9. What is a muscle?
All movements in our body are controlled by muscles, which are
living tissues and work by pulling against the skeleton. Muscles are
made of bundles of fibres, which contract when they receive a signal
from the nerves. The power of a muscle depends on the number of
fibres.
These increase with exercise, which is the reason why body builders
develop big muscles.
There are three types of muscles in the body. The first is skeletal or
voluntary muscle. Together with the bones and tendons, it is
responsible for all forms of conscious movements. The second is the
smooth muscle, which is concerned with the involuntary movement
of internal organs, such as the guts and bladder, the third is cardiac
muscle which makes up the main bulk of the heart. This type of
muscle works throughout life.
