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Physiology > Skeletal and Smooth Muscle > Flashcards

Skeletal and Smooth Muscle Flashcards

1
Q

What are the types of muscle?

A

skeletal, smooth, cardiac

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2
Q

What is the makeup of skeletal muscle from big to small?

A

large muscle bundles> myocytes/fibers> myofibrils> sarcomeres> actin and myosin

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3
Q

What are thin filaments composed of in skeletal msucle?

A

actin helix with tropomyosin and troponin complex attached

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4
Q

What are thick filaments composed of in skeletal muscle?

A

myosin 2

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5
Q

Thin and thick filaments interact to produce what in skeletal muscle?

A

force

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6
Q

What is the organization of a sarcomere?

A

2 z lines, I band, H zone

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7
Q

What is the I band made out of?

A

thin filaments ONLY; actin

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8
Q

What is the H zone made out of?

A

thick filaments ONLY; myosin heads

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9
Q

What is the neuromuscular junction of skeletal muscle cells?

A
  1. nerve axon innervating each muscle fiber
  2. releases Ach
  3. Ach binds to the AchR on muscle cell which is permeable to Na, K, Ca
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10
Q

What receptor causes depolarization in skeletal muscle cells?

A

AchR

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11
Q

What is the process of the initiation of a muscle contraction?

A
  1. Ca release from SR
  2. Ca binds to troponin C and initiates a conformational change
  3. tropomyosin slides into the groove between the actin strands
  4. myosin can bind actin
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12
Q

What are the 5 states of cross bridge cycling?

A
  1. attached
  2. released
  3. cocked
  4. cross-bridge
  5. power-stroke
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13
Q

What occurs during the attached state?

A
  1. ATP binds to myosin head
  2. dissociation of actin-myosin complex
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14
Q

What occurs during the released state?

A
  1. ATP is hydrolyzed
  2. myosin heads return to resting conformation
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15
Q

What occurs in between the released and cocked states?

A

myosin heads relax

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16
Q

What occurs during the cocked state?

A

cross-bridge forms and myosin head binds to a new position on actin

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17
Q

What occurs during the cross-bridge state?

A
  1. phosphate is released
  2. myosin heads change conformation, resulting in power stroke
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18
Q

What occurs during the power-stroke state?

A

ADP is released

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19
Q

What happens between the power-stroke state and returning to the attached state (beginning of cycle)?

A
  1. myosin heads are arched
  2. myosin heads attach
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20
Q

Is the influx of Ca through receptors necessary for contraction?

A

NO

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21
Q

What are the steps in excitation-contraction coupling?

A
    • charge carried along the plasma membrane of transverse tubules
  2. depolarization activates L-type Ca channels in transverse tubules leading to a conformational change
  3. physical conformational change induced in ryanodine receptors that are adjacent to the L-types but in SR
  4. RyR release Ca into cytosol
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22
Q

What occurs when muscles are relaxed during the sliding filament theory?

A
  • Z bands become widen
  • I bands widen
  • A bands remain the same
  • H bands widen
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23
Q

What occurs when muscles are contracted during the sliding filament theory?

A
  • Z bands narrow
  • I bands narrow
  • A bands remain the same
  • H bands narrow
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24
Q

What is the SERCA pump in skeletal muscle relaxation?

A

Ca pump that sequesters myoplasmic Ca into the SR

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25
Q

Where does SERCA pump Ca into?

A

lumen

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26
Q

What is calsequestrin?

A

Ca binding protein near RyR

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27
Q

What is sarcalumenin?

A

transfers Ca from uptake sites to release sites

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28
Q

What is considered a shuttle protein in muscle relaxation?

A

sarcalumenin

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29
Q

What is smooth muscle composed of?

A
  • thick filament: 1/4 of the one found in skeletal muscle
  • thin filament: actin, tropomyosin, NO troponin
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30
Q

Does smooth muscle have sarcomeres and Z lines?

31
Q

What are the components of a smooth muscle contraction?

A

hormones, neural, mechanical, spontaneous electrical activity (AP)

32
Q

What type of junction aloows unitary smooth muscle cells to act together?

33
Q

How is the smooth muscle cell contraction initiated?

A

by Ca bindign to calmodulin

34
Q

What is required to phosphorylate myosin?

A

myosin light chain

35
Q

What is the process of excitation-contraction coupling for smooth muscle?

A
  1. Ca enters cytoplasm through channels located in caveoli
  2. Ca release from SR via IP3 activation of SR Ca channels

CIRCA (Ca induced -> Ca released)

36
Q

What happens during smooth muscle relaxation?

A
  1. pump Ca back into SR using CIRCA
  2. activate myosin ligth chain phosphatase
37
Q

What are the factors affecting force production in skeletal muscle?

A
  • initial length of muscle fiber
  • fiber type
  • mtoor unit recrutiment
  • speed of contraction
  • muscle fiber arrangement
38
Q

What are the type of muscle actions?

