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ZOO3600 > Muscles > Flashcards

Muscles Flashcards

1
Q

sarcomere

A

basic unit of a muscle fiber, defined by the area between two Z-discs, containing thick and thin filaments

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2
Q

myofilament

A

protein filaments in muscle fibers; thick filaments (myosin) and thin filaments (actin) that facilitate contraction

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3
Q

cross-bridge

A

the connection formed when a myosin head binds to an actin filament during muscle contraction

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4
Q

excitation-contraction coupling

A

the process that links electrical stimulation of a muscle to its contraction, involving calcium release and interaction between actin and myosin

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5
Q

3 types of muscle

A

skeletal, cardiac, smooth

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6
Q

which muscles are voluntary

A

skeletal muscle

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7
Q

involuntary muscle

A

cardiac and smooth muscle

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8
Q

striated muscle

A

skeletal and cardiac muscle

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9
Q

unstriated muscle

A

smooth muscle

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10
Q

what type of muscle cell is a muscle fiber

A

multinucleated

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11
Q

thin filaments

A

a two-strand actin helix + the filamentous protein tropomyosin + the troponin complex

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12
Q

actin

A

a protein found in all muscle tissues, creates smaller filaments

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13
Q

thick filmanets

A

hundreds of indentical myosin proteins

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14
Q

myosin

A

a protein found in all muscle tissue, creates large filaments

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15
Q

what do the head regions of myosin contain

A

actin and atp-binding sites

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16
Q

what happens to sarcomeres during muscle contraction

A

they shorten; thin filaments actively slide along the thick filaments

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17
Q

what do cross-bridges convert

A

chemical energy into mechanical energy

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18
Q

where does the cross-bridge cycle start

A

binding site

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19
Q

what are the stages of the cross-bridge cycle

A
  1. release - binding of ATP causes myosin to detach from actin
  2. binding - hydrolysis of ATP causes myosin head to extend and attach to actin
  3. power stroke - release of phosphate promotes myosin head rotation
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20
Q

how does rigor mortis occur

A

without ATP, myosin binds irreversibly to actin causing stiffening of muscles

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21
Q

what mineral is myosin movement dependent on

A

calcium

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22
Q

when Ca is low

A

tropomyosin blocks the myosin binding sites on actin, muscles relaxed

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23
Q

when Ca is high

A

troponin pulls tropomyosin out of the way, allowing cross bridges to form

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24
Q

excitation-contraction coupling

A

muscle fibers contract when a postsynaptic end plate potential at the neuromuscular junction causes a propagated AP in the fiber sarcolemma

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25
Q

what type of tubules conduct action potentials into cell interior

A

transverse

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26
Q

what molecules are involved in excitation-contraction coupling

A

voltage sensitive DHPR and RyR
Ca pumps
Calsequestrin

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27
Q

what is a twitch

A

a single AP leading to a momentary flood of Ca inside cell, allows cross bridges to form, develops tension (last 5 - 20x longer than action potential)

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28
Q

temporal summation

A

addition of tension due to repeated and rapid stimulation, can result in max tension

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29
Q

how many muscle fibers are innervated by one motor neuron

A

one

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30
Q

how to increase muscle tension

A
  • increasing AP frequency (temporal summation)
  • recruiting more motor units
  • recruiting higher intensity contraction fibers
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31
Q

force-velocity relationship

A

as load increases, velocity of shortening decreases

32
Q

reason for inverse relationship between load and velocity

A

cross bridge cycling takes time, when slowed more myosin heads can act at same time leading to greater force potential

33
Q

force transducer

A

measures tension generated by the muscle fiber when stimulated to contract

34
Q

FG fiber ATP production

A

glycolysis

35
Q

SO fiber ATP production

A

oxidative phosphorylation

36
Q

is rate of Ca uptake by SR higher in FG or SO

A

FG

37
Q

roles of ATP

A

cross bridge cycling, regulating intracellular Ca levels, maintaining nerve membrane potential

38
Q

what type of movement demands less ATP

A

high force, low speed

39
Q

what would let an athlete win in a 50 m spring

A

more FG fibers (unsustained)

40
Q

what would let an athlete win a marathon

A

more SO fibers (sustained)

