The primary function of muscular system is to produce voluntary gross and fine movements. Large movements include walking, standing, running, playing sports and lifting weights and smaller movements include chewing, closing the eyes, writing and talking are all produced by the muscular system of the body.

The contraction of the heart muscle is involuntary and primarily controlled by the heart’s own electrical system. In the human body, the heart is responsible for receiving blood back from your muscles, pumping it into the lungs then pumping it out into the arteries to supply the entire body.

The abdominal muscles and the muscles of the lower back help protect the vital organs of the body. For instance, bones do not protect the abdominal cavity like the rib cage protects the heart and the lungs. The rectus abdominus, or “six pack” muscle, the obliques found at the sides of the torso and the transverse abdominus running side to side across the front of the abdominal cavity protect the organs from the front and sides. Similarly, the lats, quadrates lumborum and the psoas muscles, which run from the bottom area of the ribs to the pelvic bones protect the organs from the back of the abdominal cavity.

The smooth muscles of the stomach and intestines work to process the food we ingest. The involuntary contractions in the stomach and intestines aid in digestion and in moving the food along the digestive tract, ultimately directing indigestible substances to the rectum.

There are smooth muscles in the walls of the blood vessels. When the heart contracts, the arteries expand to accept blood. The smooth muscles in your arteries contract to push the blood throughout the blood vessel systems in the body. This is why when plaque builds up on the inside of the walls of the arteries, the arteries harden and the muscles in your arteries do not contract properly

Flexion and Extension: movements that take place within the sagittal plane and involve anterior or posterior movements of the body or limbs

Lateral flexion: the bending of the neck or body toward the right or left side

Abduction and adduction: occur within the coronal plane and involve medial-lateral motions of the limbs, fingers, toes, or thumb

Circumduction: the movement of a body region in a circular manner, in which one end of the body region being moved stays relatively stationary while the other end describes a circle

Rotation: the neck or body is the twisting movement produced by the summation of the small rotational movements available between adjacent vertebrae

Pronation: the motion that moves the forearm from the anatomical position to the pronated position

Dorsiflexion and plantar flexion: movements at the ankle joint

The sliding filament theory is the explanation for how muscles contract to produce force. As we have mentioned on previous pages, the actin and myosin filaments within the sarcomeres of muscle fibres bind to create cross-bridges and slide past one another, creating a contraction

The reaction, created from the arrival of an impulse stimulates the 'heads' on the myosin filament to reach forward, attach to the actin filament and pull actin towards the centre of the sarcomere. This process occurs simultaneously in all sarcomeres, the end process of which is the shortening of all sarcomeres.

When the muscle is stimulated to contract by the nerve impulse, calcium channels open in the sarcoplasmic reticulum and release calcium into the sarcoplasm. Some of this calcium attaches to troponin which causes a change in the muscle cell that moves tropomyosin out of the way so the cross bridges can attach and produce muscle contraction.