Logan Steele
The human body has more than 600 muscles, which can be categorised into three types: skeletal, cardiac, and smooth muscle. The first two types of muscles are voluntary muscles, meaning you control how and when they move and work. Skeletal muscles, which are attached to bones, make up between 30% and 40% of your total body mass. Cardiac muscles, on the other hand, are involuntary muscles that help pump blood throughout your body. Smooth muscles, also involuntary, are usually found in sheets or layers, with one layer behind the other, and are responsible for various functions, including digestion.
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What You'll Learn
- Skeletal muscle is the most common type of muscle and is under voluntary control
- Cardiac muscle is found in the walls of the heart and is an involuntary muscle
- Smooth muscle is usually in sheets or layers and is also involuntary
- Voluntary vs involuntary movements: Voluntary movements are conscious actions, while involuntary movements happen automatically
- Muscle pain: While occasional muscle aches are normal, chronic soreness or weakness could indicate serious issues
Skeletal muscle is the most common type of muscle and is under voluntary control
The human body has more than 600 muscles, which help us do everything from pumping blood around our bodies to helping us lift heavy objects. There are three types of muscles in the body: skeletal, cardiac, and smooth muscle.
The name "skeletal muscle" comes from the fact that these muscles always connect to the skeleton in at least one place. Most skeletal muscles are attached to two bones across a joint through tendons, which are tough bands of dense regular connective tissue. When the muscles pull on them, tendons are under extreme stress, so they are very strong and woven into the coverings of both muscles and bones.
Skeletal muscles are made up of thousands of small fibres woven together, which contract and relax to allow for movement. These fibres are flexible and range from less than half an inch to just over 3 inches in diameter. Each skeletal muscle can contain thousands of fibres, which are surrounded by different types of sheaths or coverings. The outermost layer is the epimysium, which surrounds the entire muscle. The perimysium is the middle layer, which surrounds bundles of muscle fibres. Finally, the endomysium is the innermost layer, surrounding individual muscle fibres.
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Cardiac muscle is found in the walls of the heart and is an involuntary muscle
There are over 600 muscles in the human body, and they can be categorised into three types: skeletal muscle, cardiac muscle, and smooth muscle. Cardiac muscle, also known as myocardium or heart muscle, is one of these three types of muscle tissues found in vertebrates. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart.
Cardiac muscle forms a thick middle layer of the heart, between the outer layer of the heart wall (the pericardium) or epicardium and the inner layer (the endocardium). The heart wall is a three-layered structure, with the myocardium sandwiched between the inner endocardium and the outer epicardium. The inner endocardium lines the cardiac chambers, covers the cardiac valves, and joins with the endothelium that lines the blood vessels connected to the heart. The outer epicardium forms part of the pericardial sac, which surrounds, protects, and lubricates the heart.
Cardiac muscle is composed of individual cardiac muscle cells or cardiomyocytes, which are joined by intercalated discs. These discs are made up of finger-like projections from two neighbouring cells that interlock, providing a strong bond between the cells. The intercalated discs also allow the muscle cells to resist high blood pressures and the strain of pumping blood throughout a lifetime. Additionally, they facilitate the rapid spread of electrochemical signals from cell to cell, enabling the heart to beat as a unit.
Cardiac muscle cells have a unique structure that enables them to contract and relax in a coordinated manner. They contain sarcomeres, which are the fundamental contractile units of the muscle cells. These sarcomeres are composed of long proteins that form thick and thin filaments called myofilaments. The myofilaments slide past each other during muscle contraction and relaxation, generating the force needed to pump blood through the circulatory system. The rapid and involuntary contraction and relaxation of cardiac muscle are vital for pumping blood throughout the body.
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Smooth muscle is usually in sheets or layers and is also involuntary
There are over 600 muscles in the human body, which help us do everything from moving and breathing to staying alive. There are three types of muscles: skeletal, smooth, and cardiac.
Smooth muscles, also called involuntary muscles, are usually found in sheets or layers, with one layer of muscle behind the other. They are non-striated and are not under our conscious control. This means that they work without us having to think about them. Our brain and body tell these muscles what to do without our conscious intervention.
Smooth muscles are found within the walls of organs and structures such as the oesophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin that control the erection of body hair. In our stomach and digestive system, they contract (tighten) and relax to allow food to make its journey through the body. Smooth muscles are also found in our bladder and help us hold in urine until we can get to the bathroom.
