Muscular System

Three Types

• Skeletal or striated – attached to bones, allows motion, voluntary control

• Smooth - work internal systems, involuntary i. e. digestive and circulatory

• Cardiac – heart muscle, involuntary

Skeletal Muscle

• Works in pairs, one bends joint the other extends or straightens joint

• For full motion opposite muscle must relax while one flexes or contracts

• Muscle cells contract in response to nerves signals

• Contracting unit of a muscle – myofibril• Under voluntary control

Myofibril

• Two types of proteins in contracting unit: myosin and actin

• Proteins slide over each other and overlap when contracted

Skeletal Muscle cont.

• Two proteins (myosin and actin) give muscles a striped effect under a microscope – striated means banded or striped

• Two types of cells:– Red muscle cells – work longer– White muscle cells – work stronger

Skeletal Muscle cont.

• Humans have muscles with both types of cells

• Exercise increases the size of your cells• Skeletal muscles have multiple nuclei

Cardiac Muscle

• Found in the heart• Average adult heart rate – 60 – 100 bpm• Less striped than skeletal muscle• Have only one nucleus per cell• involuntary

Smooth Muscle

• Short non-striped muscle cells• One nucleus per cell• Found in cell walls of veins, arteries,

digestive system, respiratory system etc.• involuntary

Healthy Muscles

• Diet needs to include enough protein• Enough energy to fuel muscles• Strongest at about 25 years old

Identifying Injuries

• X-Rays – form of energy that travels in waves

• Shows bones, good for detecting fractures• Goes through soft tissue but not bones• Bones show up as white areas• Need to be careful of exposure to X-Rays

MRI

• Magnetic Resonance Imaging• Clear images of both bones and soft tissue• Magnetic energy causes atoms in your

body to vibrate (resonate). Computer analyzes vibration pattern to form image

• No evidence it cause any harm• Fairly expensive

Muscles to Know