The Muscular System

Muscular System  The body has more than 600 muscles that make up 40 to 45% of the body’s weight

Types of Muscle Tissue  Skeletal muscle  Striated  Dark and light bands in fibers  Voluntary  Conscious control over these muscles

Cardiac Muscle  Indistinctly striated  Involuntary  Under control of the autonomic nervous system

Smooth Muscle  Visceral  Unstriated  No dark and light bands  Involuntary

Smooth Muscle  Located:  Walls of internal organs  Respiratory and digestive tracts  Digestive tract=peristalsis  Wavelike movement  Causes contents to be propelled onward

Muscle Function

 Aid in movement of:  Body  Blood  Food  Waste  Provide and maintain posture  Protect internal organs  Provide heat

How Muscles Are Named

How Muscles are Named MMMMuscle origin PPPPlace where muscle begins MMMMore fixed end nearest midline MMMMuscle insertion PPPPlace where muscle ends FFFFarthest from midline

 Size  Maximus  Minimus  Shape  Deltoid  Trapezius  Direction of fibers  Rectus  Oblique  Location  Anterior  Posterior  Bone  Number  Bi  Tri  Quad

Muscle Characteristics  Muscle tone or tonus  Partial state of contraction  Balanced muscle tension required to hold body in position  Flaccid  Soft when not contracted

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

Accessory Structures

Tendons  Strong, fibrous connective tissue that connect muscle to bone

Fascia  Fibrous membrane that covers, supports, and separates muscle

Types of Muscle Contractions  Fibrillation: uncoordinated contractions  Convulsions: contractions of groups of muscles in abnormal manner  Spasms: involuntary, sudden, prolonged  Twitch: quick, jerky movement

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

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

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

Body Movements Caused by Skeletal Muscle  Pronation:  Turning hand downward  Supination:  Turning hand upward

Pathology of the Muscular System

Muscle atrophy  Weakening and wasting away of muscle tissue  Occurs with paralysis and other conditions  Can lead to contractures:  Joint remains in flexed position 

Muscular dystrophy  Genetic disease  Gradual atrophy of muscle tissue  No cure  Treatment:  Medication to slow  Braces  Corrective surgery

Muscular Dystrophy

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

Hernia  The abnormal protrusion of a body part into another body area  Result from weakness in stomach muscles  Treatment: bracing or surgery

Hernia

Poliomyelitis  A viral infection  Results in paralysis of muscles  Prevented by vaccination  No cure

Gangrene  Cause: bacterial infection  Destroy living tissue by toxin  Treatment:  Removal of dead tissue  Antibiotics  Meds against toxin

Pes planus  Flatfoot or fallen arches  Either congenital or from weakened foot muscles  May cause extreme pain

Tetanus  AKA “lock jaw”  Caused by a bacterial infection  Toxin causes sustained contractions  Prevention: immunization  No cure-palliative care of symptoms

Muscle Strain  Torn or stretched tendons or muscles

The End