Muscle Structure and Function Flashcards
sarcomere
fundamental unit within muscle fiber
contractile proteins
shorten muscle fiber and generate active force
actin and myosin
non-contractile proteins
support the structure of the muscle fiber
titin: provides passive tension
desmin: stabilizes alignment of adjacent sarcomeres
what extracellular connective tissues are in muscle?
collagen and elastin
fusiform muscle
parallel fibers attach to central tendon
longer
greater ROM potential
pennate muscle
oblique fibers approach central tendon
shorter
smaller ROM
which muscle fiber type has more fibers per area?
pennate
results in greater strength and force production
force couple
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
advantage of isometric movements
allows contraction of the muscle without movement thru full ROM
useful for early post op rehab
advantage of isokinetic
allows ability to adjust resistance throughout ROM of the muscle to account for stronger/weaker areas
high forces generated by eccentric contractions are a result of what?
greater average forced produced per cross bridge
more rapid reattachment phase of cross bridge formation
passive tension produced by viscoelastic properties of stretched muscle
which type of movement caused more overall muscle damage?
eccentric movements
more force production and less metabolic fatigue, greater microtrauma and strength gains, greater muscle hypertrophy
tension
force built up within a muscle
where does active tension come from?
contractile units
what builds passive tension?
stretching
total tension
combination of active and passive tension
tone
slight tension in muscle at all times; state of readiness
what happens when a muscle is stretched?
spring-like resistance (stiffness) is generated within the muscle
passive tension
when a muscle is stretched and resistance is generated
attributed to elastic forces produced by non-contractile elements
passive length tension curve
created after critical length
tension is increased as the tissue is stretched
high tensions results in rupture or failure
what does steepness depend on in the passive length tension curve?
muscle architecture
amount and type of supporting connect tissue
what effect does passive tension have on a joint?
stabilize or move a joint
what are some limited functional effectiveness in the passive length tension curve?
delayed mechanical responsiveness
significant amount of lengthening that occurs before meaningful passive tension is generated
active length tension curve
generating active force
potential cross bridges decrease as the muscle is stretched or shortened from resting length, therefore less active force can be generated
what does the peak of curve in the active length tension curve indicate?
ideal resting length: length that allows the greatest number of cross bridges which ultimately produce the greatest force
total length tension curve
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
what happens to passive tension once it’s stretched beyond resting length in the total length tension curve?
it contributes to overall force
what happens when passive tension is added?
active force is diminished
what happens after active force is completely gone?
passive tension dominates
what determines the amount of tension present?
muscle length
how can a muscle produce greater force?
by putting a stretch on it prior to contracting
ex: pulling a rubber band before snapping it
what is significant about 1 joint muscles?
have sufficient excursion to allow joint to move through the entire ROM
less contracting force as compared to 2 joint muscles
what is significant about 2 joint muscles?
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
what is passive tension dependent on? where do we see high levels of this?
stiffness of the muscle
muscles that cross multiple joints
passive insufficiency
when a muscle is of insufficient length to permit full ROM
can only occur at 2 joint muscles
tenodesis grasp
passive movement of tendons in response to passive insufficiency
active insufficiency
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
what does isometric force indicate?
indicator of peak strength and the measure of neuromuscular recovery
its the max effort against a known external force
shape dependent on muscle group
how can internal torque be measured?
by isometric contraction at several joint angles
larger moment arm creates greater torque
what is the best way to measure isometric force?
handheld dynamometer
what is force output highly dependent on?
muscle length
force velocity curve
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
force time relationship
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
what is the purpose of stretching?
lengthen the resting length of a muscle
should be performed on relaxed muscle
different stretches depending on how many joints it crosses
how do you stretch a 1 joint muscle?
you must put the 2 joint muscle on slack to stretch the 1 joint muscle
example: gastroc vs soleus