A

dynamic and static

39
Q

What are the types of dynamic actions?

A

concentric and eccentric

40
Q

What is a concentric action?

A
  • muscle develops tension and shortens
  • muscle force > extrenal force

example: lifting a weight

41
Q

What is an eccentric action?

A
  • muscle develops tension and lenghtens
  • muscle force < external force

examples: braking force = hiking downhill; putting weight down

42
Q

What is a type of static action?

43
Q

What happens during an isometric action?

A
  • muscle develops tension with NO change in length
  • muscle force = external force

example: doing a planck

44
Q

How can a muscle generate force without shortening?

A

with the use of contractile elements and connective/elastic components

45
Q

How do isometric and eccentric actions help the muscle generate force without shortening?

A
  • elastic components are stretched; contributes passively to total muscle force
  • sarcomeres ratchet and pull toward their center which actively generates force
46
Q

What is titin?

A

elastic protein that runs from Z lines to M line of sarcomere

47
Q

What is the largest protein and 3rd most abundant protein in muscle?

48
Q

How is titin responsible for producing the passive force in muscle?

A

acts as a molecular spring

49
Q

What are the metabolic properties of fasta nd slow twitch fibers?

A
  1. primary energy pathways utilized to make ATP (oxidative, glycoytic)
  2. determined by differences in mitochondria, capillary density, myoglobin conc., enzymatic activity
50
Q

What are the contractile properties of fast and slow twitch fibers?

A
  1. speed of contraction
  2. maximal force production
  3. fatigue resistance
51
Q

What happens in the speed of contraction for fast and slow twicth fibers?

A
  • myosin ATPase activity: faster in type 2 isozyme
  • Ca cycling
52
Q

What is the maximal force production for fast and slow twicth fibers?

A
  • # of cross bridges formed/cross sectional area
  • fiber diameter
  • rate of cross bridge formation
53
Q

What does the fatigue resistance for fast and slow twicth fibers depend on?

A

energy pathways utilized

54
Q

What is the difference in faitgue for slow and fast twitch fibers?

A
  • slow type 1: resistant
  • fast type 2a: resistant
  • fast type 2b: fatigable
55
Q

What is the difference in color for slow and fast twitch fibers?

A
  • slow type 1: red (myoglobin)
  • fast type 2a: red (myoglobin)
  • fast type 2b: white (low myoglobin)
56
Q

What is the difference in metabolism for slow and fast twitch fibers?

A
  • slow type 1: oxidative
  • fast type 2a: oxidative
  • fast type 2b: glycolytic
57
Q

What is the difference in mitchondria for slow and fast twitch fibers?

A
  • slow type 1: high
  • fast type 2a: higher
  • fast type 2b: fewer
58
Q

What is the difference in glycogen for slow and fast twitch fibers?

A
  • slow type 1: low
  • fast type 2a: abundant
  • fast type 2b: high
59
Q

Whatis the name when ALL muscle fibers are innervated by a single motor neuron?

A

the motor unit

60
Q

What is the difference bewteen temporal and spatial summation?

A
  • temporal: increased frequency of stimulation of motor units
  • spatial: increased # of motor units that are recruited
61
Q

What is summation?

A

how muscle increases force

62
Q

What is recruitment?

A

NOT ALL muscle fibers are participating all the time, some are inactive

63
Q

What exactly happens during temporal summation?

A

singl AP releases Ca for short duration to cause a twitch and can summated

64
Q

Stimulating a muscle with an AP before it has had time to relax leads to what?

A
  • increased Ca duration
  • new contraction occurs before preceding one is over
  • force progressivle increases
  • fusion of the twitch contractions
  • sustained contraction
  • force is amplified
65
Q

What exactly occurs in spatial summation?

A

all muscle fibers in a motor unit are activated simultaneously

66
Q

What is creatine phosphate ?

A

ATP buffer system that keeps ATP constant

67
Q

How is glycogen a muscle energy source during exercise?

A

plays part in glycolysis (3ATP + lactic acid) and aerobic oxidation (37 ATP)

68
Q

Plasma fatty acid, adipose create what as a muscle energy source?

A

oxidative phosphorylation

69
Q

What are the muscle energy sources during exercise?

A
  • ATP
  • creatine phosphate
  • glycogen
  • plasma glucose + glycogen
  • plasma fatty acid, adipose
70
Q

What is the difference between tonic and phasic muscles?

A
  • tonic: continuously active to maintain a level of tone
  • phasic: rhythmic or intermittent contractions
71
Q

What is an exmple of a tonic muscle?

A

blood vessels, respiratory tract, sphincters

72
Q

What is an example of a phasic muscle?

A

GI tract, urogenital, lymphatic

73
Q

What is the unit for tonic muscles?

A

multiunit: tone associated with action potentials

74
Q

What is the unit for a phasic muscle?

A

single unit: AP propagates from cell-to-cell

Physiology (9 decks)

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