Muscle Structure and Function

Question 1

sarcomere

Answer 1

fundamental unit within muscle fiber

Question 2

contractile proteins

Answer 2

shorten muscle fiber and generate active force

actin and myosin

Question 3

non-contractile proteins

Answer 3

support the structure of the muscle fiber

titin: provides passive tension
desmin: stabilizes alignment of adjacent sarcomeres

Question 4

what extracellular connective tissues are in muscle?

Answer 4

collagen and elastin

Question 5

fusiform muscle

Answer 5

parallel fibers attach to central tendon

longer

greater ROM potential

Question 6

pennate muscle

Answer 6

oblique fibers approach central tendon

shorter

smaller ROM

Question 7

which muscle fiber type has more fibers per area?

Answer 7

pennate

results in greater strength and force production

Question 8

force couple

Answer 8

like a synergist

formed when 2 or more muscles simultaneously produce force in different linear directions but produce torque in the same direction

angular motion in the same direction

Question 9

advantage of isometric movements

Answer 9

allows contraction of the muscle without movement thru full ROM

useful for early post op rehab

Question 10

advantage of isokinetic

Answer 10

allows ability to adjust resistance throughout ROM of the muscle to account for stronger/weaker areas

Question 11

high forces generated by eccentric contractions are a result of what?

Answer 11

greater average forced produced per cross bridge

more rapid reattachment phase of cross bridge formation

passive tension produced by viscoelastic properties of stretched muscle

Question 12

which type of movement caused more overall muscle damage?

Answer 12

eccentric movements

more force production and less metabolic fatigue, greater microtrauma and strength gains, greater muscle hypertrophy

Question 13

tension

Answer 13

force built up within a muscle

Question 14

where does active tension come from?

Answer 14

contractile units

Question 15

what builds passive tension?

Answer 15

stretching

Question 16

total tension

Answer 16

combination of active and passive tension

Question 17

tone

Answer 17

slight tension in muscle at all times; state of readiness

Question 18

what happens when a muscle is stretched?

Answer 18

spring-like resistance (stiffness) is generated within the muscle

Question 19

passive tension

Answer 19

when a muscle is stretched and resistance is generated

attributed to elastic forces produced by non-contractile elements

Question 20

passive length tension curve

Answer 20

created after critical length

tension is increased as the tissue is stretched

high tensions results in rupture or failure

Question 21

what does steepness depend on in the passive length tension curve?

Answer 21

muscle architecture

amount and type of supporting connect tissue

Question 22

what effect does passive tension have on a joint?

Answer 22

stabilize or move a joint

Question 23

what are some limited functional effectiveness in the passive length tension curve?

Answer 23

delayed mechanical responsiveness

significant amount of lengthening that occurs before meaningful passive tension is generated

Question 24

active length tension curve

Answer 24

generating active force

potential cross bridges decrease as the muscle is stretched or shortened from resting length, therefore less active force can be generated

Question 25

what does the peak of curve in the active length tension curve indicate?

Answer 25

ideal resting length: length that allows the greatest number of cross bridges which ultimately produce the greatest force

Question 26

total length tension curve

Answer 26

passive and active tension working together to achieve greater force prior to resting length force generated by active means a force must be produced to get rid of the slack

Question 27

what happens to passive tension once it's stretched beyond resting length in the total length tension curve?

Answer 27

it contributes to overall force

Question 28

what happens when passive tension is added?

Answer 28

active force is diminished

Question 29

what happens after active force is completely gone?

Answer 29

passive tension dominates

Question 30

what determines the amount of tension present?

Answer 30

muscle length

Question 31

how can a muscle produce greater force?

Answer 31

by putting a stretch on it prior to contracting ex: pulling a rubber band before snapping it

Question 32

what is significant about 1 joint muscles?

Answer 32

have sufficient excursion to allow joint to move through the entire ROM less contracting force as compared to 2 joint muscles

Question 33

what is significant about 2 joint muscles?

Answer 33

may not have sufficient excursion to allow joint to move through combined range of all joints that it crosses advantage of maintaining greater contracting force through a wider range

Question 34

what is passive tension dependent on? where do we see high levels of this?

Answer 34

stiffness of the muscle muscles that cross multiple joints

Question 35

passive insufficiency

Answer 35

when a muscle is of insufficient length to permit full ROM can only occur at 2 joint muscles

Question 36

tenodesis grasp

Answer 36

passive movement of tendons in response to passive insufficiency

Question 37

active insufficiency

Answer 37

point at which a 2-joint muscle reaches a point where it cannot shorten any farther and diminished ability of a muscle to produce force -- ex: when a muscle is over shortened insufficient power to contract further

Question 38

what does isometric force indicate?

Answer 38

indicator of peak strength and the measure of neuromuscular recovery its the max effort against a known external force shape dependent on muscle group

Question 39

how can internal torque be measured?

Answer 39

by isometric contraction at several joint angles larger moment arm creates greater torque

Question 40

what is the best way to measure isometric force?

Answer 40

handheld dynamometer

Question 41

what is force output highly dependent on?

Answer 41

muscle length

Question 42

force velocity curve

Answer 42

velocity of the shortening of a muscle is concentrically contracting is inversely related to the external load; increase load = decrease speed velocity of the lengthening of an eccentrically contracting muscle is proportional to the external load; increase load = increase speed

Question 43

force time relationship

Answer 43

force generated by a muscle is proportional to the contraction time up until max contraction greater the contraction time the greater the force up to max contraction

Question 44

what is the purpose of stretching?

Answer 44

lengthen the resting length of a muscle should be performed on relaxed muscle different stretches depending on how many joints it crosses

Question 45

how do you stretch a 1 joint muscle?

Answer 45

you must put the 2 joint muscle on slack to stretch the 1 joint muscle example: gastroc vs soleus