The Body’s Muscular System Physiology

XoJLNYLTLClwfk0pSH4q_3127063-130504224023Muscular System Anatomy 

What is is the function of the Muscle Tissue?

The primary role of the muscular system is movement. Muscles are the only tissue within the body that can contract and move the other parts of the body.

Related to function of movement is the muscular system’s second function.: The support of posture and body position. Muscles often contract to keep the body still or in a distinct area rather than to cause movement. The tissue responsible for the body’ posture have the greatest endurance of all muscles in the body – they hold up the body through the day without becoming tired.

sarcomere02Another function based on the movement is the movement of substance within the body. The cardiac and visceral muscles are mostly responsible for carrying materials, such as blood or food from one area of the body to another.

The last function of muscle tissue is to generate heat for the body. As a result of the height metabolic rate of contracting muscle, the body muscular system produces a significant amount of waste heat. Many small muscle constrictions within the body produce our natural body heat. When the body exerts itself more the usually. The increased muscle contractions lead to a rise in body temperature and ultimately sweating.

images (8)Skeletal Muscles work as levers.
Skeletal muscle works together with bones and joints to develop lever system. The muscles act as the effort force; the joint function as the fulcrum; the bone that the muscle moves operates as the lever; and the object being moved function as the load.

There are several classes of levers. The majority of these levers are third class levers in the body. A third class lever is a mechanism in which the fulcrum is at the end of the lever, and the force is between the load at the other level and the fulcrum. The third class levers in the body assist to extend the distance moved by his load compared to the distance that the muscles contracts.

The tradeoff for the development in the distance is the force required to move the load must be larger than the mass of the load. An example of this, the biceps brachia of the arm pulls on the radius of the forearm, causing flexion at the elbow joint in a third class lever system. A very sight change in the range of the biceps causes a much larger movement of the forearm and hand, but the force applied by the biceps must be higher than the load move by the muscle.

Muscular Motor UnitsMotor Units
Nerve cells called motor neurons regulate the skeletal muscles. Each motor neuron controls several muscles cells in a group known as a motor unit. When a motor neuron gets a signal from the brain, it induces all of the muscles cells in its motor unit at the same time.

The size of motor units differs within the body, based on the function of the muscle. Muscles that have additional functions, such as the eyes or finger, have very few muscle fibers in each motor unit so that the precision of the brain’s control over these structures. Muscles that need much strength to operate, such as the leg, or arms muscles – have many muscle cells in each motor unit. B determining how many motor units to active for a given function, the body can control the strength of each muscle. This is the reason this same muscles that are used to write with a pencil also can be used to pick up a bowling ball.

Contraction Cycle

The muscle contract, when stimulated by signals, from their motor neurons. The pointed end of motor neuron contact muscle cells is called the neuromuscular junction (NMJ). Motor neurons release neurotransmitter chemicals at the NMJ that bond to a particular part fo the sarcolemma identified as the motor end plate. The motor end plate contains many ion channels that open in response to neurotransmitters and allow positive ions to enter the muscle fiber. The positive ions form an electrochemical gradient to from the inside of the cell, which spreads throughout the sarcolemma and the T-table by opening, even more, ion channels.

When the positive ions reach the sarcoplasmic reticulum, Ca2_ ions are released and allowed to flow into the myofibrils; CA+ ions bind to troponin, which causes the troponin molecule to change shape and move nearby molecules of tropomyosin. Tropomyosin is moved away from myosin binding sites on actin molecules, allowing actin and myosin to bind together.

ATP-to-ADP-fuels-muscle-contractionsATP molecules power myosin proteins in the thick filaments to bend and pull on actin molecules in the thin filaments Myosin proteins act like oars on a boat, in which they pull thin filaments near the center of the sarcomere. As the thin filament are pulled together, the sarcomere shrinks and contracts. Myofibrils of muscle fibers consist of several sarcomeres in a row, so that when all of the sarcomeres contract, the muscle cells shortens with a great force about its size.

Muscles continue contraction as long as they are stimulated by a neurotransmitter. When a motor neuron discontinues releasing neurotransmitters, the process of reverse contraction itself. Calcium returns to the sarcoplasmic reticulum: tropomyosin and troponin, return to their resting states; and actin and myosin are inhibited from binding. Sarcomeres return to their elongated dormant state once the force of myosin pulling on actin has stopped.

