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Muscle Physiology Flashcards

1
Q

Types of Muscle

A

skeletal, smooth, and cardiac
Skeletal- movement
Smooth- autonomic functions
Cardiac- pumping blood

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2
Q

Flexion

A

decrease angle of a joint

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3
Q

Extension

A

increase angle of a joint

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4
Q

Size of muscle cells

A

several inches.

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5
Q

Another name for muscle cells

A

muscle fibers

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6
Q

Contents of muscle fibers

A

multiple nuclei and mitochondria

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7
Q

Sarcolemma

A

outer membrane of the muscle fiber. Equivalent to the plasma membrane of a regular cell

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8
Q

Sarcomere

A

contractile units that make up the myofibrils. Have discs at each end called Z disks

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9
Q

Troponin

A

protein that binds tropomyosin and actin. Has an affinity for calcium ions

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10
Q

Actin

A

thin protein filaments that attach to the z discs and extend toward the center. Intertwines with tropomyosin. Troponin bound intermittently

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11
Q

Myosin

A

thick filaments suspended among the actin. Resembles a golf club with globular heads that can bind ATP and actin

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12
Q

Sarcoplasmic Reticulum

A

surrounds the myofibrils in a reticulated network. Stores calcium during contraction

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13
Q

T tubules

A

invaginations of the sarcolemma that transverse the network of myofibrils similar to poking straws into a bowl of spaghetti noodles. Filled with extracellular fluid and aid with action potential depolarization

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14
Q

Sarcomere Organization

A
  1. Z-line
  2. I-band
  3. A-band
  4. H-zone
  5. M-line
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15
Q

Z line

A

forms periphery of sarcomere where thin actin filaments attach.

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16
Q

I band

A

light area, only actin

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17
Q

A band

A

dark area with actin and myosin overlapping

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18
Q

H zone

A

center light zone, only myosin

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19
Q

M line

A

middle of the myosin

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20
Q

Action Potential

A
  1. acetylcholine is released at the NMJ
  2. activates nicotinic acetylcholine receptors on sarcolemma
  3. Voltage gated Na ion channels open
  4. action potential spreads
  5. calcium released from sarcoplasmic reticulum
  6. contraction initiated
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21
Q

Other name for milk fever

A

parturient paresis

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22
Q

Milk Fever

A

state of semi-paralysis seen in dairy cows after calving. Fewer calcium ions are available at the NMJ and less acetylcholine is released from the axon end. Less acetylcholine means less depolarization of the sarcolemma

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23
Q

Excitation-Contraction Coupling

A
  1. increased calcium in sarcoplasm
  2. additional calcium binds troponin
  3. tropomysin moves deeper in groove- exposes myosin binding site on actin
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24
Q

Rigor Mortis

A

shortening of muscle fibers without an action potential. Actin and myosin remain contracted because there is not enough ATP to release the myosin head

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25
Q

Puerperal Tetany

A

hypocalcemia following whelping. Dogs differ from cows at the NMJ in that calcium deficiency causes voltage-gated Ca and Na to become more permeable to sodium. The influx of sodium make the membrane less polarized (less negative) and this means less stimulus is needed for depolarization. The nerve fibers become more excitable and discharge repetitively. This results in tetanic muscle contractions.

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26
Q

Skeletal Muscle Fiber Types

A
  1. Type I slow twitch
  2. Type II fast twitch
  3. intermediate fibers with characteristics of I and II
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27
Q

Type I Muscle Fibers

A

slow twitch. Darker color due to myoglobin. Rich blood supply. More mitochondria. More aerobic

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28
Q

Type II Muscle Fibers

A

Fast twitch. Larger fibers with expansive sarcoplasmic reticulum. Fewer mitochondria, less extensive blood supply, fatigue quickly.

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29
Q

Type IIA Muscle Fibers

A

intermediate between fast and slow twitch

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30
Q

Type IIB Muscle FIbers

A

traditional fast twitch fibers

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31
Q

Muscle Fibers in Dogs

A

Endurance athletes have more Type I muscle fibers, so a high capacity for aerobic metabolism. Dogs use fatty acids and glucose for fuel.

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32
Q

Motor Unit

A

one alpha motor neuron and all the striated muscle fibers it innervates. The muscle fibers are the same type and will contract at the same time.

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33
Q

How to increase contraction?

A

Spatial summation and temporal summation

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34
Q

Spatial Summation

A

increase the number of motor units firing at the same time

35
Q

Temporal Summation

A

increase the frequency of motor unit activation

36
Q

Myocardial Cells

A

striated involuntary muscle cells. Have a single nucleus per cell and are connected to each other by junctions called intercalated discs

37
Q

How many nuclei does a skeletal muscle cell have?

38
Q

Where are the nuclei in a skeletal muscle cell

A

at periphery

39
Q

Characteristics of skeletal muscle cell

A

long and tubular. T tubules, sarcoplasmic reticulum. Voluntary control

40
Q

How many nuclei are in a cardiac muscle cell?

