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CSF block 4 > MUSCLE I > Flashcards

MUSCLE I Flashcards

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1
Q

what is the purpose of structural proteins in muscle

A

to transmit movement or force outside of the cell

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2
Q

name the 4 structural proteins discussed

A

titin, nebulin, a-actin and dystrophin

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3
Q

describe the structure of titin

A

large, elastic protein

2 titin molecules running parallel to myosin

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4
Q

what is the function of titin?

A

anchors thick filament to Z-disc (main)

also acts as molecular ruler during myogenesis, helps with passive length tension and prevents overstretching

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5
Q

what is the structure of nebulin?

A

long inelastic protein with 2 strands for each actin, running the length of each actin

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6
Q

what is the function of nebulin?

A

anchors thin filament to Z disc

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7
Q

what is another (secondary) function of nebulin?

A

can be used to determine the length of the actin filament

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8
Q

what is the purpose of alpha-actinin?

A

attachment point for actin filaments to z-disc

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9
Q

what are dystrophins?

A

focal contact points between sarcomere and membrane/extracellular matrix

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10
Q

what type of myosin is in muscle?

A

myosin II

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11
Q

what is the structure of myosin II?

A

hexameric protein with 2 heavy chains and 2 light chains

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12
Q

when is myosin “bent”?

A

when bound to ADP and Pi

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13
Q

when is myosin “straight”?

A

when bound to ADP only

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14
Q

function of troponin T

A

binds to tropomyosin, positions actin and exposes myosin binding sites

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15
Q

function of troponin I

A

binds to actin, prevents myosin from binding actin

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16
Q

function of troponin C

A

calcium binds causing a conformational change that disrupts actin-TnI interaction

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17
Q

function of caldesmon

A

acts similar to TnT in smooth muscles

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18
Q

function of calponin

A

acts similar to TnI in smooth muscle

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19
Q

A-band

A

entire length of thick filament

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20
Q

H-zone

A

thick only

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21
Q

I-band

A

thin only

22
Q

what happens to the A-band, H-zone and I-band during muslce contraction?

A

H and I shorten, A is stable

23
Q

what is the consequence of increased muscle fiber length?

A

decreased cross linkages, decreased force of contraction

24
Q

what is the consequence of decreased muscle fiber length?

A

thick filament clashes with z-disc, less lesion and less force of contraction

25
Q

describe the steps in muscle contraction (5)

A

1-ATP binds to actomyosin and disrupts bond between them
2- myosin hydrolyzes ATP to ADP and Pi
3- Pi is released from myosin and power stroke occurs
4- ADP released from myosin, causing myosin to rotate further
5- ATP free to bind and start cycle over

26
Q

what is the power stroke in muscle contraction?

A

dissociation of Pi is the power stroke

27
Q

what controls the rate of muscle contraction?

A

dissociation of ADP controls the rate of contraction

28
Q

describe slow twitch type I muscle (6)

A

small, fatigue resistant, red myoglobin, lots of mitochondria, Ox metabolism and low glycogen

29
Q

describe fast twitch type IIA (6)

A

intermediate, fatigue resistant, red myoglobin, lots of mitochondria, Ox metabolism and high glycogen

30
Q

describe fast twitch IIB/IIX (6)

A

large, fatiguable, white myoglobin, few mitochondria, glycolytic metabolism and high glycogen

31
Q

what does endurance training change regarding muscle fibers? (4)

A

increases type IIA, increases mitochondria, increases myoglobin, decreases type IIX

32
Q

what neurotransmitter is involved with skeletal muscle contraction?

A

acetylcholine

33
Q

describe the interaction between DHP receptors and RyR-1 receptors in skeletal mm

A

there is a physical interaction between DHP receptors and RyR-1 receptors in skeletal mm that leads to Ca release from sarcoplasmic reticulum

34
Q

what is the role of calcium in skeletal muscle contraction?

A

binds troponin C to increase Pi dissociation and allow power stroke to occur

35
Q

what neurotransmitter is involved with cardiac muscle contraction? what receptors?

A

norepinephrine, beta-adrengeric receptors

36
Q

discuss RyR-2 receptors

A

found in cardiac muscle, involved in calcium induced calcium release

37
Q

what is chronotrophy?

A

heart rate

38
Q

what is inotrophy?

A

heart contractility

39
Q

what is lusitrophy?

A

heart relaxation (rate)

40
Q

which receptors are responsible for calcium-induced calcium release in smooth muscle cells?

A

IP3 receptors on sarcoplasmic reticulum

41
Q

what does calcium bind in smooth muscle cells?

A

calmodulin, Rho-A kinase, caldesmon and calponin

42
Q

what is the function of calcium-calmodulin?

A

activation of myosin light chain kinase (MLCK) to phosphorylate myosin and allow it to interact with actin

43
Q

what is the function of Rho-A Kinase?

A

Rho-A Kinase inhibits myosin light chain phosphatase (MLCP) so that the light chains can remain phosphorylated for a prolonged period

44
Q

what causes myosin to return to the the relaxes state in smooth muscle?

A

MLCP (dephosphorylates)

45
Q

what can activate MLCP?

A

cGMP

46
Q

what are the functions of caldesmon and calponin in smooth muscle?

A

expose tropomyosin and allow MLC to bind

47
Q

what causes muscular dystrophy?

A

defective focal adhesion proteins leading to weak contraction, disruption of membranes

48
Q

what is malignant hyperthermia?

A

autosomal, myopathy secondary to defect in RyR-1 causing uncontrolled mm contraction and hyperthermia

49
Q

what causes familial hypertrophic cardiomyopathy?

A

single amino acid mutation in the myosin heavy chain that changes ATP hydrolysis and decreases contractile force leading to wall hypertrophy

50
Q

what receptors are reduced in the setting of heart failure?

A

RyR-2

51
Q

how doe viagra work?

A

inhibits breakdown of cGMP (through inhibition of PDE5) that enhances the relaxation of smooth mm allowing blood to collection for erection

CSF block 4 (5 decks)

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