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Physiology Exam 1 > Lecture 5: Skeletal Muscle Contraction > Flashcards

Lecture 5: Skeletal Muscle Contraction Flashcards

(73 cards)

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1
Q

connective tissue surrounding an entire muscle

A

epimysium

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2
Q

made up of several fascicles

A

Muscle

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3
Q

connective tissue surround individual fascicles

A

perimysium

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4
Q

a bundle of myofibers

A

fascicle

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5
Q

a delicate connective tissue surrounding each myofiber

A

endomysium

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6
Q

membrane of a myofiber

A

sarcolemma or plasmalemma

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7
Q

myofiber is also know as a _____

A

muscle cell

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8
Q

muscle cells are _____ in reference to an important organelle

A

multinucleated

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9
Q

individual multinucleated muscle cell

A

myofiber

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10
Q

a chain of sarcomeres within a myofiber

A

myofibril

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11
Q

actin and myosin filaments that make up a sarcomere

A

myofilament

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12
Q

T-tubules are inside what type of cells

A

muscle cells

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13
Q

_____ spans from the sarcolemma to ____ of the sarcoplasmic reticulum and forms _____ with it

A

T-tubules reach down close to cisternae and form triads

1 triad = 1 tubule & 2 cisternae on either side

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14
Q

How many triads are present in each sarcomere?

A

2

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15
Q

name the 4 major landmarks in sarcomeres

A

Z-lines — on each side of sarcomere
I-bands
A-bands
H-bands

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16
Q

which bands of the sarcomere change width in contraction and which do not?

A

H-band, I-band = change width

A-band = does not change

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17
Q

I-bands are composed of?

A

actin

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18
Q

A-bands are composed of?

A

actin and myosin

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19
Q

H-bands are composed of?

A

myosin

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20
Q

Z-lines are made up of?

A

actin filaments

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21
Q

what does the M line refer to in a sarcomere?

A

the middle line when the sarcomere is in a contracted state

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22
Q

H band is part of the ___ -band that is not overlapped in a relaxed state

A

a-band

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23
Q

which band disappears in a contracted state and why?

A

H-band

because actin and myosin now overlap, the H-band is the region of no overlap in the myosin/A-band

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24
Q

going from one side of a sarcomere to the other name the lines/bands in order

A

Z-line to I-band to A-band –>H-band (center of A)–>continuation of A-band to I-band to Z-line

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25
sarcomeres are aligned to produce a banding pattern which is a major characteristic of what type of muscle?
striated muscle
26
in a muscle contraction, does myosin or actin require ATP to release?
myosin requires ATP to release actin
27
when does a contraction stop?
when ATP-dependent calcium pumps sequester calcium ions back into sarcoplasmic reticulum
28
what is the first step in muscle contraction?
arrival of an action potential to terminal end of nerve fiber/alpha motor unit
29
what receptor on the SR, undergoes conformational change in order for calcium ions to be released?
ryanodine receptors
30
increasing Ca concentration in the cytosol will …..?
activate the sliding filament mechanism
31
sarcoplasmic reticulum calcium ATPase
SERCA
32
uses ATP to pump Ca back into the SR
SERCA
33
does SERCA utilize active or passive transport of Ca into the SR?
active transport | the Ca concentration is higher inside the SR, so it must move Ca up it's concentration gradient
34
maintains optimum Ca concentration gradient to facilitate the return of Ca into the SR
calsequestrin | helps out so that SERCA doesn't have to work so hard to get Ca back inside SR
35
describe DHP receptors
located on t-tubules --- voltage sensitive allow small amounts of Ca into cytosol cause conformational change to ryanodine receptors
36
describe ryanodine receptors
Ca release channels located on cisternae of SR open due to conformational change caused by DHP allowing Ca into cytosol from SR
37
load on a muscle in the relaxed state, no contraction has occurred
pre-load
38
preload generates ____?
passive tension
39
load the muscle works against
afterload
40
force generated by muscle is greater than the afterload
isotonic contraction
41
force generated by muscle is less than the afterload
isometric contraction
42
active tension is produced by...?
produced by cross-bridge cycling
43
this refers to the contracting and re-tracting of the sliding filaments continuously
cross-bridge cycling
44
cross-bridge cycling will continue until.....?
Ca is recaptured or ATP depleted
45
sarcomere at _____ micrometers | tension = 0
3.5 | no actin overlap
46
sarcomere at ____ micrometers | tension = maximum
all actin cross-bridges overlapped | 2.2
47
sarcomere at _____ micrometers | actin filaments touch
1.65 | tension = maximum
48
sarcomere at _____ micrometers | actin filaments overlap
<1.65 | tension = dropping to zero
49
sarcomere length at rest
2.0 micrometers
50
where is ATP required through one cycle of contraction/relaxation?
ATP is required for myosin to release actin | SERCA requires ATP to sequester Ca
51
concentration of ATP allows 1-2 second contraction
ATP is muscle fiber
52
phosphocreatine
releases energy fast by transferring P bond from phosphocreatine to store ADP
53
concentration of ATP allows 5-8 second contraction
phosphocreatine ATP release
54
concentration of ATP allows 60 second contraction
glycolysis ATP release
55
concentration of ATP allows >1 min contractions
aerobic metabolism
56
>95% of all energy needed for long term contraction is derived from this pathway
aerobic metabolism
57
an increase in tension but no mvt of muscle fibers
isometric contraction
58
increase in tension results in changing of muscle fiber lengths
isotonic contraction
59
other names for fast twitch fibers
white fibers | light fibers
60
characteristics of white fibers
``` contract rapidly fatigue quickly anaerobic respiration few mitochondria little myoglobin ```
61
other names for slow twitch fibers
red fibers | dark fibers
62
characteristics of red fibers
``` contract slowly fatigue slowly aerobic respiration many mitochondria high myoglobin conc. = gives it red color ```
63
how can fibers and fibrils be changed after birth?
``` # of fibers cannot be increased # of fibrils can be increased ```
64
lost muscle tissue is replaced by....?
scar tissue = fibrous CT
65
a neuron plus all the myofibers it innervates
motor unit
66
relate the all or none principle to motor units
all fibers within a motor until will contract but not all motor units will fire
67
additional contractions that occur before Ca ions have been recaptured
summation
68
if frequency of _____ is fast enough, no ______ time will exist between ______ . result?
frequency no relaxation time between contractions result: tetany - muscle remains maximally contracted
69
fulcrum in center | in and out forces move in opposite directions
``` 1st class lever teeter totter ```
70
another name for out force
resistance
71
out force in center | in and out force on same side of fulcrum
2nd class levers
72
another name for in force
effort
73
in force in center in and out force on same side of fulcrum in and out force move in same directions
``` 3rd class levers designed to move things more rapidly ```

Physiology Exam 1 (6 decks)

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