How To Move a Muscle

The mechanisms behind how our body's function are tremendously intricate.  For specific processes to occur, a handful of things need to go right to get the desired action.  Moving our skeletons through muscular contraction is no different.  Have you ever wondered what it is that actually makes our muscles move? Well here is how. 

1. An action potential is created in the central nervous system.  

Our cells have a slight negative electric charge at normal states.  Sodium and potassium work to regulate this electric charge.  When we have a stimulus to move a muscle it creates a massive positive charge to be formed in the neuron that is caused by sodium being pumped into the cell.  This process is called depolarization.  

2. The action potential travels down an alpha motor neuron to the motor end plate.  

This is where the neuron meets with the muscle fiber.  There is a small gap between the two called the neuromuscular junction. 

3. A neurotransmitter called acetylcholine is released into the neuromuscular junction from a vesicle in the motor end plate. 

Neurotransmitters are chemical messengers within the body.  

4. Acetylcholine binds to receptors on the sarcolemma (muscle cell membrane) causing the sarcolemma to depolarize. 

Similar to how the change in membrane potential caused the neuron to depolarize, the acetylcholine has a similar affect on the muscle cell.

5. The action potential travels along the sarcolemma and down a cellular component known as T-tubules, this causes calcium to be released from the sarcoplasmic reticulum.

Inside of our muscle cells is an organelle called the sarcoplasmic reticulum and its function is to regulate the concentration of calcium within the muscle cells.  When the action potential reaches this area of the cell, it signals to the sarcoplasmic reticulum to release calcium into the sarcoplasm to prepare for contraction. 

6. Calcium binds to troponin and the troponin moves tropomyosin off of the myosin binding site on actin. 

In our cells we have proteins called myosin and actin.  These are the main proteins used in muscle contraction.  When they bind together and initiate a power stroke, a contraction occurs.  However, there are two additional proteins that help to regulate this process called troponin and tropomyosin.  Tropomyosin sits over the site where myosin binds on actin.  When calcium is released, it binds to troponin which acts to move tropomyosin off of the binding site on actin.

7. Myosin binds to actin and a power stroke is initiated. 

8. ATP is used to release myosin off of actin.  

9. The contraction ends when calcium is actively pumped out of the sarcoplasm.  

 

While this information isn't necessary to be successful in your fitness or nutrition goals, it is interesting to know and could help you better understand some basic biology.  I believe that lack of knowledge is the driving factor in the world's obesity epidemic today.  Learning more about basic physiology will only help to expand your knowledge in the areas of nutrition and exercise that directly impact your goals.