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The Muscular System
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Muscular System The body has more than 600 muscles that make up 40 to 45% of the body’s weight
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Types of Muscle Tissue Skeletal muscle Striated Dark and light bands in fibers Voluntary Conscious control over these muscles
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Cardiac Muscle Indistinctly striated Involuntary Under control of the autonomic nervous system
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Smooth Muscle Visceral Unstriated No dark and light bands Involuntary
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Smooth Muscle Located: Walls of internal organs Respiratory and digestive tracts Digestive tract=peristalsis Wavelike movement Causes contents to be propelled onward
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Muscle Function
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Aid in movement of: Body Blood Food Waste Provide and maintain posture Protect internal organs Provide heat
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How Muscles Are Named
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How Muscles are Named MMMMuscle origin PPPPlace where muscle begins MMMMore fixed end nearest midline MMMMuscle insertion PPPPlace where muscle ends FFFFarthest from midline
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Size Maximus Minimus Shape Deltoid Trapezius Direction of fibers Rectus Oblique Location Anterior Posterior Bone Number Bi Tri Quad
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Muscle Characteristics Muscle tone or tonus Partial state of contraction Balanced muscle tension required to hold body in position Flaccid Soft when not contracted
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Muscle Characteristics Irritability Ability to respond to stimulus Contractibility Ability to shorten Extensibility Ability to stretch and lengthen Elasticity Ability to return to original length at rest
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Accessory Structures
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Tendons Strong, fibrous connective tissue that connect muscle to bone
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Fascia Fibrous membrane that covers, supports, and separates muscle
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Types of Muscle Contractions Fibrillation: uncoordinated contractions Convulsions: contractions of groups of muscles in abnormal manner Spasms: involuntary, sudden, prolonged Twitch: quick, jerky movement
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Rules for Muscle Movement Pull never push on bones Always cross a joint Work in pairs: Prime mover (agonist): pulls to cause movement Antagonist: relaxes when agonist pulls
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Body Movements Caused by Skeletal Muscle Flexion: Decrease angle between two bones or bending a limb at a joint Elbow bent and lower arm brought upward Plantar flexion: bending foot forward Dorsiflexion: bending foot toward knee Extension Increase angle between two bones or straightening out a limb Elbow straightened and lower arm downward
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Body Movements Caused by Skeletal Muscle Abduction Movement away from body midline Arm moves outward, away from side of body Adduction Movement toward midline of body Arm moves inward, toward side of body Rotation Circular or semi-circular movement around an axis Turning the head when saying no
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Body Movements Caused by Skeletal Muscle Pronation: Turning hand downward Supination: Turning hand upward
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Pathology of the Muscular System
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Muscle atrophy Weakening and wasting away of muscle tissue Occurs with paralysis and other conditions Can lead to contractures: Joint remains in flexed position
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Muscular dystrophy Genetic disease Gradual atrophy of muscle tissue No cure Treatment: Medication to slow Braces Corrective surgery
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Muscular Dystrophy
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Fibromyalgia A group of muscle disorders affecting the tendons, ligaments, and other fibrous tissues Common sites of pain Neck, shoulders, thorax, lower back, thighs Myalgia (pain) common Treatment: reduce stress, therapy, exercise
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Hernia The abnormal protrusion of a body part into another body area Result from weakness in stomach muscles Treatment: bracing or surgery
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Hernia
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Poliomyelitis A viral infection Results in paralysis of muscles Prevented by vaccination No cure
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Gangrene Cause: bacterial infection Destroy living tissue by toxin Treatment: Removal of dead tissue Antibiotics Meds against toxin
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Pes planus Flatfoot or fallen arches Either congenital or from weakened foot muscles May cause extreme pain
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Tetanus AKA “lock jaw” Caused by a bacterial infection Toxin causes sustained contractions Prevention: immunization No cure-palliative care of symptoms
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Muscle Strain Torn or stretched tendons or muscles
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The End
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