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EXSC 463 Exam 1 > Chapter 11 > Flashcards

Chapter 11 Flashcards

1
Q

How do you “type” a muscle fiber?

A
  1. Myosin ATpase

2. Myosin heavy chain characteristics

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2
Q

What are the three fiber types?

A

Type I
Type IIa
Type IIx

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3
Q

What are the most common fiber types?

A

Type I

Type IIa

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4
Q

How abundant are Type IIx in humans?

A

least abundant

1-2% of fibers in muscle

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5
Q

T/F

All muscle fibers in a motor unit are the same type.

A

True

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6
Q

Myosin heavy chain has many ______.

A

isoforms that represent different types

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7
Q

Isoforms?

A

proteins that have different structures but similar functions

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8
Q

What determines the speed of contraction?

A

Myosin ATPase activity

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9
Q

Describe the ATPase activity of Type II fibers?

A

have high activity can complete cross bridge cycles more rapidly, have faster shortening velocities, and achieve peak tension faster than type I

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10
Q

Oxidative capacity?

A

refers to the capacity for oxidative (aerobic) metabolism

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11
Q

Glycolytic capacity?

A

refers to the capacity for anaerobic metabolism of carbohydrate

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12
Q

When does fatigue occur?

A

hindering of resynthesis of ATP

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13
Q

What type has greatest resistance to fatigue? lowest?

A

Type 1
Type IIx

IIa are moderately fatigable

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14
Q

What is the Capillary to fiber ratio?

A

number of capillaries surrounding a muscle fiber

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15
Q

What do capillaries do for muscle fiber? why capillaries and not arteries?

A
  • supply muscle with oxygen and nutrients

- more diffusion can occur when blood remains for longer periods

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16
Q

Transit time?

A

amount of time the blood remains in the capillary

17
Q

What happens when you increase capillary to fiber ratio?

A
  • reduce velocity of blood flow
  • increase transit time
  • decrease distance nutrients and oxygen have to travel
  • increases slow twitch fibers oxidative capacity
18
Q

Mitochondrial density? FT vs ST?

A
  • fibers have many mitochondria
  • more oxidative capacity
  • slow twitch fibers have more than fast twitch
19
Q

What is Myoglobin?

A
  • equivalent of hemoglobin in the blood, but in muscle fibers
  • binds with oxygen in fibers and carries it to mitochondria
20
Q

Why are slow twitch fibers more red in color?

A

Myoglobin is red, slow twitch have a high content of it

21
Q

What is peak tension?

A

contractile force of a single twitch of an isolated fiber or motor unit

22
Q

The amount of force a fiber can produce during contraction is directly related to _____ of the fiber.

A

size (CSA)

23
Q

FT fibers are generally ______ than ST fibers. Result?

A

larger, they have more myofibrils in parallel and produce more force

24
Q

What is a better way to compare fibers other than peak tension? why?

A

peak specific tension b/c it is relative to fiber size

25
Q

Peak specific tension?

A

amount of force produced per unit of CSA (Po/CSA)

26
Q

When normalized with peak specific tension, why do FT fibers still produce more force?

A

more densely packed myofibrils

27
Q

What happens when the sarcomere is longer or shorter than normal?

A
  • force of production is reduced
  • shortened- actin/myosin overlap too much
  • lengthened- fewer myosin heads can attach the actin
28
Q

What is the optimal length of a muscle fiber?

A

sarcomeres are 100-120% of normal resting length

-optimal overlap of actin and myosin, maximizing number of myosin heads that can attach

29
Q

What is shortening velocity?

A

speed at which a single unloaded fiber can shorten, it is directly related to activity of Myosin ATPase (Fiber Lengths per second, FL/s)

30
Q

Higher shortening velocities are expected in what fibers?

A

longer fibers that have more sarcomeres in series (IIx)

31
Q

Maximal shortening velocity (Vmax) occurs when ______.

A

muscle is unloaded

32
Q

At maximal loading, shortening velocity is _____.

A

zero (isometric)

33
Q

At any give peak tension, type I fibers contract _____ than type II and produce _____ force.

A

slower

less

34
Q

Time to peak tension?

A

faster shortening velocity = faster time to peak tension

Type IIx

35
Q

How is contractile power calculated?

A

Force * Velocity (IIx has most power, I has least)

36
Q

What is twitch duration?

A

sum of its contraction phase and relaxation phase

37
Q

What largely determines twitch duration?

A
  • how fast the sarco reticulum can re-uptake calcium from sarcoplasm
  • faster=shorter twitch duration
  • FT= shorter duration

EXSC 463 Exam 1 (12 decks)

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