skeletal muscle contraction (midterm 1) - look at figures as well Flashcards

1
Q

what are satellite cells

A

resident progenitor cells which matures into either another satellite cell or a myoblast

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2
Q

what is a myoblast

A

mononucleated cells that fuse to form myotubes

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3
Q

what are myotubes (myofibrils)

A

multinucleated, function cell of skeletal muscle

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4
Q

what are myofibers

A

organized structures of myotubes

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5
Q

what happens to satellite cells during skeletal muscle regeneration

A

they become activated and proliferate -> they can repopulate the reserve or differentiate into myoblasts (absolute number of satellite cells decreases with age)

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6
Q

in the muscle, how are myofibers organized

A

they’re stacked and bound by connective tissues that contain nerves and blood vessels

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7
Q

what are skeletal muscles composed of

A

muscle cells, connective tissue, blood vessels, and nerve fibers

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8
Q

what are the primary functions of skeletal muscle

A

contraction, force generation, and induction of movement

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9
Q

what is the parenchymal cell

A

muscle fiber responsible for muscle contraction

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10
Q

what is muscle fiber composed of

A

(10-80 um diameter) sarcolemma -> membrane: muscle -> tendon -> bone

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11
Q

what are myofibrils composed of

A

sarcomere: actin and myosin

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12
Q

what is an A-band

A

anisotropic (polarized light) => dark -> areas with both myosin and actin

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13
Q

what is an I-band

A

isotropic => light -> areas with just actin that helps identify a z-disk

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14
Q

what does a skeletal muscle look like

A

PICTURE IN NOTES PG 5

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15
Q

what is the sarcolemma

A

cell membrane of the muscle fiber

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16
Q

what are the ends of actin filaments attached to

A

a Z disc, which interdigitates with the myosin filaments

17
Q

what is a sarcomere

A

the portion of the myofibril that lies between two successive z discs -> normally 2 um when fully stretched resting length

18
Q

what is titin

A

maintains the side-by-side relationship between the myosin and actin filaments

19
Q

what is sarcoplasm

A

intracellular fluid the spaces between the myofibrils are filled with

20
Q

what is myosin molecules composed of

A

two heavy chains (make up myosin tail) and four light chains (make up myosin head)

21
Q

what are actin filaments composed of

A

actin, tropomyosin, and troponin
- composed of polymerized G-actin molecules, which each contain one ADP

22
Q

what are ASP molecules thought to be

A

active sites on which the cross-bridges of myosin filaments interact to cause muscle contraction

23
Q

what does it mean when z-bands are closer

A

more actin and myosin connection = more FORCE

24
Q

what are the three loosely bound protein subunits of troponin

A

troponin I = strong affinity for actin
troponin T = strong affinity for tropomyosin
troponin C = strong affinity for calcium ions

25
what is the walk-along theory of contraction
after Ca++ activation, the heads of the cross-bridges from the myosin filaments become attracted to the active sites of the actin filament, and causes contraction to occur
26
what is the energy source for contraction
ATP
27
what determines tension in muscles
actin overlap - more overlap = more tension
28
how long are sarcomeres
2.2 um - know the figures on slide 24 and 25
29
what occurs with more fast fibers
faster muscles
30
what provides 5-8 seconds of additional contraction
phosphocreatine
31
what provides 60 seconds of contraction
glycogen
32
what occurs with isometric contraction
muscle length does not change during contraction
33
what occurs with isotonic contraction
muscle tension does not change during contraction