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EPHE 441 - Post Midterm > Muscle Physiology - New Slides > Flashcards

Muscle Physiology - New Slides Flashcards

1
Q

With training, how does MU type change to influence force production?

A 
Aerobic = shift to Type I 
Anaerobic = shift to Type II
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2
Q

When we train muscle, what are we trying to increase?

A

force production

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3
Q

How are the enzymes different in fast twitch muscles?

A
  • Myosin ATPase causes faster cross bridge cycling (contract faster)
  • Calcium ATPase is faster, pumps calcium into SR (relax faster)
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4
Q

Neurons serving ___ twitch motor units are much larger

A

fast

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5
Q

Speed of contraction - force velocity is n-shaped. What does this mean?

A

We have optimal speeds of contraction (in the middle)

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6
Q

What type of contraction produces the most force?

A

eccentric

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7
Q

With regard to length of muscle, how do you have to train to make sure you get a full response from the muscle?

A

You must train through a full ROM - develop force through the full ROM - must do this because actin and myosin need to have optimal overlap in the full range

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8
Q

Skeletal muscle contains two main types of fibers that differ in what three characteristics?

A
  • primary mechanics used to produce ATP
  • type of motor neuron innervation
  • type of myosin heavy chain expressed
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9
Q

Your ___ have a lot to do with how you respond to training

A

genetics (genetic makeup of fiber types)

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10
Q

What are they two biochemical properties of muscle fibers?

A
  1. Oxidative Capacity
    - -> # of capillaries, mitochondria, and amnt of myoglobin
  2. Type of Myosin ATPase
    - -> speed of ATP generation
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11
Q

What are the three contractile properties of muscle fiber?

A
  1. Maximal force production
    - -> force per unit of cross-sectional area
  2. Speed of Contraction (Vmax)
    - -> myosin ATPase activity
  3. Muscle Fiber Efficiency
    - -> how much energy being produced is heat and how much is ATP for muscles
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12
Q

Which type of muscle fiber has the slower ATPase activity?

A

Type I - this means it doesn’t produce force as fast as Type II

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13
Q

What is the rate limiting step of crossbridge cycling?

A

ATP hydrolysis –> Fibers with fast ATPase activity produce force quicker because a higher rate = faster crossbridge cycling

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14
Q

Fast twitch fibers exhibit what 4 characteristics?

A
  1. HIGH capacity for AP transmission
  2. HIGH myosin ATPase activity
  3. RAPID Ca release and uptake by efficient SR
  4. HIGH rate of crossbridge turnover
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15
Q

Why is it important that we can increase the size of the SR with training?

A

This allows for faster uptake of Ca and therefore a higher rate of crossbridge turnover - Quicker Ca uptake means the the muscle relaxes faster and can then contract again sooner

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16
Q

Fast Twitch Fibers: Intrinsic speed of shortening and tension development ranges from __-__ times faster than slow-twitch fibers

A

3-5

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17
Q

Fast twitch fibers rely on well-developed, short term ____ system for energy transfer

A

glycolytic

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18
Q

When trying to train fast-twitch fibers, how must you exercise?

A

must get into anaerobic zone and train to fatigue and failure to train your fast-twitch fibers

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19
Q

Type IIx is in the middle cause it is the x-over between the two types

A

nifty trick :)

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20
Q

“represents fast-oxidative-glycolytic fibers (FOG)”

A

Type IIa

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21
Q

“Possesses greatest anaerobic potential and most rapid shortening velocity; represents “true” fast-glycolytic fiber”

A

Type IIb

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22
Q

Slow-twitch fibers generate energy for ATP resynthesis through _____ system of energy transfer

A

aerobic

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23
Q

What are the 4 distinct characteristics of slow-twitch fibers?

A
  1. LOW myosin ATPase activity
  2. SLOW calcium handling ability and shortening speed
  3. LESS well-developed glycolytic capacity than fast-twitch fibers
  4. LARGE and numerous mitochondria
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24
Q

Why are shortening and relaxing speeds slower in slow twitch fibers?

A

Shortening speed is compromised at the SR because there is not as many channels.

Relaxation speed is slower because calcium ATPase is slower.

25
Q

Mitochondria is present in higher numbers in slow-twitch fibers, but has less ____ ____.

A

Lactate dehydrogenase

26
Q

Slow twitch fibers are highly ____ resistant and are ideally suited for what exercise?

A

fatigue; prolonged aerobic

27
Q

Slow twitch fibers have slow-oxidative fibers with slow shortening speed; they rely on _____ metabolism

A

oxidative

28
Q

High intensity will always recruit all muscle types - what is true with regards to low intensity?

