Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology > muscle contraction > Flashcards

muscle contraction Flashcards

1
Q

Muscle Contraction Occurs by a ________

A

Sliding
Filament Mechanism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Mechanical forces generated by interactions
between actin and myosin filaments causes the ACTIN
filaments to slide _________among the myosin
filaments. And under resting conditions, these
forces are inhibited

A

inward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

When an action potential travels over the muscle
fiber membrane, the sarcoplasmic reticulum
releases large quantities of ____________, which
activate the forces between myosin and actin
filaments, causing contraction to begin

A

calcium ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Calcium is supposed to be lower
intracellularly than extracellularly. But for _______its different and interesting

A

muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Myosin Filaments are Composed of
Multiple ________

A

Myosin Molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

There are tails of myosin molecules bundle together to form the _______

A

body of the filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Myosin heads and part of each myosin molecule hang outward to the sides of the body, providing an
arm that extends the head ______.

A

outward from the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Protruding arms + heads =

A

cross bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

An important feature of Myosin head functions as
an _________enzyme

A

adenosine triphosphatase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

the high energy currency of cells.

A

Adenosine triphosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

These myosin head function as ___________ which allows to cleave the adenosine
triphosphate and release energy to energized the
contraction process

A

adenosine
triphosphatase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The other filament is the_____.

A

actin filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Actin Filaments are Composed of ______

A

Actin,
Tropomyosin
Troponin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Remember the muscles particularly the actin, it is
supposed to interact with ______after.

A

myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Each actin filament is about _______ long

A

1 micrometer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The bases of the actin filaments are inserted strongly into the ___________,

whereas the other ends protrude in both directions into the adjacent
sarcomeres where they lie in the spaces between the
myosin molecules.

A

Z disks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

There is a little bit already of adjacent positioning of actin and myosin and what it
does wait for is for the activation of ________ to start the contraction.

A

ATP and Calcium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The actin filament is inhibited by the __________ complex

A

troponin-tropomyosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

It mediates the inhibition of contraction. The active sites on the normal actin filament of the relax
muscles are inhibited by the physically covered
__________complex

A

troponin- tropomyosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Inhibition by the troponin-tropomyosin complex –
prevents the ___________

A

actin myosin contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Activation by _________ activate the
contraction

There is an inhibitory effect on the actin.

A

calcium ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Calcium ions can combine with ___________,
causing the troponin complex to tug on the tropomyosin molecule.

Allow the myosin to attach and allows the contraction.

A

Troponin C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Calcium binds to Troponin C, pulls on the ____________, thereby allowing the binding
of your actin with your myosin.

A

tropomyosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

When a myosin head attaches to an _________, the
head tilts (power stroke) automatically toward the arm that is dragging along the actin filament.

A

active site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

tilting of the head

A

Power stroke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Immediately after tilting, the head automatically
_______away from the active site.

The head then returns to its normal
perpendicular direction.

A

breaks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

it combines with a new active site
farther along the actin filament. Thus, the head of cross-bridging bend back and forth to allow the step
by step _______ to happen.

Resulting in
pulling of the ends of actin filaments towards the
center of the myosin filament.

A

walk - along theory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Once the contraction starts, eventually this Power stroke is going to drag along the actin, to further
allowing the binding of the ______ to _____

A

active site to the myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

A muscle cannot develop tension at very long, nonphysiological sarcomere lengths because there is no
OVERLAP between _________

A

actin and myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

As the sarcomere shortens and actin and myosin
filaments begin to _______,

the tension increases
progressively

A

overlap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Whole tension is maintained at the sarcomere at ________.

This is due to the actin filaments
overlapping all the cross-bridges of the myosin
filament

A

2 micrometers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q
  • Cross-bridges can be found in _______
A

Myosin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q
  • Active sites can be found in ______
A

Actin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Upon further shortening, the ends of the two filaments begin to overlap (in addition to
overlapping the myosin filaments), causing muscle
tension to ______

A

decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

If the sarcomere is further shortened to 1/65 micrometers, the 2 z-discs of the sarcomere will
about the ___________, decreasing
the strength of contraction greatly

A

ends of the myosin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

are where the actin filaments are
attached to.

A

z-discs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Muscle Contraction Requires ATP to perform Three Main Functions

A
  1. Most of the ATP is used to activate the walk-along mechanism of muscle contraction
  2. Active transport of calcium ions back into the sarcoplasmic reticulum causes contraction to
    terminate.
  3. Active transport of sodium and potassium ions
    through the muscle fiber membrane maintains an
    appropriate ionic environment for the propagation
    of action potentials.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

After the action potential, Calcium is
released from the sarcoplasmic reticulum to
the cytoplasm.

