Human Biology 1.3 The muscular system makes movement possible.

Muscles perform important functions
They produce movement,
keep body temperature stable and maintain posture.

Movement
The muscular system works with the skeletal system to allow movement.
The muscles are made up of individual cells called muscle fibers which contract and relax.
Most of the muscles work in pairs. As they contract, muscles shorten. They do not push but pull in one direction, while another muscle relaxes.
Muscles are attached to bones by
stretchy connective tissue.

Maintaining Body Temperature
•When muscles contract, they release heat. Without this heat from muscle contraction, the body could not maintain its normal temperature.

Maintaining Posture

•Muscles work against gravity.
•Most muscles in your body are always a little bit contracted.
•The muscles that maintain posture relax completely only when you are unconscious.


Skeletal Muscle (Voluntary muscles)
-Attached to your skeleton.
-Perform voluntary movement.
-Made out of long fibers which are
made up of many smaller bundles.
(slow twitch muscles, fast twitch muscles)
Together, the skeletal muscles work
with your bones to give your body power and strength

Smooth Muscle (involuntary muscles)
-Found inside organs such as intestines or the stomach.
- Smooth muscles are not fast twitch. They contract slowly.

Cardiac Muscle (involuntary muscles)
-Found only in heart
-A special group of cells within the heart are known as the pacemaker of the heart because it controls the heartbeat

Humans develop muscular coordination and become more graceful in their movements.
When you exercise regularly, your muscles may get bigger. Exercise also stimulates growth of individual muscle cells, making them larger.
During exercise, chemicals can build up in the muscles and make them cramp or ache.
The muscle soreness after exercise is caused by damage to the muscle fibers.