exam 2: diversity of skeletal muscles Flashcards

1
Q

diversity of skeletal muscle fibers 3 types:

A

slow twitch: type I

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

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2
Q

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

A

oxidative

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3
Q

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

A

I=red
IIA=red
IIB=white

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4
Q

myosin ATPase activity:
I=
II=
III=

A

I= slow
II=fast
III=fast

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5
Q

diameter
I=
II=
III=

A

I=small
II=moderate
III=large

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6
Q

oxidative capacity
I=
II=
III=

A

I= high
II= moderate
III=low

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7
Q

fatigue
I=
II=
III=

A

I=slow
II=fast resistance
III= fast fatigable

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8
Q

what type takes longer to reach peak tension?

which takes least amount to reach peak tension?

A

longer= slow twitch Type I
least amount= Type IIB

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9
Q

certain characteristic of skeletal muscle fibers can change in response to

A
  1. changes in size
  2. changes in fiber types (proportion of fiber types changes)
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10
Q

changes in size of skeletal muscle fibers:
1
2
3

A
  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)
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11
Q

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

A

contraction

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12
Q

force produced is LESS than the load= no movement

generating tension but the muscle is not shortening

A

isometric contraction

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13
Q

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

has happened which allows muscle length to remain the same

A

sarcomeres have shortened and elastic elements have stretched

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14
Q

force produced is great enough to move a load

A

isotonic contraction

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15
Q

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

A

shorten

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16
Q

the force of contraction increases until the isometric contraction becomes an

A

isotonic contraction
-not always possible!

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17
Q

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

A

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)

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18
Q

contraction of a whole skeletal muscle is

A

graded

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19
Q

increase of crossbridges= increase of

20
Q

increase total force by:
1
2

A
  1. increasing the number of muscle fibers contracting (motor unit recruitment)
  2. increasing the frequency of fiber activation
21
Q

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

A

alpha motor neuron (LMN) or by releasing ACh

22
Q

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

A

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

and

increasing frequency of fiber activation

23
Q

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

smallest motor units control ______

A

small

control fewer fibers

24
Q

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

A

spatial summation

25
increasing the frequency of activation increases:
action potential frequency (tetanus)
26
are composed of slow-twitch oxidative fibers. they have the lowest threshold for firing and are recruited first
small motor units
27
what has the lowest threshold for firing
slow-twitch oxidative fibers
28
composed of fast-twitch glycolytic fibers. have the highest threshold and are recruited last
large motor units
29
highest threshold and recruited last
fast twitch (type IIB)
30
an increase in the frequency of an alpha motor neuron stimulation will increase the amount of what produced
amount of tension
31
the tension produced in response to each action potential will sum if the muscle:
has not yet completely relaxed
32
can come to a point where you have such high AP frequency that you get fuzed tentaus where what happens:
absolutely no relaxation period
33
every actional potential causes ___ to be released
calcium
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:
calcium not enough relaxation between the stimuli
35
1. increase ca, increase # cross-bridges= 2. AP's have already stretched that series elastic elements=
1. increase in force 2. why much stronger force production
36
for a single muscle twitch (one muscle fiber), the tension developed is altered by
sarcomere length
37
where there is best degree of overlap between the thick and thin filaments
optical length
38
at the optical length the greater number of actin/myosin cross-bridges can form, which results to maximal
tension produced
39
tension is reduced if
the muscle is not stretched enough or if it is stretched too much
40
if we increase the muscle length,
we decrease the amount of thick and thin overlap
41
if we decrease the muscle length, we
increase the overlap
42
the velocity of contraction(distance moved/time) depends on the
load a fiber is contracting again (fast with less weight compared to something heavier)
43
decrease in velocity:
increase in load
44
load isnt the only factor that dictates the speed of contraction. _____ also dictates it
fiber type
45
Type I fibers have an isoform of myosin with ______ ATPase activity while Type II fibers have a _____ myosin ATPase
type I- slower type II- faster myosin atpase
46