Section 2: Muscle Mechanics Lec 2-1 Flashcards
Ft
total force
Fc
contraction force
Fp
passive force
l0
length for greatest tension
isometric contraction
no shortening of the sarcomere
force is dependent on
of crossbridges (muscle, fiber, myofibril)
species differences in sarcomere length at peak tension due to :
myosin: length is constant at ~1.6 microm
actin: frog .95 microm
actin: human 1.27 micrometers
true or false: mammals are able to generate force over larger ranges of sarcomere lengths than the frog
true
parallel elastic (PE) elements
connective tissue surrounding contractile elements
series elastic (SE) elements
connective tissue in series with contractile elements (tendon, sarcomeres, titon, nebulin)
summation
-increasing force due to increased frequency of stimulation
summation is due to
decreased time for deactivation between stimuli
-partly, but not entirely, due to slow Ca++ ATPase
tension=
F(muscle/sarcomere length)/ # of crossbridges
**this is true for twitch, submax, and MVC
isotonic contraction
constant load, muscle allowed to shorten
slope
distance/time or velocity of contraction
latency period
the time to lengthen the series elastic elements until tension equals load to be lifted
power
work/time or FxD/time or force x velocity
peak power occurs at _____ of peak force (Po)
30%
true or false: a small female subject performing the eccentric exercise could easily fatigue a large man
true
vO2 was significantly less for the eccentric work than for the concentric exercise. what is the equation?
VO2 concentric= 5 x VO2 eccentric
eccentric contractions
lengthening of muscle while it is activated to contract
F external > F muscle
force» peak isometric force
what does the force response suggest?
muscle is very resistant to lengthening
velocity reponse
has almost no effect on force
Much of daily movement is a combination of _____ and ______ contractions
concentric and eccentric contractions
concentric contractions F/V due to
F/V due to time to move to the active state and attach myosin heads
* the faster the contraction the fewer the attachments**
eccentric contractions F/V due to
number of crossbridges which physically have to be broken
at high concentric velocities force is
Force is low and independent of length
at low concentric velocities force is
force is strongly determined by length
at eccentric velocities force is
force is determined mostly by length very little by velocity
factors which affect the isometric tension in a submaximally activated muscle:
- average overlap of actin strands and myosin heads
- Free ca++ concentration in cytosol
- force/Ca++ (calcium sensitivity)
calcium sensitivity defined as
force produced at a given Ca++
proposed mechanism for enhanced Ca++ sensitivity
changes in actin-myosin filament spacing
Free Ca++ in the cytosol is due to
the number of troponin binding cites occupied
optimal length of individual motor units varies within a given muscle suggesting that:
at a given muscle length, different motor units have different mean sarcomere lengths
consequences of optimal length of individual motor units varying within a given muscle
- decreases peak force
- extends the length span for available force leading to smooth muscle performance through Greater ROM
