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Physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

where do action potentials in muscles propagate?

A

sarcolemma

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2
Q

Triad Junction

A
  • T tubule w/ 2 terminal cisternae, which are specialized regions of sarcoplasmic reticulum
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3
Q

what is happening when the muscle shortens?

A

it means it’s contracting and producing tension

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4
Q

where can we find ryanidine receptors?

A

skeletal and cardiac muscles

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5
Q

sarcomere

A

repeating unit b/w adjacent Z disks/lines

smallest functional unit of skeletal muscle

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6
Q

proteins tethered to z disk of skeletal muscles

A

actin
nebulin
titin
alpha actinin

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7
Q

alpha actinin

A

crosslinks antiparallel thin filaments at z disk

helps to anchor myofibrillar actin filaments

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8
Q

titin

A

connects myosin to z disk

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9
Q

stretch sensing and signal communication to nucleus of skeletal muscle

A

titin, nebulin

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10
Q

a filament that forms internal support and attachment for actin

A

nebulin

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11
Q

what is the back bone of thin filament?

A

F-actin

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12
Q

structure of F-actin

A

right-handed, two-stranded helix of non-covalently polymerized actin molecules

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13
Q

what is another calcium-binding protein that is closely related to troponin C?

A

calmodulin

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14
Q

Troponin T binds to…

A

a single molecule of tropomyosin

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15
Q

Troponin I

A

binds to actin and inhibits contraction

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16
Q

what enhances myosin cross-bridge interactions?

A

phosphorylation of RLC (myosin regulatory light chain) by myosin light chain kinases

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17
Q

myosin light chain phosphatase function

A

dephosphorylates regulatory light chain of the motor protein myosin II

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18
Q

how do calcium ions exert their effect in muscle contraction?

A

they bind to regulatory proteins rather than directly interacting w/ contractile proteins

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19
Q

myosin II

A

responsible for ATP-dependent force generation in all types of myocytes

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20
Q

location of the 2 high affinity sites on skeletal muscles

A

c lobe of TNNC2 (troponin C subtype)

21
Q

location of 2 low affinity sites on skeletal muscle

A

n lobe of TNNC2

22
Q

how many molecules of ATP are consumed after one round of cross-bridge cycle?

A

only one ATP molecule

23
Q

what is the most important mechanism for the termination of muscle contraction?

A

calcium ion reuptake by SR via the SARCOPLASMIC ENDOPLASMIC RETICULUM Ca-ATPase.

24
Q

calreticulin

A
  • a calcium binding protein that is found in smooth muscles in high concentration
25
Q

calsequestrin

A

calcium-binding protein in SKELETAL MUSCLES

buy may also be present in cardiac and smooth muscle

26
Q

minor mechanism in termination of muscle contraction

A

NCX or PMCA

na-ca exchanger or plasma membrane ca-atpase

27
Q

what determines the amount of tension developed?

A

degree of overlap between actin and myosin filaments

28
Q

how is the shortening velocity affected with higher loads?

A

velocity is slower because more cross-bridges are simultaneously active.

29
Q

relationship b/w load and velocity

A

they’re INVERSELY PROPORTIONAL

30
Q

what structures interconnect cardiac myocytes from end to end?

A

intercalated disks

31
Q

what is an absolute requirement for cardiac muscle contraction?

A

influx of Ca++ through the L-type calcium channels

32
Q

what type of junction is made b/w single terminal cisterna of SR and t-tubule?

A

dyad junction

33
Q

what is needed IOT pump calcium back into SR?

A

ATP

34
Q

what maintains Na+ gradient during EC coupling in cardiac muscle?

A

Na-K ATPase

35
Q

In skeletal muscle, how many calcium ions bind to TNNC2 subtype?

A

4 calcium ions

36
Q

In cardiac muscle, how many calcium ions bind to TNNC2 subtype?

A

3 calcium ions

37
Q

what inhibits SR calcium pump?

A

PHOSPHOLAMBAN

38
Q

nerve bundles that release NTs in smooth muscles

A

varicosities (close to postsynaptic membrane of smooth muscle cell)

smooth muscles don’t have synaptic clefts

39
Q

multiunit smooth muscle

A

each SM cell receives its own synaptic input

iris, walls of blood vessels

40
Q

unitary smooth muscle

A

only a few cells receive direct synaptic input

hollow organs

41
Q

function of gap junctions in smooth muscles

A

permit coordinated contraction

42
Q

why is the rate of rising of action potential lower in smooth muscles?

A

calcium channels open much slower than Na+ channels in cardiac and skeletal muscles.

43
Q

purpose of fast, voltage Na+ channels in smooth muscles

A

hasten activation of voltage-gated Ca++ channels, which contribute to faster rate of depolarization

44
Q

what causes spontaneous electrical activity in smooth muscles?

A

regular, repetitive oscillations in Vm and contractions (SLOW WAVE POTENTIAL)

45
Q

what can activate contract in smooth muscles?

A

both extracellular and intracellular calcium ions

46
Q

2 proteins that tonically inhibit interaction b/w actin and myosin

A

caldesmon and calponin

47
Q

tonically inhibit actin-activated ATPase activity of myosin

A

caldesmon

48
Q

tonically inhibits ATPase activity of myosin

A

calponin

Physiology (9 decks)

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