Muscular System Flashcards
Muscle Facts
650 in human body
30-40% of total body weight
speak, move and breathe
number of skeletal muscle fibers are fixed after post natal period, genetically determined.
Skeletal muscle
striated fibers that attach to bone and contract to produce voluntary movement
Smooth muscle
non striated fibers, attach to organ systems, involuntary movement
Cardiac muscle
specialized striated fibers, walls of heart
Muscle Fascicles
bundles of many skeletal muscle fibers
Myofibrils
contractile units within tissue, voluntary contraction produces movement.
each fiber has one nuclei,
Myofilaments
smaller units within myofibrils that contain actin and myosin proteins
Myoblasts
stem cells which form new muscle tissue, set at the end of development
Myotubes
developmental stage of a muscle fiber composed of a syncytium formed by fusion of myoblasts, undergo differentiation to become muscle fibers
Satellite cells
facilitate protein synthesis necessary for muscle growth
Inflammatory phase
immediately after injury
3-5 days
bleeding may form hematoma
Proliferative phase (reparative)
first few days of injury, peaking 7-10 days
lasts 2-4 weeks
muscle is still unstable, no loading
hematoma reabsorbed, satellite cells begin protein synthesis
extensive injury: fibrosis, scar tissue (contracture)
Remodeling (maturation) phase
begins 3 weeks after injury
peaks 6-8 weeks
lasts 6-24 months
Can load, begin with ROM then progressive loading
Muscle Regeneration Risk Factors
movement of muscle tissue during healing
poor circulation: smoking, diabetes
medications: corticosteroids, immunosuppressants
advanced age
poor nutrition, lacking amino acids for protein synthesis
Davis’ Law
Soft tissue will adapt according to biomechanical load placed on it. High load: hypertrophy. Low load: atrophy
Immobilization effects
1-10 days immobilization: rapid protein breakdown, decline in protein synthesis
results in decreased muscle size and functional strength
Sarcopenia
reduction of both number and size of muscle fiber
major contributor to frailty syndrome
fast decline in ADL / IADL
greater risk for hospitalization, post surgery complications, complications chronic and acute conditions, shorter life span
Strength Training
progressive resistance results in hypertrophy, increased protein synthesis within muscle tissue by satellite cells
increase in power, strength and endurance due to muscle size
greater mass: greater forces can be placed on limb
OT practice implications
inflammatory and proliferative phase: modify/adapt approach toward occupation and activity
proliferative phase and remodeling phase: resorb (remediation) approach using progressive strengthening
