Muscular System

Question 1

Muscle Facts

Answer 1

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.

Question 2

Skeletal muscle

Answer 2

striated fibers that attach to bone and contract to produce voluntary movement

Question 3

Smooth muscle

Answer 3

non striated fibers, attach to organ systems, involuntary movement

Question 4

Cardiac muscle

Answer 4

specialized striated fibers, walls of heart

Question 5

Muscle Fascicles

Answer 5

bundles of many skeletal muscle fibers

Question 6

Myofibrils

Answer 6

contractile units within tissue, voluntary contraction produces movement.
each fiber has one nuclei,

Question 7

Myofilaments

Answer 7

smaller units within myofibrils that contain actin and myosin proteins

Question 8

Myoblasts

Answer 8

stem cells which form new muscle tissue, set at the end of development

Question 9

Myotubes

Answer 9

developmental stage of a muscle fiber composed of a syncytium formed by fusion of myoblasts, undergo differentiation to become muscle fibers

Question 10

Satellite cells

Answer 10

facilitate protein synthesis necessary for muscle growth

Question 11

Inflammatory phase

Answer 11

immediately after injury
3-5 days
bleeding may form hematoma

Question 12

Proliferative phase (reparative)

Answer 12

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)

Question 13

Remodeling (maturation) phase

Answer 13

begins 3 weeks after injury
peaks 6-8 weeks
lasts 6-24 months
Can load, begin with ROM then progressive loading

Question 14

Muscle Regeneration Risk Factors

Answer 14

movement of muscle tissue during healing
poor circulation: smoking, diabetes
medications: corticosteroids, immunosuppressants
advanced age
poor nutrition, lacking amino acids for protein synthesis

Question 15

Davis’ Law

Answer 15

Soft tissue will adapt according to biomechanical load placed on it. High load: hypertrophy. Low load: atrophy

Question 16

Immobilization effects

Answer 16

1-10 days immobilization: rapid protein breakdown, decline in protein synthesis
results in decreased muscle size and functional strength

Question 17

Sarcopenia

Answer 17

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

Question 18

Strength Training

Answer 18

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

Question 19

OT practice implications

Answer 19

inflammatory and proliferative phase: modify/adapt approach toward occupation and activity
proliferative phase and remodeling phase: resorb (remediation) approach using progressive strengthening