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Physiology > Physiology Exam 3 - Muscular System > Flashcards

Physiology Exam 3 - Muscular System Flashcards

1
Q

What are the three types of muscle?

A

skeletal, smooth, cardiac

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2
Q

Structure of skeletal muscle

A
  • striated, tubular, and multinucleated
  • multiple mitochondria
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3
Q

Where skeletal muscle is found

A

attached to bones (tendon)

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4
Q

Structure of smooth muscle

A

non-striated, spindle-shaped, and mononucleated

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5
Q

Where smooth muscle is found

A

covering walls of internal organs

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6
Q

Structure of cardiac muscle

A

striated, branched, and bi- or mononucleated

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7
Q

Where cardiac muscle is found

A

covering walls of the heart

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8
Q

Striation

A

occurs due to light and dark bands originating from difference in myofilaments

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9
Q

What makes up a muscle fiber?

A

sarcolemma, sarcoplasm, and myofibrils

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10
Q

Sarcolemma

A

plasma membrane

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11
Q

Sarcoplasm

A

cytoplasm (almost entirely made up of myofibrils)

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12
Q

Myofibrils

A

contractile structure of cell

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13
Q

Transverse (T-) tubule

A

invaginations of sarcolemma into sarcoplasm (surround myofibrils)

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14
Q

Action potentials go through the sarcolemma and travel into the muscle fiber via…

A

T-tubules

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15
Q

Sarcoplasmic reticulum

A

internal membrane complex (smooth ER)

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16
Q

Terminal cisternae

A

sacs at the end of sarcoplasmic reticulum adjacent to T-tubules

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17
Q

Triad

A

T-tubule between two terminal cisternae

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18
Q

What does the sarcoplasmic reticulum do?

A

Stores calcium (Ca2+ binding protein calsequestrin in the terminal cisternae allows for storage of a large quantity of Ca2+)

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19
Q

What results in the contraction of a cell?

A

shortening of myofibrils

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20
Q

What are myofilaments?

A

strands of protein used for contraction

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21
Q

What is the thick filament?

A

myosin

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22
Q

What is the thin filament?

A

actin

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23
Q

Actin

A

globular protein that has a binding site for myosin

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24
Q

Nebulin

A

might play a role in thin filament assembly (actin wraps around it)

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25
Q

Troponin

A

Ca2+ binding site and changes conformity of tropomyosin

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26
Q

Tropomyosin

A

covers the binding region of actin

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27
Q

Myosin

A

two large polypeptide heavy chains

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28
Q

Globular heads

A

at the end of myosin, form cross-bridges to make contact with actin

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29
Q

What does each globular head contain?

A

two light chains and two binding sites for actin and ATP

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30
Q

What does the ATP binding site on myosin function as?

A

an enzyme - myosin-ATPase

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31
Q

Sarcomere

A

structural and functional unit within a myofibril

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32
Q

What does a sarcomere contain?

A

overlapping thin and thick filaments

33
Q

Where does a sarcomere span?

A

from one Z disc to the next

34
Q

Z disc

A

protein that anchors thin filaments

35
Q

What does contraction mean?

A

activation of cross-bridges, force-generating sites within a muscle fiber (Z discs come in)

36
Q

What does relaxation mean?

A

mechanisms generating force are turned off and tension declines (Z discs expand)

37
Q

M line

A

middle of sarcomere

38
Q

H zone

A

thick filaments only

39
Q

I band

A

thin filaments only

40
Q

A band

A

thick and thin filaments

41
Q

Motor unit

A

A motor neuron and all of the muscle fibers it innervates

42
Q

How are action potentials initiated in skeletal muscle?

A

neurons are stimulated to a skeletal muscle

43
Q

Alpha motor neurons

A

neurons whose axons innervate skeletal muscle fibers (cell bodies in brainstem and spinal cord)

44
Q

What are the three subunits of troponin?

A

Troponin I (inhibitory)

Troponin T (tropomyosin binding)

Troponin C (Ca2+ binding)

45
Q

What happens when Ca2+ binds to troponin?

A

its shape changes, it relaxes its inhibitory grip and allows tropomyosin to expose the myosin-binding stie on actin and starts contraction

46
Q

What happens when Ca2+ is removed from troponin?

A

tropomyosin moves back into place to block the cross bridge binding sites, contraction stops

47
Q

What happens when a muscle fiber shortens?

A

the overlapping thick and thin filaments move past each other in each sarcomere propelled by movements of cross-bridges

48
Q

What happens to the lengths of filaments during shortening of sarcomeres?

A

they do not change in length, they change their amount of overlap

49
Q

What is the mechanism for muscle contraction called?

