More Than You Ever Wanted to Know About Diet (PART 2)

   In the last section (More Than You Ever Wanted to Know About Diet: Part 1) we broke down the different types of muscle; skeletal, smooth, and cardiac. We also covered the three types of fibers; Type I, Type IIa, and Type IIb.

    Part 2 is going to focus on how the muscles actually work. How you go from "thinking" about an action to actually performing that action.

     To understand how the muscle works, you need to go into a lot more detail. Start at the muscle group, this is made up of muscle fibers. These fibers are like long cylinders. Each of these muscle fibers are made up of MYOFIBRILs that are like cylinders of muscle proteins. Myofibrils have two types of filaments that run through them. One thick and six thin. They are arranged in a hexagonal pattern. These thick and thin filaments are attached to another structure called the Z-disk or Z-line. The Z-line runs perpendicular to the long axis of the fiber (the myofibril that runs from one Z-line to another is called a sarcomere). Running vertically down the Z-line is a small tube called the TRANSVERSE or T-tubule, which is actually part of the cell membrane that extends deep inside the fiber. Inside the fiber, running  between T-tubules is a membrane system called the sarcoplasmic reticulum. This membrane is where the calcium ions that trigger muscle contraction are stored and released.

 

 

          Now from here things start to get complicated. If you really want to get down and dirty check-out http://science.howstuffworks.com/environmental/life/human-biology/muscle.htm. It has pages of info and some cool animations that do a lot better job of explaining it than I can. However, I'm still gonna try to give a good rundown that's detailed but not to the point of being hard to read.

      Muscle contaction: the signal you send from you brain to the muscle to perform an action is called an "action Potential." This action potentail is an electrical signal that travels down a nerve cell and causes it to release a neurotransmitter into a gap between the nerve cell and muscle cell. This gap is called the synapse. The neurotransmitter crosses the gap, binds to a protein  on the muscle-cell membrane (receptor) and causes an action potential in the muscle cell. The action potential spreads along the muscle cell and enters the cell through the T-tubule.The action  potential opens gates in the muscle's calcium store (sarcoplasmic reticulum). Calcium ions then flow into the cytoplasm. The cytoplasm is where the actin and myosin filaments are. Calcium ions bind to troponin-tropomyosin molecules located in the grooves of the actin filaments. Normally, the rod-like tropomyosin molecule covers the sites on actin where myosin can form crossbridges. Upon binding calcium ions, troponin changes shape and slides tropomyosin out of the groove, exposing the actin-myosin binding sites. Myosin interacts with actin by cycling crossbridges, as described previously. The muscle thereby creates force, and shortens. After the action potential has passed, the calcium gates close, and calcium pumps located on the sarcoplasmic reticulum remove calcium from the cytoplasm. As the calcium gets pumped back into the sarcoplasmic reticulum, calcium ions come off the troponin. The troponin returns to its normal shape and allows tropomyosin to cover the actin-myosin binding sites on the actin filament. Because no binding sites are available now, no crossbridges can form, and the muscle relaxes.
      That's it for part 2. Part 3 will examine the energy that is used for these processes. I've also had a couple of weeks training with the Elevation Training Mask 2.0 now and have started my write-up. It should be up in the next couple of days barring me getting sidetracked. Tomorrrow I'll start a 12 week diet/workout program and give weekly updates and post before and after pics.