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Muscle contractions are the basis of movement in many animal species, but not all. Muscle cells are specialised for contraction and allow animals to carry out essential activities such as walking, as well as facilitating bodily processes like respiration and digestion. The body contains three types of muscle tissue: skeletal, cardiac, and smooth muscle. Skeletal muscle is attached to and moves the skeleton, and its movement can be controlled by thought. Cardiac muscle is only found in the heart and is not under conscious control. Smooth muscle carries out unconscious routine tasks such as moving food through the digestive system and adjusting the diameter of blood vessels.
| Characteristics | Values |
|---|---|
| Definition | Muscle is a contractile tissue grouped into coordinated systems for greater efficiency. |
| Location | Muscle is found in animals and humans. |
| Types | There are three types of muscle tissue: skeletal, cardiac, and smooth muscle. |
| Appearance | Skeletal muscle is long and cylindrical, while smooth muscle is short and tapered at each end. Cardiac muscle is branched and striated, but short. |
| Function | Muscles allow for movements such as walking and also facilitate bodily processes such as respiration and digestion. |
| Control | Skeletal muscle is under voluntary control, while smooth and cardiac muscle are under involuntary control. |
| Structure | Muscle is made up of groups of muscle fibers surrounded by connective tissue. |
| Energy | Muscle cells fuel their actions by converting chemical energy in the form of adenosine triphosphate (ATP), derived from the metabolism of food, into mechanical energy. |
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What You'll Learn
- Muscle cells are specialised for contraction, allowing animals to move, and facilitating bodily processes such as respiration and digestion
- Skeletal muscle is attached to the bones or skin and controls locomotion and movement
- Cardiac muscle is only found in the heart and is responsible for pumping blood throughout the body and maintaining blood pressure
- Smooth muscle is found in the walls of organs such as the intestines, stomach, and bladder, and around passages such as the respiratory tract and blood vessels
- The different types of skeletal muscles are recruited depending on whether an animal needs fast and short or steady and prolonged locomotion
Muscle cells are specialised for contraction, allowing animals to move, and facilitating bodily processes such as respiration and digestion
Muscle cells are specialised for contraction, which allows animals to move and facilitates essential bodily processes such as respiration and digestion.
The body contains three types of muscle tissue: skeletal, smooth, and cardiac. Skeletal muscle is a type of striated muscle tissue that is long and cylindrical in shape. It is responsible for movements of the body and is also known as voluntary muscle because it can be controlled by thought. When examined under a microscope, skeletal muscle tissue appears striped or striated due to the regular arrangement of contractile proteins actin and myosin. These contractile proteins interact with each other to cause movement.
Smooth muscle, on the other hand, is non-striated and involuntary. It is found within the walls of organs and structures such as the intestines, stomach, and blood vessels. Smooth muscle contractions help move substances through organs, such as moving food through the digestive tract. Cardiac muscle is also a type of striated muscle, but it is not under voluntary control. It is found only in the heart and is responsible for pumping blood throughout the body and maintaining blood pressure.
The ability of muscle cells to contract is due to the sliding filament theory, where thick and thin filaments of sarcomeres slide by one another, causing the sarcomere to shorten while the filaments remain the same length. This mechanism is essential for various bodily functions, from voluntary movements to the functioning of internal organs. For example, in mollusks like the abalone Haliotis, the shell muscle connects the domed shell of the animal to its adhesive foot. When the muscle shortens, the shell is pulled down to protect the animal, and when it lengthens, the shell is raised, allowing respiratory water currents to circulate.
In summary, muscle cells are specialised for contraction through the interaction of contractile proteins and the sliding filament theory. This contraction allows animals to move and facilitates essential bodily processes such as respiration and digestion, highlighting the critical role of muscle cells in animal survival and function.
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Skeletal muscle is attached to the bones or skin and controls locomotion and movement
Muscle is one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle is attached to the bones by tendons or sometimes by aponeuroses and controls locomotion and movement. It is found throughout the body, including the tongue, diaphragm, eye socket, and upper oesophagus. Skeletal muscles are also called voluntary muscles because they are under voluntary control, meaning you decide how and when they work.
Skeletal muscle tissue is striated, consisting of elongated, multinucleate muscle cells called muscle fibres. These fibres usually span the length of the muscle and can range from less than half an inch to just over 3 inches in diameter. Each muscle can contain thousands of fibres. The fibres contract (tighten), which allows the muscles to move bones so you can perform a wide range of movements. Skeletal muscles make up between 30% and 40% of your total body mass.
The structure of striated muscle tissue, such as the tissue of the human biceps muscle, consists of long, fine fibres, each of which is a bundle of finer myofibrils. Within each myofibril are filaments of the proteins myosin and actin, which interact to cause movement. These filaments slide past one another as the muscle contracts and expands. On each myofibril, regularly occurring dark bands, called Z lines, can be seen where actin and myosin filaments overlap. The region between two Z lines is called a sarcomere, which can be considered the primary structural and functional unit of muscle tissue.
The different muscle types vary in their response to neurotransmitters and hormones such as acetylcholine, noradrenaline, adrenaline, and nitric oxide, depending on the muscle type and its location. For example, in small animals like rodents, the major fast muscle type is Type IIb, which is anaerobic, glycolytic, and less dense in mitochondria and myoglobin, explaining the pale colour of their flesh.
