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PHSI 208 > Muscle 3 > Flashcards

Muscle 3 Flashcards

1
Q

Action potentials propagate from the sarcolemma to the interior of muscle fibres along the…

A

t-tubule networks

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2
Q

initiation of muscle action potential

A
  • motor neuron release ACh at neuromuscular junction

- net entry of Na+ through ACh receptor-channels initiate AP

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3
Q

DHP

A

dihydropyridine; L-type Ca2+ channel

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4
Q

RyR

A

ryanodine; ca2+ release channel on sarcoplasmic reticulum

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5
Q

excitation-contraction coupling

A
  • AP in t-tubule alters conformation of DHP receptor

- DHP receptor opens RyR and Ca2+ enters cytoplasm

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6
Q

Besides mechanically, ryanodine receptors can also be activated by..

A

Calcium (calcium induced calcium release)

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7
Q

An increase in calcium conc. triggers….

A

contraction by removing the inhibition of cross bridge cycling

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8
Q

describe the removal of the inhibition of cross bridge cycling

A
  • Calcium binds on troponin C, inducing conformation change in troponin conplex
  • troponin complex and tropomyosin move and reveal myosin binding site on actin
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9
Q

4 steps of cross bridge cycling

A
  • ATP binding
  • ATP hydrolysis
  • the power stroke
  • ADP release
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10
Q

ATP binding

A

ATP binds to the head of myosin heavy chain, reducing affinity of myosin for actin

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11
Q

ATP hydrolysis

A

ATP is broken down to ADP and inorganic phosphate resulting in myosin head pivoting around hinged into cocked state

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12
Q

cocked state

A

when head is aligned with and binds to a new actin molecule on thin filament

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13
Q

the power stroke

A

dissociation of Pi from myosin head strengthens bon between actin and myosin and triggers power stroke; a conformational change in which myosin head returns to uncocked state and pulls actin filament generating force and motion

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14
Q

ADP release

A

dissociation of ADP from myosin causes myosin to remain bound to actin until ATO initiates the cycle again

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15
Q

Termination of contraction requires removal of…

A

Calcium

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16
Q

Calcium can be removed to the extracellular space by…

A

Na-Ca exchanger or by the Ca2+ pump which uses ATP

17
Q

Calsequestrin and calreticulin

A

maximize Ca2+ uptake by the SR

18
Q

Up to how many Ca2+ binding sites per molecule?

A

50

19
Q

elastic recoil of titin and other connective tissue

A

causes sarcomeres to return to initial resting position

20
Q

rigor mortis

A

development of rigid muscle several hours after death; Ca2+ leaks into sarcoplasm and binds troponin

21
Q

SERCA pump

A

reuptake of Ca2+

22
Q

When ATP production stops

A
  • Ca2+ cannot be removed
  • myosn head cannot be released from actin
  • latched cross bridge formation
23
Q

timing of E-C coupling

A

-delays between motor neuron AP and muscle fibre AP and between muscle fibre AP and contraction

24
Q

sources of ATP

A
  • free intracellular ATP

- stored as phosphocreatine

25
Q

ATP needed for:

A
  • myosin ATPase (contraction)
  • Ca2+ ATPase (relaxation)
  • Na+/K+ ATPase (after AP in muscle fibre)
26
Q

Resting muscle stores energy from ATP in high energy bonds of…

A

phosphocreatine

27
Q

glycohenolysis

A

when ATP is needed and glycogen is converted back to glucose

28
Q

glycolysis

A

when one glucose molecule is broken down to pyruvate resulting in production of 2 ATP molecules

29
Q

pyruvate can be further broken down to…

A

lactate

30
Q

glycolysis is….

A

anaerobic metabolism

31
Q

citric acid cycle

A
  • after glycolysis
  • pyruvate produces 2 more molecules of ATP, electrons, and H+
  • electron and H+ with oxygen produce 26-28 more ATP
32
Q

glycolysis occurs in….

A

sarcoplasm of muscle

33
Q

citric acid cycle is….

A

oxidative (aerobic) metabolism

34
Q

citric acid cycle occurs is..

A

mitochondria

PHSI 208 (64 decks)

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