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

Lecture 5: Skeletal Muscle Contraction Flashcards

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
Q

sarcomeres are aligned to produce a banding pattern which is a major characteristic of what type of muscle?

A

striated muscle

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26
Q

in a muscle contraction, does myosin or actin require ATP to release?

A

myosin requires ATP to release actin

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27
Q

when does a contraction stop?

A

when ATP-dependent calcium pumps sequester calcium ions back into sarcoplasmic reticulum

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28
Q

what is the first step in muscle contraction?

A

arrival of an action potential to terminal end of nerve fiber/alpha motor unit

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29
Q

what receptor on the SR, undergoes conformational change in order for calcium ions to be released?

A

ryanodine receptors

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30
Q

increasing Ca concentration in the cytosol will …..?

A

activate the sliding filament mechanism

31
Q

sarcoplasmic reticulum calcium ATPase

A

SERCA

32
Q

uses ATP to pump Ca back into the SR

A

SERCA

33
Q

does SERCA utilize active or passive transport of Ca into the SR?

A

active transport

the Ca concentration is higher inside the SR, so it must move Ca up it’s concentration gradient

34
Q

maintains optimum Ca concentration gradient to facilitate the return of Ca into the SR

A

calsequestrin

helps out so that SERCA doesn’t have to work so hard to get Ca back inside SR

35
Q

describe DHP receptors

A

located on t-tubules — voltage sensitive
allow small amounts of Ca into cytosol
cause conformational change to ryanodine receptors

36
Q

describe ryanodine receptors

A

Ca release channels
located on cisternae of SR
open due to conformational change caused by DHP
allowing Ca into cytosol from SR

37
Q

load on a muscle in the relaxed state, no contraction has occurred

A

pre-load

38
Q

preload generates ____?

A

passive tension

39
Q

load the muscle works against

A

afterload

40
Q

force generated by muscle is greater than the afterload

A

isotonic contraction

41
Q

force generated by muscle is less than the afterload

A

isometric contraction

42
Q

active tension is produced by…?

A

produced by cross-bridge cycling

43
Q

this refers to the contracting and re-tracting of the sliding filaments continuously

A

cross-bridge cycling

44
Q

cross-bridge cycling will continue until…..?

A

Ca is recaptured or ATP depleted

45
Q

sarcomere at _____ micrometers

tension = 0

A

3.5

no actin overlap

46
Q

sarcomere at ____ micrometers

tension = maximum

A

all actin cross-bridges overlapped

2.2

47
Q

sarcomere at _____ micrometers

actin filaments touch

A

1.65

tension = maximum

48
Q

sarcomere at _____ micrometers

actin filaments overlap

A

<1.65

tension = dropping to zero

49
Q

sarcomere length at rest

A

2.0 micrometers

50
Q

where is ATP required through one cycle of contraction/relaxation?

A

ATP is required for myosin to release actin

SERCA requires ATP to sequester Ca

51
Q

concentration of ATP allows 1-2 second contraction

A

ATP is muscle fiber

52
Q

phosphocreatine

A

releases energy fast by transferring P bond from phosphocreatine to store ADP

53
Q

concentration of ATP allows 5-8 second contraction

A

phosphocreatine ATP release

54
Q

concentration of ATP allows 60 second contraction

A

glycolysis ATP release

55
Q

concentration of ATP allows >1 min contractions

A

aerobic metabolism

56
Q

> 95% of all energy needed for long term contraction is derived from this pathway

A

aerobic metabolism

57
Q

an increase in tension but no mvt of muscle fibers

A

isometric contraction

58
Q

increase in tension results in changing of muscle fiber lengths

A

isotonic contraction

59
Q

other names for fast twitch fibers

A

white fibers

light fibers

60
Q

characteristics of white fibers

A 
contract rapidly
fatigue quickly
anaerobic respiration
few mitochondria
little myoglobin
61
Q

other names for slow twitch fibers

A

red fibers

dark fibers

62
Q

characteristics of red fibers

A 
contract slowly
fatigue slowly
aerobic respiration
many mitochondria
high myoglobin conc. = gives it red color
63
Q

how can fibers and fibrils be changed after birth?

A 
# of fibers cannot be increased
# of fibrils can be increased
64
Q

lost muscle tissue is replaced by….?

A

scar tissue = fibrous CT

65
Q

a neuron plus all the myofibers it innervates

A

motor unit

66
Q

relate the all or none principle to motor units

A

all fibers within a motor until will contract
but
not all motor units will fire

67
Q

additional contractions that occur before Ca ions have been recaptured

A

summation

68
Q

if frequency of _____ is fast enough, no ______ time will exist between ______ . result?

A

frequency
no relaxation time between contractions
result:
tetany - muscle remains maximally contracted

69
Q

fulcrum in center

in and out forces move in opposite directions

A 
1st class lever
teeter totter
70
Q

another name for out force

A

resistance

71
Q

out force in center

in and out force on same side of fulcrum

A

2nd class levers

72
Q

another name for in force

A

effort

73
Q

in force in center
in and out force on same side of fulcrum
in and out force move in same directions

A 
3rd class levers
designed to move things more rapidly

Physiology Exam 1 (6 decks)

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