A

sliding-filament mechanism

50
Q

Structure of a neuromuscular junction

A

motor neuron axon (myelinated), axon terminal (synaptic vesicles and active zone), synaptic cleft (space between axon and sarcolemma), motor end plate (ACh receptors and junctional folds)

51
Q

Steps of initiation of excitation-contraction coupling at the neuromuscular junction

A
  1. The action potential arrives at the presynaptic terminal
  2. Voltage-gated Ca2+ channels open
  3. Ca2+ enters the terminal and causes vesicles to release ACh from synaptic vesicles to the synaptic cleft
  4. ACh diffuses across the synaptic cleft
  5. ACh binds to receptors on the muscle fiber membrane
  6. ACh binding increases the permeability of Na+ channels.
  7. Na+ enters the cell and depolarizes the membrane to produce an action potential
  8. The action potential propagates over the muscle cell membrane
  9. Ach is broken into acetic acid and choline by acetylcholinesterase
  10. Choline is reabsorbed into the presynaptic cell and combines with acetic acid to form ACh
  11. ACh enters synaptic vesicles
52
Q

What do action potentials cause terminal cisterns to do?

A

release Ca2+

53
Q

What happens at the end of an action potential?

A
  1. Ca2+ ATPase pumps return Ca2+ ions to the sarcoplasmic reticulum by active transport
  2. Ca2+ concentration around actin and myosin decreases
  3. thick and think filaments disengage and the muscle relaxes
54
Q

What two factors is muscle contraction based on?

A

force and length

55
Q

Muscle tension

A

the force generation by a muscle on an object (contraction)

56
Q

Muscle load

A

the force by an object on a muscle (its weight)

57
Q

What are the two types of isotonic contraction?

A

concentric and eccentric

58
Q

Isotonic contraction

A

the muscle changes length while the load on the muscle remains constant (when a muscle actively moves an object)

59
Q

Concentric contraction

A

tension exceeds the load and shortening occurs

60
Q

Eccentric contraction

A

when an unsupported load is greater than the tension generated by the sarcomeres, the load pulls the muscle to a longer length

61
Q

Isometric contraction

A

muscle develops tension but does not shorten or lengthen (when a muscle supports a load in a constant position)

62
Q

Twitch

A

single stimulus-contraction-relaxation sequence in a muscle fiber (mechanical response of one muscle fiber to one action potential)

63
Q

What happens when you increase the load?

A

it shortens the action potential and diminishes the time of the twitch

64
Q

Frequency-tension relation

A

NOTES

65
Q

Tetanus

A

a maintained contraction in response to repetitive stimulation

66
Q

Tetanus disease

A
  • caused by Clostridium Tetani
  • causes permanent contraction
  • inhibits release of inhibitory neurotransmitters
67
Q

Botulism

A
  • caused by Clostridium Botulinum
  • found in raw honey
  • causes muscles to stay relaxed and flaccid
68
Q

Summation

A

the increase in muscle tension from successive action potentials occurring during the phase of mechanical activity

69
Q

What are the three ways a muscle fiber can form ATP?

A
  • direct phosphorylation of ADP by creatine phosphate
  • aerobic respiration of ADP in mitochondria
  • anaerobic glycolysis - phosphorylation of ADP in cytosol
70
Q

Muscle fatigue

A

when a skeletal muscle fiber is repeatedly stimulated, the tension will eventually decrease even though the stimulation continues

71
Q

What are skeletal muscle fibers classified based on?

A
  • their maximal velocities of shortening (fast or slow-twitch)
  • their major pathway they use to form ATP (oxidative or glycolytic)
72
Q

What are the three types of skeletal muscle fibers?

A
  1. slow oxidative fibers - Type I
  2. fast oxidative/glycolytic - Type IIa
  3. fast glycolytic - Type IIb
73
Q

What type of muscle fiber is best for long distance running?

A

Type 1

74
Q

What type of muscle fiber is best for brisk running?

A

Type IIa

75
Q

What type of muscle fiber is best for sprints?

A

Type IIb

76
Q

What is the rate of fatigue in each skeletal muscle fiber?

A
  1. Type I = almost nonexistent
  2. Type IIa = 8 minutes
  3. Type IIb = 2-4 minutes
77
Q

Hypertrophy

A

increase in size of muscle fibers resulting from increase amounts of contractile activity (regular exercise)

78
Q

Atrophy

A

muscle fibers get smaller due to decrease in exercise

79
Q

What are the two types of atrophy?

A
  1. disuse atrophy (arm in a cast)
  2. denervation atrophy (nerve damage = loss of function)

Physiology (6 decks)

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