exam 2: diversity of skeletal muscles

Question 1

diversity of skeletal muscle fibers 3 types:

Answer 1

slow twitch: type I

fast twitch:
oxidative-glycolytic: type IIA
glycolytic: type IIB

Question 2

type I is slow and ____, which means it has a very rich blood supply

Answer 2

oxidative

Question 3

color (myoglobin/capillaries for:
type I
type IIa
type IIb

Answer 3

I=red
IIA=red
IIB=white

Question 4

myosin ATPase activity:
I=
II=
III=

Answer 4

I= slow
II=fast
III=fast

Question 5

diameter
I=
II=
III=

Answer 5

I=small
II=moderate
III=large

Question 6

oxidative capacity
I=
II=
III=

Answer 6

I= high
II= moderate
III=low

Question 7

fatigue
I=
II=
III=

Answer 7

I=slow
II=fast resistance
III= fast fatigable

Question 8

what type takes longer to reach peak tension?

which takes least amount to reach peak tension?

Answer 8

longer= slow twitch Type I
least amount= Type IIB

Question 9

certain characteristic of skeletal muscle fibers can change in response to

Answer 9

1. changes in size
2. changes in fiber types (proportion of fiber types changes)

Question 10

changes in size of skeletal muscle fibers:
1
2
3

Answer 10

1. hypertrophy (increase in cell size)
2. atrophy (decrease in size of muscle cell)
3. sarcopenia (decrease in muscle cell from aging/loss of muscle tissue)

Question 11

the amount of load and the force the muscle generates determines the type of

Answer 11

contraction

Question 12

force produced is LESS than the load= no movement

generating tension but the muscle is not shortening

Answer 12

isometric contraction

Question 13

in isometric contraction, the muscle length has not shortened but :

has happened which allows muscle length to remain the same

Answer 13

sarcomeres have shortened and elastic elements have stretched

Question 14

force produced is great enough to move a load

Answer 14

isotonic contraction

Question 15

sarcomeres shorten even more with even more overlap and because elastic elements are already stretched, the entire muscle must

Answer 15

shorten

Question 16

the force of contraction increases until the isometric contraction becomes an

Answer 16

isotonic contraction
-not always possible!

Question 17

muscle can only contract up to 17 grams. so with 20 grams what will happen?

Answer 17

muscle will not reach isotonic contraction bc the muscle will not be able to SHORTEN to move the LOAD. so it will stay as isometric contraction(generate tension but NO movement)

Question 18

contraction of a whole skeletal muscle is

Answer 18

graded

Question 19

increase of crossbridges= increase of

Answer 19

force

Question 20

increase total force by:
1
2

Answer 20

1. increasing the number of muscle fibers contracting (motor unit recruitment)
2. increasing the frequency of fiber activation

Question 21

a motor unit is the _______ and the muscle fibers it innervates

Answer 21

alpha motor neuron (LMN) or by releasing ACh

Question 22

two ways nervous system can cause a greater muscle tension production aka increase total force:

Answer 22

increasing the number of muscle fibers contracting (motor unit recruitment)

and

increasing frequency of fiber activation

Question 23

motor units are recruited in order of size.
_____ motor units are recruited first.

smallest motor units control ______

Answer 23

small

control fewer fibers

Question 24

an increase in the number of motor units activated increases the TOTAL TENSION produced by a contraction of a muscle=

(asynchronous recruitment)- alternate what is active and when

Answer 24

spatial summation

Question 25

increasing the frequency of activation increases:

Answer 25

action potential frequency (tetanus)

Question 26

are composed of slow-twitch oxidative fibers. they have the lowest threshold for firing and are recruited first

Answer 26

small motor units

Question 27

what has the lowest threshold for firing

Answer 27

slow-twitch oxidative fibers

Question 28

composed of fast-twitch glycolytic fibers. have the highest threshold and are recruited last

Answer 28

large motor units

Question 29

highest threshold and recruited last

Answer 29

fast twitch (type IIB)

Question 30

an increase in the frequency of an alpha motor neuron stimulation will increase the amount of what produced

Answer 30

amount of tension

Question 31

the tension produced in response to each action potential will sum if the muscle:

Answer 31

has not yet completely relaxed

Question 32

can come to a point where you have such high AP frequency that you get fuzed tentaus where what happens:

Answer 32

absolutely no relaxation period

Question 33

every actional potential causes ___ to be released

Answer 33

calcium

Question 34

twitches are close enough together that ____ from the first twitch is still present in the sarcoplasm when the second twitch is activated.
this means there is not enough:

Answer 34

calcium

not enough relaxation between the stimuli

Question 35

1. increase ca, increase # cross-bridges=
2. AP’s have already stretched that series elastic elements=

Answer 35

1. increase in force
2. why much stronger force production

Question 36

for a single muscle twitch (one muscle fiber), the tension developed is altered by

Answer 36

sarcomere length

Question 37

where there is best degree of overlap between the thick and thin filaments

Answer 37

optical length

Question 38

at the optical length the greater number of actin/myosin cross-bridges can form, which results to maximal

Answer 38

tension produced

Question 39

tension is reduced if

Answer 39

the muscle is not stretched enough or if it is stretched too much

Question 40

if we increase the muscle length,

Answer 40

we decrease the amount of thick and thin overlap

Question 41

if we decrease the muscle length, we

Answer 41

increase the overlap

Question 42

the velocity of contraction(distance moved/time) depends on the

Answer 42

load a fiber is contracting again (fast with less weight compared to something heavier)

Question 43

decrease in velocity:

Answer 43

increase in load

Question 44

load isnt the only factor that dictates the speed of contraction. _____ also dictates it

Answer 44

fiber type

Question 45

Type I fibers have an isoform of myosin with ______ ATPase activity
while Type II fibers have a _____ myosin ATPase

Answer 45

type I- slower
type II- faster myosin atpase