Muscle cells change their shape and shorten at the cellular level by utilizing special proteins that respond to nervous electrical impulses, leading to new arrangements of proteins that result in the muscle cells adopting a shorter form.

The vertebral column or backbone is a hard, bumpy structure that protects the spinal cord, a crucial part of the nervous system, by providing a physical barrier.

The brain is protected by being enclosed in a bony box, and within this, it is surrounded by a fluid-filled balloon, which acts as an additional layer for shock absorption.

The cerebellum is responsible for ensuring the precision of voluntary actions, as well as maintaining the posture and balance of the body during activities such as walking, riding a bicycle, or picking up a pencil.

The medulla in the hind-brain is identified as the region responsible for controlling various involuntary actions, including blood pressure regulation, salivation, and vomiting.