What causes muscles to contract?

Answer 1

The process of the muscle contraction takes place in the protein filaments of the Sarcomere.

Typically muscles move
by a process called a contraction which causes the muscle belly to shorten. Muscles work in opposition. The muscle that contracts is called the agonist, while the one that relaxes is called the antagonist. The muscle belly is composed of bundles of muscle
fibers called fascicles. It is the muscle fibers which are composed of myofibrils} that actually do the contracting because of specialized units called sarcomeres.

A sarcomere runs from z-lineto z-line. And is composed of a thick filament called myosin and a thin filament called actin. When energy is released in the form of ATP the thick filament called myosin spins very rapidly and pulls on the two proteins found on the thin actin filament. These two proteins are called tropomyosin and troponin.

When this occurs the z-lines are pulled closer together and the sarcomere contracts. This is better known as the sliding filament theory.

When the sarcomere contracts all of the sarcomeres contract and the myofibril contracts. Then the fiber contracts and the fascicle and finally, the belly contracts. When the belly contracts it pulls on the tendon which in turn pulls on the bone to make the skeleton move.

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Answer 2

Lydia Adams

Here is a simplified summary of the process that leads to muscle contraction: 1. Nerve Impulse: A nerve impulse (action potential) from the central nervous system travels to a muscle fiber via a motor neuron, triggering the release of the neurotransmitter acetylcholine at the neuromuscular junction. 2. Action Potential in Muscle Cell: The release of acetylcholine causes depolarization of the muscle fiber's membrane, generating an action potential that travels along the sarcolemma and down into the muscle fiber through the T-tubules. 3. Calcium Release: The action potential causes the sarcoplasmic ret

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.