*Yawn*I'm so sleepy, I'm going to go brush my teeth
Hold on! Before you go, let me tell you something interesting!
Before you go to brush your teeth, an amazing set of events happen inside your body. This allows you to move you arm so you can brush your teeth!
Message released from the CNS
Just as you're moving your arm (bicep brachii) to brush your teeth, a message is originates and released from the central nervous system (CNS), specifically at the elbow flexor control center of the brain.
This message travels down the spinal cord and branches off at the shoulder level and travels to the peripheral nervous system.
The message travels from the axon branch to the axon terminal of the elbow flexors. Only a few muscle fibers (small motor unit) will be reunited, since the weight of the toothbrush is minimal.
The calcium ions find their way to the attachemnt sites on the troponin, which are located on the actin's tropomyosin.
This message then is carried through the axon terminal via acetylcholine (ACh) to the sarcolemma of each of the muscle fibres involved. The ACh causes the sarcoplasmic reticulum to release calcium ion from the terminal cisterna.