![]() The muscle responds to acetylcholine by contracting.This triggers the release of the chemical acetylcholine from the presynaptic terminals.The brain sends a message to the motor neurones.The point of contact between the presynaptic terminal and the muscle is called the neuromuscular junction. The tip of each branch is called a presynaptic terminal. These plug directly into the skeletal muscle. A typical muscle is serviced by anywhere between 50 and 200 (or more) branches of specialised nerve cells called motor neurones. This is collectively known as the neuromuscular system. The brain, nerves and skeletal muscles work together to cause movement. This shortens the length of the muscle fibre which, in turn, shortens the entire muscle if enough fibres are stimulated at the same time. Each myofibril contains filaments that fold together when given the signal to contract. Each bundle is wrapped in a thin transparent membrane called a perimysium.Īn individual muscle fibre is made up of blocks of proteins called myofibrils, which contain a specialised protein (myoglobin) and molecules to provide the oxygen and energy required for muscle contraction. A muscle is made up of thousands of elastic fibres bundled tightly together. Skeletal, smooth and cardiac muscle have very different functions, but they share the same basic composition. The heart contracts and relaxes without our conscious awareness. ![]() Cardiac muscle – the muscle specific to the heart.Another common term is involuntary muscle, since the motion of smooth muscle happens without our conscious awareness. Smooth muscle is arranged in layered sheets that contract in waves along the length of the structure. Smooth muscle – located in various internal structures including the digestive tract, uterus and blood vessels such as arteries.Another term is striated muscles, since the tissue looks striped when viewed under a microscope. Skeletal muscles are under our conscious control, which is why they are also known as voluntary muscles. Generally speaking, skeletal muscle is grouped into opposing pairs such as the biceps and triceps on the front and back of the upper arm. Together, skeletal muscles and bones are called the musculoskeletal system (also known as the locomotor system). Skeletal muscle – the specialised tissue that is attached to bones and allows movement.Muscle disorders may cause weakness, pain or even paralysis. To work properly, muscle tissue also needs particular minerals, electrolytes and other dietary substances such as calcium, magnesium, potassium and sodium.Ī range of problems can affect muscles – these are collectively known as myopathy. Glucose from carbohydrates in our diet fuels our muscles. This movement may be voluntary (meaning the movement is made consciously) or done without our conscious awareness (involuntary). Muscles work by either contracting or relaxing to cause movement. Muscles have a range of functions from pumping blood and supporting movement to lifting heavy weights or giving birth. There are about 600 muscles in the human body.
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