Muscular System

• Over 600 muscles that make up muscular system
• 45% Of total body weight of an adult

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• made up of bundles of muscle fibers (long slender cells) held together by CT
• when muscle fibers are stimulated by nerves they contract (become short and thick) which causes movement.
• contraction depends on myofilaments: actin and myosin.

Properties

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• Excitability
• Contactility
• Extensibility
• Elasticity
• Automaticity

Functions

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• Movement
• Posture maintenance
• Joint Stabilization
• Heat Generation
• Protection of some internal organs

Types of Muscles

Cardiac

• forms walls of heart
• contracts to circulate blood
• striated (lots of mitochondria)
• involuntary
• contracts at a steady rate

Visceral/Smooth

• internal hollow organs
• no striations = smooth
• involuntary
• steadies constant contractions, automaticity

Skeletal

• 40% of the body
• attaches to and covers bony skeleton
• longest fibers of muscle cells
• striated
• voluntary
• contract rapidly, tire easily; tremendous power, adaptable
• causes body movement

methods of attachment

Tendon

• connects muscle to bone
• strong, tough CT cord
• Ex: Achilles tendon

Fascia

• tough, sheet like membrane
• cover and protect tissue
• Ex: lumbodorsal fascia

Aponeurosis

• a broad flat sheet

Raphe

• a seam of fibrous tissue

Origin and Insertion

• Origin- the end that does not move
• Insertion- the end that moves when muscle contracts

Direct (fleshy)

• the epimysium is fused to the periosteum or perichondrium

Indirect

• more common due to size
• CT wrappings extend to form tendons; aponeurosis
• Anchors muscle to the CT of bone or cartilage, the fascia of other muscles or raphe

Interactions of Skeletal Muscles

Prime Movement/Agonist

• Provides the major force for producing a specific movement
• Initiates movement
• Ex: biceps brachii- elbow flexion

Antagonist

• opposes or reverses a particular movement
• Example - triceps brachii- elbow extension

Synergist

• aid the agonist by promotion of the same movement, or by reducing undesirable or unnecessary movements
• Ex: muscles which help make a fist with out bending the wrist

Fixator

• synergists which immobilize a bone or a muscle origin

Actions and Movements

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• Goniometry- measurement of joint movement
• Adduction- moving a body part toward the midline
• Abbduction- moving a body part away from the midline
• Flexion- decreasing the angle of a joint
• Extension- increasing the angle of a joint
• Hyperextension- increases the angle beyond the anatomical position

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• Hyperextension- increases the angle beyond the anatomical position
• Circumduction- the distal end of an extremmity inscribes a circle while the shaft inscribes a cone
• Rotation- revolving a body part about the longitudinal axis. (internal rotation & external rotation)

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• supination- turn the palm upward; what's up
• pronation- turn the palm downward
• inversion- turn the plantar surface toward the midline
• eversion- turn the plantar surface laterally
• plantar flexion- move the sole of the foot downward (press the pedal)
• Dorsiflexion- move the sole of the foot upwards (toes to your nose)

Muscle Nomenclature

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• Location, ex: external oblique, pectoralis
• Origin & insertion, ex: brachioradialis, occipitofrontal
• Number of heads/bellies, ex: biceps & triceps
• Function-, ex: ulnar flexor, buccinator
• Size- ex: vastus medialis

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• shape- ex: deltoid
• orientation of the muscle fiber bundles- ex: rectus abdominus, orbicularis oris

Adjectives to describe muscles

• bi, tri, quadri - 2, 3, 4
• externus- exterior
• gracilis-slender
• latissimus-wide
• longus-long
• medius- intermediate
• orbicularis- around

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• quadratus- square
• Rectus- straight
• Rhomboideus- diamond shaped
• Scalenes- irregular triangle
• Teres- round
• Transverse- crosswise
• Vastus- great