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Anatomy and Physiology
7:5 Muscular System
 600+ muscles in the body
 Bundles of muscle fibers held together with connective
tissue
Properties of Muscles
 Properties of muscles
 Excitability/irritability

The ability to respond to a stimulus such as a nerve impulse.
 Contractibility
 Muscle fibers that are stimulated by nerves contract, or
become short and thick, which causes movement.
 Extensibility
 The ability to be stretched.
 Elasticity
 Allows the muscle to return to its original shape after it has
contracted or stretched.
Kinds of Muscles
 Cardiac—involuntary
 Visceral or smooth—involuntary
 Skeletal—voluntary
Smooth Muscle
• Has narrow, tapered rod-shaped
cells.
• Has nonstriated, uninucleated
fibers
• Occurs in walls of internal organs
and blood vessels
• Is involuntary
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Cardiac Muscle
• Has striated, tubular, branched,
uninucleated fibers
• Occurs in walls of heart
• Is involuntary
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Skeletal Muscle
• Has striated, tubular,
multinucleated fibers.
• Is usually attached to skeleton
• Is voluntary
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Functions of Muscles
 Attach to bones to provide movement
 Produce heat and energy
 Help maintain posture
 Protect internal organs

Skeletal muscles

Smooth muscle

Cardiac muscle
◦ Attached to bones by tendons
◦ Connected across joints so when they contract,
bones they attach to move
◦ Found on organ walls such as digestive system
◦ Contractions produce movement of organ
contents
◦ Produces heart chamber contractions
◦ This pumps blood from the heart into the blood
vessels
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
Hold bones tightly
together
◦ Stabilize joints

Small muscles hold
vertebrae together
◦ Stabilize the spinal column
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
Sphincters
◦ Valve-like structures formed by muscles
◦ Control movement of substances in and out of
passages
◦ Example:

A urethral sphincter prevents or allows urination
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
Heat is released with
muscle contraction
◦ Helps the body maintain a
normal temperature
◦ Moving your body can make
you warmer if you are cold
◦ Shivers is an extreme
example of this
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Attachments to Bone
 Tendon
 Strong, tough, connective-tissue cords.
 Fascia
 Tough, sheetlike, membrane that covers and protects
the tissue.
 Origin
 The end that does not move when the muscle contracts.
 Insertion
 The end that moves when the muscle contracts.
Actions or Movements of Muscles
 Adduction
 Moving a body part toward the midline.
 Abduction
 Moving a body part away from the midline.
 Flexion
 Decreasing the angle between two bones, or bending a
body part.
Actions or Movements of Muscles
 Extension
 Increasing the angle between two bones, or
straightening a body part.
 Rotation
 Turning a body part around its own axis (Example:
Turning head side to side).
 Circumduction
 Moving in a circle at a joint.
Muscle Tone
 Partially contracted at all times
 Muscle tone allows for state of readiness
 Loss of muscle tone
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Diseases and Abnormal Conditions
 Fibromyalgia
 Chronic, wide-spread pain in a specific muscle sites.
 Muscular dystrophy
 A group of inherited diseases that lead to chronic,
progressive muscle atrophy.
 Duchenne’s dystrophy
 Type of muscular dystrophy; caused by a genetic defect.
Diseases and Abnormal Conditions
 Myasthenia gravis
 Chronic condition where nerve impulses are not
properly transmitted to the muscles.
 Muscle spasms or cramps
 Painful, sudden, involuntary muscle contractions.
 Strain
 Overstretching of or injury to a muscle and/or tendon.