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Muscle physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

The human body has 3 types of muscle tissue

A

skeletal muscle
cardiac muscle
smooth muscle

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2
Q

Elongated cells
•Multiple peripheral nuclei
•Visible striations
•Voluntary

A

skeletal muscle

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3
Q
  • Branching cells
  • Single central nucleus
  • Visible striations
  • Involuntary
A

Cardiac muscle

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4
Q
  • Spindle shaped cells
  • Single central nucleus
  • No visible striations
  • Involuntary
A

Smooth muscle

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5
Q

bundles of muscle cells

A

Fascicles

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6
Q

individual cells

A

muscle fibers

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7
Q

arrangement of myofilaments consisting of thick and thin filaments

A

Myofibrils

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8
Q

two types of myofilament

A

myosin and actin

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9
Q

Muscle fibers

A

muscle cells

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10
Q

Sarcolemma

A

cell membrane; also called T-tubule

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11
Q

Sarcoplasm

A

cytoplasm

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12
Q

Sarcosomes

A

mitochondria

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13
Q

Sarcoplasmic reticulum

A

smooth endoplasmic reticulum

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14
Q

consists of longitudinal tubules, which release Ca 2+ and terminal cistern, enlarged regions at the end
of the tubules that concentrate and sequester Ca 2+.

A

Sarcoplasmic reticulum

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15
Q

pass down into the muscle cell and go around the myofibrils, conduct impulses from the surface of the cell (sarcolemma) to SR.

A

Transverse tubules (T tubules)

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16
Q

One T tubule and its two flanking cisternae are called

A

a triad

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17
Q

Thin filaments are mainly composed of ______. Thick filaments are mainly composed from _____

A

actin

myosin

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18
Q

______ ______ from crossbridges between thick and thin filaments. Each cross-bridge has two sites crucial for muscle contraction: _____ binding site and _____ binding site.

A

Myosin heads
ATP
actin

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19
Q

the arrangement of thick and thin filaments forms light and dark alternating bands called ______ along the myofibril.

A

striations

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20
Q

A bands are ______

I bands are ______

A

dark

light

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21
Q

functional unit of skeletal muscle (Z line to Z line)

A

Sarcomere

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22
Q

the proper alignment of filaments within a sacromere is ensured by two proteins:

A

titin (the largest known protein) and nebulin.

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23
Q

force created by contracting muscle

A

Muscle tension

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24
Q

weight that opposes contraction

A

Load

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25
Q

creation of tension in muscle, active process requires energy input from ATP.

A

contraction

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26
Q

release of tension

A

relaxation

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27
Q

summary of muscle contraction

A 
events at NMJ
excitation-contraction coupling
Ca signal
contraction-relaxation
muscle twitch or sliding filament theory
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28
Q

During muscle contraction, each sarcomere _____ as the thin filaments _____ ______ between the thick filaments so that Z lines are pulled closer together.

A

shortens

slide inward

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29
Q

how does calcium signals initiate contraction

A 
Ca level increase in cytosol
Ca binds to troponin
troponin-tropomyosin complex separate
myosin binding site exposed
power stroke
actin filaments move
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30
Q

what is the molecular basis of contraction

A
  • atp bind to myosin (affinity for actin decrease)
  • myosin hydrolysis atp, rotates head & binds to new actin
  • Ca signal/power stroke
  • myosin releases ADP
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31
Q

troponin contains 3 subunits which bind to

A

Ca
actin
tropomyosin

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32
Q

molecules that help align actin

A

nebulin

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33
Q

provides elasticity and stabilizes myosin

A

Titin

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34
Q

actin molecules bind to form _______

A

helix

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35
Q

state where there’s a lack of ATP; ATP has been exhausted

A

rigor mortis state

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36
Q

The Action Potential (AP) of a skeletal muscle fiber begins at the_________, where the terminal of a motor neuron contacts and forms a synapse with the muscle fiber.

