Muscle Growth Flowchart

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imported_dkm1987

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This came up in another thread and I thought it would be a good idea.

Developing a flowchart that flows out the Hypertrophy process from Load sensing to cell differentiation.

This little snippet is from Rennie's Review

If anyone would like to add perhaps this the place.
 
and of course

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Some Basic Physiology
Structural hierarchy of skeletal muscle. The hierarchical structure of skeletal muscle is such that muscles are composed of many elongated, parallel-running fibers, with the fibers in turn composed of many approximately cylindrical subcellular structures called myofibrils. The myofibrils display a repeating banding pattern due to the underlying highly ordered array of overlapping myosin thick and actin thin filaments with a single repeat of the banding pattern, referred to as a sarcomere.
 
During a contraction, the A band stays the same width, but the Z lines move closer together and the I band gets smaller.
 
The contraction cycle involves five interlocking steps:

STEP 1: Exposure of active sites. The calcium ions entering the sarcoplasm bind to troponin. This binding weakens the bond between the troponin–tropomyosin complex and actin. The troponin molecule then changes position, pulling the tropomyosin molecule away from the active sites and allowing cross-bridges to form.

STEP 2: Attachment of cross-bridges. When the active sites are exposed, the myosin cross-bridges bind to them.

STEP 3: Pivoting. In the resting sarcomere, each cross-bridge points away from the M line. In this position, the myosin head is “cocked” like the spring in a mousetrap. Cocking the myosin head requires energy, and the energy is obtained by breaking down ATP into ADP and a phosphate group. In the cocked position, both the ADP and the phosphate are still bound to the myosin head. After cross-bridge attachment has occurred, the stored energy is released as the myosin head pivots toward the M line. This action is called the power stroke. When this occurs, the ADP and phosphate group are released.

STEP 4: Detachment of cross-bridges. When an ATP binds to the myosin head, the link between the active site on the actin molecule and the myosin head is broken. The active site is now exposed and able to interact with another cross-bridge.

STEP 5: Reactivation of myosin. Myosin reactivation occurs when the free myosin head splits the ATP into ADP and a phosphate group. The energy released in this process is used to recock the myosin head. The entire cycle can now be repeated. If calcium ion concentrations remain elevated and ATP reserves are sufficient, each myosin head will repeat this cycle about five times per second. Each power stroke shortens the sarcomere by about 1 percent, so each second the sarcomere can shorten by roughly 5 percent. Because all the sarcomeres contract together, the entire muscle shortens at the same rate.

To appreciate the overall effect, imagine that you are pulling on a large rope. You are the myosin head, and the rope is a thin filament. You reach forward, grab the rope with both hands, and pull it toward you. This action corresponds to cross-bridge attachment and pivoting. You now release the rope, reach forward, and grab it once again. By repeating the cycle over and over, you can gradually pull in the rope.

Now consider several people lined up, all pulling on the same rope, as in a tug-of-war team. Each person reaches forward, grabs the rope, pulls it, releases it, and then grabs it again to repeat the cycle. The individual actions are not coordinated: At any one moment, some people are grabbing, some are pulling, and others are letting go. The amount of tension produced is a function of how many people are pulling at any given instant. A comparable situation applies to tension in a muscle fiber, where the myosin heads along a thick filament work together to pull a thin filament toward the center of the sarcomere.
 
In a resting skeletal muscle the demand for ATP is low. More than enough oxygen is available for the mitochondria to meet that demand, and they produce a surplus of ATP. The extra ATP is used to build up reserves of CP and glycogen. Resting muscle fibers absorb fatty acids and glucose that are delivered by the bloodstream. The fatty acids are broken down in the mitochondria, and the ATP generated is used to convert creatine to creatine phosphate and glucose to glycogen.
 
At moderate levels of activity the demand for ATP increases. This demand is met by the mitochondria. As the rate of mitochondrial ATP production rises, so does the rate of oxygen consumption. Oxygen availability is not a limiting factor, because oxygen can diffuse into the muscle fiber fast enough to meet mitochondrial needs. But all the ATP produced is needed by the muscle fiber, and no surplus is available. The skeletal muscle now relies primarily on the aerobic metabolism of pyruvic acid to generate ATP. The pyruvic acid is provided by glycolysis, which breaks down glucose molecules obtained from glycogen in the muscle fiber. If glycogen reserves are low, the muscle fiber can also break down other substrates, such as lipids or amino acids. As long as the demand for ATP can be met by mitochondrial activity, the ATP provided by glycolysis makes a relatively minor contribution to the total energy budget of the muscle fiber.
 
At peak levels of activity, the ATP demands are enormous and mitochondrial ATP production rises to a maximum. This maximum rate is determined by the availability of oxygen, and oxygen cannot diffuse into the muscle fiber fast enough to enable the mitochondria to produce the required ATP. At peak levels of exertion, mitochondrial activity can provide only about one-third of the ATP needed. The remainder is produced through glycolysis.

When glycolysis produces pyruvic acid faster than it can be utilized by the mitochondria, pyruvic acid levels rise in the sarcoplasm. Under these conditions, pyruvic acid is converted to lactic acid, a related three-carbon molecule.
 
LOL
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Yeah I guess KISS just got thrown out the window

But I think it is beneficial, so far most of what Ihave posted is based on contraction info I have gathered, I'm still diggin throuhg it all to come up with more Hypertrophy Info (ya got any you want to contribute).

Pictures help though I think or at least they helped me
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On to some Neural stuff

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FIGURE 1 (A) Schematic illustration of the human nervous system and muscle. The brain sends down a command (voluntary drive) through the spinal cord and peripheral nerves to muscle. Muscle is made of motor units. A motor unit contains a motoneuron and the muscle fibers it innervates. When a stimulus arrives at a motor unit and it is strong enough, it triggers an action potential, which in turn activates the motor unit. Force is generated by contraction of muscle fibers. (B) Action potential series. If the brain command continues, it triggers a series of action potentials, which keep activating the motor units to produce a sustained force.
 
A myogram showing differences in tension over time for a twitch contraction in different skeletal muscles. (b) The details of tension over time for a single twitch contraction in the gastrocnemius muscle. Notice the presence of a latent period, which corresponds to the time needed for the conduction of an action potential and the subsequent release of calcium ions by the sarcoplasmic reticulum.
 
Wave summation occurs when successive stimuli arrive before the relaxation phase (the downturn of the curve) has been completed. (b) Incomplete tetanus occurs if the rate of stimulation increases further. Tension production will rise to a peak, and the periods of relaxation will be very brief. © During complete tetanus, the frequency of stimulation is so high that the relaxation phase is eliminated; tension plateaus at maximal levels. (d) Treppe is an increase in peak tension with each successive stimulus delivered shortly after the completion of the relaxation phase of the preceding twitch.
 
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