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From Flashcardlet > Smooth Muscle > Flashcards

Smooth Muscle Flashcards

1
Q

What are three influences that effect the velocity and duration of contraction (time before muscle fatigues)?

A
  1. Muscle fiber type
  2. Load
  3. Recruitment
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2
Q

What are the two types of ATP forming pathways?

A

Oxidative (aerobic)

Glycolytic (anaerobic)

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3
Q

What influences the speed of contraction (2)?

A

How fast myosin ATPases split ATP and how quickly Ca+2 moves to the SR

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4
Q

What are the three types of skeletal fibers?

A
  1. Slow oxidative fibers
  2. Fast oxidative-glycolytic fibers
  3. Fast glycolytic fibers
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5
Q

What types of muscles have slow/fast oxidative/glycolytic fibers?

A

All muscles usually have all three allowing a range of contraction speeds and durations

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6
Q

How can the types of skeletal fibers be modified?

A

Through genetics or exercise

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7
Q

What three characteristics do red muscle fibers have?

A
  1. High myoglobin content
  2. More mitochondria
  3. Larger capillary supply
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8
Q

What three characteristics do white muscle fibers have?

A
  1. Low myoglobin content
  2. Less mitochondria
  3. Smaller capillary supply
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9
Q

Which kinds of muscle fibers are slow/fast twitch?

A

Slow - Type I

Fast - Type II

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10
Q

Do slow oxidative fibers have type I or II fibers?

A

Type I - slow twitch

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11
Q

Describe slow oxidative fibers (size, power, red/white)

A
  1. Smallest in diameter
  2. Least powerful
  3. Red muscle fibers
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12
Q

Does the slow oxidative fibers’ ATPase hydrolyze ATP slow or fast?

A

Slow, resulting in slow speed of contractions

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13
Q

What are slow oxidative fibers best suited for and why?

A

Postural muscles and aerobic endurance exercises because they are very resistant to fatigue and capable of prolonged sustained contractions

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14
Q

Describe fast oxidative-glycolytic fibers (size, power, red/white)

A
  1. Intermediate in size
  2. Intermediate in power
  3. Red muscle fibers
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15
Q

Are fast oxidative-glycolytic fibers slow or fast twitch?

A

Fast twitch

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16
Q

What are fast oxidative-glycolytic fibers best suited for and why?

A

Walking and sprinting because they reach peak tension more quickly than slow ox but are briefer in duration

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17
Q

How is ATP generated in fast oxidative-glycolytic fibers?

A

Aerobic and anaerobic respiration

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18
Q

Are fast glycolytic fibers slow or fast twitch?

A

Fast twitch - type II

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19
Q

Describe fast glycolytic fibers (size, power, red/white)

A
  1. Largest in diameter
  2. Most powerful
  3. White muscle fibers
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20
Q

How is ATP generated in fast glycolytic fibers?

A

Glycolysis with large amounts of glycogen

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21
Q

What are fast glycolytic fibers best suited for and why?

A

Weight lifting and throwing ball because they contract strongly and quickly, best suited for intense anaerobic movement of short duration

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22
Q

Which fibers fatigue very quickly?

A

Fast glycolytic fibers

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23
Q

What muscles would you find mostly slow oxidative fibers?

A

Postural muscles of the back, neck, and legs

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24
Q

What muscles would you find mostly fast glycolytic fibers?

A

Shoulders and arms

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25
Q

What is the sequence of recruitment of fibers?

A

First slow oxidative, then fast oxidative glycolytic, then glycolytic

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26
Q

What happens to the muscle and duration of contraction as the size of the load increases?

A

The less the muscle shortens and the shorter the duration of the contraction

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27
Q

What happens to the velocity of the contraction when the size of the load increases?

A

The slower the contraction

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28
Q

Is contraction velocity slower or faster for smooth muscle?

A

Contraction velocity is slower in smooth muscle because myosin has a lower rate of ATPase activity

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29
Q

How fast does smooth muscle fatigue?

A

Smooth muscle does not undergo fatigue during muscle contraction due to the low energy usage

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30
Q

What are the steps of EC coupling in smooth muscle?

A
  1. Ca enters the cytosol from the ECF or the SR via voltage gated channels
  2. Ca binds and activates cadmodulin
  3. Cadmodulin activates the myosin light chain kinase enzymes
  4. Activated kinases catalyze the transfer of phosphate to myosin, activating myosin ATPase
  5. Myosin can now form cross bridges with actin and shortening begins
31
Q

What is the regulatory protein in smooth muscle? What binds to it?

A

Cadmodulin, Ca binds to it instead of troponin in smooth muscle

32
Q

What molecules do cadmodulin interact with?

