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Undeleted > Lecture 9: Anatomical Components of Muscle (Hayward) > Flashcards

Lecture 9: Anatomical Components of Muscle (Hayward) Flashcards

1
Q

what property is common to all muscles?*

A

contractility

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2
Q

why does skeletal muscle have banded appearance?*

A

regular arrangement of actin and myosin

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3
Q

cytoplasm of muscle cell = *

A

sarcoplasm

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4
Q

endoplasmic reticulum of muscle cell = *

A

sarcoplasmic reticulum

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5
Q

muscle cell = *

A

myofiber

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6
Q

components of myofibril*

A

actin and myosin myofilaments

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7
Q

hierarchy of skeletal muscle structure*

A

myofilament –> myofibril –> myofiber –> muscle fascicle –> muscle belly

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8
Q

what are a bunch of myofibrils surrounded by to make a myofiber (muscle cell)?*

A

endomysial layer

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9
Q

what structure surrounds a muscle belly?*

A

fascia

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10
Q

name the bands in a sarcomere*

A

A (anisotropic), I (Isotropic), M, H, and Z bands

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11
Q

What happens to the length of the different bands in a sarcomere during a muscle contraction?**

A

I and H bands shorten. A and M bands stay the same length. Total sarcomere length (distance between Z bands) decreases.

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12
Q

what happens to sarcomere if only one Z band contracts?*

A

no force is produced. Z bands on both ends of sarcomere must contract to produce force.

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13
Q

fx of M-line*

A

anchors adjacent thick filaments (myosin)

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14
Q

fx of Z bands*

A

anchor thin filaments (actin)

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15
Q

H-band is composed of thick and/or thin filaments?*

A

Thick filaments only

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16
Q

What are Z-lines composed of?*

A

alpha-actinin and Z-line filaments

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17
Q

What are M-lines composed of?*

A

M-line filaments and creatine kinase enzyme

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18
Q

intermyofibrillar space*

A

space between adjacent myofibrils. Contains SR, mitochondria, glycogen, and lipids

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19
Q

alpha-actinin*

A

an anchoring filament that helps anchor thin-line filaments to the Z band

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20
Q

3 intermediate anchoring filaments**

A

vimentin, desmin, and vinculin

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21
Q

fx of vinculin*

A

scaffold protein that connects myofibrils adjacent to the sarcolemma to the sarcolemma

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22
Q

fx of vimentin*

A

scaffold protein that extends b/w Z lines of the same sarcomere

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23
Q

fx of desmin*

A

scaffold protein that hold Z-lines of adjacent myofibrils together

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24
Q

fx of titin***

A

large springy globular protein that anchors M-bands and imparts a portion of passive elastic component of muscle. Connects thick myofilaments with the Z-line. Spans distance between M and Z lines. Elasticity of titin helps restore the stretched sarcomere (muscle) back to its correct length and transfers force down to the tendon.

25
Q

In which band of sarcomere is there never overlap of thin and thick filaments?*

A

H band region (thick only)

26
Q

fx of T (transverse) tubule system*

A

an invagination of surface membrane into the muscle cell. Connects to the intracellular SR and facilitates Ca release from SR following a depolarization

27
Q

dystropin**

A

cytoskeletal protein located on the inner surface of the sarcolemma. Involved in the structural integrity of the sarcolemma (anchors actin, regulates membrane proteins). Main fx = transmission of force to extracellular matrix of muscle cell.

28
Q

what happens to muscle cell in absence of dystropin?*

A

muscle cell can’t generate force and degenerates. Cause of muscular dystrophy

29
Q

what enzyme is a good marker for cardiac disease/muscle death/abnormalities of skeletal muscle?

A

creatine kinase (will be elevated in muscular dystrophy)

30
Q

myostatin

A

a SKELETAL muscle growth inhibitor. If inhibited, will facilitate muscle growth. Potential cure for muscular dystrophy. Not effective in cardiac muscle.

31
Q

follistatin

A

muscle growth activator. Potential cure for M.D.

32
Q

Could myostatin regulate hypertrophy or fibrosis?

A

No. Thus, myostatin may prevent muscle wasting without causing cardiac dysfunction in cases of cardiac failure.

33
Q

where is T tubule system located?

A

at interconnection of A and I bands in the sarcolemma

34
Q

fx of Ca in sarcomere

A

allows actin and myosin to interact

35
Q

describe path of Ca from release to reuptake in sarcomere

A

wave of depolarization moves down T tubules, conformationally changes the DHP and RyR receptors, allowing Ca to be released from SR, diffuse around cell and bind to regulatory proteins before being re-taken up by longitudinal proteins of the SR via Ca ATPase

36
Q

what stimulates Ca ATPase on SR?

A

increases in intracellular Ca

37
Q

sliding filament hypothesis

A

there must be a central component (A band) that doesn’t change but has the capacity to pull other bands over it. In other words, globular heads on A bands bind to thin filaments and pull other them inward. This is accomplished by the formation and breaking of bonds between actin and myosin at the crossbridges in the presence of ATP.

38
Q

conductility

A

the propagation of membrane depolarization over the cell surface

39
Q

What corresponds to the dark staining bands of muscle fibers on light microscope?

A

A-bands. Composed of parallel arrays of thick myofilaments composed of myosin. Have cross-bridges that extend toward adjacent thin myofilaments

40
Q

What corresponds to the light staining bands of fibers on light microscope?

A

I bands. (thin filaments of actin). Attach at one end to Z lines.

41
Q

sarcomere =

A

repeating Z-line to Z-line interval of myofibrils

42
Q

myofilament ratio

A

6 thin myofilaments to 1 thick myofilament. Each thick filament is surrounded by a hexagonal array of 6 thin filaments.

43
Q

2 main components of muscle membrane system that serve to activate the contractile apparatus

A

1) transverse (t) tubular system

2) Sarcoplasmic reticulum

44
Q

What is a triad?

A

complex of T-tubule flanked by 2 terminal cisternae on the SR. There are 2 triads per sarcomere. Forms a gap which is bridged by junctional feet. A conformational change in the junctional feet leads to Ca release from the SR.

45
Q

components of junctional feet

A

DHP and RyR receptors

46
Q

sarcotubules

A

netowork of longitudinally arranged tubular membranes. Fx in re-uptake of Ca back into SR

47
Q

main fx. of SR

A

reservoir of Ca. Controls the Ca conc. of the sarcoplasm surrounding myofibrils and myofilaments through its ability to concentrate and release Ca.

48
Q

Ca ATPase pumps Ca from where to where?

A

from sarcoplasm to lumen of SR

49
Q

fx of calsequestrin

A

binds Ca. Regulated by intracellular concentrations

50
Q

How does the length of thin and thick filaments change during muscle contraction?

A

They don’t change! The filaments slide over one another, but they don’t actually change in length

51
Q

general fx of myosin

A

generates force of contraction, ATPase activity

52
Q

general fx of actin

A

interacts with myosin for muscle contraction, activates myosin ATPase

53
Q

general fx of alpha-actinin

A

structural; harnesses thin filaments

54
Q

general fx of tropomyosin

A

regulation; limits availability of myosin binding sites on actin

55
Q

general fx of troponin

A

regulation; calcium sensitive “switch” to initiate myosin-actin interactions

56
Q

principal protein comprising thick myofilaments

A

myosin

57
Q

principal structural protein of thin myofilaments

A

actin

58
Q

length-tension relationship

A

tension generated is directly proportional to the number of cross-bridges overlapped by thin filaments

59
Q

state of actin and myosin during rigor mortis

A

they are bound and unable to disassociate in the absence of ATP

Undeleted (134 decks)

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