A

Neuromuscular Junction (NMJ)

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37
Q

what are the steps that occur after action potential is reach which leads to the release of calcium in the cytosol

A
  • AP causes release of Ach into synaptic cleft
  • Ach binds to nicotenic receptors
  • receptor activation causes opening of channels (Na, K influx/efflux)
  • threshold is reached
  • AP is then propagated along muscle fiber and -enters t-tubule (invagination)
  • allows for electrical transmission inside cell and SR
  • DHP receptor changes confirmation when AP reached
  • causes ryanodine to open releasing Ca to cytosol
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38
Q

how is contraction terminated

A

SR pumps Ca back to lumen via Ca ATPase decreasing cytosolic Ca
this causes troponin to release Ca and tropomyosin block binding site
contraction ends and muscle fibers relax

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39
Q

single contraction-relaxation cycle in a skeletal muscle fiber

A

Muscle twitch

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40
Q

toxic effects of batrachotoxin (BTX)

A

caused by sustained, irreversible opening of voltage-gated sodium channels of nerve and muscle.

41
Q

non-depolarizing blocker

A 
acts as competitive antagonist to nicotinic receptors occupying site of Ach.
Prevents depolarization (channels don't open)
42
Q

depolarization

A

acts on the nicotinic receptor inducing irreversible opening of the channels.
Depolarizes membrane to where muscle fibers become non-responsive to stimulation

43
Q

antibodies affect neurotransmission in 3 ways

A
  • complement
  • antigenic modulation (cross linking of receptors increase nicotinic receptor degradation, decreasing # of receptors)
  • Ach receptor blocker
44
Q

what are the two phases of the depolarizing blocker

A

phase 1: depolarizing phase (twitches)

phase 2: desensitizing phase (full neuromuscular block)

45
Q

succinylcholine

A

depolarizing blocker; relax skeletal muscles during surgery. It does not relieve pain or produce sedation.

46
Q

interferes with muscle contraction by binding the RyR1 receptor channel and inhibiting Ca2+ release from SR.

A

Dantrolene

47
Q

Used to treat muscle spasm, associated with spinal cord injuries, stroke, multiple sclerosis or cerebral palsy

A

Dantrolene

48
Q

dantrolene contains a special application in treatment of _______ ______

A

malignant hyperthermia

49
Q

a neurologic syndrome caused by a toxic proteolytic enzyme produced by the bacterium Clostridium botulinum - spore-forming, obligate anaerobe found most commonly in soil.

A

Botulism

50
Q

can result from ingestion of contaminated

food, colonization of the gastrointestinal tract in an infant, or wound infection

A

Botulism

51
Q

major steps in botulinum toxin action

A
  • enters lumen of digestive tract
  • absored and enters blood stream
  • reaches target cell at motor neuron terminal
  • gets internalized
  • light chain/heavy chain dissociate
  • light chain acts as protease and degrades snare complex
  • Ach release inhibited
52
Q

important for synaptotagmin exocytosis; cannot occur when degraded by light chains of botulin toxin (neurotransmission inhibited)

A

snare complex

53
Q

blocking acetylcholine release at the NMJ, botulinum toxins cause ______ ______. The mortality of botulism is usually secondary to paralysis of the respiratory muscles.

A

flaccid paralysis

54
Q

small doses of this drug is effective in the treatment of conditions characterized by muscle hyperactivity: cervical dystonia, blepharospasm, strabismus, urinary incontinence. Also used to prevent headaches in adults with chronic migraine, treat the symptoms of severe underarm sweating and reduce the facial wrinkles.

A

botulinum toxin A (Botox)

55
Q

tetrootoxin
batrachotoxin
local anesthetics
these inhibit:

A

Action potential

56
Q

botulinus toxin inhibits

A

ACH release

57
Q

curare alkaloids inhibit

A

depolarization (permeability of Na, K)

58
Q

succinylcholine inhibits

A

depolarization (permeability of Na, K)

59
Q

tetrodoxin also inhibits

A

muscle ation potential

60
Q

dantrolene inhitbits

A

muscle contraction

61
Q

extraocular muscle weakness (ptosis or diplopia) and later develop limb and bulbar muscle weakness. Worsening of weakness after prolonged and sustained muscle contraction (fatigability).
Reduces efficiency of neuromuscular transmission

A

Myasthenia gravis

62
Q

inhibitor of acetylcholinesterase

A

neostigmine

63
Q

contains wide synaptic folds. Leads to muscle weakness and fatigue

A

neostigmine

64
Q

Myasthenia gravis treatment

A

acetylcholinesterase inhibitor neostigmine

65
Q

what causes Myasthenia gravis

A

presence of antibodies which target the nicotinic receptors

66
Q

a reversible condition on which a muscle is no longer able to generate or sustain the expected power output