A

Myosin light chain kinases

33
Q

What does the myosin light chain kinase do?

A

It phophorylates myosin

34
Q

Does the kinase work slow or fast?

A

Slowly, producing slow contractions

35
Q

Where is smooth muscle found?

A

The walls f all body’s hollow organs

36
Q

Is smooth muscle striated?

A

No

37
Q

What is smooth muscle lacking that skeletal has?

A

Sarcomeres

38
Q

Is smooth muscle in/voluntary?

A

Involuntary

39
Q

What CT sheaths does smooth muscle have/lack?

A

Has endomysium but is lacking the coarse CT sheaths

40
Q

Can smooth muscle divide?

A

Yes can divide throughout life

41
Q

How is smooth muscle arranged?

A

In sheets oriented at right angles

42
Q

What are the two smooth muscle sheets?

A
  1. Longitudinal layer

2. Circular layer

43
Q

What is the longitudinal layer?

A

Parallel to long axis of organs, when the muscle contracts, the organ dilates and shortens

44
Q

What is the circular layer?

A

Fibers run around the circumference of the organ, contraction constricts lumen and elongates the organ

45
Q

What do alternating contractions of the longitudinal and circular layers result in?

A

Peristalsis

46
Q

What does smooth muscle have instead of a complex NMJ?

A

Innervating nerve have varicosities - bulbous swellings that release NT into the synaptic cleft

47
Q

What is different about smooth muscle’s SR system?

A

No T tubules

48
Q

What structure is located on the sarcolemma of smooth muscle cells?

A

Caveolae - infolding of the sarcolemma that takes in ECF rich in Ca and holds the fluid until Ca channels open

49
Q

Where does smooth muscle’s Ca come from?

A

The ECF, not usually the SR

50
Q

When does contraction end in smooth muscle?

A

When Ca is moved to the SR (like skeletal)

51
Q

What are the two types of smooth muscle?

A
  1. Visceral (single unit)

2. Multiunit

52
Q

Which muscles have single/multiunit smooth muscle?

A

Most muscles have characteristics of both

53
Q

Where is single unit smooth muscle found?

A

Walls of all hollow organs, skin, tubular structures

54
Q

What structures are abundant in single unit smooth muscle?

A

Gap junctions

55
Q

How do single unit muscle fibers contract?

A

As a single unit

56
Q

How are single unit muscle fibers arranged?

A

In opposing sheets

57
Q

What are single unit muscle fibers induced by?

A

Stretch

58
Q

Where is multiunit muscle found?

A
  1. Large unit airway
  2. Arteries
  3. Eyes for focus
  4. Internal eye for pupils
  5. Arrector pili
59
Q

How do multiunit muscle fibers interact together?

A

They are structurally independent of one another, each with its own motor neuron. Stimulation of the fiber results in contraction of that fiber only

60
Q

What influences the activity of multiunit muscle fibers?

A

Hormones can increase or decrease activity (not activated by stretch)

61
Q

Does smooth muscle have more/less thick/thin filaments than skeletal muscle?

A

Has less thick filaments, and more thin filaments (ratio of 1:15 thick to thin)

62
Q

If smooth muscle has less myosin, does the maximum tension per unit change?

A

No, can still generate the same amount of tension as skeletal muscle

63
Q

How do actin, myosin, troponin, and tropomyosin function in smooth muscle?

A

Actin and myosin still react in a sliding manner
No troponin
Tropomyosin is NOT in a blocking position

64
Q

What are thin filaments anchored to in smooth muscle?

A

Dense bodies

65
Q

What is the SR like in smooth muscle?

A

Small

66
Q

Where are dense bodies located?

A

Some in sarcoplasm, some attached to sarcolemma

67
Q

What are dense bodies homologous to?

A

Z disc

68
Q

The optimal length for smooth muscle is shorter/wider than skeletal muscle. Why?

A

Wider, useful for distendable organs like bladder

69
Q

Does contraction starts slower or faster in smooth muscle? Does it last shorter or longer? Why?

A

Starts slower and lasts longer because it takes longer for Ca to reach the filaments without T tubules

70
Q

Smooth muscle can shorten and extend less/more than skeletal?

A

Can shorten and extend further

71
Q

What is the stress relaxation response for smooth muscle?

A

Smooth muscle can stretch considerably and still retain contractile function

72
Q

What happens to the smooth muscles in an organ when the organ empties?

A

The smooth muscle rebounds and the wall retains firmness

73
Q

What is depolarization of smooth muscle due to?

A

The entry of Ca (not Na!)

From Flashcardlet (133 decks)

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