Chapter 7
Muscular System
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Functions of Muscular System
• Body heat to maintain body temperature
• Body movement
• Body form and shape to maintain posture
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Types of Muscles
• Skeletal muscle
– Under conscious control (voluntary)
– Striated
– Attached to bone
• Smooth muscle
– Not under conscious control (involuntary)
– Non-striated
– Controlled by the autonomic nervous system
• Cardiac muscle
– In the heart only
– Involuntary
– Striated and branched
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Characteristics of Muscles
• Contractibility
– Shorten in response to a stimuli
• Excitability or irritability
– Electrical signals called action potentials
• Extensibility
– Stretching
• Elasticity
– Return to original length when relaxing
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Muscle Attachments
and Functions (1 of 2)
• Over 650 muscles in the body
• Muscles must be attached to bones for
leverage
• Muscles only pull, never push
• Attached to bone by tendons
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Muscle Attachments
and Functions (2 of 2)
• Muscles are attached at both ends
• Attachments may be to bones, cartilage,
ligaments, tendons, skin, or to each other
• Origin and insertion
• Prime mover
– Movement in a single direction
• Antagonist
– Pulls from the opposite direction
• Synergists
– Steady the movement or stabilize the joint
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Sources of Energy and Heat
• Narrow range of normal body temperature
• 98.6° F to 99.8° F
• Major source of energy is ATP (adenosine
triphosphate)
– Production requires oxygen, glucose, and other materials
– By-product is lactic acid
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Contraction of Skeletal Muscles
• Myoneural stimulation
– Stimulation by a nerve impulse causes contraction
(muscle twitch)
– Motor unit consists of a nerve cell plus the muscle fiber
it stimulates
– Junction between the nerve cell axon and the muscle
cell membrane is called the neuromuscular junction
• Contraction of muscle proteins
– Begins with an action potential
– Requires energy
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Effects of Aging
• Muscle atrophy
• Fibrous tissue replaces the muscle tissue
• Decrease in muscular strength and
endurance
• Loss of energy storage
– Fatigue
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Muscle Fatigue
• Caused by accumulation of lactic acid
in the muscles
• When not enough oxygen can be
transported to oxidize all the glucose in the
muscle
– Muscles contract anaerobically (without oxygen)
• Excess lactic acid causes fatigue and
cramps
• Need to repay oxygen debt
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Muscle Tone
• Muscle tone
– Muscles are always slightly contracted and ready to
pull
• Proper nutrition and regular exercise
• Isotonic
– When muscles contracts and shorten
• Isometric
– When the tension increases but the muscle does not
shorten
• Atrophy and hypertrophy
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Principle Skeletal Muscles
• Skeletal or voluntary muscles
– Move the skeleton
• Also control movement of the eyeballs,
eyelids, lips, tongue, and skin
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Naming of Skeletal Muscles
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Location
Size
Direction
Number of origins
Location of origin and insertion
Not all muscles are named by this method
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Muscles (1 of 2)
• 656 muscles
• 327 antagonistic muscles and two unpaired
muscles
– Orbicularis oris
– Diaphragm
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Muscles (2 of 2)
• Head muscles
• Neck muscles
• Trunk and extremity muscles
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Muscles of the Head and Neck
• Control expressions
• Mastication
• Movement of the head
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Figure 7-10 Head and neck muscle arrangement
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Muscles
• Muscles of the upper extremities
– Shoulder, arm, and hand movements
• Muscles of the trunk
– Breathing and movement of the abdomen and pelvis
• Muscles of the lower extremities
– Thigh, leg, ankle, foot, and toes
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Figure 7-11 Muscles of the upper extremity: (A) anterior view, (B)
posterior view
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Figure 7-12 Muscles of the trunk
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Figure 7-13 Muscles of the lower extremity: (A) anterior view, (B)
posterior view
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Exercise (1 of 2)
• Alters the size, structure, and strength of a
muscle
• Atrophy
– Shrinking of muscle size
• Hypertrophy
– Enlargement of muscle size
• Scar formation from injury
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Exercise (2 of 2)
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Improved coordination
Improved respiratory and circulatory system
Elimination or reduction of excess fat
Improved joint movement
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Training and Strength
• Increase in muscle size
• Improved antagonistic muscle coordination
• Improved functioning in the cortical brain
region, where the nerve impulses that start
muscular contraction originate
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Massage Muscles
• Potential health benefits
• Terms used in massage therapy to describe
type of massage
• Location of surface body muscles
• Physiotherapy and general massage
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Electrical Stimulation
• Passing electrical currents through the skin
into the body for therapeutic uses
• Stimulate nerve tissue
• Do not produce heat or cold
• Used in physical therapy
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Intramuscular Injections
• Deltoid (upper arm)
• Vastus lateralis (anterior thigh)
• Dorsal gluteal or ventral gluteal (buttocks)
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Musculoskeletal Disorders (1 of 2)
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Muscle atrophy
Muscle strain
Muscle spasm
Myalgia
Dystonia
Hernia
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Musculoskeletal Disorders (2 of 2)
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Flatfeet (talipes)
Tetanus (lockjaw)
Torticollis (wry neck)
Muscular dystrophy
Myastenia gravis
Heel spur
Plantar fasciitis
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Recreational Injuries
• Tennis elbow
• Shin splints
• Rotator cuff injury
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Treatment
• Short-term treatment for sprains, tears,
pulls, and other minor muscle or joint
injuries
• RICE
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Rest
Ice
Compression
Elevation
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