A

Really low intensity might not necessarily recruit all fiber types (like type IIb)

29
Q

Force production is __-__% higher in fast fibers (IIa and IIx) compared to slow (type I) fibers

A

10-20

30
Q

High force production in fast twitch fibers is due to what?

A

the number of myosin cross-bridges in strong binding state

–> fast fibers contain more cross bridges per cross-sectional area (more actin and myosin filaments)

31
Q

Exercise induced changes in skeletal muscles - 2 from strength training?

A
  1. Increase in muscle fiber size (hypertrophy)

2. Increase in muscle fiber # (hyperplasia - limited human evidence)

32
Q

Exercise induced changes in skeletal muscles - endurance training?

A

increase in oxidative capacity - myoglobin, mitochondrial stores, etc.

33
Q

How do fiber types alter with training?

A

Fast to slow shift: Type IIx –> IIa

Type IIa –> I with further training

34
Q

If someone is weak and can’t do a pullup, what should they do?

A

If someone can’t do a pullup we can help them through the concentric phase and then have them do the eccentric phase - this will help with training

35
Q

At any absolute force the speed of a movement is greater in muscle with a higher % of ____-twitch fibers

A

fast twitch

36
Q

The maximum velocity of shortening is greatest at the ____ force

A

lowest - this is true for both fast and slow twitch

37
Q

Fast vs slow fiber contractions? (3)

A

Fast fibers:

  • contract 2-3 times faster
  • relax more rapidly due to faster rate of Ca ATPase

Slow fibers:
-contractions last 10x longer

38
Q

At the same velocity of movement, which fibers produce more force?

A

Fast twitch fibers! They have a higher power output at a same given velocity.

39
Q

Normal muscle activity - isometric vs isotonic contraction occurrences?

A
  • Some purely isometric contractions can occur

- Purely isotonic contractions are very rare

40
Q

Force generation depends on what three things?

A
  1. Types and # of MOTOR UNITS recruited
  2. Initial MUSCLE LENGTH
  3. Nature of the NEURAL stimulation of motor units
41
Q

DOes recruiting more or less motor units produce a greater force?

A

more = greater force

42
Q

What were the 7 points under force production and fiber type that contribute to better force production?

A
  1. Extensive SR development
  2. Troponin affinity to Ca = > actin active site availability and faster x-bridge cycling
  3. Higher threshold for Ca release, but a high force response to Ca
  4. Rate of x-bridge turnover (myosin phosphatase)
  5. Elasticity (> compliance) = rapid forceful contractions
  6. Summation of forces (faster, tetanize)
  7. Enzymatic kinetics (ATPase)
43
Q

MU nerves innervating type __ fibers are smaller and have lower excitation threshold

A

Type I - they will be recruited first

44
Q

How can we increase synchrony of MU recruitment?

A

weight training

synchrony increases strength without changes in muscle fiber size

45
Q

As the amount of tension required increases, how does MU recruitment change?

A

SO –> FOG –> FG

46
Q

What happens if the sources of ATP for muscle contraction are limited for some reason?

A

It is going to impact the effect of these enzymes (myosin ATPase and Ca ATPase) and therefore impact the force and rate of contraction we are going to be able to produce

47
Q

Myosin ATPase does ____ of muscle while Ca ATPase does _____

A

contraction

relaxation

48
Q

_____ ______ is an important mechanism in regulating contractile activity in muscle

A

myosin phosphorylation

49
Q

What are the 2 enzymes involved in myosin phosphorylation?

A
  1. Myosin light chain kinase (MLCK)

2. Myosin Phosphatase (MP)

50
Q

Where is MLCK located?

A

The neck of the myosin molecule - we really want to see conformational changes here in the light chain cause it is what moves the head!

51
Q

Where is myosin heavy chain located?

A

embedded inside the thick filament as well as in the myosin head

52
Q

What enzyme is associated with x-bridges?

A

MLC

53
Q

____ phosphorylates MLC, enhancing ability to form x-bridges with actin

A

MLCK

54
Q

MLCK control: ____/_____ activation

A

Ca++/calmodulin

55
Q

What are the 3 myosin heavy chain (MHC) isoforms?

A

MHC I = slow twitch

MHC IIa and IIx = fast twitch

56
Q

What are myosin heavy chain hybrid fibers?

A

When greater than one MHC isoform is expressed: IC, IIC, IIAX
-C fibers: both fast and slow characteristics

57
Q

What are the 7 fiber types in the continuum from slow to fast?

A

I, IC, IIC, IIa, IIax, IIx, IIb

58
Q

MLC is associated with ______

A

x-bridges

EPHE 441 - Post Midterm (5 decks)

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