To terminate it, Calcium is actively ____________, stopping the contraction.

A

pumped back into the sarcoplasmic
reticulum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Active transport of sodium and potassium ions
through the muscle fiber membrane maintains an
appropriate _________ for the propagation
of action potentials.

A

ionic environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

The concentration of ATP in the muscle fiber is sufficient to maintain full contraction for only _________

A

1 to 2 seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

There are several sources of energy for this rephosphorylation:

A

Phosphocreatine

The breakdown of glycogen

Oxidative metabolism

42
Q

It carried high energy bonds similar to ATP, but have more free energy.

The released energy bonds inorganic
phosphate to ADP, reconstituting
ATP.

A

Phosphocreatine

43
Q

Its combination with ATP is enough
for 5-8 seconds of maximal contraction.

A

Phosphocreatine

44
Q

is broken into pyruvic acid
and lactic acid, which liberates
energy that is used to convert ADP
to ATP.

A

Glycogen

45
Q

The Glycolytic reaction can happen
without oxygen, which makes it ____
faster

A

2.5x

46
Q

It can sustain maximal contraction
for about 1 minute

A

The breakdown of glycogen

47
Q

Occurs when oxygen reacts with foodstuffs (carbohydrates, fats,
proteins), liberating more ATP

A

Oxidative metabolism

48
Q

95% of the energy for sustained
muscle contraction is derived from
here, hence our body’s high oxygen
need

A

Oxidative metabolism

49
Q

Isometric Contractions Do Not Shorten Muscle,

whereas Isotonic Contractions
____

A

Shorten Muscle at a Constant Tension

50
Q

occurs when the muscle does not shorten during contraction.

True ___________ cannot be generated in the intact body
because the so-called series elastic components

A

Isometric contraction

51
Q

are the tendons,
sarcolemmal ends of muscle fibers, and
hinge arms of the myosin cross bridges

A

elastic components

52
Q

occurs when the muscle shortens and the tension on the muscle remains
constant

A

Isotonic contraction

53
Q

The characteristics of the isotonic
contraction depend on the ______against which the
muscle contracts, as well as on the ________

A

load

inertia of the load

54
Q

Fast Fibers are Adapted for _______

A

Powerful Muscle Contractions

55
Q

Slow Fibers
are Adapted for _______

A

Prolonged Muscle Activity

56
Q

Skeletal muscles are composed of 2 fibers:

Some of the fibers in the
muscle can be between the 2 extremes.

A

Fast fibers

slow fibers

57
Q

are smaller muscle fibers

  • have high capillarity and large numbers of
    mitochondria to support high levels of oxidative metabolism
A

Slow fibers (Type I, red muscle)

58
Q

contain large amounts of myoglobin, which gives the slow muscle a reddish appearance

A

Slow fibers (Type I, red muscle)

59
Q

The deficit of red
myoglobin in fast muscle provides the name

A

“white muscle”

60
Q

are larger for greater strength of contraction.

  • have extensive sarcoplasmic reticulum for
    rapid release of calcium ions.
A

Fast fibers (Type II, white muscle)

61
Q

have large amounts of glycolytic enzymes for
rapid release of energy.

  • have lower capillarity and fewer
    mitochondria because oxidative metabolism
    is of secondary importance
A

Fast fibers (Type II, white muscle)

62
Q

Mechanisms of Skeletal Muscle
Contraction Force Summation is the
Adding Together of ____________ to Increase the Intensity of
Overall Muscle Contraction

A

Individual Twitch
Contractions

63
Q

Summation occurs in two ways:

A
  1. Multiple motor unit summation is when multiple units are stimulated.
  2. Frequency summation and tetanization.
64
Q

is when
multiple units are stimulated.

A

Multiple motor unit summation

65
Q

When the central
nervous system sends a WEAK SIGNAL to contract a muscle, the motor units in the muscle that contain the ____________
are stimulated in preference to the larger motor
units.

A

smallest and fewest muscle fibers

66
Q

As the
frequency of muscle contraction increases,
there comes a point at which each new
contraction occurs before the preceding one has
ended.

A

Frequency summation and tetanization.

67
Q

second contraction is added partially to the first one so that the total strength of contraction would rise progressively with _________

A

increasing frequency

68
Q

When the frequency reaches the critical
level, _________ are going to fuse and action would tend to appear completely smooth

A

successive contractions

69
Q

as a result of summation you will no longer see the small contractions as it will appear as ______

A

tetanization

70
Q

is an Increase in the Total Mass of a Muscle;

in the presence of
activity

A

Muscle Hypertrophy

71
Q

is a Decrease in the Mass

in the absence of activity or
stimulation

A

Muscle Atrophy

72
Q

results from an increase in the
number of actin and myosin filaments in each muscle fiber.

