The tedious process of muscle contraction

I'm pretty sure my body knows more biology then I do.

So muscle contraction requires ATP and Ca, Na, K, Cl ions. In order to acquire these, we have to eat food. Food enters our digestive system and encounters digestive enzymes. The nutritions are then absorbed in jejunum, and minerals like Ca, Na, K and Cl are absorbed in large intestine. All of these nutritions will then enter the blood stream.
In order to acquire ATP, one have to have glucose, fructose and galactose first. After glucose, fructose and galactose enters the blood stream. They may break the homeostasis of glucose in blood and have too high of a glucose level. As a result, the Beta cells in pancreas will release insulin into blood.

The body will send chemicals to the Beta cells. The receptors on the surface of the Beta cells will receive these chemicals and signal the nucleus of the Beta cell, which contains DNA of insulin and secrets insulin. Insulin will stimulate the body cells to take up more glucose and store it as glycogen.
If the glucose level in blood is too low, the body will secret chemicals that signal the receptors on the surface of pancreas Alpha cells. The receptors will then send the chemicals to the nucleus of Alpha cell, which contains DNA of glucagon. Alpha cells produce glucagon, which stimulates the liver to break down glycogen and release glucose into blood.

Glucose goes through cell respiration, and then ATP is made. 

Now, here's what happens to Ca homeostasis. When the level of Ca in blood is too low, parathyroid will detect the low Ca level and secret PTH, which stimulates kidney to secret Ca and activate Vitamin D to help Ca absorbing. It also activates Osteoclast, which crushes bones to release Ca into blood. When Ca level is too high in blood, thyroid will secret Calcitonin, which signals the kidney to take in Ca and signal Osteoblasts to build bone matrix to lower Ca level. 

With Ca, Na, Cl, K and ATP in the system, muscles are able to contract in the following way:

Sodium and potassium is pumped through the plasma membrane to produce an electrical current, which repels Ca to move tropomyosin to move away from the actin binding sites. ATP binds to the tip of the cross bridges on myosin and turns into ADP and P. The cross bridges then binds to the exposed active sites and move the muscle and contracts it.