86Thousand400: Muscle Innervation and Positivity

Acetycholine (Ach) is the substance the nervous system uses to activate skeletal muscle. Skeletal muscles are directly controlled by motor neurons located in the spinal chord. (Another key reason why chiropractic care is so important).

When a motor neuron generates action potential, it travels rapidly along the nerve until it reaches the neuromuscular junction, where it initiates an electrochemical process that causes Ach to be released into the space between the presynaptic terminal and the muscle fibre.

Ach leaves the nerve fibre and docks on receptors in the muscle membrane, causing that area of the muscle fibre to become slightly more positive ("depolarized")

Sodium channels open in response to this small depolariazation, permitting a huge flow of positively charged sodium ions to enter the muscle fibre. The depolarization is greatly amplified, and a brief electrical impulse ("action potential") spreads throughout the fibre

Depolarization of the muscle fibre is sensed by calcium channels and triggers the release of calcium ions from internal storage areas. This flood of released internal calcium is the chemical signal that causes the thick and thin filaments of the muscle fibre to slide past each other (contract)

The sodium channels spontaneously close, potassium channels open, and positively charged potassium ions exit the fibre

Chloride channels also stay open, and negatively charged chloride ions enter the fibre

All these actions cause the inside of the fibre to become negative ("repolarized")

The muscle fibre returns to its resting state, calcium is pumped back into the internal storage vesicles, and the fibre is now ready to accept another surge of positively charged ions in response to stimulation from a nerve fibre.

Two things to take from the above that we find fascinating:

1. A key point to everything is that muscles in a resting state are ‘depolarized’ and in a negative/relaxed ie not positively charged state. In order for a muscle to innervate we must send it a positive signal in the form of a neurotransmitter through the nervous system. Once the muscle has been innervated, although it is only a short term positive signal the muscles have at least experienced this 'feeling' which in turn leaves us (the person) feeling more positive in the long run as we have had to initiate the initial positive burst of energy to begin with. We all know that exercise leaves us feeling more positive afterwards and this simple explanation could be a big reason why.

2. So much happens within the body, with every muscle movement. The human body is highly complex and this is the reason why nutrition is key to get the correct vitamins and minerals such as calcium, sodium and potassium on board. This is a big reason why we make a lot of smoothies, but then also include things such as fish, nuts and leafy veg in our diet as these are a great source of many of these nutrients.

Further info on the Sliding filament theory can be seen on the following website if you would like a little more info:

http://www.mda.org/disease/inherited-and-endocrine-myopathies/causes-inheritance/ion-channels-muscle-contraction