The Muscular System

Functions Stabilize joints with their tendons Produce movement Produce heat to maintain body temperature muscle – an organ that can relax, contract, and provide force to move your body parts.

Muscle Types Voluntary – muscles you can control hand, arm, leg, face… Involuntary – muscles you cannot consciously control Continuously work all day heart, peristalsis, eyes…

Working Levers The action of muscles, bones, and joints working together is very similar to a simple machine Bones = rods Joints = fulcrum Muscle contraction/relaxation = force

3 Classes of Levers 1 st class – the fulcrum lies between the effort force and the load 2 nd class – the load lies between the fulcrum and the effort force 3 rd class – the effort force is between the fulcrum and the load

1 st Class Lever

2 nd Class Lever

3 rd Class Lever

Skeletal Muscle Muscles that move bone Voluntary muscles that are striated (striped) Contract quickly and tire more easily Tendons – thick bands of tissue that connect bones to muscles Ligaments connect bone to bone to form a joint

Skeletal Muscle

Cardiac Muscle Found only in the heart Striated, involuntary Contracts 70 times per minute

Smooth Muscle Found in internal organs Intestines, bladder, blood vessels… Nonstriated, involuntary muscles that slowly contract and relax

Working Muscles Pairs of skeletal muscles work together When one muscle pair contracts, and the other one relaxes, or returns to original length Muscles always pull, they never push When muscles are used they increase in size (and sometimes number) However, when muscles are not used they can shrink

Remember… Muscles require energy to contract and relax Blood carries energy filled molecules to your muscle cells, then the stored chemical energy is released When a muscle uses all of its energy, it becomes tired, and blood supplies more energy-rich molecules to your muscles while they are at rest