A

fatigue

67
Q

two types of fatuge

A

central fatigue

peripheral fatigue

68
Q

fatigue resistant, smaller in diameter, and darker color

A

slow-twitch

69
Q

easily fatigued, pale in color and larger diameter (sprinter)

A

fast-twitch

70
Q

single twitches

A

muscle relaxes completely between stimuli

71
Q

summation

A

stimuli closer together of not allow the muscle to relax fully

72
Q

when AP continues to stimulate the muscle fiber at high frequency, relation between contractions diminishes until the muscle fiber achieves state of maximal contraction

A

tetanus

73
Q

basic unit of contraction in a skeletal muscle is

A

motor unit

74
Q

Although motor neuron innervates multiple muscle fibers, each muscle fiber is innervated by _____ motor neuron.

A

one

75
Q

muscles used for fine motor actions, such as the muscles that move the eyes, a motor unit contains only ~____________

A

3-5 muscle fibers.

76
Q

In muscles used for gross motor actions such as standing or walking, each motor unit may contain _________ of muscle fibers.

A

hundreds or thousands

77
Q

All muscle fibers in a single motor unit are of the same fiber type:

A

fast-twitch motor units and slow-twitch motor units.

78
Q

Muscle can vary contraction force and duration by changing: (2)

A

1) the types of motor units that are active

2) the number of motor units that are responding at any one time.

79
Q

Sequential activation of motor units to perform a designated task is called

A

motor unit recruitment

80
Q

Asynchronous recruitment of motor units help avoid ________.

A

fatigue

81
Q

sustained painful contraction of skeletal muscles
-caused by hyperexcitability of the motor neuron: as it fires repeatedly, muscle fibers of its motor unit go into state of painful sustained contraction.

A

Muscle cramp (“charley horse”)

82
Q

Muscle cramp (“charley horse”) can be relieved by

A

forcibly stretching

83
Q

Muscular Dystrophies

A
  • cause progressive weakness of skeletal muscle

- Associated with genetic defects that involve proteins expressed exclusively in muscle

84
Q

what are the events that occur in Duchenne muscle dystrophy

A
  • deletion/duplication of gene encoding dystrophin
  • causes frameshift
  • mRNA syn. diminishes for dystrophin
  • low levels of dystrophin affect structural integrity of muscle cell
  • contraction stres muscle
  • cell dies
  • fatal muscular weakness
85
Q

what causes duchenne muscle dystrophy

A

deletion or duplication of gene encoding dystrophin- causes frame shifts; located on x-chromosome

86
Q

Death associated with Duchenne is generally due to _________ insufficiency

A

respiratory

87
Q

extensively used to treat many chronic inflammatory disorders (systemic lupus, sarcoidosis, rheumatoid arthritis, bronchial asthma, etc.)

A

Glucocorticoids

88
Q

antagonist for transcription factor NF-KB activated by inflammation

A

glucocorticoid

89
Q

increase levels of glucocorticoid lead to

A

atrophy

90
Q

Weakness of the diaphragm may develop in asthmatics on prolonged use of _______ therapy

A

glucocorticoid

91
Q

insulin-like growth factor is inhibited by

A

glucocorticoid

92
Q

inhibits protein degradation, stimulates protein synthesis and does not diff into muscle cells

A

growth-like factor 1

93
Q

stimulated by glucocorticoid, inhibits protein synthesis, stimulates protein degradation reducing muscle mass

A

myostatin

94
Q

a class of drugs used to lower cholesterol levels.

A

Statins (or HMG-CoA reductase inhibitors)

95
Q

the used of this drug my lead to adverse effects which include myalgia, exercise intolerance, fatigability, and potentially fatal rhabdomyolysis. (myotoxicity)

A

statin

96
Q

When tang statin periodic blood work is done to check _______ levels, which indicate muscle breakdown

A

creatine kinase

97
Q

are anabolic hormones that promote protein synthesis - anabolic steroids.

A

Androgens

98
Q

adverse effects of this drug include liver tumors, infertility, and aggression

A

androgens

99
Q

addictiveness to steroids resuts in

A

mood swings, fatigue, restlessness, depression

Muscle physiology (1 decks)

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