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oneoseven > lecture 30 - Skeletal muscle 1 > Flashcards

lecture 30 - Skeletal muscle 1 Flashcards

1
Q

which type of muscle tissue is pictured here?

A

skeletal

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2
Q

what is shown by numbers 1 - 5 and by the red arrow?

A
  1. Z disc
  2. H zone
  3. I band
  4. A band
  5. M line

arrow shows 1 sarcomere

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3
Q

label number 1-7

A
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4
Q

which muscle type if pictured here?

A

cardiac

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5
Q

what muscle type is this?

A

skeletal

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6
Q

what’s this mayne?

A

smooth muscle

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7
Q

is this cardiac, smooth, or skeletal muscle? why?

A

smooth (no strirations)

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8
Q

which muscle type is under voluntary control?

A

skeletal

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9
Q

which muscle types are striated?

A

cardiac and skeletal

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10
Q

in skeletal muscle the nuclei are ________ whereas in cardiac muscle there are 1-3 ______ nuclei. Smooth muscles are _____-shaped and u______d

A

in skeletal muscle the nuclei are _peripheral_ whereas in cardiac muscle there are 1-3 _central_ nuclei. Smooth muscles are _spindle_-shaped and uninucleated.

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11
Q

structure of skeletal muscle

A
  • attach to bones via tendons
  • 1 muscle fibre/cell goes from tendon to tendon (up to 35cm)
  • reasonably wide at 0.1mm
  • composed of myofibrils, containing filaments
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12
Q

protein of thick filament

A

myosin

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13
Q

protein of thin filament

A

globular actin

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14
Q

myofibrils connect at the…

A

Z-disc

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15
Q

where would you find only myosin and no actin?

A

H-zone

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16
Q

at the _-line thick filaments are held together by the protein ______.

A

at the _M_-line thick filaments are held together by the protein _myomesin_.

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17
Q

T-tubules

A

deep invaginations, continuous with the sarcolemma, which circle each sarcomere at the junctions of the A and I bands.

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18
Q

in skeletal muscle, how many tubules per sarcomere?

A

2

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19
Q

function of transverse tubules

A

allow action potentials to be carried deep within the muscle cell.

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20
Q

sarcoplasmic reticulum

A

calcium storage site. The terminal cisternae of the SR lie close to the T-tubules

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21
Q

what does this image show

A

contracted myofibril

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22
Q

order the follwing from smallest to largest

  • myofibril
  • muscle
  • sarcomere
  • myofilament
  • myocyte
A

smallest

  1. myofilament
  2. sarcomere
  3. myofibril
  4. myocyte
  5. muscle

largest

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23
Q

How many myosin subunits?

A
  • 2
  • one globular head and one tail
  • tails intertwine to form a helix
24
Q

Each myosin head is an enzyme that…

A

hydrolyses ATP (ATPase)

25
Q

where would you find the binding site to which actin attaches?

A

myosin head

26
Q

how is actin arranged in thin filaments

A

double stranded helical actin chains

27
Q

__________ and _________ are regulatory proteins associated with actin in skeletal/cardiac muscle

A

_Troponin_ and _tropomyosin_ are regulatory proteins associated with actin in skeletal/cardiac muscle

28
Q

label 1,2 and 3

A

1 .troponin

  1. actin
  2. tropomyosin
29
Q

sliding filament theory of muscle conrtaction

A

sarcomere shortens as thin filaments are pulled over thick filaments

30
Q

outline the 4 steps of the cross-bridge cycle

A
  1. cross-bridge formation
  2. power stroke
  3. detachment
  4. energization of myosin head
31
Q

what must be present for the cross-bridge to form? why?

A

Ca2+ makes the actin site available

32
Q

what is the one region of the sarcomere that doesn’t change in length/size during contraction?

A

A bands

33
Q

what is happening when the crossbridge forms?

A

myosin binds to the actin binding site (to form the crossbridge)

34
Q

what is occuring in the power stroke

A
  • ADP is released (energy has been used)
  • the myosin head rotates to its low energy state (45o to the actin)

= sarcomere shortens

35
Q

what must happen for myosin to detach from actin?

A

a new ATP molecule binds to the myosin. This weakens the actin-myosin binding.

36
Q

energization of the myosin head

A
  • myosin head hydrolyses the ATP to ADP + Pi
  • myosin moves back to its high energy conformation (90o to the actin)
37
Q

Calcium binds to the _______, inducing a conformational change which pulls _________ off the ______ binding site. Therefore these sites are now available. As long as _______ is present above its threshold of (____-____mM) the cycle will continue.

A

Calcium binds to the _troponin_, inducing a conformational change which pulls _tropomyosin_ off the _myosin_ binding site. Therefore these sites are now available. As long as _calcium_ is present above its threshold of (_0.001_-_0.01_mM) the cycle will continue.

38
Q

how does calcium enter the cytosol of muscle fibres/cells?

A

calcium moves down its electrochemical gradient when the calcium channels in the sarcoplasmic reticulum open

39
Q

how does Ca2+ return to the SR?

A

Ca2+ ATPase transport pumps are constantly working to move calcium from the cytoplasm to the SR.

40
Q

what is Isotonic muscle contraction? what stays the same and what changes?

A
  • shortening
  • tension constant
  • velocity variable
41
Q

what is isomeric muscle contraction? what stays the same and what changes?

A
  • no shortening
  • length constant
  • tension variable
42
Q

where would you find Intercalated discs?

A

in cardiac muscle, connecting the cells together

43
Q

where would you find the I-band and the A-band?

A

I band = 2 (notice how it has become much smaller in length during contraction)

A band = 1 (same length always)

44
Q

calcium interact with troponin in ______ regulated muscle and interact with calmodulin in _______ regulated muscle.

A

calcium interact with troponin in _actin_ regulated muscle and interact with calmodulin in _myosin__ regulated muscle.

45
Q

what is rigor mortis and what causes it?

A

stiff muscles caused by the absence of ATP, so the cross bridge can’t detach

46
Q

when does the cross bridge cycle end?

A

when Ca2+ is actively transported back into the sarcoplasmic reticulum

47
Q

which number shows…

(a) active tension
(b) passive tension
(c) total tension

A
  1. = total tension
  2. = passive tension
  3. = active tension
48
Q

length-tension relationship

A

maximum force produced by the sarcomere is dependent on the degree of actin and myosin overlap

49
Q

in which type of muscle contraction can the legth-tension relationship be observed?

A

isometric

50
Q

what happens when the sarcomere is less than 2.0μm?

A

filaments collide and interfere with each other, reducing the force developed

51
Q

what happens, in the sarcomere, at lengths greater than 2.2μm?

A

active forced decline because the extent of overlap between filaments reduces, reducing the number of cross-bridges that can form

52
Q

at which length is the sarcomere able to produce the greatest force?

A

2.0μm-2.2μm

53
Q

pasive force =

A

as muscle is streched, the connective tissue around the muscle fibres resist the stretch

54
Q

active tension is dependent on?

A

sarcomere legnth

55
Q

total tension =

A

passive tension + active tension

56
Q

myocyte

A

another name for a muscle cell

oneoseven (18 decks)

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