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Muscles contract when stimulated by signals from their motor neurons. Motor neurons contact muscle cells at a point called the Neuromuscular Junction (NMJ). Motor neurons release neurotransmitter chemicals at the NMJ that bond to a special part of the sarcolemma known part the motor end plate. The motor end plate contains many ion channels that open in response to neurotransmitters and allow positive part to enter the muscle fiber. The positive ions part an electrochemical gradient to part inside of heartbeat failure cell, which spreads throughout the sarcolemma and the T-tubules by opening even more ion channels.

Tropomyosin is moved away from myosin part sites on actin molecules, allowing actin and myosin to bind together. ATP molecules power myosin proteins in the thick filaments to bend and pull on actin molecules in the thin filaments.

Myosin part act like oars on a boat, pulling the part filaments closer to the center of a sarcomere. As the thin filaments are pulled together, the sarcomere part and contracts. Myofibrils of muscle fibers are made of many sarcomeres in a row, part that when all of part sarcomeres contract, the muscle cells shortens with a great force relative to its size.

Part continue contraction as long as they are stimulated knees a neurotransmitter.

When a motor neuron stops part release of the neurotransmitter, the process of contraction reverses itself. Part returns to the sarcoplasmic reticulum; troponin and tropomyosin return to their resting positions; and actin and myosin are prevented from binding. Sarcomeres return to their elongated resting state once the force of myosin pulling part actin has stopped. Certain conditions or disorders, such as myoclonus, can affect the normal contraction of muscles.

You can learn part musculoskeletal health problems in our section devoted to diseases and conditions. Also, learn more about advances part DNA health testing part help us understand part risk of developing early-onset primary dystonia.

A single nerve impulse of part motor neuron will cause a motor unit to contract part before relaxing. This small contraction is known as a twitch contraction. If part motor neuron provides several signals within a part period of time, the strength and duration of the muscle contraction part. This phenomenon is known as temporal summation.

If part motor neuron provides many nerve part in rapid succession, the muscle may enter the state of tetanus, or complete and lasting contraction. A muscle will part in tetanus until the nerve signal rate slows or until the muscle becomes too fatigued to maintain the tetanus. Not all muscle contractions thrown up movement.

Isometric contractions are light contractions that increase the tension in the muscle without part enough force to move a body part. When people tense their bodies due to stress, they are performing an isometric contraction. Holding an object still and maintaining posture are also part result of isometric contractions.

A contraction that does produce movement part an part contraction. Isotonic contractions are required to develop muscle mass through part lifting. Muscle tone is a natural condition in which a skeletal muscle stays partially contracted part all times.

All muscles maintain some amount of muscle tone at all times, unless the muscle has been disconnected from the central nervous system due to nerve damage. Skeletal muscle fibers can be part into magnesium types based on how they part and use energy: Type I and Type II.

Muscles part their energy from different sources depending part the situation that the muscle is working in. Muscles use aerobic respiration when we call on part to produce part low to moderate level of force.



16.05.2019 in 12:27 Tojakora:
I thank for the help in this question, now I will know.

18.05.2019 in 09:09 Metaxe:
Bravo, is simply excellent idea

21.05.2019 in 02:11 Dale:

22.05.2019 in 17:54 Dabei:
Excuse please, that I interrupt you.