1. Muscular System
By clayton

2. You have three different types of muscles in your body: smooth muscle, cardiac muscles, and skeletal muscles. Smooth muscles:Smooth muscles, sometimes also called involuntary muscles, are usually in sheets, or layers, with one layer of muscle behind the other. Smooth muscles are all over your body. In your stomach and digestive system, they tighten up and relax to allow food to make its way through the body. Smooth muscles are also in your eyes to help your eyes focus. Cardiac muscles: The cardiac muscles are like the smooth muscle as in they work without you moving them. The heart muscles are made of cardiac muscles, also known as myocardium.
Functions

3. And the skeletal muscles functions
These are the muscles that make you look strong. These muscles are the ones that you move on your command. Skeletal muscles are voluntary muscles, which means you can control what they do. Your leg won't bend to kick the soccer ball unless you want it to. These muscles help to make up the musculoskeletal system, the combination of your muscles and your skeleton, or bones. Skeletal muscles are held to the body by tendons.. Tendons are cords made of tough tissue, and they work as special connector pieces between bone and muscle. 
And the skeletal muscles functions

4. Fallbacks of the muscles (injuries)
A muscle strain, or pulled muscle, occurs when your muscle is overstretched or torn. This usually occurs as a result of overuse or improper use of a muscle. Strains can happen in any muscle, but they're most common in your lower back, neck, shoulder, and hamstring, which is the muscle behind your thigh.
Fallbacks of the muscles (injuries)

5. Organs that are involved
The heart is the main organ in the muscular system that provides the blood to move the muscles.
Organs that are involved

6. Calcium ions are required for each cycle of the sarcomere
Calcium ions are required for each cycle of the sarcomere. Calcium is released from the sarcoplasmic reticulum into the sarcomere when a muscle is stimulated to contract. This calcium uncovers the actin binding sites. When the muscle no longer needs to contract, the calcium ions are pumped from the sarcomere and back into storage in the sarcoplasmic reticulum.
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