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Cardiac muscle is only found in the heart and is responsible for pumping blood throughout the body and maintaining blood pressure
Muscle is a soft tissue and one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle.
Cardiac muscle, also called myocardium, is found only in the walls of the heart. It is an involuntary muscle controlled by the autonomic nervous system. The primary function of cardiac muscle is to pump blood into circulation by generating sufficient force. The rhythmic contraction of cardiac muscle is regulated by the sinoatrial node, the heart's pacemaker. The cardiac muscle must contract with enough force and pump enough blood to supply the metabolic demands of the entire body.
Cardiac muscle tissue contains cells that expand and contract in response to electrical impulses from the nervous system. These cardiac cells work together to produce the rhythmic, wave-like contractions known as the heartbeat. The interconnected cardiac muscle cells or fibres give the tissue its strength and flexibility.
Regular aerobic exercise can help strengthen cardiac muscle tissue and lower the risk of heart attack, stroke, and other cardiovascular conditions. The American Heart Association recommends at least 150 minutes of moderate exercise per week.
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Smooth muscle is found in the walls of organs such as the intestines, stomach, and bladder, and around passages such as the respiratory tract and blood vessels
Smooth muscle is a type of muscle tissue found in the walls of hollow organs and structures such as the stomach, bladder, and intestines. It is also present in the walls of passageways, including arteries, veins, and the cardiovascular system. Smooth muscle is an involuntary, non-striated muscle, meaning it contracts and relaxes without conscious thought or control. This is in contrast to skeletal muscle, which is under voluntary control and responsible for movements of the body.
Smooth muscle plays a crucial role in various organ systems, such as the gastrointestinal tract, where it aids in digestion and the propulsion of food. It is also found in the urinary system, where it helps maintain electrolyte balance and rids the body of toxins. Smooth muscle is instrumental in the respiratory system, where it is involved in the respiratory airways, and in the cardiovascular system, where it helps regulate blood flow and pressure.
The presence of smooth muscle in the walls of hollow organs, such as the stomach and bladder, is essential for maintaining muscle tone. This prevents "flabbiness" in the organ when it empties and shrinks. Smooth muscle produces slow and steady contractions, allowing substances like food to move through the body efficiently.
Smooth muscle is triggered by various factors, including hormones, neural stimulation by the
Smooth muscle is organized into two types: single-unit and multi-unit. Single-unit smooth muscle is more common and is found in the walls of all visceral organs, except the heart. It contracts as a single unit due to the muscle fibers being joined by gap junctions. On the other hand, multi-unit smooth muscle cells are independent and require individual innervation, allowing for more precise control. They are found in the iris, hair erector muscles, and other locations.
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The different types of skeletal muscles are recruited depending on whether an animal needs fast and short or steady and prolonged locomotion
Skeletal muscles are attached to the bones in the body and allow us to perform a wide range of movements and functions. They are voluntary muscles, meaning we control how and when they move. There are three types of muscles in the body: skeletal, cardiac, and smooth muscle. The different types of skeletal muscles are recruited depending on whether an animal needs fast and short or steady and prolonged locomotion.
Skeletal muscles are made up of muscle fibres that contract and allow the muscles to move bones. Each muscle can contain thousands of fibres. Skeletal muscle fibres are red and white and are striated, or striped, so they are often called striated muscles. Cardiac muscles are also striated, but smooth muscles are not. The multinucleated fibres in striated muscles are under the control of the somatic nervous system and elicit movement by forces exerted on the skeleton similar to levers and pulleys. The sense of where our bodies are in space is called proprioception, the perception of body awareness, the "unconscious" awareness of where the various regions of the body are located at any one time.
The strength of a muscle depends on its length, shortening speed, cross-sectional area, and more. If "strength" refers to the force exerted by the muscle itself, then the strongest muscles are those with the largest cross-sectional area. A shorter muscle will be stronger "pound for pound" than a longer muscle of the same cross-sectional area. In animals, "exercise training" will look more like the need for long durations of movement or short explosive movements to escape predators or catch prey. Aerobic exercise will shift the muscle fibre composition towards slow-twitch fibres, while explosive powerlifting and sprinting will transition fibres towards fast-twitch.
In simple multicellular animals like the hydra, a kind of cell serves as both muscle and epithelial cells. The body wall consists of two layers of cells with a middle gelatinous layer called mesoglea. The base of each cell, where it meets the mesoglea, is drawn out into a long muscle fibre. The hydra can reduce its volume by using its muscles to squeeze water out of its gut cavity through its mouth. It can reinflate using cilia to circulate water into the gut cavity.
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Frequently asked questions
Muscles are contractile tissues grouped into coordinated systems for greater efficiency. They are made up of groups of muscle fibres surrounded by connective tissue.
There are three types of muscles based on appearance and function: smooth, skeletal, and cardiac.
Muscles allow animals to carry out normal activities like walking, running, and bringing food to themselves. They also facilitate bodily functions like respiration, digestion, and maintaining blood pressure.
Skeletal muscles are attached to the bones and control locomotion and any movement that can be consciously controlled. They are also called voluntary muscles.
Smooth muscles carry out the unconscious routine tasks of the body, such as moving food down the digestive system, keeping the eyes in focus, and adjusting the diameter of blood vessels. They are also called involuntary muscles.
