This Science quiz is called 'Basic Anatomy - The Muscles' and it has been written by teachers to help you if you are studying the subject at middle school. Playing educational quizzes is a fabulous way to learn if you are in the 6th, 7th or 8th grade - aged 11 to 14.
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In middle school science on basic anatomy you will study the skeleton of the human body and learn that every adult possesses a total of 206 bones. That seems like quite a lot but when compared to the muscles of the body, the number of bones is only a fraction. There are close to 640 plus muscles in the human body or 320 pairs of muscles. The muscles attach to bones and connect at joints.
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.