles make up around 43% of a man’s and 36% of a woman’s whole body mass, making it the most abundant tissue in the human body.

Skeletal Muscles

Most skeletal muscles are found on the exterior of our body and nearly all are connected to our limbs via tendons. All Skeletal muscles are voluntary muscles meaning we can control their movement with our conscious.

It is generally thought that Skeletal muscles can be further divided into two types of muscles fibers: Slow Twitch (Type 1) and Fast Twitch (Type 2). These two types of muscle fibbers which make up the skeletal muscles distinguish how individual muscles respond to training or physical exertion as the different twitch muscles fibers contract differently to one another. The percentage of Type 1 and Type 2 muscle fibers that our muscles possess is determined through our genetics, however, in most cases it is believed that most human beings have on average 50% slow twitch and 50 % fast Twitch muscle fibers.

Slow Twitch (Type 1)

As the name suggests, Slow Twitch Muscle fibers fire more slowly than fast twitch muscles and have the ability to function over a longer period of time therefore they are considered to be an endurance muscle fiber. Slow Twitch Fibers are more red because they are dense with capillaries as well as have an abundance of Mitochondria and Myoglobin making it more efficient in carrying oxygen and therefore sustaining aerobic activity for longer periods of time. Slow Twitch muscle fibbers are predominantly powered by the oxidation of fats and carbohydrates to continue contracting for longer periods of time with little force. As a result of the endurance qualities of slow twitch muscle fibers, it is believed that endurance athletes such as marathon runners, long distance swimmers and cyclist have a greater percentage of slow twitch muscle fibers compared to fast twitch muscle fibers in their Skeletal muscle make up.

Fast Twitch (TYPE 1)

Fast twitch muscle fibbers function using anaerobic chemical reaction in the muscle to create adenosine triphosphate (ATP) molecules which are the fuel used to power the movement and as a result they are much more proficient at generating short bursts of contractions resulting in higher levels of strength and speed. However due to the explosive nature of Fast twitch muscle fibber they fatigue rapidly, only able to sustain short anaerobic bursts of activity before the muscle becomes painful. Fast twitch muscle fibbers contribute to more muscle strength than it’s counterpart and has the greater potential to increase in size. Fast Twitch muscle fibbers are more white in color due to the fact that they possess less mitochondria and Myoglobin. It is considered that sprinters, weight lifters have more Fast Twitch muscle fibers providing them with the explosive power and strength required to partake in their give sports. Type IIa – Fibers 
These fast twitch muscle fibers are also known as intermediate fast-twitch fibers. They can use both aerobic and anaerobic metabolism almost equally to create energy. In this way, they are a combination of Type I and Type II muscle fibers. Type IIb – Fibers 
These fast twitch fibers use predominately anaerobic metabolism to create the high energy needed to producing quick, powerful bursts of speed. This muscle fiber has the highest rate of contraction (rapid firing) of all the muscle fiber types, but it also has a much faster rate of fatigue and cannot function very long before requiring rest.

Cardiac Muscles

As the name suggest the cardiac muscle is the only muscle of it’s kind in the body and it is responsible for our beating heart. The cardiac muscle is an involuntary muscle meaning we have no conscious control of it’s motion. The cardiac muscle is responsible for coordinated contractions (heart beats) of cardiac muscle cells in the organ which pumps oxygenated blood throughout the body.

Heart muscle

The cardiac muscle can only be found in and around the heart organ. It is an involuntary muscle and beats from the day we are born till the very day we die, without stopping!

Smooth Muscles

Smooth muscles are also involuntary muscles which are usually found internally in the human body. These Smooth muscles surround or are part of internal organs such as the lungs, intestines, bladder, the reproductive tracts, the iris of the eyes as well as within the walls of blood vessels. These smooth muscles play a huge importance to the day to day functions of our bodily organs and like the Cardiac Muscle we have no conscious control of their motion.

Internal organ muscles

Smooth muscles are involuntary like the cardiac muscle and is usually found surrounding our internal organs helping with digestion, liver functions, breathing and seeing.


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