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Tissues 1 > muscle physiology > Flashcards

muscle physiology Flashcards

1
Q

what makes muscles contact?

A

excitation-contraction coupling

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2
Q

what is excitation-contraction coupling?

A

series of events that produce an electrical stimulus that triggers the release of Ca from the sarcoplasmic reticulum, initiating the mechanism of muscle contraction by sarcomere shortening

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3
Q

what are positively charged ions referred to as?

A

cations

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4
Q

what are negatively charged ions referred to as?

A

anions

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5
Q

is the inside of the cell negative or positive in comparison the the extracellular area?

A

negative

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6
Q

what charge does the extracellular area of the cell have?

A

neutral

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7
Q

what is the the potential difference in voltage across a cell called?

A

resting membrane potential (Em)

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8
Q

what is the calculation used to calculate Em?

A

voltage in cytoplasm - voltage in ECF

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9
Q

what structure maintains Em?

A

Na/K-ATPase

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10
Q

which ions pass in and out of the cell via passive leak channels?

A

Na and K

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11
Q

how many sodium ions enter the cell by the Na/K-ATPase?

A

3

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12
Q

how many potassium ions leave cell by the Na/K-ATPase?

A

2

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13
Q

what is the Em of a neutron?

A

-70mV

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14
Q

what is the Em of a muscle cell?

A

-90mV

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15
Q

name the 3 types of active (gated) channels?

A

. chemically-regulated channels (ligand gated)
. Voltage-regulatd channels
. mechanically-regulated channels

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16
Q

describe the series of events that lead to an AP in a muscle cell

A

. voltage-sensitive Na channels are activated when voltage threshold is reached
. this causes depolarisation
. as membrane potential increases to a positive number, the threshold for voltage-dependant K channels is reached, and K enters the cell
. K influx quickly decreases Em, depolarising cell

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17
Q

what is an action potential?

A

rapid change in Em caused by rapid activation and fluxes of ion currents, followed by a return to resting em

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18
Q

what is the term used for sustained muscle contractions?

A

tetanic contaction

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19
Q

what do action potentials allow?

A

synchronous contraction/relaxation in muscle and communication in neutrons

20
Q

what is the refractory period?

A

a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation

21
Q

what propagates action potentials in the heart?

A

SA node

22
Q

what propagates action potentials in skeletal muscles?

A

ACh binding to motor unit on skeletal muscle

23
Q

describe the series of events by which an AP leads to muscle contraction?

A

. depolarisation activates plasma membrane voltage-sensitive Ca channels that allow Ca to enter cell
. inward entry of Ca activates release of Ca from sarcoplasmic reticulum
. intracellular Ca conc increases trigering myofilamnet contraction

24
Q

describe the series of events by which cytoplasmic Ca exposes myosin binding sites

A

. cytoplasmic Ca bins to troponin C, inducing a conformational change that exposes myosin-binding sites on actin filament
. this allows myosin head to bind to actin

25
Q

how does the release of Ca differ in smooth muscle?

A

receptors also contribute by activating agonist-mediated Ca channels

26
Q

which channels stimulate SR Ca release through RyR receptors in cardiac/skeletal muscle?

A

L-type Ca channels

27
Q

Ca is released from the SR through which channels in smooth muscle?

A

RyR and IP3R

28
Q

which molecule blocks myosin binding sites on actin filaments?

A

tropomyosin

29
Q

tropomyosin contains which 3 proteins?

A

troponin C, troponin I and troponin T

30
Q

where on the actin filament does cytoplasmic Ca bind?

A

troponin C

31
Q

describe myosin chains?

A

2 myosin heavy chains and 4 myosin light chains

32
Q

describe the series of events that lead to smooth muscle contraction?

A

. Ca binds to cytoplasmic calmodium changing its conformation
. Ca-calmodium complex activates myosin light chain kinase (MLCK)
. MLCK phosphorylates myosin light chain to catalyse cross-bridge activation

33
Q

what is ATP most important for in terms of ECC?

A

relaxation

34
Q

at which stage of ECC id ATP broken down to ADP + Pi? ?

A

cocking of myosin head

35
Q

when during ECC is an inorganic phosphate released?

A

when myosin head binds to actin

36
Q

when is ADP released during ECC?

A

power stroke

37
Q

at which point during ECC is ATP supply depleted?

A

when the muscle has contacted

38
Q

how is the myosin head released from actin?

A

by the binding of ATP to the myosin head

39
Q

what happens to Ca release as a result of RyR dysfunction?

A

Ca sparks, abberent Ca release, loss of SR Ca

40
Q

which muscles types is RyR dysfunction most severe in?

A

cardiac and skeletal

41
Q

what may a consequence of RyR dysfunction in cardiac muscle be?

A

Heart failure

42
Q

what may a consequence of RyR dysfunction in skeletal muscle be?

A

muscular dystrophy

43
Q

what does muscular dystrophy cause?

A

muscle weakness, loss of skeletal muscle function and control, muscle degeneration, paralysis

44
Q

what type of mutation is muscular dystrophy?

A

X-linked recessive

45
Q

what is a possible way of treating RyR dysfunction?

A

increasing SERCA

46
Q

how may SERCA be increased?

A

gene therapy, exercise training

Tissues 1 (8 decks)

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