Dominic Stone
The human body is made up of more than 600 muscles that help us move, breathe, swallow, and stay alive. These muscles can be categorised into three types: skeletal, smooth, and cardiac. Cardiac muscle, also known as myocardium or heart muscle, is a type of muscle tissue that forms the heart and is responsible for keeping the heart pumping blood around the body. Unlike skeletal muscle, which is present in the arms and legs, cardiac muscle produces involuntary movements, meaning they are automatic and a person cannot control them.
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What You'll Learn
- Cardiac muscle is striated, like skeletal muscle
- It is the only type of muscle tissue that is intrinsically controlled
- The cardiac muscle is involuntary due to regions of the brain stem and hypothalamus
- The heart contains specialised 'pacemaker' cells that respond to electrical impulses
- Cardiac muscle tissue is responsible for the heart's pumping and relaxing functions
Cardiac muscle is striated, like skeletal muscle
The human body is made up of three types of muscle tissue: cardiac, smooth, and skeletal. Cardiac muscle, also called myocardium, is a type of striated or striped muscle, similar to skeletal muscle. Striated muscles are a vital part of the musculoskeletal system. They help with functions like chewing and swallowing, which are the first parts of digestion, and expanding and contracting the chest cavity to inhale and exhale.
Cardiac muscle is involuntary, meaning it works without conscious thought. It constitutes the main tissue of the heart wall and is responsible for the heart's contractility and pumping action. The heart is made up of three layers: the pericardium, myocardium, and endocardium. The cardiac muscle forms a thick middle layer between the outer layer of the heart wall (pericardium) and the inner layer (endocardium).
The cardiac muscle is composed of individual cardiac muscle cells or cardiomyocytes, joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix. These muscle cells are the contractile myocytes of the cardiac muscle, allowing the heart to pump blood into circulation by generating sufficient force. The sheets of muscle wrapping around the left ventricle contract in a coordinated manner, allowing the ventricle to squeeze in several directions simultaneously.
Skeletal muscle, on the other hand, is under voluntary control. These muscles are attached to the skeleton and are located between the bones throughout the body. They consist of flexible muscle fibres that range from less than half an inch to just over 3 inches in diameter. Skeletal muscle mass varies from person to person and tends to be higher in males and taller or overweight individuals.
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It is the only type of muscle tissue that is intrinsically controlled
The human body is composed of hundreds of muscles that help us move, breathe, swallow, and stay alive. These muscles are made up of fibrous tissue that contracts to produce movement. There are three types of muscle tissue in the body: skeletal, smooth, and cardiac.
Cardiac muscle, also called heart muscle or myocardium, is the only type of muscle tissue that is intrinsically controlled. It is composed of cardiac muscle cells, or cardiomyocytes, that are located only in the heart. These cells are responsible for keeping the heart pumping and relaxing normally. They contract and release involuntarily to pump blood through the cardiovascular system.
Cardiac muscle is considered involuntary because it is controlled unconsciously by regions of the brain stem and hypothalamus. It is also considered intrinsic or self-controlled because the normal cardiac rhythm is set by specialized pacemaker cardiac muscle cells in the heart itself. These pacemaker cells are only weakly contractile and are connected to neighbouring contractile cells via gap junctions. They carry the impulses that are responsible for the beating of the heart.
The cardiac muscle forms a thick middle layer of the heart wall, with the outer layer being the pericardium and the inner layer being the endocardium. The cardiac muscle contracts in a similar manner to skeletal muscle, but with some important differences. For example, T-tubules in cardiac muscle are bigger and wider than those in skeletal muscle but are fewer in number.
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The cardiac muscle is involuntary due to regions of the brain stem and hypothalamus
The cardiac muscle, also known as the myocardium, is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the heart wall. The heart is made up of three layers: the pericardium, the myocardium, and the endocardium.
The hypothalamus is a component of the autonomic nervous system (ANS), which is the part of the peripheral nervous system that controls cardiac muscle contraction, visceral activities, and glandular functions. The ANS functions continuously without conscious effort and can regulate heart rate, blood pressure, body temperature, and more. The hypothalamus produces and releases vasopressin, an antidiuretic hormone, in response to hypovolemic shock, helping to regulate water retention and vasoconstriction.
In summary, the cardiac muscle is involuntary due to the regulatory functions of the brain stem and hypothalamus, which control and influence the heartbeat, blood pressure, and other vital functions necessary for survival.
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The heart contains specialised 'pacemaker' cells that respond to electrical impulses
The cardiac muscle is an involuntary muscle, meaning it beats on its own without any conscious input. The heart is composed of cardiac muscle cells, also called cardiomyocytes, which are contractile myocytes. These cardiac muscle cells are specialised, with some functioning as pacemaker cells that respond to electrical impulses.
The heart's conduction system is a network of nodes, cells, and signals that controls the heartbeat. This system includes specialised cells and nodes that regulate the heartbeat. The sinoatrial (SA) node, located in the upper right atrium, is the heart's natural pacemaker. It generates electrical impulses that initiate the heartbeat. The SA node has the highest rate of depolarisation, reaching the threshold for generating impulses faster than any other component of the conduction system.
The SA node is regulated by the autonomic nervous system, which controls the rate at which it sends electrical signals. This regulation is based on the body's activities, such as physical exertion or sleep. When the SA node malfunctions, the lower segments of the conduction system, including the atrioventricular (AV) node, act as backup pacemakers. The AV node can generate a heart rate of 40-60 beats per minute.
The electrical impulses generated by the pacemaker cells travel through the heart's conduction system, causing different parts of the heart to expand and contract. This coordination of contractions regulates blood flow through the heart and body. The pacemaker cells respond to signals from the autonomic nervous system, which modulate the heart rate to control blood pressure.
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Cardiac muscle tissue is responsible for the heart's pumping and relaxing functions
Cardiac muscle tissue, also known as myocardium, is a specialised tissue that exists only in the heart. It is responsible for the heart's pumping and relaxing functions, keeping blood circulating around the body. The myocardium forms a thick middle layer of the heart wall, between the outer layer (the pericardium or epicardium) and the inner layer (the endocardium).
The cardiac muscle is made up of cardiac muscle cells, or cardiomyocytes, which are joined by intercalated discs to form long fibres. These cells work together in a highly coordinated way to produce the rhythmic, wave-like contractions of the heartbeat. Each cardiomyocyte must contract in coordination with its neighbouring cells, in a process known as a functional syncytium. This coordinated contraction allows the ventricles to squeeze in several directions simultaneously, maximising the amount of blood squeezed out of the heart with each heartbeat.
The contractile functions of the heart are controlled by electrical impulses from the nervous system. These impulses trigger the release of calcium from the cell's internal store, the sarcoplasmic reticulum, which causes the cell's myofilaments to slide past each other in a process called excitation-contraction coupling. The cardiac muscle must contract with enough force to pump blood into circulation and meet the metabolic demands of the entire body.
Cardiac muscle tissue is involuntary, meaning it contracts and relaxes automatically without conscious input. This is in contrast to skeletal muscle, which is under voluntary control.
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Frequently asked questions
Yes, the cardiac muscle is involuntary. It is a type of muscle tissue that forms the heart and is responsible for keeping the heart pumping and relaxing normally.
Involuntary muscles are those that move automatically without conscious thought. They are controlled unconsciously by regions of the brain stem and hypothalamus.
Other examples of involuntary muscles include smooth muscles, which line the inside of some organs like the intestines and lungs. Smooth muscles play an important role in the female and male reproductive systems, urinary system, respiratory system, and digestive system.
