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 controlhand, arm, leg, face…

Involuntary – muscles you cannot consciously controlContinuously work all day heart, peristalsis, eyes…

Working Levers

The action of muscles, bones, and joints working together is very similar to a simple machineBones = rodsJoints = fulcrumMuscle contraction/relaxation = force

3 Classes of Levers

1st class – the fulcrum lies between the effort force and the load

2nd class – the load lies between the fulcrum and the effort force

3rd class – the effort force is between the fulcrum and the load

1st Class Lever

2nd Class Lever

3rd Class Lever

Skeletal Muscle

Muscles that move boneVoluntary 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 heartStriated, involuntaryContracts 70 times per minute

Smooth Muscle

Found in internal organsIntestines, bladder, blood vessels…Nonstriated, involuntary muscles that

slowly contract and relax

Working MusclesPairs 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