Types of Muscle Contraction

The two factors that control muscle’s contraction; The amount of stimulates from the nervous systems and the number of motors units used to contract. One nerve impulse of a motor neuron can cause a motor unit to contract moment before relaxing. The small contraction is also called a twitch contraction. If the motor neuron can produce several signals within a very short period, in which the strength and duration of the muscle contraction increase. This action is known as a temporal summation. If the motor neurons produce many nerve impulses in rapid succession, the muscle will enter into a state of tetanus, or complete contraction. The muscle reaminson tetanus until the nerve signal rate slows or the mulch becomes to fatigue to maintain the tetanus position.

However, not all muscle contractions will result in movement. Isometric contractions that increase the strain in the muscle while not exerting enough force to move a body part. People do this when their body become tense due to stress; this is an isometric contraction. If you are holding an object still and maintaining posture this also due to isotonic contraction. Isotonic contraction requires you to develop muscle mass through weight lifting.

Muscle tone is a natural condition in which the skeleton muscle is partially contracted at all times. Muscle tone provides a slight level of tension on the muscle to prevent damage to the muscle and joints due to sudden movements, and this helps the body maintain posture. All muscle have some amount fo muscle tone at all times unless the muscle is discounted from the central nervous system due to nerve damage.

Functional Types of Skeletal Muscle Fibers
Skeltela muscle fiber can be divided into two different types based on how they produce and use energy. Type I and Type II

1. Type I fibers are very slow and methodical in their contractions. They are extremely resistant to fatigue due to the fact they use aerobic respiration to produce energy from sugar. Type one fibers are in muscle all through the body for posture and stamina. They are near the spine and neck areas, These areas with a very high concentration of Type I fiber hold the body up on a continual basis.

2. Type II fivers are subcategorized into two grouping. Type II A and Type II B.
Type II A fibers are stronger and faster than Type I fibers, however, there is not as much endureacne. Type II A fibers are also located throughout the body, specifically in the legs and function to support the body with walking and standing.

Type II B fibers are stronger and faster than Type IIA, with even lesser levels of endurance. Type II B fibers are ligher in color than Type I and Type II A due to a lack of an oxygen-storing pigment called myoglobin. Type II B fibers are all through the body, and are particular in the upper body, where the speed and strenght of the chest and arms, comes a the expense of stamina.

Understanding Muscle Metabolism and Fatigue

Muscles get their energy from various sources based on the circumstances that muscle is working in. Aerobic respiration is used the muscle needs to produce a low to moderate level of force. Aerobic respiration needs oxygen to generate about 36-38 ATP molecules form a molecule of glucose. Aerobic respiration is efficent and can continue as long as the muscles consumes considerable levels of oxygen and glucose to keep contracting. When the mulse needs to produce a high level of force, it becomes highly contracted, to the point where oxygen-carrying blood cannot enter the muscle. IN this case, the muscle will create energy using lactic acid fermentation, which is a form of anaerobic respiration. Anaerobic respiration is much less efficient than aerobic respiration; just 2 ATP are built for each molecule of glucose. Muscles will quickly exhaust as they burn through their energy reserves using anaerobic respiration.

To maintain a muscle’s ability to work over longer periods of time, the body muscle fibers contain several important energy molecules. Myoglobin, a red pigment found in muscles, encompass iron and stores oxygen in a similar method to hemoglobin in the blood. Muscles can continue aerobic respiration when there is limited oxygen due to myoglobin producing oxygen for them. Creatine phosphate is another chemical that helps keep the muscle working. Muscles use energy in the form of ATP and converts ATP to ADP to release energy. Creatine phosphate gives its phosphate goup to ADP in turn it back into ATP to give additional energy to the muscles. Lastly muscle fibers have energy-storing glycogen; which is a large macromolecule consisting of many linked glucoses. Active muscles break glucose off of glycogen molecules to provide e an internal fuel supply.

When muscles deplete their energy during either aerobic or anaerobic respiration, the muscles will tire quickly and lose its ability to conract. This is known as mucle fatigue. The muscle that is fatigue contains a minuscule amount of oxygen, glucose or ATP. COnversly it has many waste products from respiration such as ADP and lactic acid. The must take in additional oxygen after muscle fatigue to restore the oxygen that was deposited in myoglobin in the muscle fiber as well as to influence the aerobic respiration that will build the energy supplies inside of the cell. Oxygen debt ( or recovery oxygen uptake) is thename of the additional oxygen that the body must take into rebuild the muscle cells to their resting state. This explains why one may feel out of breath for a few minutes after an exhaustive activity; your body is attempting to restore itself to its normal state.


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by
Health Life Media Team