41
Q

glycolysis

A

glucose is broken down into pyruvate, producing energy in the form of ATP in absence or presence of oxygen

42
Q

oxidative phosphorylation

A

takes place in mitochondria, energy from nutrients is used to produce ATP via electron transport chain and oxygen is final electron acceptor

43
Q

creatine phosphate

A

high energy molecule stored in muscles that quickly donates a phosphate group to ADP to regenerate ATP during short bursts of high intensity activity

44
Q

how is burst energy ATP made available so quickly

A

creatine phosphate system and anaerobic glycolysis

45
Q

how does sustained energy have an uninterupted supply of ATP

A

aerobic respiration and fatty acid oxidation

46
Q

what determines the rate at which a muscle can work

A

ATP production rate

47
Q

2 definining features of ATP

A

not transported between cells, not stored

48
Q

what did the mouse experiment demonstratae

A

mice mutants with full Creatine kinase activity had higher burst activity performance than those with no CK activity, showing that the ability of muscle to perform burst activity is proportional to CK activity

49
Q

what does high-intensity and short term activity produce

A

lactic acid (indicator of fatigue)

50
Q

what causes fatigue in sustained exercise

A

inadequate muscle glucose

51
Q

muscle fatigue results from (3 answers)

A

depletion of energy reserves (ATP, glycogen), ion disturbances, and pH imbalance

52
Q

how can you recover from muscle fatigue

A

replenishing energy stores (using Cori cycle)
reestablishing ion balance (gradients, Ca stores, pH)

53
Q

where does ATP have to come from to recover muscle (recovery metabolism)

A

aerobic pathways

54
Q

EPOC

A

Excess post-exercise oxygen recovery

55
Q

why is there an o2 deficit at beginning of exercise

A

demand of O2 > supply of O2

56
Q

what is the repayment phase

A

exercise has stopped but oxygen remains high to restore the bodys energy balance

57
Q

what do superfast muscles do

A

contract synchronously at rates that would put regular muscles into tetanus

58
Q

what is tetanus

A

sustained contraction with no relaxation

59
Q

what conditions allow superfast muscles to work

A
  1. short Ca transients (rapid cycling between SR and cytoplasm)
  2. quick cross-bridge cycling (force generation extremely fast)
60
Q

what does flight require

A

continuous aerobic high power output at high contraction frequencies

61
Q

adaptations to flying

A

increasing muscle temperature, skeletal adaptations, increasing mitochondria inner membrane for more ATP production

62
Q

synchronous flight muscles

A

connect to the wing, one set of muscles raises the wing (elevator muscle) and another lowers them (depressor muscle)

63
Q

what animals have synchronous flight muscles

A

vertebrates and some insects

64
Q

asynchronous flight muscles

A

connected to the whole body, vertical muscles contract to make body vertically compressed, longitudinal muscles contract to shorten the body

65
Q

oppositional muscles

A

when one stretches the other contracts

66
Q

effect of oppositional muscles on Ca

A

as muscle stretches, Ca increases, triggering contraction

67
Q

AP and contraction relation in asynch flight

A

single AP initiates series of contractions , frequency of contr is not synched w frequency of AP

68
Q

space distribution in asynch flight muscles

A

less space for SR and mitochondria, more space for myofibrils

69
Q

what type of muscle is internalized to retain heat in tuna

A

red muscle

70
Q

what type of muscle is red muscle

A

slow oxidative muscle, packed with ATP

71
Q

regional heterothermy

A

parts of the fish are kept warmer than surrounding environment, improving the efficiency of muscles

72
Q

rete mirabile

A

structure that retains heat in muscle and prevents loss of heat to gill

73
Q

heater organs

A

specialized eye muscles that keep brain/eye temp stable and warmer than surrounding water

74
Q

what is the carotid rete

A

collects heat generated by the heater muscle

75
Q

differences between skeletal muscle cells and heater organ muscle cells

A

increase in mitochondria content (increased ATP production)
increased SR content (increase storage and release of Ca)
proliferation of T-tubules (increase release of Ca into cell)
no contractile apparatus

76
Q

what is responsible for storing and releasing Ca

A

SR and T tubule

77
Q
A

ZOO3600 (3 decks)

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