Section 2: Muscle Mechanics Lec 2-1

Question 1

Ft

Answer 1

total force

Question 2

Fc

Answer 2

contraction force

Question 3

Fp

Answer 3

passive force

Question 4

l0

Answer 4

length for greatest tension

Question 5

isometric contraction

Answer 5

no shortening of the sarcomere

Question 6

force is dependent on

Answer 6

of crossbridges (muscle, fiber, myofibril)

Question 7

species differences in sarcomere length at peak tension due to :

Answer 7

myosin: length is constant at ~1.6 microm
actin: frog .95 microm
actin: human 1.27 micrometers

Question 8

true or false: mammals are able to generate force over larger ranges of sarcomere lengths than the frog

Answer 8

true

Question 9

parallel elastic (PE) elements

Answer 9

connective tissue surrounding contractile elements

Question 10

series elastic (SE) elements

Answer 10

connective tissue in series with contractile elements (tendon, sarcomeres, titon, nebulin)

Question 11

summation

Answer 11

-increasing force due to increased frequency of stimulation

Question 12

summation is due to

Answer 12

decreased time for deactivation between stimuli

-partly, but not entirely, due to slow Ca++ ATPase

Question 13

tension=

Answer 13

F(muscle/sarcomere length)/ # of crossbridges

**this is true for twitch, submax, and MVC

Question 14

isotonic contraction

Answer 14

constant load, muscle allowed to shorten

Question 15

slope

Answer 15

distance/time or velocity of contraction

Question 16

latency period

Answer 16

the time to lengthen the series elastic elements until tension equals load to be lifted

Question 17

power

Answer 17

work/time or FxD/time or force x velocity

Question 18

peak power occurs at _____ of peak force (Po)

Answer 18

30%

Question 19

true or false: a small female subject performing the eccentric exercise could easily fatigue a large man

Answer 19

true

Question 20

vO2 was significantly less for the eccentric work than for the concentric exercise. what is the equation?

Answer 20

VO2 concentric= 5 x VO2 eccentric

Question 21

eccentric contractions

Answer 21

lengthening of muscle while it is activated to contract
F external > F muscle
force» peak isometric force

Question 22

what does the force response suggest?

Answer 22

muscle is very resistant to lengthening

Question 23

velocity reponse

Answer 23

has almost no effect on force

Question 24

Much of daily movement is a combination of _____ and ______ contractions

Answer 24

concentric and eccentric contractions

Question 25

concentric contractions F/V due to

Answer 25

F/V due to time to move to the active state and attach myosin heads
* the faster the contraction the fewer the attachments**

Question 26

eccentric contractions F/V due to

Answer 26

number of crossbridges which physically have to be broken

Question 27

at high concentric velocities force is

Answer 27

Force is low and independent of length

Question 28

at low concentric velocities force is

Answer 28

force is strongly determined by length

Question 29

at eccentric velocities force is

Answer 29

force is determined mostly by length very little by velocity

Question 30

factors which affect the isometric tension in a submaximally activated muscle:

Answer 30

• average overlap of actin strands and myosin heads
• Free ca++ concentration in cytosol
• force/Ca++ (calcium sensitivity)

Question 31

calcium sensitivity defined as

Answer 31

force produced at a given Ca++

Question 32

proposed mechanism for enhanced Ca++ sensitivity

Answer 32

changes in actin-myosin filament spacing

Question 33

Free Ca++ in the cytosol is due to

Answer 33

the number of troponin binding cites occupied

Question 34

optimal length of individual motor units varies within a given muscle suggesting that:

Answer 34

at a given muscle length, different motor units have different mean sarcomere lengths

Question 35

consequences of optimal length of individual motor units varying within a given muscle

Answer 35

• decreases peak force

- extends the length span for available force leading to smooth muscle performance through Greater ROM