The other two types of muscles, skeletal and cardiac, are both striated. Skeletal muscles are voluntary muscles, meaning we control how and when they move and work. They are the most common type of muscle in our body and make up between 30% and 40% of our total body mass. They are attached to our bones and allow us to perform a wide range of movements and functions.
Cardiac muscles, on the other hand, are involuntary. They are found only in the walls of the heart and are controlled by the autonomic nervous system. They are responsible for the rhythmic contractions that propel blood out of the heart and into the circulatory system.
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Voluntary vs involuntary movements: Voluntary movements are conscious actions, while involuntary movements happen automatically
Human movements can be broadly classified into two types: voluntary and involuntary. Voluntary movements are conscious actions that are self-generated and willed, resulting from cognitive processes. They are controlled by the somatic nervous system and include skeletal muscles, which are attached to bones and skin. These muscles play a crucial role in body movement by contracting and relaxing. Examples of voluntary movements include scrolling through a phone or sprinting.
In contrast, involuntary movements occur automatically without conscious thought and are mediated by the autonomic nervous system. They are essential for survival and include the cardiac and smooth muscles found in internal organs like the heart, blood vessels, intestines, stomach, uterus, and lungs. These involuntary muscles maintain proper blood circulation by controlling heartbeat and internal blood vessel diameter, aid in breathing by expanding the lungs, and facilitate digestion by pushing food through the alimentary canal.
While voluntary movements are typically associated with skeletal muscles, involuntary movements primarily involve cardiac and smooth muscles. Cardiac muscles, found only in the heart, are responsible for pumping blood throughout the body. Smooth muscles, on the other hand, are found inside organs like the blood vessels, stomach, intestines, and uterus, where they help move substances and maintain organ function.
The distinction between voluntary and involuntary movements is not always clear-cut, and there are semi-voluntary movements that lie in between. These can occur due to dysfunction in certain brain areas, resulting in movements that appear voluntary but are experienced as unexpected and involuntary. Additionally, abnormal oscillations can lead to abnormal involuntary movements that can negatively impact a patient's daily life and require treatment.
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Muscle pain: While occasional muscle aches are normal, chronic soreness or weakness could indicate serious issues
Muscle pain is a common ailment that most people experience at some point in their lives. While occasional muscle aches are typically nothing to worry about, persistent or chronic muscle pain and soreness could indicate a more serious underlying issue.
There are more than 600 muscles in the human body, and they are all susceptible to various injuries and health conditions. These muscles are made up of thousands of small fibres that work together to produce movement. When muscles are overworked or injured, these fibres can become strained or torn, resulting in pain and soreness.
Most muscle pain is related to tension, overuse, or injury from exercise or physically demanding work. For example, muscle stress from overuse can lead to repetitive strain injuries, and using muscles beyond their capacity can cause small tears and muscle strains. Traumatic injuries, such as accidents or sports injuries, can also result in muscle contusions or pulls. In these cases, rest, ice, and over-the-counter medications like acetaminophen or ibuprofen are usually sufficient treatments.
However, chronic muscle pain that persists or worsens despite rest and home care may signal a more serious condition. For instance, widespread and long-lasting muscle pain could be a symptom of chronic muscle diseases (myopathies) or infections that attack muscle fibres. Certain medications, such as statins, can also cause muscle damage as a side effect. Additionally, muscle pain can be associated with connective tissue disorders or infections like Lyme disease or lupus, which affect the body's connective tissues.
If muscle pain is accompanied by other symptoms, such as joint pain, fever, vomiting, weakness, or difficulty using the affected muscle, it may indicate a more severe condition. In such cases, it is important to seek medical attention to determine the underlying cause and receive appropriate treatment.
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Frequently asked questions
There are more than 600 muscles in the human body.
The three types of muscles in the human body are skeletal, cardiac, and smooth muscle.
Skeletal muscles are the most common type of muscle in the human body, comprising 30% to 40% of total body mass. They are attached to bones and allow a wide range of movements and functions.
Cardiac muscles are found only in the walls of the heart and are responsible for its rhythmic contractions.
Smooth muscles are usually in sheets or layers and are controlled involuntarily by the brain and body. They are found in the stomach, digestive system, and bladder.
