Logan Steele
The human body has over 600 muscles, which help us do everything from moving our bodies to breathing and staying alive. There are three types of muscles: skeletal, smooth, and cardiac. Skeletal muscles are the most common type, comprising 30% to 40% of our total body mass. They are attached to our bones and allow us to perform a wide range of movements. These muscles are voluntary, meaning we control how and when they move. Smooth muscles, on the other hand, are found in the walls of hollow organs like the liver, pancreas, and intestines, and are responsible for involuntary movements like pushing food through the intestinal walls. Lastly, cardiac muscles are located in the heart and are also involuntary, contracting and relaxing to pump blood throughout the body.
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Skeletal muscles
Skeletal muscle fibres are formed from the fusion of myoblasts, resulting in long multinucleated cells. The nuclei of these cells are called myonuclei, and they are located along the inside of the cell membrane. Skeletal muscle fibres are also composed of myofibrils, which are made up of actin and myosin filaments, or myofilaments.
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Cardiac muscles
The human body contains three types of muscle tissue: skeletal, smooth, and cardiac. Cardiac muscle, also known as myocardium, is a type of muscle tissue that forms the heart. It is made up of sarcomeres, which allow for contractility, and is under involuntary control.
Cardiac muscle cells, or cardiomyocytes, are striated, branched, and contain many mitochondria. Each cardiomyocyte contains a single, centrally located nucleus surrounded by a cell membrane known as the sarcolemma. The sarcolemma contains voltage-gated calcium channels, which are specialized ion channels that skeletal muscle does not possess. The t-tubules within the sarcolemma function in excitation-contraction coupling, action potential initiation and regulation, maintaining the resting membrane potential, and signal transduction.
Cardiomyocytes are tubular structures composed of chains of myofibrils, which are rod-like units within the cell. The myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. Sarcomeres are composed of long proteins that organize into thick and thin filaments, called myofilaments. Thin myofilaments contain the protein actin, and thick myofilaments contain the protein myosin. The sliding of actin and myosin past each other produces the formation of “cross-bridges,” which causes contraction of the heart and generation of force.
The primary function of cardiac muscle is to pump blood into circulation by generating sufficient force. The contractile functions of the heart require ATP, which can be obtained through various substrates, including fatty acids, carbohydrates, proteins, and ketones. The heart may also use anaerobic processes in a limited capacity. Cardiac muscle tissue gets its strength and flexibility from its interconnected cardiac muscle cells, or fibers.
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Smooth muscles
Smooth muscle is one of the three main types of muscle tissues in the body, the other two being skeletal and cardiac muscle. Smooth muscle is an involuntary muscle, meaning it works without conscious thought. It is controlled by the autonomic nervous system.
Smooth muscle is found in various places in the body and serves a variety of functions. It is present in the walls of hollow organs, including the stomach, intestines, bladder, and uterus. It is also found in the urinary and reproductive systems, as well as in the skin and eyes. In the skin, smooth muscle cells cause hair to stand up in response to fear or cold temperatures, resulting in goosebumps. In the eyes, smooth muscles control how the pupils dilate or constrict, and how the eyes focus.
Smooth muscle is also involved in the process of childbirth. During labour, contractions happen due to the presence of smooth muscles in the uterus. Smooth muscle is also involved in digestion and nutrient collection, as well as helping to rid the body of toxins and maintaining electrolyte balance.
Smooth muscle differs from skeletal muscle in structure, function, and regulation of contraction. Smooth muscle cells have narrow ends, a wider middle, and are shorter than skeletal muscle cells. They also have greater elastic properties, which is important for certain organ systems, such as the urinary bladder, to maintain contractile tone. Smooth muscle is also important in the regulation of blood pressure and circulation.
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Muscle fibres
There are three types of muscle tissue: skeletal, cardiac, and smooth muscle. Skeletal muscle fibres are attached to the skeleton and are under voluntary control. They are the most common type of muscle in the body, comprising 30-40% of total body mass. They are also known as muscle fibres and are much longer than the other types of muscle tissue. Skeletal muscle fibres are further classified into two types: type 1 and type 2. Type 1 fibres are dark due to a higher density of mitochondria, and they use oxygen to generate energy for movement. Type 2 fibres are lighter in colour and can be further divided into subtypes 2A and 2B. Type 2A fibres contain less mitochondria and can also use oxygen to generate energy, while type 2B fibres do not use oxygen and store energy for short bursts of movement.
Cardiac muscle fibres are striated and found only in the heart. They have their own rhythm and are under involuntary control. Special pacemaker cells generate impulses that cause the cardiac muscle to contract, facilitating the beating of the heart. Smooth muscle fibres are located in the walls of hollow visceral organs like the liver, pancreas, and intestines. They are under involuntary control, have a uniform appearance, and are thousands of times shorter than skeletal muscle fibres.
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Muscle cramps
The human body has over 600 muscles, which are made up of thousands of small fibres woven together. These fibres contract and stretch to enable movement. There are three types of muscles in the body: skeletal, cardiac, and smooth muscle. Skeletal muscles are attached to the bones and enable a wide range of movements and functions. They are voluntary muscles, meaning we control how and when they move. Cardiac and smooth muscles are involuntary muscles, which contract without conscious thought.
While muscle cramps are typically not serious, they can sometimes indicate an underlying neurological condition, especially when accompanied by other symptoms such as pain, muscle weakness, or poor coordination. If muscle cramps are severe or persistent, it is recommended to consult a healthcare provider for advice and treatment options.
To prevent and manage muscle cramps, it is important to stay properly hydrated, stretch regularly, and ensure adequate electrolyte intake, especially during intense exercise or in hot environments. In cases of severe or persistent cramps, muscle relaxants and massage may also be recommended by a healthcare provider.
Although muscle cramps are common and often manageable, they can cause discomfort and impact daily activities. Understanding the triggers and adopting preventive measures can help reduce the occurrence and severity of muscle cramps.
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