Grades 6, 7 and 8 - Science - Middle School - Basic Anatomy - The Muscles — Flashcards

The muscular system makes up nearly half of the weight of a body. Muscles exert a force upon the body which in turn allows the body to move. Muscles rarely work alone however. Rather, muscles work in pairs. For example, when walking, one muscle moves the legs forward while another muscle moves the legs backwards.

Muscle movement is a voluntary movement. In other words, if you want to walk, the desire travels through the nervous system to the brain which then transmits that signal to the appropriate pair of muscles. The muscles receive the signal and quickly respond by performing the desired action. This quick response makes it a voluntary movement.

In order to perform movement, muscles have to contract (pull inward) and then relax or expand by stretching outward. This contracting, relaxing and expanding is done in a rhythmic pattern until the movement ceases.

There are over 600 muscles in the human body