Lesson 19 - Myosin and Actin Physiology - WORK THOSE MUSCLES!!!!

MYOSIN AND ACTIN

    In this post, I will try to make you understand muscle contractions and how they work. Now, the 2 major proteins that you may have heard of are myosin and actin. First, what do these structures actually look like? And how do they work?

    This is diagram of myosin and actin. So basically, actin is a helical protein. Myosin is like a protein that has a head that climbs up the actin and this causes muscle contraction.

http://pixgood.com/myosin-and-actin.html

    Now let's get deeper into all the physiology behind this. There are two other proteins that work also. These proteins are tropomyosin and troponin. Tropomyosin is a protein that wraps around the actin and the troponin helps keep the tropomyosin bound to the actin. The function of tropomyosin in rest, is to keep the myosin head from being able to bind or move along the actin.
    Now if there is a high calcium concentration in the muscle cell, troponin (since it is bound to the tropomyosin) is used to move tropomyosin out of the way.
    1. This allows the ATP to be hydrolyzed.
    2. This causes the ADP + Phosphate group to form and the myosin head can attach to the that actin.
    3. This also causes the release of energy which causes the movement of the myosin head up the actin filament.
    4. These steps end in muscle movement.
    5. Then the myosin returns to its resting position.

So let's summarize:
    Actin: A helical filament which helps cause muscle contraction.
    Myosin: A motor protein that climbs along the actin filament to create muscle movement.
    ATP: Adenosine Triphosphate - sometimes called the biological currency of all living organisms.
    Tropomyosin: A protein which wraps around the actin filament and when there is a low calcium concentration it will block and prevent the movement of myosin up the actin filament. But in a high concentration, it will let the myosin head move up the actin filament.
    Troponin: A protein which binds the tropomyosin to the actin filament. It helps the tropomyosin block the myosin movement.
    Calcium: A very important ion that is important in muscle movement.

I hope this helped you understand muscle movement! Muscle movement is VERY VERY VERY important because then you wouldn't be able to move.