HUMAN NUTRITION

Detailed explanation-1: -Muscles move body parts by contracting and then relaxing. Muscles can pull bones, but they can’t push them back to the original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint.

Detailed explanation-2: -Muscles provide the tug on the bones needed to bend, straighten, and support joints. Muscles can pull on bones, but they can’t push them back to their original position, so the muscles work in pairs of flexors and extensors. The extensor muscle relaxes and stretches as the flexor muscle contracts to bend the joint.

Detailed explanation-3: -Muscle contraction is initiated by the nervous system which together with the endocrine system controls the human organism. They are responsible for the steadiness of the inner environment and coordination of all the bodily functions. The nerve cell, a neuron, is the basic unit of the nervous system (Fig.