41
Q

Where are the nuclei in cardiac muscle cells?

42
Q

Characteristics of cardiac muscle cell

A

branching networks, T tubules. Less abundant sarcoplasmic reticulum. autonomic control. Intercalated discs

43
Q

Smooth Muscle Cells Size

A

smaller and shorter than skeletal muscle cells

44
Q

Smooth Muscle Cells

A

no visible striations, no T tubules, less developed sarcoplasmic reticulum. Can receive input from more than one neuron, autonomic

45
Q

Types of Smooth Muscle Cell

A

multiunit, single-unit

46
Q

Multiunit Smooth Muscle Cell

A

contract independently. Each fiber innervated separately. Allows for fine movement. Found in the iris

47
Q

Single-Unit Smooth Muscle Cell

A

communicate and contract in a coordinated manner. Important for intestinal, uterine, and urethral contractions

48
Q

Smooth Muscle Stimuli

A

mechanical pressure, blood pH, oxygen status, and extracellular ion concentration

49
Q

Variscocities

A

found along the nerve fiber of smooth muscle. Releases acetylcholine (parasympathetic) or norepinephrine (sympathetic) diffusely along a muscle fiber sheet

50
Q

Smooth Muscle Contraction

A
  1. Intracellular concentrations of calcium increase when calcium enters the cell and is released from the sarcoplasmic reticulum
  2. Calcium binds to calmodulin
  3. Activates myosin light chain kinase
  4. MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity
51
Q

What shape are smooth muscle cells

A

spindle-shaped with single nuclei packed closely

52
Q

Which muscles have striations?

A

skeletal and cardiac

53
Q

Which muscle does not have striations?

A

smooth muscle

54
Q

Where are the nuclei in smooth muscle cells?

A

in the center of the cell

55
Q

Description of T tubules in skeletal muscle

A

part of triads at A-I junction

56
Q

Description of T tubules in cardiac muscle

A

part of dyads at Z disc

57
Q

Skeletal muscle sarcoplasmic reticulum

A

abundant with two terminal cisterns in the triads

58
Q

Cardiac muscle sarcoplasmic reticulum

A

less abundant with one terminal cistern per sarcomere in dyads

59
Q

Smooth muscle sarcoplasmic reticulum

A

no distinctive organization

60
Q

Distinctive structural feature of skeletal muscle

A

highly organized sarcomeres and triads

61
Q

Distinctive structural feature of cardiac muscle

A

intercalated discs with adhesion and gap junctions

62
Q

Distinctive structural feature of smooth muscle

A

gap junctions, caveolae, and dense bodies

63
Q

Contraction Mechanism of Skeletal Muscle

A

Ca binding to troponin C exposes myosin binding site on actin

64
Q

Contraction Mechanism of Cardiac Muscle

A

similar to skeletal muscle

65
Q

Contraction Mechanism of Smooth Muscle

A

Ca binds calmodulin, triggers MLCK mediated phosphorylation of myosin and actin binding

66
Q

Skeletal Muscle Connective Tissue

A

endomysium, perimysium, and epimysium

67
Q

Cardiac Muscle Connective Tissue

A

endomysium, subendocardial, and subpericardial

68
Q

Smooth Muscle Connective Tissue

A

endomysium and less organized CT sheaths

69
Q

Locations of Skeletal Muscle

A

muscle, tongue, upper esophagus, eyes

70
Q

Locations of Cardiac Muscle

71
Q

Locations of Smooth Muscle

A

blood vessels and walls of most organs

72
Q

Innervation of Skeletal Muscle

A

motor for voluntary movement

73
Q

Innervation of Cardiac Muscle

A

autonomic for involuntary pumping of blood

74
Q

Innervation of Smooth Muscle

A

autonomic for involuntary movement

75
Q

Growth of Skeletal Muscle

A

hypertrophy, limited renewal involving satellite cells

76
Q

Growth of Cardiac Muscle

A

hypertrophy, little/no renewal

77
Q

Growth of Smooth Muscle

A

hypertrophy and hyperplasia/mitosis

78
Q

What makes up muscle fibers?

A

myofibrils

79
Q

What are cardiac muscle cells called?

A

myocytes. Shorter and connected through intercalated discs

80
Q

What anchors actin thin filaments in smooth muscle?

A

dense bodies

81
Q

What are the sarcoplasmic invaginations of smooth muscle?

82
Q

What regulates actin/myosin binding in smooth muscle contraction?

A

calmodulin

83
Q

Electromyogram

A

measure the strength of muscle contraction. Used to determine if paresis or paralysis is from issues with the CNS, NMJ, motor neuron, or skeletal muscle

84
Q

Cross-bridging

A

when myosin is bound to actin

Physiology (16 decks)

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