The human body comprises of more than 600 muscles differentiated in three classifications, and all are under the control of the nervous system. The activities like picking up a dropped pen or leaning over incorporate the combined effort of various muscle groups.
The alert mind relays this instruction to the central nervous system that conducts it in the form of electrical impulses. These are then mediated via the somatic segment of the peripheral nervous system to the nerves accountable for monitoring the essential muscles.
When the signals arrive, a chemical known as acetylcholine gets discharged from the nerve terminals, activating the membranes of muscle fibers and making them to contract. The receptors present in the muscles provide the brain with the instruction regarding the movement and position of the body, the brain monitors the contraction of skeletal muscles.