When the number of contractile
proteins increases sufficiently, the myofibrils split
within each muscle fiber to form new myofibrils.

A

Muscle hypertrophy

73
Q
  • Enlargement of the muscle is dependent on protein synthesis.
  • Great increase in number of additional
    myofibrils causes muscle fibers to undergo hypertrophy
A

Muscle Hypertrophy

74
Q

under very intensive trainings (eg.
endurance training) the total number of muscle
fibers also

A

increased

75
Q

Skeletal muscles do not undergo cell division anymore (is partially correct),
however, these muscles contain a little bit of _________ within them but the regenerative capacity of it
is actually low similar to that of the brain as well as
the cardiac muscles.

A

stem cells

76
Q

on the other hand, which lines the hollow organs can undergo cell division.

A

Smooth muscles

77
Q

When a muscle remains unused
for a long period, the rate of decay of the contractile
proteins occurs more rapidly than the rate of
replacement

A

Muscle atrophy

78
Q

Atrophy of the muscle begins almost immediately when the muscle loses its

A

nerve supply

79
Q

nerves have charged
axon potentials which causes the

A

muscle tone

80
Q

losing the nerve, the muscle does not receive a contractile signal anymore
that are required to maintain the normal
_____

A

muscle size

81
Q

Each _______contains several hundred
to several thousand myofibrils

composed of about 1500 adjacent
myosin filaments and 3000 actin filaments

A

muscle fiber

82
Q

contain only actin filaments
and are called I bands because they are isotropic to polarized light.

A

light bands

83
Q

contain myosin filaments, as
well as the ends of the actin filaments where they overlap
the myosin,

they are
anisotropic to polarized light.

A

dark bands

84
Q

small projections from the sides of the myosin filaments

A

cross-bridges

85
Q

the ends of the actin filaments are attached to a

composed of filamentous proteins different from the actin and myosin
filaments, passes crosswise across the myofibril and also
crosswise from myofibril to myofibril, attaching the myofibrils to one another all the way across the muscle fiber

A

Z disk

86
Q

The portion of the myofibril (or of the whole muscle
fiber) that lies between two successive Z disks is

A

sarcomere

87
Q

The side-by-side relationship
between the myosin and actin filaments is maintained by
a large number of filamentous molecules of a protein
called _____

A

titin

88
Q

molecular weight of about 3 million, which makes it one of the largest protein molecules in the body filamentous, it is very springy.

A

titin

89
Q

The spaces
between the myofibrils are filled with intracellular fluid
called __________, containing large quantities of potassium, magnesium, and phosphate, plus multiple protein
enzymes.

A

sarcoplasm

90
Q

is composed of 6 polypeptide chains—two heavy chains, each with a
molecular weight of about 200,000, and four light chains with molecular weights of about 20,000 each

A

myosin molecule

91
Q

The two heavy chains wrap spirally around each other to form a double helix, which is called the ___________of the myosin molecule.

A

tail

92
Q

One end of each of these chains is folded bilaterally
into a globular polypeptide structure called a

A

myosin head

93
Q

Attached
intermittently along the sides of the tropomyosin molecules are additional protein molecules called

A

troponin

94
Q

has a strong affinity for actin

A

troponin I

95
Q

has a strong affinity for tropomyosin

A

troponin T

96
Q

has a strong affinity for calcium ions

A

(troponin C)

97
Q

When a muscle contracts, work is performed and energy is required.

Large amounts of ATP are cleaved to form ADP
during the contraction process, and the greater the
amount of work performed by the muscle, the greater the amount of ATP that is cleaved;

A

Fenn effect

98
Q

is important because it allows the gradations of muscle
force during weak contraction to occur in small steps,
whereas the steps become progressively greater when
large amounts of force are required

A

size principle

99
Q

When a
muscle begins to contract after a long period of rest, its initial strength of contraction may be as little as one half its strength 10 to 50 muscle twitches later.

That is, the strength of contraction increases to a plateau, a phenomenon called the

A

staircase effect, or treppe

100
Q

Prolonged and strong contraction of a
muscle leads to the well-known state of

A

muscle fatigue

101
Q

The study of different types of muscles,
lever systems, and their movements is called

A

kinesiology

102
Q

This increase in fiber number is called fiber

A

hyperplasia

Physiology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions